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fuchsia / third_party / rust / e6ee8a0d44fcedb583067bbaf36bcdf325029cdd / . / src / librustc / hir / lowering.rs
blob: 1b8e2999afe6ae3060a669bafcd482d51cbca856 [file] [log] [blame]
// ignore-tidy-filelength
//! Lowers the AST to the HIR.
//!
//! Since the AST and HIR are fairly similar, this is mostly a simple procedure,
//! much like a fold. Where lowering involves a bit more work things get more
//! interesting and there are some invariants you should know about. These mostly
//! concern spans and IDs.
//!
//! Spans are assigned to AST nodes during parsing and then are modified during
//! expansion to indicate the origin of a node and the process it went through
//! being expanded. IDs are assigned to AST nodes just before lowering.
//!
//! For the simpler lowering steps, IDs and spans should be preserved. Unlike
//! expansion we do not preserve the process of lowering in the spans, so spans
//! should not be modified here. When creating a new node (as opposed to
//! 'folding' an existing one), then you create a new ID using `next_id()`.
//!
//! You must ensure that IDs are unique. That means that you should only use the
//! ID from an AST node in a single HIR node (you can assume that AST node-IDs
//! are unique). Every new node must have a unique ID. Avoid cloning HIR nodes.
//! If you do, you must then set the new node's ID to a fresh one.
//!
//! Spans are used for error messages and for tools to map semantics back to
//! source code. It is therefore not as important with spans as IDs to be strict
//! about use (you can't break the compiler by screwing up a span). Obviously, a
//! HIR node can only have a single span. But multiple nodes can have the same
//! span and spans don't need to be kept in order, etc. Where code is preserved
//! by lowering, it should have the same span as in the AST. Where HIR nodes are
//! new it is probably best to give a span for the whole AST node being lowered.
//! All nodes should have real spans, don't use dummy spans. Tools are likely to
//! get confused if the spans from leaf AST nodes occur in multiple places
//! in the HIR, especially for multiple identifiers.
use crate::dep_graph::DepGraph;
use crate::hir::{self, ParamName};
use crate::hir::HirVec;
use crate::hir::map::{DefKey, DefPathData, Definitions};
use crate::hir::def_id::{DefId, DefIndex, CRATE_DEF_INDEX};
use crate::hir::def::{Res, DefKind, PartialRes, PerNS};
use crate::hir::{GenericArg, ConstArg};
use crate::lint::builtin::{self, PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
ELIDED_LIFETIMES_IN_PATHS};
use crate::middle::cstore::CrateStore;
use crate::session::Session;
use crate::session::config::nightly_options;
use crate::util::common::FN_OUTPUT_NAME;
use crate::util::nodemap::{DefIdMap, NodeMap};
use errors::Applicability;
use rustc_data_structures::fx::FxHashSet;
use rustc_data_structures::indexed_vec::IndexVec;
use rustc_data_structures::thin_vec::ThinVec;
use rustc_data_structures::sync::Lrc;
use std::collections::{BTreeSet, BTreeMap};
use std::mem;
use smallvec::SmallVec;
use syntax::attr;
use syntax::ast;
use syntax::ast::*;
use syntax::errors;
use syntax::ext::hygiene::{Mark, SyntaxContext};
use syntax::print::pprust;
use syntax::ptr::P;
use syntax::source_map::{self, respan, ExpnInfo, CompilerDesugaringKind, Spanned};
use syntax::source_map::CompilerDesugaringKind::IfTemporary;
use syntax::std_inject;
use syntax::symbol::{kw, sym, Symbol};
use syntax::tokenstream::{TokenStream, TokenTree};
use syntax::parse::token::{self, Token};
use syntax::visit::{self, Visitor};
use syntax_pos::{DUMMY_SP, Span};
const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF;
pub struct LoweringContext<'a> {
crate_root: Option<Symbol>,
/// Used to assign ids to HIR nodes that do not directly correspond to an AST node.
sess: &'a Session,
cstore: &'a dyn CrateStore,
resolver: &'a mut dyn Resolver,
/// The items being lowered are collected here.
items: BTreeMap<hir::HirId, hir::Item>,
trait_items: BTreeMap<hir::TraitItemId, hir::TraitItem>,
impl_items: BTreeMap<hir::ImplItemId, hir::ImplItem>,
bodies: BTreeMap<hir::BodyId, hir::Body>,
exported_macros: Vec<hir::MacroDef>,
trait_impls: BTreeMap<DefId, Vec<hir::HirId>>,
modules: BTreeMap<NodeId, hir::ModuleItems>,
generator_kind: Option<hir::GeneratorKind>,
/// Used to get the current `fn`'s def span to point to when using `await`
/// outside of an `async fn`.
current_item: Option<Span>,
catch_scopes: Vec<NodeId>,
loop_scopes: Vec<NodeId>,
is_in_loop_condition: bool,
is_in_trait_impl: bool,
is_in_dyn_type: bool,
/// What to do when we encounter either an "anonymous lifetime
/// reference". The term "anonymous" is meant to encompass both
/// `'_` lifetimes as well as fully elided cases where nothing is
/// written at all (e.g., `&T` or `std::cell::Ref<T>`).
anonymous_lifetime_mode: AnonymousLifetimeMode,
/// Used to create lifetime definitions from in-band lifetime usages.
/// e.g., `fn foo(x: &'x u8) -> &'x u8` to `fn foo<'x>(x: &'x u8) -> &'x u8`
/// When a named lifetime is encountered in a function or impl header and
/// has not been defined
/// (i.e., it doesn't appear in the in_scope_lifetimes list), it is added
/// to this list. The results of this list are then added to the list of
/// lifetime definitions in the corresponding impl or function generics.
lifetimes_to_define: Vec<(Span, ParamName)>,
/// Whether or not in-band lifetimes are being collected. This is used to
/// indicate whether or not we're in a place where new lifetimes will result
/// in in-band lifetime definitions, such a function or an impl header,
/// including implicit lifetimes from `impl_header_lifetime_elision`.
is_collecting_in_band_lifetimes: bool,
/// Currently in-scope lifetimes defined in impl headers, fn headers, or HRTB.
/// When `is_collectin_in_band_lifetimes` is true, each lifetime is checked
/// against this list to see if it is already in-scope, or if a definition
/// needs to be created for it.
in_scope_lifetimes: Vec<Ident>,
current_module: NodeId,
type_def_lifetime_params: DefIdMap<usize>,
current_hir_id_owner: Vec<(DefIndex, u32)>,
item_local_id_counters: NodeMap<u32>,
node_id_to_hir_id: IndexVec<NodeId, hir::HirId>,
allow_try_trait: Option<Lrc<[Symbol]>>,
allow_gen_future: Option<Lrc<[Symbol]>>,
}
pub trait Resolver {
/// Resolve a path generated by the lowerer when expanding `for`, `if let`, etc.
fn resolve_ast_path(
&mut self,
path: &ast::Path,
is_value: bool,
) -> Res<NodeId>;
/// Obtain resolution for a `NodeId` with a single resolution.
fn get_partial_res(&mut self, id: NodeId) -> Option<PartialRes>;
/// Obtain per-namespace resolutions for `use` statement with the given `NoedId`.
fn get_import_res(&mut self, id: NodeId) -> PerNS<Option<Res<NodeId>>>;
/// Obtain resolution for a label with the given `NodeId`.
fn get_label_res(&mut self, id: NodeId) -> Option<NodeId>;
/// We must keep the set of definitions up to date as we add nodes that weren't in the AST.
/// This should only return `None` during testing.
fn definitions(&mut self) -> &mut Definitions;
/// Given suffix `["b", "c", "d"]`, creates an AST path for `[::crate_root]::b::c::d` and
/// resolves it based on `is_value`.
fn resolve_str_path(
&mut self,
span: Span,
crate_root: Option<Symbol>,
components: &[Symbol],
is_value: bool,
) -> (ast::Path, Res<NodeId>);
}
/// Context of `impl Trait` in code, which determines whether it is allowed in an HIR subtree,
/// and if so, what meaning it has.
#[derive(Debug)]
enum ImplTraitContext<'a> {
/// Treat `impl Trait` as shorthand for a new universal generic parameter.
/// Example: `fn foo(x: impl Debug)`, where `impl Debug` is conceptually
/// equivalent to a fresh universal parameter like `fn foo<T: Debug>(x: T)`.
///
/// Newly generated parameters should be inserted into the given `Vec`.
Universal(&'a mut Vec<hir::GenericParam>),
/// Treat `impl Trait` as shorthand for a new existential parameter.
/// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually
/// equivalent to a fresh existential parameter like `existential type T; fn foo() -> T`.
///
/// We optionally store a `DefId` for the parent item here so we can look up necessary
/// information later. It is `None` when no information about the context should be stored
/// (e.g., for consts and statics).
Existential(Option<DefId> /* fn def-ID */),
/// `impl Trait` is not accepted in this position.
Disallowed(ImplTraitPosition),
}
/// Position in which `impl Trait` is disallowed.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum ImplTraitPosition {
/// Disallowed in `let` / `const` / `static` bindings.
Binding,
/// All other posiitons.
Other,
}
impl<'a> ImplTraitContext<'a> {
#[inline]
fn disallowed() -> Self {
ImplTraitContext::Disallowed(ImplTraitPosition::Other)
}
fn reborrow(&'b mut self) -> ImplTraitContext<'b> {
use self::ImplTraitContext::*;
match self {
Universal(params) => Universal(params),
Existential(fn_def_id) => Existential(*fn_def_id),
Disallowed(pos) => Disallowed(*pos),
}
}
}
pub fn lower_crate(
sess: &Session,
cstore: &dyn CrateStore,
dep_graph: &DepGraph,
krate: &Crate,
resolver: &mut dyn Resolver,
) -> hir::Crate {
// We're constructing the HIR here; we don't care what we will
// read, since we haven't even constructed the *input* to
// incr. comp. yet.
dep_graph.assert_ignored();
LoweringContext {
crate_root: std_inject::injected_crate_name().map(Symbol::intern),
sess,
cstore,
resolver,
items: BTreeMap::new(),
trait_items: BTreeMap::new(),
impl_items: BTreeMap::new(),
bodies: BTreeMap::new(),
trait_impls: BTreeMap::new(),
modules: BTreeMap::new(),
exported_macros: Vec::new(),
catch_scopes: Vec::new(),
loop_scopes: Vec::new(),
is_in_loop_condition: false,
is_in_trait_impl: false,
is_in_dyn_type: false,
anonymous_lifetime_mode: AnonymousLifetimeMode::PassThrough,
type_def_lifetime_params: Default::default(),
current_module: CRATE_NODE_ID,
current_hir_id_owner: vec![(CRATE_DEF_INDEX, 0)],
item_local_id_counters: Default::default(),
node_id_to_hir_id: IndexVec::new(),
generator_kind: None,
current_item: None,
lifetimes_to_define: Vec::new(),
is_collecting_in_band_lifetimes: false,
in_scope_lifetimes: Vec::new(),
allow_try_trait: Some([sym::try_trait][..].into()),
allow_gen_future: Some([sym::gen_future][..].into()),
}.lower_crate(krate)
}
#[derive(Copy, Clone, PartialEq)]
enum ParamMode {
/// Any path in a type context.
Explicit,
/// Path in a type definition, where the anonymous lifetime `'_` is not allowed.
ExplicitNamed,
/// The `module::Type` in `module::Type::method` in an expression.
Optional,
}
enum ParenthesizedGenericArgs {
Ok,
Warn,
Err,
}
/// What to do when we encounter an **anonymous** lifetime
/// reference. Anonymous lifetime references come in two flavors. You
/// have implicit, or fully elided, references to lifetimes, like the
/// one in `&T` or `Ref<T>`, and you have `'_` lifetimes, like `&'_ T`
/// or `Ref<'_, T>`. These often behave the same, but not always:
///
/// - certain usages of implicit references are deprecated, like
/// `Ref<T>`, and we sometimes just give hard errors in those cases
/// as well.
/// - for object bounds there is a difference: `Box<dyn Foo>` is not
/// the same as `Box<dyn Foo + '_>`.
///
/// We describe the effects of the various modes in terms of three cases:
///
/// - **Modern** -- includes all uses of `'_`, but also the lifetime arg
/// of a `&` (e.g., the missing lifetime in something like `&T`)
/// - **Dyn Bound** -- if you have something like `Box<dyn Foo>`,
/// there is an elided lifetime bound (`Box<dyn Foo + 'X>`). These
/// elided bounds follow special rules. Note that this only covers
/// cases where *nothing* is written; the `'_` in `Box<dyn Foo +
/// '_>` is a case of "modern" elision.
/// - **Deprecated** -- this coverse cases like `Ref<T>`, where the lifetime
/// parameter to ref is completely elided. `Ref<'_, T>` would be the modern,
/// non-deprecated equivalent.
///
/// Currently, the handling of lifetime elision is somewhat spread out
/// between HIR lowering and -- as described below -- the
/// `resolve_lifetime` module. Often we "fallthrough" to that code by generating
/// an "elided" or "underscore" lifetime name. In the future, we probably want to move
/// everything into HIR lowering.
#[derive(Copy, Clone)]
enum AnonymousLifetimeMode {
/// For **Modern** cases, create a new anonymous region parameter
/// and reference that.
///
/// For **Dyn Bound** cases, pass responsibility to
/// `resolve_lifetime` code.
///
/// For **Deprecated** cases, report an error.
CreateParameter,
/// Give a hard error when either `&` or `'_` is written. Used to
/// rule out things like `where T: Foo<'_>`. Does not imply an
/// error on default object bounds (e.g., `Box<dyn Foo>`).
ReportError,
/// Pass responsibility to `resolve_lifetime` code for all cases.
PassThrough,
/// Used in the return types of `async fn` where there exists
/// exactly one argument-position elided lifetime.
///
/// In `async fn`, we lower the arguments types using the `CreateParameter`
/// mode, meaning that non-`dyn` elided lifetimes are assigned a fresh name.
/// If any corresponding elided lifetimes appear in the output, we need to
/// replace them with references to the fresh name assigned to the corresponding
/// elided lifetime in the arguments.
///
/// For **Modern cases**, replace the anonymous parameter with a
/// reference to a specific freshly-named lifetime that was
/// introduced in argument
///
/// For **Dyn Bound** cases, pass responsibility to
/// `resole_lifetime` code.
Replace(LtReplacement),
}
/// The type of elided lifetime replacement to perform on `async fn` return types.
#[derive(Copy, Clone)]
enum LtReplacement {
/// Fresh name introduced by the single non-dyn elided lifetime
/// in the arguments of the async fn.
Some(ParamName),
/// There is no single non-dyn elided lifetime because no lifetimes
/// appeared in the arguments.
NoLifetimes,
/// There is no single non-dyn elided lifetime because multiple
/// lifetimes appeared in the arguments.
MultipleLifetimes,
}
/// Calculates the `LtReplacement` to use for elided lifetimes in the return
/// type based on the fresh elided lifetimes introduced in argument position.
fn get_elided_lt_replacement(arg_position_lifetimes: &[(Span, ParamName)]) -> LtReplacement {
match arg_position_lifetimes {
[] => LtReplacement::NoLifetimes,
[(_span, param)] => LtReplacement::Some(*param),
_ => LtReplacement::MultipleLifetimes,
}
}
struct ImplTraitTypeIdVisitor<'a> { ids: &'a mut SmallVec<[NodeId; 1]> }
impl<'a, 'b> Visitor<'a> for ImplTraitTypeIdVisitor<'b> {
fn visit_ty(&mut self, ty: &'a Ty) {
match ty.node {
| TyKind::Typeof(_)
| TyKind::BareFn(_)
=> return,
TyKind::ImplTrait(id, _) => self.ids.push(id),
_ => {},
}
visit::walk_ty(self, ty);
}
fn visit_path_segment(
&mut self,
path_span: Span,
path_segment: &'v PathSegment,
) {
if let Some(ref p) = path_segment.args {
if let GenericArgs::Parenthesized(_) = **p {
return;
}
}
visit::walk_path_segment(self, path_span, path_segment)
}
}
impl<'a> LoweringContext<'a> {
fn lower_crate(mut self, c: &Crate) -> hir::Crate {
/// Full-crate AST visitor that inserts into a fresh
/// `LoweringContext` any information that may be
/// needed from arbitrary locations in the crate,
/// e.g., the number of lifetime generic parameters
/// declared for every type and trait definition.
struct MiscCollector<'tcx, 'interner> {
lctx: &'tcx mut LoweringContext<'interner>,
hir_id_owner: Option<NodeId>,
}
impl MiscCollector<'_, '_> {
fn allocate_use_tree_hir_id_counters(
&mut self,
tree: &UseTree,
owner: DefIndex,
) {
match tree.kind {
UseTreeKind::Simple(_, id1, id2) => {
for &id in &[id1, id2] {
self.lctx.resolver.definitions().create_def_with_parent(
owner,
id,
DefPathData::Misc,
Mark::root(),
tree.prefix.span,
);
self.lctx.allocate_hir_id_counter(id);
}
}
UseTreeKind::Glob => (),
UseTreeKind::Nested(ref trees) => {
for &(ref use_tree, id) in trees {
let hir_id = self.lctx.allocate_hir_id_counter(id);
self.allocate_use_tree_hir_id_counters(use_tree, hir_id.owner);
}
}
}
}
fn with_hir_id_owner<F, T>(&mut self, owner: Option<NodeId>, f: F) -> T
where
F: FnOnce(&mut Self) -> T,
{
let old = mem::replace(&mut self.hir_id_owner, owner);
let r = f(self);
self.hir_id_owner = old;
r
}
}
impl<'tcx, 'interner> Visitor<'tcx> for MiscCollector<'tcx, 'interner> {
fn visit_pat(&mut self, p: &'tcx Pat) {
match p.node {
// Doesn't generate a HIR node
PatKind::Paren(..) => {},
_ => {
if let Some(owner) = self.hir_id_owner {
self.lctx.lower_node_id_with_owner(p.id, owner);
}
}
};
visit::walk_pat(self, p)
}
fn visit_item(&mut self, item: &'tcx Item) {
let hir_id = self.lctx.allocate_hir_id_counter(item.id);
match item.node {
ItemKind::Struct(_, ref generics)
| ItemKind::Union(_, ref generics)
| ItemKind::Enum(_, ref generics)
| ItemKind::Ty(_, ref generics)
| ItemKind::Existential(_, ref generics)
| ItemKind::Trait(_, _, ref generics, ..) => {
let def_id = self.lctx.resolver.definitions().local_def_id(item.id);
let count = generics
.params
.iter()
.filter(|param| match param.kind {
ast::GenericParamKind::Lifetime { .. } => true,
_ => false,
})
.count();
self.lctx.type_def_lifetime_params.insert(def_id, count);
}
ItemKind::Use(ref use_tree) => {
self.allocate_use_tree_hir_id_counters(use_tree, hir_id.owner);
}
_ => {}
}
self.with_hir_id_owner(Some(item.id), |this| {
visit::walk_item(this, item);
});
}
fn visit_trait_item(&mut self, item: &'tcx TraitItem) {
self.lctx.allocate_hir_id_counter(item.id);
match item.node {
TraitItemKind::Method(_, None) => {
// Ignore patterns in trait methods without bodies
self.with_hir_id_owner(None, |this| {
visit::walk_trait_item(this, item)
});
}
_ => self.with_hir_id_owner(Some(item.id), |this| {
visit::walk_trait_item(this, item);
})
}
}
fn visit_impl_item(&mut self, item: &'tcx ImplItem) {
self.lctx.allocate_hir_id_counter(item.id);
self.with_hir_id_owner(Some(item.id), |this| {
visit::walk_impl_item(this, item);
});
}
fn visit_foreign_item(&mut self, i: &'tcx ForeignItem) {
// Ignore patterns in foreign items
self.with_hir_id_owner(None, |this| {
visit::walk_foreign_item(this, i)
});
}
fn visit_ty(&mut self, t: &'tcx Ty) {
match t.node {
// Mirrors the case in visit::walk_ty
TyKind::BareFn(ref f) => {
walk_list!(
self,
visit_generic_param,
&f.generic_params
);
// Mirrors visit::walk_fn_decl
for argument in &f.decl.inputs {
// We don't lower the ids of argument patterns
self.with_hir_id_owner(None, |this| {
this.visit_pat(&argument.pat);
});
self.visit_ty(&argument.ty)
}
self.visit_fn_ret_ty(&f.decl.output)
}
_ => visit::walk_ty(self, t),
}
}
}
struct ItemLowerer<'tcx, 'interner> {
lctx: &'tcx mut LoweringContext<'interner>,
}
impl<'tcx, 'interner> ItemLowerer<'tcx, 'interner> {
fn with_trait_impl_ref<F>(&mut self, trait_impl_ref: &Option<TraitRef>, f: F)
where
F: FnOnce(&mut Self),
{
let old = self.lctx.is_in_trait_impl;
self.lctx.is_in_trait_impl = if let &None = trait_impl_ref {
false
} else {
true
};
f(self);
self.lctx.is_in_trait_impl = old;
}
}
impl<'tcx, 'interner> Visitor<'tcx> for ItemLowerer<'tcx, 'interner> {
fn visit_mod(&mut self, m: &'tcx Mod, _s: Span, _attrs: &[Attribute], n: NodeId) {
self.lctx.modules.insert(n, hir::ModuleItems {
items: BTreeSet::new(),
trait_items: BTreeSet::new(),
impl_items: BTreeSet::new(),
});
let old = self.lctx.current_module;
self.lctx.current_module = n;
visit::walk_mod(self, m);
self.lctx.current_module = old;
}
fn visit_item(&mut self, item: &'tcx Item) {
let mut item_hir_id = None;
self.lctx.with_hir_id_owner(item.id, |lctx| {
if let Some(hir_item) = lctx.lower_item(item) {
item_hir_id = Some(hir_item.hir_id);
lctx.insert_item(hir_item);
}
});
if let Some(hir_id) = item_hir_id {
self.lctx.with_parent_item_lifetime_defs(hir_id, |this| {
let this = &mut ItemLowerer { lctx: this };
if let ItemKind::Impl(.., ref opt_trait_ref, _, _) = item.node {
this.with_trait_impl_ref(opt_trait_ref, |this| {
visit::walk_item(this, item)
});
} else {
visit::walk_item(this, item);
}
});
}
}
fn visit_trait_item(&mut self, item: &'tcx TraitItem) {
self.lctx.with_hir_id_owner(item.id, |lctx| {
let hir_item = lctx.lower_trait_item(item);
let id = hir::TraitItemId { hir_id: hir_item.hir_id };
lctx.trait_items.insert(id, hir_item);
lctx.modules.get_mut(&lctx.current_module).unwrap().trait_items.insert(id);
});
visit::walk_trait_item(self, item);
}
fn visit_impl_item(&mut self, item: &'tcx ImplItem) {
self.lctx.with_hir_id_owner(item.id, |lctx| {
let hir_item = lctx.lower_impl_item(item);
let id = hir::ImplItemId { hir_id: hir_item.hir_id };
lctx.impl_items.insert(id, hir_item);
lctx.modules.get_mut(&lctx.current_module).unwrap().impl_items.insert(id);
});
visit::walk_impl_item(self, item);
}
}
self.lower_node_id(CRATE_NODE_ID);
debug_assert!(self.node_id_to_hir_id[CRATE_NODE_ID] == hir::CRATE_HIR_ID);
visit::walk_crate(&mut MiscCollector { lctx: &mut self, hir_id_owner: None }, c);
visit::walk_crate(&mut ItemLowerer { lctx: &mut self }, c);
let module = self.lower_mod(&c.module);
let attrs = self.lower_attrs(&c.attrs);
let body_ids = body_ids(&self.bodies);
self.resolver
.definitions()
.init_node_id_to_hir_id_mapping(self.node_id_to_hir_id);
hir::Crate {
module,
attrs,
span: c.span,
exported_macros: hir::HirVec::from(self.exported_macros),
items: self.items,
trait_items: self.trait_items,
impl_items: self.impl_items,
bodies: self.bodies,
body_ids,
trait_impls: self.trait_impls,
modules: self.modules,
}
}
fn insert_item(&mut self, item: hir::Item) {
let id = item.hir_id;
// FIXME: Use `debug_asset-rt`.
assert_eq!(id.local_id, hir::ItemLocalId::from_u32(0));
self.items.insert(id, item);
self.modules.get_mut(&self.current_module).unwrap().items.insert(id);
}
fn allocate_hir_id_counter(&mut self, owner: NodeId) -> hir::HirId {
// Set up the counter if needed.
self.item_local_id_counters.entry(owner).or_insert(0);
// Always allocate the first `HirId` for the owner itself.
let lowered = self.lower_node_id_with_owner(owner, owner);
debug_assert_eq!(lowered.local_id.as_u32(), 0);
lowered
}
fn lower_node_id_generic<F>(&mut self, ast_node_id: NodeId, alloc_hir_id: F) -> hir::HirId
where
F: FnOnce(&mut Self) -> hir::HirId,
{
if ast_node_id == DUMMY_NODE_ID {
return hir::DUMMY_HIR_ID;
}
let min_size = ast_node_id.as_usize() + 1;
if min_size > self.node_id_to_hir_id.len() {
self.node_id_to_hir_id.resize(min_size, hir::DUMMY_HIR_ID);
}
let existing_hir_id = self.node_id_to_hir_id[ast_node_id];
if existing_hir_id == hir::DUMMY_HIR_ID {
// Generate a new `HirId`.
let hir_id = alloc_hir_id(self);
self.node_id_to_hir_id[ast_node_id] = hir_id;
hir_id
} else {
existing_hir_id
}
}
fn with_hir_id_owner<F, T>(&mut self, owner: NodeId, f: F) -> T
where
F: FnOnce(&mut Self) -> T,
{
let counter = self.item_local_id_counters
.insert(owner, HIR_ID_COUNTER_LOCKED)
.unwrap_or_else(|| panic!("no `item_local_id_counters` entry for {:?}", owner));
let def_index = self.resolver.definitions().opt_def_index(owner).unwrap();
self.current_hir_id_owner.push((def_index, counter));
let ret = f(self);
let (new_def_index, new_counter) = self.current_hir_id_owner.pop().unwrap();
debug_assert!(def_index == new_def_index);
debug_assert!(new_counter >= counter);
let prev = self.item_local_id_counters
.insert(owner, new_counter)
.unwrap();
debug_assert!(prev == HIR_ID_COUNTER_LOCKED);
ret
}
/// This method allocates a new `HirId` for the given `NodeId` and stores it in
/// the `LoweringContext`'s `NodeId => HirId` map.
/// Take care not to call this method if the resulting `HirId` is then not
/// actually used in the HIR, as that would trigger an assertion in the
/// `HirIdValidator` later on, which makes sure that all `NodeId`s got mapped
/// properly. Calling the method twice with the same `NodeId` is fine though.
fn lower_node_id(&mut self, ast_node_id: NodeId) -> hir::HirId {
self.lower_node_id_generic(ast_node_id, |this| {
let &mut (def_index, ref mut local_id_counter) =
this.current_hir_id_owner.last_mut().unwrap();
let local_id = *local_id_counter;
*local_id_counter += 1;
hir::HirId {
owner: def_index,
local_id: hir::ItemLocalId::from_u32(local_id),
}
})
}
fn lower_node_id_with_owner(&mut self, ast_node_id: NodeId, owner: NodeId) -> hir::HirId {
self.lower_node_id_generic(ast_node_id, |this| {
let local_id_counter = this
.item_local_id_counters
.get_mut(&owner)
.expect("called `lower_node_id_with_owner` before `allocate_hir_id_counter`");
let local_id = *local_id_counter;
// We want to be sure not to modify the counter in the map while it
// is also on the stack. Otherwise we'll get lost updates when writing
// back from the stack to the map.
debug_assert!(local_id != HIR_ID_COUNTER_LOCKED);
*local_id_counter += 1;
let def_index = this
.resolver
.definitions()
.opt_def_index(owner)
.expect("you forgot to call `create_def_with_parent` or are lowering node-IDs \
that do not belong to the current owner");
hir::HirId {
owner: def_index,
local_id: hir::ItemLocalId::from_u32(local_id),
}
})
}
fn generator_movability_for_fn(
&mut self,
decl: &ast::FnDecl,
fn_decl_span: Span,
generator_kind: Option<hir::GeneratorKind>,
movability: Movability,
) -> Option<hir::GeneratorMovability> {
match generator_kind {
Some(hir::GeneratorKind::Gen) => {
if !decl.inputs.is_empty() {
span_err!(
self.sess,
fn_decl_span,
E0628,
"generators cannot have explicit arguments"
);
self.sess.abort_if_errors();
}
Some(match movability {
Movability::Movable => hir::GeneratorMovability::Movable,
Movability::Static => hir::GeneratorMovability::Static,
})
},
Some(hir::GeneratorKind::Async) => {
bug!("non-`async` closure body turned `async` during lowering");
},
None => {
if movability == Movability::Static {
span_err!(
self.sess,
fn_decl_span,
E0697,
"closures cannot be static"
);
}
None
},
}
}
fn record_body(&mut self, arguments: HirVec<hir::Arg>, value: hir::Expr) -> hir::BodyId {
let body = hir::Body {
generator_kind: self.generator_kind,
arguments,
value,
};
let id = body.id();
self.bodies.insert(id, body);
id
}
fn next_id(&mut self) -> hir::HirId {
self.lower_node_id(self.sess.next_node_id())
}
fn lower_res(&mut self, res: Res<NodeId>) -> Res {
res.map_id(|id| {
self.lower_node_id_generic(id, |_| {
panic!("expected node_id to be lowered already for res {:#?}", res)
})
})
}
fn expect_full_res(&mut self, id: NodeId) -> Res<NodeId> {
self.resolver.get_partial_res(id).map_or(Res::Err, |pr| {
if pr.unresolved_segments() != 0 {
bug!("path not fully resolved: {:?}", pr);
}
pr.base_res()
})
}
fn expect_full_res_from_use(&mut self, id: NodeId) -> impl Iterator<Item = Res<NodeId>> {
self.resolver.get_import_res(id).present_items()
}
fn diagnostic(&self) -> &errors::Handler {
self.sess.diagnostic()
}
/// Reuses the span but adds information like the kind of the desugaring and features that are
/// allowed inside this span.
fn mark_span_with_reason(
&self,
reason: CompilerDesugaringKind,
span: Span,
allow_internal_unstable: Option<Lrc<[Symbol]>>,
) -> Span {
let mark = Mark::fresh(Mark::root());
mark.set_expn_info(ExpnInfo {
def_site: Some(span),
allow_internal_unstable,
..ExpnInfo::default(source_map::CompilerDesugaring(reason), span, self.sess.edition())
});
span.with_ctxt(SyntaxContext::empty().apply_mark(mark))
}
fn with_anonymous_lifetime_mode<R>(
&mut self,
anonymous_lifetime_mode: AnonymousLifetimeMode,
op: impl FnOnce(&mut Self) -> R,
) -> R {
let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
self.anonymous_lifetime_mode = anonymous_lifetime_mode;
let result = op(self);
self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
result
}
/// Creates a new `hir::GenericParam` for every new lifetime and
/// type parameter encountered while evaluating `f`. Definitions
/// are created with the parent provided. If no `parent_id` is
/// provided, no definitions will be returned.
///
/// Presuming that in-band lifetimes are enabled, then
/// `self.anonymous_lifetime_mode` will be updated to match the
/// argument while `f` is running (and restored afterwards).
fn collect_in_band_defs<T, F>(
&mut self,
parent_id: DefId,
anonymous_lifetime_mode: AnonymousLifetimeMode,
f: F,
) -> (Vec<hir::GenericParam>, T)
where
F: FnOnce(&mut LoweringContext<'_>) -> (Vec<hir::GenericParam>, T),
{
assert!(!self.is_collecting_in_band_lifetimes);
assert!(self.lifetimes_to_define.is_empty());
let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
self.anonymous_lifetime_mode = anonymous_lifetime_mode;
self.is_collecting_in_band_lifetimes = true;
let (in_band_ty_params, res) = f(self);
self.is_collecting_in_band_lifetimes = false;
self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
let lifetimes_to_define = self.lifetimes_to_define.split_off(0);
let params = lifetimes_to_define
.into_iter()
.map(|(span, hir_name)| self.lifetime_to_generic_param(
span, hir_name, parent_id.index,
))
.chain(in_band_ty_params.into_iter())
.collect();
(params, res)
}
/// Converts a lifetime into a new generic parameter.
fn lifetime_to_generic_param(
&mut self,
span: Span,
hir_name: ParamName,
parent_index: DefIndex,
) -> hir::GenericParam {
let node_id = self.sess.next_node_id();
// Get the name we'll use to make the def-path. Note
// that collisions are ok here and this shouldn't
// really show up for end-user.
let (str_name, kind) = match hir_name {
ParamName::Plain(ident) => (
ident.as_interned_str(),
hir::LifetimeParamKind::InBand,
),
ParamName::Fresh(_) => (
kw::UnderscoreLifetime.as_interned_str(),
hir::LifetimeParamKind::Elided,
),
ParamName::Error => (
kw::UnderscoreLifetime.as_interned_str(),
hir::LifetimeParamKind::Error,
),
};
// Add a definition for the in-band lifetime def.
self.resolver.definitions().create_def_with_parent(
parent_index,
node_id,
DefPathData::LifetimeNs(str_name),
Mark::root(),
span,
);
hir::GenericParam {
hir_id: self.lower_node_id(node_id),
name: hir_name,
attrs: hir_vec![],
bounds: hir_vec![],
span,
pure_wrt_drop: false,
kind: hir::GenericParamKind::Lifetime { kind }
}
}
/// When there is a reference to some lifetime `'a`, and in-band
/// lifetimes are enabled, then we want to push that lifetime into
/// the vector of names to define later. In that case, it will get
/// added to the appropriate generics.
fn maybe_collect_in_band_lifetime(&mut self, ident: Ident) {
if !self.is_collecting_in_band_lifetimes {
return;
}
if !self.sess.features_untracked().in_band_lifetimes {
return;
}
if self.in_scope_lifetimes.contains(&ident.modern()) {
return;
}
let hir_name = ParamName::Plain(ident);
if self.lifetimes_to_define.iter()
.any(|(_, lt_name)| lt_name.modern() == hir_name.modern()) {
return;
}
self.lifetimes_to_define.push((ident.span, hir_name));
}
/// When we have either an elided or `'_` lifetime in an impl
/// header, we convert it to an in-band lifetime.
fn collect_fresh_in_band_lifetime(&mut self, span: Span) -> ParamName {
assert!(self.is_collecting_in_band_lifetimes);
let index = self.lifetimes_to_define.len();
let hir_name = ParamName::Fresh(index);
self.lifetimes_to_define.push((span, hir_name));
hir_name
}
// Evaluates `f` with the lifetimes in `params` in-scope.
// This is used to track which lifetimes have already been defined, and
// which are new in-band lifetimes that need to have a definition created
// for them.
fn with_in_scope_lifetime_defs<T, F>(&mut self, params: &[GenericParam], f: F) -> T
where
F: FnOnce(&mut LoweringContext<'_>) -> T,
{
let old_len = self.in_scope_lifetimes.len();
let lt_def_names = params.iter().filter_map(|param| match param.kind {
GenericParamKind::Lifetime { .. } => Some(param.ident.modern()),
_ => None,
});
self.in_scope_lifetimes.extend(lt_def_names);
let res = f(self);
self.in_scope_lifetimes.truncate(old_len);
res
}
// Same as the method above, but accepts `hir::GenericParam`s
// instead of `ast::GenericParam`s.
// This should only be used with generics that have already had their
// in-band lifetimes added. In practice, this means that this function is
// only used when lowering a child item of a trait or impl.
fn with_parent_item_lifetime_defs<T, F>(&mut self,
parent_hir_id: hir::HirId,
f: F
) -> T where
F: FnOnce(&mut LoweringContext<'_>) -> T,
{
let old_len = self.in_scope_lifetimes.len();
let parent_generics = match self.items.get(&parent_hir_id).unwrap().node {
hir::ItemKind::Impl(_, _, _, ref generics, ..)
| hir::ItemKind::Trait(_, _, ref generics, ..) => {
&generics.params[..]
}
_ => &[],
};
let lt_def_names = parent_generics.iter().filter_map(|param| match param.kind {
hir::GenericParamKind::Lifetime { .. } => Some(param.name.ident().modern()),
_ => None,
});
self.in_scope_lifetimes.extend(lt_def_names);
let res = f(self);
self.in_scope_lifetimes.truncate(old_len);
res
}
/// Appends in-band lifetime defs and argument-position `impl
/// Trait` defs to the existing set of generics.
///
/// Presuming that in-band lifetimes are enabled, then
/// `self.anonymous_lifetime_mode` will be updated to match the
/// argument while `f` is running (and restored afterwards).
fn add_in_band_defs<F, T>(
&mut self,
generics: &Generics,
parent_id: DefId,
anonymous_lifetime_mode: AnonymousLifetimeMode,
f: F,
) -> (hir::Generics, T)
where
F: FnOnce(&mut LoweringContext<'_>, &mut Vec<hir::GenericParam>) -> T,
{
let (in_band_defs, (mut lowered_generics, res)) = self.with_in_scope_lifetime_defs(
&generics.params,
|this| {
this.collect_in_band_defs(parent_id, anonymous_lifetime_mode, |this| {
let mut params = Vec::new();
// Note: it is necessary to lower generics *before* calling `f`.
// When lowering `async fn`, there's a final step when lowering
// the return type that assumes that all in-scope lifetimes have
// already been added to either `in_scope_lifetimes` or
// `lifetimes_to_define`. If we swapped the order of these two,
// in-band-lifetimes introduced by generics or where-clauses
// wouldn't have been added yet.
let generics = this.lower_generics(
generics,
ImplTraitContext::Universal(&mut params),
);
let res = f(this, &mut params);
(params, (generics, res))
})
},
);
lowered_generics.params = lowered_generics
.params
.into_iter()
.chain(in_band_defs)
.collect();
// FIXME(const_generics): the compiler doesn't always cope with
// unsorted generic parameters at the moment, so we make sure
// that they're ordered correctly here for now. (When we chain
// the `in_band_defs`, we might make the order unsorted.)
lowered_generics.params.sort_by_key(|param| {
match param.kind {
hir::GenericParamKind::Lifetime { .. } => ParamKindOrd::Lifetime,
hir::GenericParamKind::Type { .. } => ParamKindOrd::Type,
hir::GenericParamKind::Const { .. } => ParamKindOrd::Const,
}
});
(lowered_generics, res)
}
fn with_catch_scope<T, F>(&mut self, catch_id: NodeId, f: F) -> T
where
F: FnOnce(&mut LoweringContext<'_>) -> T,
{
let len = self.catch_scopes.len();
self.catch_scopes.push(catch_id);
let result = f(self);
assert_eq!(
len + 1,
self.catch_scopes.len(),
"catch scopes should be added and removed in stack order"
);
self.catch_scopes.pop().unwrap();
result
}
fn make_async_expr(
&mut self,
capture_clause: CaptureBy,
closure_node_id: NodeId,
ret_ty: Option<&Ty>,
span: Span,
body: impl FnOnce(&mut LoweringContext<'_>) -> hir::Expr,
) -> hir::ExprKind {
let capture_clause = self.lower_capture_clause(capture_clause);
let output = match ret_ty {
Some(ty) => FunctionRetTy::Ty(P(ty.clone())),
None => FunctionRetTy::Default(span),
};
let ast_decl = FnDecl {
inputs: vec![],
output,
c_variadic: false
};
let decl = self.lower_fn_decl(&ast_decl, None, /* impl trait allowed */ false, None);
let body_id = self.lower_fn_body(&ast_decl, |this| {
this.generator_kind = Some(hir::GeneratorKind::Async);
body(this)
});
let generator = hir::Expr {
hir_id: self.lower_node_id(closure_node_id),
node: hir::ExprKind::Closure(capture_clause, decl, body_id, span,
Some(hir::GeneratorMovability::Static)),
span,
attrs: ThinVec::new(),
};
let unstable_span = self.mark_span_with_reason(
CompilerDesugaringKind::Async,
span,
self.allow_gen_future.clone(),
);
let gen_future = self.expr_std_path(
unstable_span, &[sym::future, sym::from_generator], None, ThinVec::new());
hir::ExprKind::Call(P(gen_future), hir_vec![generator])
}
fn lower_body(
&mut self,
f: impl FnOnce(&mut LoweringContext<'_>) -> (HirVec<hir::Arg>, hir::Expr),
) -> hir::BodyId {
let prev_gen_kind = self.generator_kind.take();
let (arguments, result) = f(self);
let body_id = self.record_body(arguments, result);
self.generator_kind = prev_gen_kind;
body_id
}
fn lower_fn_body(
&mut self,
decl: &FnDecl,
body: impl FnOnce(&mut LoweringContext<'_>) -> hir::Expr,
) -> hir::BodyId {
self.lower_body(|this| (
decl.inputs.iter().map(|x| this.lower_arg(x)).collect(),
body(this),
))
}
fn lower_const_body(&mut self, expr: &Expr) -> hir::BodyId {
self.lower_body(|this| (hir_vec![], this.lower_expr(expr)))
}
fn with_loop_scope<T, F>(&mut self, loop_id: NodeId, f: F) -> T
where
F: FnOnce(&mut LoweringContext<'_>) -> T,
{
// We're no longer in the base loop's condition; we're in another loop.
let was_in_loop_condition = self.is_in_loop_condition;
self.is_in_loop_condition = false;
let len = self.loop_scopes.len();
self.loop_scopes.push(loop_id);
let result = f(self);
assert_eq!(
len + 1,
self.loop_scopes.len(),
"loop scopes should be added and removed in stack order"
);
self.loop_scopes.pop().unwrap();
self.is_in_loop_condition = was_in_loop_condition;
result
}
fn with_loop_condition_scope<T, F>(&mut self, f: F) -> T
where
F: FnOnce(&mut LoweringContext<'_>) -> T,
{
let was_in_loop_condition = self.is_in_loop_condition;
self.is_in_loop_condition = true;
let result = f(self);
self.is_in_loop_condition = was_in_loop_condition;
result
}
fn with_dyn_type_scope<T, F>(&mut self, in_scope: bool, f: F) -> T
where
F: FnOnce(&mut LoweringContext<'_>) -> T,
{
let was_in_dyn_type = self.is_in_dyn_type;
self.is_in_dyn_type = in_scope;
let result = f(self);
self.is_in_dyn_type = was_in_dyn_type;
result
}
fn with_new_scopes<T, F>(&mut self, f: F) -> T
where
F: FnOnce(&mut LoweringContext<'_>) -> T,
{
let was_in_loop_condition = self.is_in_loop_condition;
self.is_in_loop_condition = false;
let catch_scopes = mem::replace(&mut self.catch_scopes, Vec::new());
let loop_scopes = mem::replace(&mut self.loop_scopes, Vec::new());
let ret = f(self);
self.catch_scopes = catch_scopes;
self.loop_scopes = loop_scopes;
self.is_in_loop_condition = was_in_loop_condition;
ret
}
fn def_key(&mut self, id: DefId) -> DefKey {
if id.is_local() {
self.resolver.definitions().def_key(id.index)
} else {
self.cstore.def_key(id)
}
}
fn lower_label(&mut self, label: Option<Label>) -> Option<hir::Label> {
label.map(|label| hir::Label {
ident: label.ident,
})
}
fn lower_loop_destination(&mut self, destination: Option<(NodeId, Label)>) -> hir::Destination {
let target_id = match destination {
Some((id, _)) => {
if let Some(loop_id) = self.resolver.get_label_res(id) {
Ok(self.lower_node_id(loop_id))
} else {
Err(hir::LoopIdError::UnresolvedLabel)
}
}
None => {
self.loop_scopes
.last()
.cloned()
.map(|id| Ok(self.lower_node_id(id)))
.unwrap_or(Err(hir::LoopIdError::OutsideLoopScope))
.into()
}
};
hir::Destination {
label: self.lower_label(destination.map(|(_, label)| label)),
target_id,
}
}
fn lower_attrs(&mut self, attrs: &[Attribute]) -> hir::HirVec<Attribute> {
attrs
.iter()
.map(|a| self.lower_attr(a))
.collect()
}
fn lower_attr(&mut self, attr: &Attribute) -> Attribute {
// Note that we explicitly do not walk the path. Since we don't really
// lower attributes (we use the AST version) there is nowhere to keep
// the `HirId`s. We don't actually need HIR version of attributes anyway.
Attribute {
id: attr.id,
style: attr.style,
path: attr.path.clone(),
tokens: self.lower_token_stream(attr.tokens.clone()),
is_sugared_doc: attr.is_sugared_doc,
span: attr.span,
}
}
fn lower_token_stream(&mut self, tokens: TokenStream) -> TokenStream {
tokens
.into_trees()
.flat_map(|tree| self.lower_token_tree(tree).into_trees())
.collect()
}
fn lower_token_tree(&mut self, tree: TokenTree) -> TokenStream {
match tree {
TokenTree::Token(token) => self.lower_token(token),
TokenTree::Delimited(span, delim, tts) => TokenTree::Delimited(
span,
delim,
self.lower_token_stream(tts),
).into(),
}
}
fn lower_token(&mut self, token: Token) -> TokenStream {
match token.kind {
token::Interpolated(nt) => {
let tts = nt.to_tokenstream(&self.sess.parse_sess, token.span);
self.lower_token_stream(tts)
}
_ => TokenTree::Token(token).into(),
}
}
fn lower_arm(&mut self, arm: &Arm) -> hir::Arm {
hir::Arm {
hir_id: self.next_id(),
attrs: self.lower_attrs(&arm.attrs),
pats: arm.pats.iter().map(|x| self.lower_pat(x)).collect(),
guard: match arm.guard {
Some(ref x) => Some(hir::Guard::If(P(self.lower_expr(x)))),
_ => None,
},
body: P(self.lower_expr(&arm.body)),
span: arm.span,
}
}
/// Given an associated type constraint like one of these:
///
/// ```
/// T: Iterator<Item: Debug>
/// ^^^^^^^^^^^
/// T: Iterator<Item = Debug>
/// ^^^^^^^^^^^^
/// ```
///
/// returns a `hir::TypeBinding` representing `Item`.
fn lower_assoc_ty_constraint(&mut self,
c: &AssocTyConstraint,
itctx: ImplTraitContext<'_>)
-> hir::TypeBinding {
debug!("lower_assoc_ty_constraint(constraint={:?}, itctx={:?})", c, itctx);
let kind = match c.kind {
AssocTyConstraintKind::Equality { ref ty } => hir::TypeBindingKind::Equality {
ty: self.lower_ty(ty, itctx)
},
AssocTyConstraintKind::Bound { ref bounds } => {
// Piggy-back on the `impl Trait` context to figure out the correct behavior.
let (desugar_to_impl_trait, itctx) = match itctx {
// We are in the return position:
//
// fn foo() -> impl Iterator<Item: Debug>
//
// so desugar to
//
// fn foo() -> impl Iterator<Item = impl Debug>
ImplTraitContext::Existential(_) => (true, itctx),
// We are in the argument position, but within a dyn type:
//
// fn foo(x: dyn Iterator<Item: Debug>)
//
// so desugar to
//
// fn foo(x: dyn Iterator<Item = impl Debug>)
ImplTraitContext::Universal(_) if self.is_in_dyn_type => (true, itctx),
// In `type Foo = dyn Iterator<Item: Debug>` we desugar to
// `type Foo = dyn Iterator<Item = impl Debug>` but we have to override the
// "impl trait context" to permit `impl Debug` in this position (it desugars
// then to an existential type).
//
// FIXME: this is only needed until `impl Trait` is allowed in type aliases.
ImplTraitContext::Disallowed(_) if self.is_in_dyn_type =>
(true, ImplTraitContext::Existential(None)),
// We are in the argument position, but not within a dyn type:
//
// fn foo(x: impl Iterator<Item: Debug>)
//
// so we leave it as is and this gets expanded in astconv to a bound like
// `<T as Iterator>::Item: Debug` where `T` is the type parameter for the
// `impl Iterator`.
_ => (false, itctx),
};
if desugar_to_impl_trait {
// Desugar `AssocTy: Bounds` into `AssocTy = impl Bounds`. We do this by
// constructing the HIR for `impl bounds...` and then lowering that.
let impl_trait_node_id = self.sess.next_node_id();
let parent_def_index = self.current_hir_id_owner.last().unwrap().0;
self.resolver.definitions().create_def_with_parent(
parent_def_index,
impl_trait_node_id,
DefPathData::ImplTrait,
Mark::root(),
DUMMY_SP
);
self.with_dyn_type_scope(false, |this| {
let ty = this.lower_ty(
&Ty {
id: this.sess.next_node_id(),
node: TyKind::ImplTrait(impl_trait_node_id, bounds.clone()),
span: DUMMY_SP,
},
itctx,
);
hir::TypeBindingKind::Equality {
ty
}
})
} else {
// Desugar `AssocTy: Bounds` into a type binding where the
// later desugars into a trait predicate.
let bounds = self.lower_param_bounds(bounds, itctx);
hir::TypeBindingKind::Constraint {
bounds
}
}
}
};
hir::TypeBinding {
hir_id: self.lower_node_id(c.id),
ident: c.ident,
kind,
span: c.span,
}
}
fn lower_generic_arg(&mut self,
arg: &ast::GenericArg,
itctx: ImplTraitContext<'_>)
-> hir::GenericArg {
match arg {
ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(&lt)),
ast::GenericArg::Type(ty) => GenericArg::Type(self.lower_ty_direct(&ty, itctx)),
ast::GenericArg::Const(ct) => {
GenericArg::Const(ConstArg {
value: self.lower_anon_const(&ct),
span: ct.value.span,
})
}
}
}
fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext<'_>) -> P<hir::Ty> {
P(self.lower_ty_direct(t, itctx))
}
fn lower_path_ty(
&mut self,
t: &Ty,
qself: &Option<QSelf>,
path: &Path,
param_mode: ParamMode,
itctx: ImplTraitContext<'_>
) -> hir::Ty {
let id = self.lower_node_id(t.id);
let qpath = self.lower_qpath(t.id, qself, path, param_mode, itctx);
let ty = self.ty_path(id, t.span, qpath);
if let hir::TyKind::TraitObject(..) = ty.node {
self.maybe_lint_bare_trait(t.span, t.id, qself.is_none() && path.is_global());
}
ty
}
fn lower_ty_direct(&mut self, t: &Ty, mut itctx: ImplTraitContext<'_>) -> hir::Ty {
let kind = match t.node {
TyKind::Infer => hir::TyKind::Infer,
TyKind::Err => hir::TyKind::Err,
TyKind::Slice(ref ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)),
TyKind::Ptr(ref mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)),
TyKind::Rptr(ref region, ref mt) => {
let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
let lifetime = match *region {
Some(ref lt) => self.lower_lifetime(lt),
None => self.elided_ref_lifetime(span),
};
hir::TyKind::Rptr(lifetime, self.lower_mt(mt, itctx))
}
TyKind::BareFn(ref f) => self.with_in_scope_lifetime_defs(
&f.generic_params,
|this| {
this.with_anonymous_lifetime_mode(
AnonymousLifetimeMode::PassThrough,
|this| {
hir::TyKind::BareFn(P(hir::BareFnTy {
generic_params: this.lower_generic_params(
&f.generic_params,
&NodeMap::default(),
ImplTraitContext::disallowed(),
),
unsafety: this.lower_unsafety(f.unsafety),
abi: f.abi,
decl: this.lower_fn_decl(&f.decl, None, false, None),
arg_names: this.lower_fn_args_to_names(&f.decl),
}))
},
)
},
),
TyKind::Never => hir::TyKind::Never,
TyKind::Tup(ref tys) => {
hir::TyKind::Tup(tys.iter().map(|ty| {
self.lower_ty_direct(ty, itctx.reborrow())
}).collect())
}
TyKind::Paren(ref ty) => {
return self.lower_ty_direct(ty, itctx);
}
TyKind::Path(ref qself, ref path) => {
return self.lower_path_ty(t, qself, path, ParamMode::Explicit, itctx);
}
TyKind::ImplicitSelf => {
let res = self.expect_full_res(t.id);
let res = self.lower_res(res);
hir::TyKind::Path(hir::QPath::Resolved(
None,
P(hir::Path {
res,
segments: hir_vec![hir::PathSegment::from_ident(
Ident::with_empty_ctxt(kw::SelfUpper)
)],
span: t.span,
}),
))
},
TyKind::Array(ref ty, ref length) => {
hir::TyKind::Array(self.lower_ty(ty, itctx), self.lower_anon_const(length))
}
TyKind::Typeof(ref expr) => {
hir::TyKind::Typeof(self.lower_anon_const(expr))
}
TyKind::TraitObject(ref bounds, kind) => {
let mut lifetime_bound = None;
let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| {
let bounds = bounds
.iter()
.filter_map(|bound| match *bound {
GenericBound::Trait(ref ty, TraitBoundModifier::None) => {
Some(this.lower_poly_trait_ref(ty, itctx.reborrow()))
}
GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
GenericBound::Outlives(ref lifetime) => {
if lifetime_bound.is_none() {
lifetime_bound = Some(this.lower_lifetime(lifetime));
}
None
}
})
.collect();
let lifetime_bound =
lifetime_bound.unwrap_or_else(|| this.elided_dyn_bound(t.span));
(bounds, lifetime_bound)
});
if kind != TraitObjectSyntax::Dyn {
self.maybe_lint_bare_trait(t.span, t.id, false);
}
hir::TyKind::TraitObject(bounds, lifetime_bound)
}
TyKind::ImplTrait(def_node_id, ref bounds) => {
let span = t.span;
match itctx {
ImplTraitContext::Existential(fn_def_id) => {
self.lower_existential_impl_trait(
span, fn_def_id, def_node_id,
|this| this.lower_param_bounds(bounds, itctx),
)
}
ImplTraitContext::Universal(in_band_ty_params) => {
// Add a definition for the in-band `Param`.
let def_index = self
.resolver
.definitions()
.opt_def_index(def_node_id)
.unwrap();
let hir_bounds = self.lower_param_bounds(
bounds,
ImplTraitContext::Universal(in_band_ty_params),
);
// Set the name to `impl Bound1 + Bound2`.
let ident = Ident::from_str(&pprust::ty_to_string(t)).with_span_pos(span);
in_band_ty_params.push(hir::GenericParam {
hir_id: self.lower_node_id(def_node_id),
name: ParamName::Plain(ident),
pure_wrt_drop: false,
attrs: hir_vec![],
bounds: hir_bounds,
span,
kind: hir::GenericParamKind::Type {
default: None,
synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
}
});
hir::TyKind::Path(hir::QPath::Resolved(
None,
P(hir::Path {
span,
res: Res::Def(DefKind::TyParam, DefId::local(def_index)),
segments: hir_vec![hir::PathSegment::from_ident(ident)],
}),
))
}
ImplTraitContext::Disallowed(pos) => {
let allowed_in = if self.sess.features_untracked()
.impl_trait_in_bindings {
"bindings or function and inherent method return types"
} else {
"function and inherent method return types"
};
let mut err = struct_span_err!(
self.sess,
t.span,
E0562,
"`impl Trait` not allowed outside of {}",
allowed_in,
);
if pos == ImplTraitPosition::Binding &&
nightly_options::is_nightly_build() {
help!(err,
"add #![feature(impl_trait_in_bindings)] to the crate attributes \
to enable");
}
err.emit();
hir::TyKind::Err
}
}
}
TyKind::Mac(_) => bug!("`TyMac` should have been expanded by now."),
TyKind::CVarArgs => {
// Create the implicit lifetime of the "spoofed" `VaListImpl`.
let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
let lt = self.new_implicit_lifetime(span);
hir::TyKind::CVarArgs(lt)
},
};
hir::Ty {
node: kind,
span: t.span,
hir_id: self.lower_node_id(t.id),
}
}
fn lower_existential_impl_trait(
&mut self,
span: Span,
fn_def_id: Option<DefId>,
exist_ty_node_id: NodeId,
lower_bounds: impl FnOnce(&mut LoweringContext<'_>) -> hir::GenericBounds,
) -> hir::TyKind {
// Make sure we know that some funky desugaring has been going on here.
// This is a first: there is code in other places like for loop
// desugaring that explicitly states that we don't want to track that.
// Not tracking it makes lints in rustc and clippy very fragile, as
// frequently opened issues show.
let exist_ty_span = self.mark_span_with_reason(
CompilerDesugaringKind::ExistentialType,
span,
None,
);
let exist_ty_def_index = self
.resolver
.definitions()
.opt_def_index(exist_ty_node_id)
.unwrap();
self.allocate_hir_id_counter(exist_ty_node_id);
let hir_bounds = self.with_hir_id_owner(exist_ty_node_id, lower_bounds);
let (lifetimes, lifetime_defs) = self.lifetimes_from_impl_trait_bounds(
exist_ty_node_id,
exist_ty_def_index,
&hir_bounds,
);
self.with_hir_id_owner(exist_ty_node_id, |lctx| {
let exist_ty_item = hir::ExistTy {
generics: hir::Generics {
params: lifetime_defs,
where_clause: hir::WhereClause {
predicates: hir_vec![],
span,
},
span,
},
bounds: hir_bounds,
impl_trait_fn: fn_def_id,
origin: hir::ExistTyOrigin::ReturnImplTrait,
};
trace!("exist ty from impl trait def-index: {:#?}", exist_ty_def_index);
let exist_ty_id = lctx.generate_existential_type(
exist_ty_node_id,
exist_ty_item,
span,
exist_ty_span,
);
// `impl Trait` now just becomes `Foo<'a, 'b, ..>`.
hir::TyKind::Def(hir::ItemId { id: exist_ty_id }, lifetimes)
})
}
/// Registers a new existential type with the proper `NodeId`s and
/// returns the lowered node-ID for the existential type.
fn generate_existential_type(
&mut self,
exist_ty_node_id: NodeId,
exist_ty_item: hir::ExistTy,
span: Span,
exist_ty_span: Span,
) -> hir::HirId {
let exist_ty_item_kind = hir::ItemKind::Existential(exist_ty_item);
let exist_ty_id = self.lower_node_id(exist_ty_node_id);
// Generate an `existential type Foo: Trait;` declaration.
trace!("registering existential type with id {:#?}", exist_ty_id);
let exist_ty_item = hir::Item {
hir_id: exist_ty_id,
ident: Ident::invalid(),
attrs: Default::default(),
node: exist_ty_item_kind,
vis: respan(span.shrink_to_lo(), hir::VisibilityKind::Inherited),
span: exist_ty_span,
};
// Insert the item into the global item list. This usually happens
// automatically for all AST items. But this existential type item
// does not actually exist in the AST.
self.insert_item(exist_ty_item);
exist_ty_id
}
fn lifetimes_from_impl_trait_bounds(
&mut self,
exist_ty_id: NodeId,
parent_index: DefIndex,
bounds: &hir::GenericBounds,
) -> (HirVec<hir::GenericArg>, HirVec<hir::GenericParam>) {
// This visitor walks over `impl Trait` bounds and creates defs for all lifetimes that
// appear in the bounds, excluding lifetimes that are created within the bounds.
// E.g., `'a`, `'b`, but not `'c` in `impl for<'c> SomeTrait<'a, 'b, 'c>`.
struct ImplTraitLifetimeCollector<'r, 'a> {
context: &'r mut LoweringContext<'a>,
parent: DefIndex,
exist_ty_id: NodeId,
collect_elided_lifetimes: bool,
currently_bound_lifetimes: Vec<hir::LifetimeName>,
already_defined_lifetimes: FxHashSet<hir::LifetimeName>,
output_lifetimes: Vec<hir::GenericArg>,
output_lifetime_params: Vec<hir::GenericParam>,
}
impl<'r, 'a, 'v> hir::intravisit::Visitor<'v> for ImplTraitLifetimeCollector<'r, 'a> {
fn nested_visit_map<'this>(
&'this mut self,
) -> hir::intravisit::NestedVisitorMap<'this, 'v> {
hir::intravisit::NestedVisitorMap::None
}
fn visit_generic_args(&mut self, span: Span, parameters: &'v hir::GenericArgs) {
// Don't collect elided lifetimes used inside of `Fn()` syntax.
if parameters.parenthesized {
let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
self.collect_elided_lifetimes = false;
hir::intravisit::walk_generic_args(self, span, parameters);
self.collect_elided_lifetimes = old_collect_elided_lifetimes;
} else {
hir::intravisit::walk_generic_args(self, span, parameters);
}
}
fn visit_ty(&mut self, t: &'v hir::Ty) {
// Don't collect elided lifetimes used inside of `fn()` syntax.
if let hir::TyKind::BareFn(_) = t.node {
let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
self.collect_elided_lifetimes = false;
// Record the "stack height" of `for<'a>` lifetime bindings
// to be able to later fully undo their introduction.
let old_len = self.currently_bound_lifetimes.len();
hir::intravisit::walk_ty(self, t);
self.currently_bound_lifetimes.truncate(old_len);
self.collect_elided_lifetimes = old_collect_elided_lifetimes;
} else {
hir::intravisit::walk_ty(self, t)
}
}
fn visit_poly_trait_ref(
&mut self,
trait_ref: &'v hir::PolyTraitRef,
modifier: hir::TraitBoundModifier,
) {
// Record the "stack height" of `for<'a>` lifetime bindings
// to be able to later fully undo their introduction.
let old_len = self.currently_bound_lifetimes.len();
hir::intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
self.currently_bound_lifetimes.truncate(old_len);
}
fn visit_generic_param(&mut self, param: &'v hir::GenericParam) {
// Record the introduction of 'a in `for<'a> ...`.
if let hir::GenericParamKind::Lifetime { .. } = param.kind {
// Introduce lifetimes one at a time so that we can handle
// cases like `fn foo<'d>() -> impl for<'a, 'b: 'a, 'c: 'b + 'd>`.
let lt_name = hir::LifetimeName::Param(param.name);
self.currently_bound_lifetimes.push(lt_name);
}
hir::intravisit::walk_generic_param(self, param);
}
fn visit_lifetime(&mut self, lifetime: &'v hir::Lifetime) {
let name = match lifetime.name {
hir::LifetimeName::Implicit | hir::LifetimeName::Underscore => {
if self.collect_elided_lifetimes {
// Use `'_` for both implicit and underscore lifetimes in
// `abstract type Foo<'_>: SomeTrait<'_>;`.
hir::LifetimeName::Underscore
} else {
return;
}
}
hir::LifetimeName::Param(_) => lifetime.name,
hir::LifetimeName::Error | hir::LifetimeName::Static => return,
};
if !self.currently_bound_lifetimes.contains(&name)
&& !self.already_defined_lifetimes.contains(&name) {
self.already_defined_lifetimes.insert(name);
self.output_lifetimes.push(hir::GenericArg::Lifetime(hir::Lifetime {
hir_id: self.context.next_id(),
span: lifetime.span,
name,
}));
let def_node_id = self.context.sess.next_node_id();
let hir_id =
self.context.lower_node_id_with_owner(def_node_id, self.exist_ty_id);
self.context.resolver.definitions().create_def_with_parent(
self.parent,
def_node_id,
DefPathData::LifetimeNs(name.ident().as_interned_str()),
Mark::root(),
lifetime.span);
let (name, kind) = match name {
hir::LifetimeName::Underscore => (
hir::ParamName::Plain(Ident::with_empty_ctxt(kw::UnderscoreLifetime)),
hir::LifetimeParamKind::Elided,
),
hir::LifetimeName::Param(param_name) => (
param_name,
hir::LifetimeParamKind::Explicit,
),
_ => bug!("expected `LifetimeName::Param` or `ParamName::Plain`"),
};
self.output_lifetime_params.push(hir::GenericParam {
hir_id,
name,
span: lifetime.span,
pure_wrt_drop: false,
attrs: hir_vec![],
bounds: hir_vec![],
kind: hir::GenericParamKind::Lifetime { kind }
});
}
}
}
let mut lifetime_collector = ImplTraitLifetimeCollector {
context: self,
parent: parent_index,
exist_ty_id,
collect_elided_lifetimes: true,
currently_bound_lifetimes: Vec::new(),
already_defined_lifetimes: FxHashSet::default(),
output_lifetimes: Vec::new(),
output_lifetime_params: Vec::new(),
};
for bound in bounds {
hir::intravisit::walk_param_bound(&mut lifetime_collector, &bound);
}
(
lifetime_collector.output_lifetimes.into(),
lifetime_collector.output_lifetime_params.into(),
)
}
fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod {
hir::ForeignMod {
abi: fm.abi,
items: fm.items
.iter()
.map(|x| self.lower_foreign_item(x))
.collect(),
}
}
fn lower_global_asm(&mut self, ga: &GlobalAsm) -> P<hir::GlobalAsm> {
P(hir::GlobalAsm {
asm: ga.asm,
ctxt: ga.ctxt,
})
}
fn lower_variant(&mut self, v: &Variant) -> hir::Variant {
Spanned {
node: hir::VariantKind {
ident: v.node.ident,
id: self.lower_node_id(v.node.id),
attrs: self.lower_attrs(&v.node.attrs),
data: self.lower_variant_data(&v.node.data),
disr_expr: v.node.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
},
span: v.span,
}
}
fn lower_qpath(
&mut self,
id: NodeId,
qself: &Option<QSelf>,
p: &Path,
param_mode: ParamMode,
mut itctx: ImplTraitContext<'_>,
) -> hir::QPath {
let qself_position = qself.as_ref().map(|q| q.position);
let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx.reborrow()));
let partial_res = self.resolver
.get_partial_res(id)
.unwrap_or_else(|| PartialRes::new(Res::Err));
let proj_start = p.segments.len() - partial_res.unresolved_segments();
let path = P(hir::Path {
res: self.lower_res(partial_res.base_res()),
segments: p.segments[..proj_start]
.iter()
.enumerate()
.map(|(i, segment)| {
let param_mode = match (qself_position, param_mode) {
(Some(j), ParamMode::Optional) if i < j => {
// This segment is part of the trait path in a
// qualified path - one of `a`, `b` or `Trait`
// in `<X as a::b::Trait>::T::U::method`.
ParamMode::Explicit
}
_ => param_mode,
};
// Figure out if this is a type/trait segment,
// which may need lifetime elision performed.
let parent_def_id = |this: &mut Self, def_id: DefId| DefId {
krate: def_id.krate,
index: this.def_key(def_id).parent.expect("missing parent"),
};
let type_def_id = match partial_res.base_res() {
Res::Def(DefKind::AssocTy, def_id) if i + 2 == proj_start => {
Some(parent_def_id(self, def_id))
}
Res::Def(DefKind::Variant, def_id) if i + 1 == proj_start => {
Some(parent_def_id(self, def_id))
}
Res::Def(DefKind::Struct, def_id)
| Res::Def(DefKind::Union, def_id)
| Res::Def(DefKind::Enum, def_id)
| Res::Def(DefKind::TyAlias, def_id)
| Res::Def(DefKind::Trait, def_id) if i + 1 == proj_start =>
{
Some(def_id)
}
_ => None,
};
let parenthesized_generic_args = match partial_res.base_res() {
// `a::b::Trait(Args)`
Res::Def(DefKind::Trait, _)
if i + 1 == proj_start => ParenthesizedGenericArgs::Ok,
// `a::b::Trait(Args)::TraitItem`
Res::Def(DefKind::Method, _)
| Res::Def(DefKind::AssocConst, _)
| Res::Def(DefKind::AssocTy, _)
if i + 2 == proj_start =>
{
ParenthesizedGenericArgs::Ok
}
// Avoid duplicated errors.
Res::Err => ParenthesizedGenericArgs::Ok,
// An error
Res::Def(DefKind::Struct, _)
| Res::Def(DefKind::Enum, _)
| Res::Def(DefKind::Union, _)
| Res::Def(DefKind::TyAlias, _)
| Res::Def(DefKind::Variant, _) if i + 1 == proj_start =>
{
ParenthesizedGenericArgs::Err
}
// A warning for now, for compatibility reasons.
_ => ParenthesizedGenericArgs::Warn,
};
let num_lifetimes = type_def_id.map_or(0, |def_id| {
if let Some(&n) = self.type_def_lifetime_params.get(&def_id) {
return n;
}
assert!(!def_id.is_local());
let item_generics =
self.cstore.item_generics_cloned_untracked(def_id, self.sess);
let n = item_generics.own_counts().lifetimes;
self.type_def_lifetime_params.insert(def_id, n);
n
});
self.lower_path_segment(
p.span,
segment,
param_mode,
num_lifetimes,
parenthesized_generic_args,
itctx.reborrow(),
None,
)
})
.collect(),
span: p.span,
});
// Simple case, either no projections, or only fully-qualified.
// E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
if partial_res.unresolved_segments() == 0 {
return hir::QPath::Resolved(qself, path);
}
// Create the innermost type that we're projecting from.
let mut ty = if path.segments.is_empty() {
// If the base path is empty that means there exists a
// syntactical `Self`, e.g., `&i32` in `<&i32>::clone`.
qself.expect("missing QSelf for <T>::...")
} else {
// Otherwise, the base path is an implicit `Self` type path,
// e.g., `Vec` in `Vec::new` or `<I as Iterator>::Item` in
// `<I as Iterator>::Item::default`.
let new_id = self.next_id();
P(self.ty_path(new_id, p.span, hir::QPath::Resolved(qself, path)))
};
// Anything after the base path are associated "extensions",
// out of which all but the last one are associated types,
// e.g., for `std::vec::Vec::<T>::IntoIter::Item::clone`:
// * base path is `std::vec::Vec<T>`
// * "extensions" are `IntoIter`, `Item` and `clone`
// * type nodes are:
// 1. `std::vec::Vec<T>` (created above)
// 2. `<std::vec::Vec<T>>::IntoIter`
// 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
// * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
let segment = P(self.lower_path_segment(
p.span,
segment,
param_mode,
0,
ParenthesizedGenericArgs::Warn,
itctx.reborrow(),
None,
));
let qpath = hir::QPath::TypeRelative(ty, segment);
// It's finished, return the extension of the right node type.
if i == p.segments.len() - 1 {
return qpath;
}
// Wrap the associated extension in another type node.
let new_id = self.next_id();
ty = P(self.ty_path(new_id, p.span, qpath));
}
// We should've returned in the for loop above.
span_bug!(
p.span,
"lower_qpath: no final extension segment in {}..{}",
proj_start,
p.segments.len()
)
}
fn lower_path_extra(
&mut self,
res: Res,
p: &Path,
param_mode: ParamMode,
explicit_owner: Option<NodeId>,
) -> hir::Path {
hir::Path {
res,
segments: p.segments
.iter()
.map(|segment| {
self.lower_path_segment(
p.span,
segment,
param_mode,
0,
ParenthesizedGenericArgs::Err,
ImplTraitContext::disallowed(),
explicit_owner,
)
})
.collect(),
span: p.span,
}
}
fn lower_path(&mut self, id: NodeId, p: &Path, param_mode: ParamMode) -> hir::Path {
let res = self.expect_full_res(id);
let res = self.lower_res(res);
self.lower_path_extra(res, p, param_mode, None)
}
fn lower_path_segment(
&mut self,
path_span: Span,
segment: &PathSegment,
param_mode: ParamMode,
expected_lifetimes: usize,
parenthesized_generic_args: ParenthesizedGenericArgs,
itctx: ImplTraitContext<'_>,
explicit_owner: Option<NodeId>,
) -> hir::PathSegment {
let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args {
let msg = "parenthesized type parameters may only be used with a `Fn` trait";
match **generic_args {
GenericArgs::AngleBracketed(ref data) => {
self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
}
GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
ParenthesizedGenericArgs::Warn => {
self.sess.buffer_lint(
PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
CRATE_NODE_ID,
data.span,
msg.into(),
);
(hir::GenericArgs::none(), true)
}
ParenthesizedGenericArgs::Err => {
let mut err = struct_span_err!(self.sess, data.span, E0214, "{}", msg);
err.span_label(data.span, "only `Fn` traits may use parentheses");
if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) {
// Do not suggest going from `Trait()` to `Trait<>`
if data.inputs.len() > 0 {
err.span_suggestion(
data.span,
"use angle brackets instead",
format!("<{}>", &snippet[1..snippet.len() - 1]),
Applicability::MaybeIncorrect,
);
}
};
err.emit();
(
self.lower_angle_bracketed_parameter_data(
&data.as_angle_bracketed_args(),
param_mode,
itctx
).0,
false,
)
}
},
}
} else {
self.lower_angle_bracketed_parameter_data(&Default::default(), param_mode, itctx)
};
let has_lifetimes = generic_args.args.iter().any(|arg| match arg {
GenericArg::Lifetime(_) => true,
_ => false,
});
let first_generic_span = generic_args.args.iter().map(|a| a.span())
.chain(generic_args.bindings.iter().map(|b| b.span)).next();
if !generic_args.parenthesized && !has_lifetimes {
generic_args.args =
self.elided_path_lifetimes(path_span, expected_lifetimes)
.into_iter()
.map(|lt| GenericArg::Lifetime(lt))
.chain(generic_args.args.into_iter())
.collect();
if expected_lifetimes > 0 && param_mode == ParamMode::Explicit {
let anon_lt_suggestion = vec!["'_"; expected_lifetimes].join(", ");
let no_non_lt_args = generic_args.args.len() == expected_lifetimes;
let no_bindings = generic_args.bindings.is_empty();
let (incl_angl_brckt, insertion_sp, suggestion) = if no_non_lt_args && no_bindings {
// If there are no (non-implicit) generic args or associated type
// bindings, our suggestion includes the angle brackets.
(true, path_span.shrink_to_hi(), format!("<{}>", anon_lt_suggestion))
} else {
// Otherwise (sorry, this is kind of gross) we need to infer the
// place to splice in the `'_, ` from the generics that do exist.
let first_generic_span = first_generic_span
.expect("already checked that non-lifetime args or bindings exist");
(false, first_generic_span.shrink_to_lo(), format!("{}, ", anon_lt_suggestion))
};
match self.anonymous_lifetime_mode {
// In create-parameter mode we error here because we don't want to support
// deprecated impl elision in new features like impl elision and `async fn`,
// both of which work using the `CreateParameter` mode:
//
// impl Foo for std::cell::Ref<u32> // note lack of '_
// async fn foo(_: std::cell::Ref<u32>) { ... }
AnonymousLifetimeMode::CreateParameter => {
let mut err = struct_span_err!(
self.sess,
path_span,
E0726,
"implicit elided lifetime not allowed here"
);
crate::lint::builtin::add_elided_lifetime_in_path_suggestion(
&self.sess,
&mut err,
expected_lifetimes,
path_span,
incl_angl_brckt,
insertion_sp,
suggestion,
);
err.emit();
}
AnonymousLifetimeMode::PassThrough |
AnonymousLifetimeMode::ReportError |
AnonymousLifetimeMode::Replace(_) => {
self.sess.buffer_lint_with_diagnostic(
ELIDED_LIFETIMES_IN_PATHS,
CRATE_NODE_ID,
path_span,
"hidden lifetime parameters in types are deprecated",
builtin::BuiltinLintDiagnostics::ElidedLifetimesInPaths(
expected_lifetimes,
path_span,
incl_angl_brckt,
insertion_sp,
suggestion,
)
);
}
}
}
}
let res = self.expect_full_res(segment.id);
let id = if let Some(owner) = explicit_owner {
self.lower_node_id_with_owner(segment.id, owner)
} else {
self.lower_node_id(segment.id)
};
debug!(
"lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
segment.ident, segment.id, id,
);
hir::PathSegment::new(
segment.ident,
Some(id),
Some(self.lower_res(res)),
generic_args,
infer_args,
)
}
fn lower_angle_bracketed_parameter_data(
&mut self,
data: &AngleBracketedArgs,
param_mode: ParamMode,
mut itctx: ImplTraitContext<'_>,
) -> (hir::GenericArgs, bool) {
let &AngleBracketedArgs { ref args, ref constraints, .. } = data;
let has_non_lt_args = args.iter().any(|arg| match arg {
ast::GenericArg::Lifetime(_) => false,
ast::GenericArg::Type(_) => true,
ast::GenericArg::Const(_) => true,
});
(
hir::GenericArgs {
args: args.iter().map(|a| self.lower_generic_arg(a, itctx.reborrow())).collect(),
bindings: constraints.iter()
.map(|b| self.lower_assoc_ty_constraint(b, itctx.reborrow()))
.collect(),
parenthesized: false,
},
!has_non_lt_args && param_mode == ParamMode::Optional
)
}
fn lower_parenthesized_parameter_data(
&mut self,
data: &ParenthesizedArgs,
) -> (hir::GenericArgs, bool) {
// Switch to `PassThrough` mode for anonymous lifetimes; this
// means that we permit things like `&Ref<T>`, where `Ref` has
// a hidden lifetime parameter. This is needed for backwards
// compatibility, even in contexts like an impl header where
// we generally don't permit such things (see #51008).
self.with_anonymous_lifetime_mode(
AnonymousLifetimeMode::PassThrough,
|this| {
let &ParenthesizedArgs { ref inputs, ref output, span } = data;
let inputs = inputs
.iter()
.map(|ty| this.lower_ty_direct(ty, ImplTraitContext::disallowed()))
.collect();
let mk_tup = |this: &mut Self, tys, span| {
hir::Ty { node: hir::TyKind::Tup(tys), hir_id: this.next_id(), span }
};
(
hir::GenericArgs {
args: hir_vec![GenericArg::Type(mk_tup(this, inputs, span))],
bindings: hir_vec![
hir::TypeBinding {
hir_id: this.next_id(),
ident: Ident::with_empty_ctxt(FN_OUTPUT_NAME),
kind: hir::TypeBindingKind::Equality {
ty: output
.as_ref()
.map(|ty| this.lower_ty(
&ty,
ImplTraitContext::disallowed()
))
.unwrap_or_else(||
P(mk_tup(this, hir::HirVec::new(), span))
),
},
span: output.as_ref().map_or(span, |ty| ty.span),
}
],
parenthesized: true,
},
false,
)
}
)
}
fn lower_local(&mut self, l: &Local) -> (hir::Local, SmallVec<[NodeId; 1]>) {
let mut ids = SmallVec::<[NodeId; 1]>::new();
if self.sess.features_untracked().impl_trait_in_bindings {
if let Some(ref ty) = l.ty {
let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
visitor.visit_ty(ty);
}
}
let parent_def_id = DefId::local(self.current_hir_id_owner.last().unwrap().0);
(hir::Local {
hir_id: self.lower_node_id(l.id),
ty: l.ty
.as_ref()
.map(|t| self.lower_ty(t,
if self.sess.features_untracked().impl_trait_in_bindings {
ImplTraitContext::Existential(Some(parent_def_id))
} else {
ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
}
)),
pat: self.lower_pat(&l.pat),
init: l.init.as_ref().map(|e| P(self.lower_expr(e))),
span: l.span,
attrs: l.attrs.clone(),
source: hir::LocalSource::Normal,
}, ids)
}
fn lower_mutability(&mut self, m: Mutability) -> hir::Mutability {
match m {
Mutability::Mutable => hir::MutMutable,
Mutability::Immutable => hir::MutImmutable,
}
}
fn lower_arg(&mut self, arg: &Arg) -> hir::Arg {
hir::Arg {
hir_id: self.lower_node_id(arg.id),
pat: self.lower_pat(&arg.pat),
}
}
fn lower_fn_args_to_names(&mut self, decl: &FnDecl) -> hir::HirVec<Ident> {
decl.inputs
.iter()
.map(|arg| match arg.pat.node {
PatKind::Ident(_, ident, _) => ident,
_ => Ident::new(kw::Invalid, arg.pat.span),
})
.collect()
}
// Lowers a function declaration.
//
// `decl`: the unlowered (AST) function declaration.
// `fn_def_id`: if `Some`, impl Trait arguments are lowered into generic parameters on the
// given DefId, otherwise impl Trait is disallowed. Must be `Some` if
// `make_ret_async` is also `Some`.
// `impl_trait_return_allow`: determines whether `impl Trait` can be used in return position.
// This guards against trait declarations and implementations where `impl Trait` is
// disallowed.
// `make_ret_async`: if `Some`, converts `-> T` into `-> impl Future<Output = T>` in the
// return type. This is used for `async fn` declarations. The `NodeId` is the ID of the
// return type `impl Trait` item.
fn lower_fn_decl(
&mut self,
decl: &FnDecl,
mut in_band_ty_params: Option<(DefId, &mut Vec<hir::GenericParam>)>,
impl_trait_return_allow: bool,
make_ret_async: Option<NodeId>,
) -> P<hir::FnDecl> {
let lt_mode = if make_ret_async.is_some() {
// In `async fn`, argument-position elided lifetimes
// must be transformed into fresh generic parameters so that
// they can be applied to the existential return type.
AnonymousLifetimeMode::CreateParameter
} else {
self.anonymous_lifetime_mode
};
// Remember how many lifetimes were already around so that we can
// only look at the lifetime parameters introduced by the arguments.
let lifetime_count_before_args = self.lifetimes_to_define.len();
let inputs = self.with_anonymous_lifetime_mode(lt_mode, |this| {
decl.inputs
.iter()
.map(|arg| {
if let Some((_, ibty)) = &mut in_band_ty_params {
this.lower_ty_direct(&arg.ty, ImplTraitContext::Universal(ibty))
} else {
this.lower_ty_direct(&arg.ty, ImplTraitContext::disallowed())
}
})
.collect::<HirVec<_>>()
});
let output = if let Some(ret_id) = make_ret_async {
// Calculate the `LtReplacement` to use for any return-position elided
// lifetimes based on the elided lifetime parameters introduced in the args.
let lt_replacement = get_elided_lt_replacement(
&self.lifetimes_to_define[lifetime_count_before_args..]
);
self.lower_async_fn_ret_ty(
&decl.output,
in_band_ty_params.expect("`make_ret_async` but no `fn_def_id`").0,
ret_id,
lt_replacement,
)
} else {
match decl.output {
FunctionRetTy::Ty(ref ty) => match in_band_ty_params {
Some((def_id, _)) if impl_trait_return_allow => {
hir::Return(self.lower_ty(ty,
ImplTraitContext::Existential(Some(def_id))
))
}
_ => {
hir::Return(self.lower_ty(ty, ImplTraitContext::disallowed()))
}
},
FunctionRetTy::Default(span) => hir::DefaultReturn(span),
}
};
P(hir::FnDecl {
inputs,
output,
c_variadic: decl.c_variadic,
implicit_self: decl.inputs.get(0).map_or(
hir::ImplicitSelfKind::None,
|arg| {
let is_mutable_pat = match arg.pat.node {
PatKind::Ident(BindingMode::ByValue(mt), _, _) |
PatKind::Ident(BindingMode::ByRef(mt), _, _) =>
mt == Mutability::Mutable,
_ => false,
};
match arg.ty.node {
TyKind::ImplicitSelf if is_mutable_pat => hir::ImplicitSelfKind::Mut,
TyKind::ImplicitSelf => hir::ImplicitSelfKind::Imm,
// Given we are only considering `ImplicitSelf` types, we needn't consider
// the case where we have a mutable pattern to a reference as that would
// no longer be an `ImplicitSelf`.
TyKind::Rptr(_, ref mt) if mt.ty.node.is_implicit_self() &&
mt.mutbl == ast::Mutability::Mutable =>
hir::ImplicitSelfKind::MutRef,
TyKind::Rptr(_, ref mt) if mt.ty.node.is_implicit_self() =>
hir::ImplicitSelfKind::ImmRef,
_ => hir::ImplicitSelfKind::None,
}
},
),
})
}
// Transforms `-> T` for `async fn` into `-> ExistTy { .. }`
// combined with the following definition of `ExistTy`:
//
// existential type ExistTy<generics_from_parent_fn>: Future<Output = T>;
//
// `inputs`: lowered types of arguments to the function (used to collect lifetimes)
// `output`: unlowered output type (`T` in `-> T`)
// `fn_def_id`: `DefId` of the parent function (used to create child impl trait definition)
// `exist_ty_node_id`: `NodeId` of the existential type that should be created
// `elided_lt_replacement`: replacement for elided lifetimes in the return type
fn lower_async_fn_ret_ty(
&mut self,
output: &FunctionRetTy,
fn_def_id: DefId,
exist_ty_node_id: NodeId,
elided_lt_replacement: LtReplacement,
) -> hir::FunctionRetTy {
let span = output.span();
let exist_ty_span = self.mark_span_with_reason(
CompilerDesugaringKind::Async,
span,
None,
);
let exist_ty_def_index = self
.resolver
.definitions()
.opt_def_index(exist_ty_node_id)
.unwrap();
self.allocate_hir_id_counter(exist_ty_node_id);
let (exist_ty_id, lifetime_params) = self.with_hir_id_owner(exist_ty_node_id, |this| {
let future_bound = this.with_anonymous_lifetime_mode(
AnonymousLifetimeMode::Replace(elided_lt_replacement),
|this| this.lower_async_fn_output_type_to_future_bound(
output,
fn_def_id,
span,
),
);
// Calculate all the lifetimes that should be captured
// by the existential type. This should include all in-scope
// lifetime parameters, including those defined in-band.
//
// Note: this must be done after lowering the output type,
// as the output type may introduce new in-band lifetimes.
let lifetime_params: Vec<(Span, ParamName)> =
this.in_scope_lifetimes
.iter().cloned()
.map(|ident| (ident.span, ParamName::Plain(ident)))
.chain(this.lifetimes_to_define.iter().cloned())
.collect();
let generic_params =
lifetime_params
.iter().cloned()
.map(|(span, hir_name)| {
this.lifetime_to_generic_param(span, hir_name, exist_ty_def_index)
})
.collect();
let exist_ty_item = hir::ExistTy {
generics: hir::Generics {
params: generic_params,
where_clause: hir::WhereClause {
predicates: hir_vec![],
span,
},
span,
},
bounds: hir_vec![future_bound],
impl_trait_fn: Some(fn_def_id),
origin: hir::ExistTyOrigin::AsyncFn,
};
trace!("exist ty from async fn def index: {:#?}", exist_ty_def_index);
let exist_ty_id = this.generate_existential_type(
exist_ty_node_id,
exist_ty_item,
span,
exist_ty_span,
);
(exist_ty_id, lifetime_params)
});
let generic_args =
lifetime_params
.iter().cloned()
.map(|(span, hir_name)| {
GenericArg::Lifetime(hir::Lifetime {
hir_id: self.next_id(),
span,
name: hir::LifetimeName::Param(hir_name),
})
})
.collect();
let exist_ty_ref = hir::TyKind::Def(hir::ItemId { id: exist_ty_id }, generic_args);
hir::FunctionRetTy::Return(P(hir::Ty {
node: exist_ty_ref,
span,
hir_id: self.next_id(),
}))
}
/// Transforms `-> T` into `Future<Output = T>`
fn lower_async_fn_output_type_to_future_bound(
&mut self,
output: &FunctionRetTy,
fn_def_id: DefId,
span: Span,
) -> hir::GenericBound {
// Compute the `T` in `Future<Output = T>` from the return type.
let output_ty = match output {
FunctionRetTy::Ty(ty) => {
self.lower_ty(ty, ImplTraitContext::Existential(Some(fn_def_id)))
}
FunctionRetTy::Default(ret_ty_span) => {
P(hir::Ty {
hir_id: self.next_id(),
node: hir::TyKind::Tup(hir_vec![]),
span: *ret_ty_span,
})
}
};
// "<Output = T>"
let future_params = P(hir::GenericArgs {
args: hir_vec![],
bindings: hir_vec![hir::TypeBinding {
ident: Ident::with_empty_ctxt(FN_OUTPUT_NAME),
kind: hir::TypeBindingKind::Equality {
ty: output_ty,
},
hir_id: self.next_id(),
span,
}],
parenthesized: false,
});
// ::std::future::Future<future_params>
let future_path =
self.std_path(span, &[sym::future, sym::Future], Some(future_params), false);
hir::GenericBound::Trait(
hir::PolyTraitRef {
trait_ref: hir::TraitRef {
path: future_path,
hir_ref_id: self.next_id(),
},
bound_generic_params: hir_vec![],
span,
},
hir::TraitBoundModifier::None,
)
}
fn lower_param_bound(
&mut self,
tpb: &GenericBound,
itctx: ImplTraitContext<'_>,
) -> hir::GenericBound {
match *tpb {
GenericBound::Trait(ref ty, modifier) => {
hir::GenericBound::Trait(
self.lower_poly_trait_ref(ty, itctx),
self.lower_trait_bound_modifier(modifier),
)
}
GenericBound::Outlives(ref lifetime) => {
hir::GenericBound::Outlives(self.lower_lifetime(lifetime))
}
}
}
fn lower_lifetime(&mut self, l: &Lifetime) -> hir::Lifetime {
let span = l.ident.span;
match l.ident {
ident if ident.name == kw::StaticLifetime =>
self.new_named_lifetime(l.id, span, hir::LifetimeName::Static),
ident if ident.name == kw::UnderscoreLifetime =>
match self.anonymous_lifetime_mode {
AnonymousLifetimeMode::CreateParameter => {
let fresh_name = self.collect_fresh_in_band_lifetime(span);
self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(fresh_name))
}
AnonymousLifetimeMode::PassThrough => {
self.new_named_lifetime(l.id, span, hir::LifetimeName::Underscore)
}
AnonymousLifetimeMode::ReportError => self.new_error_lifetime(Some(l.id), span),
AnonymousLifetimeMode::Replace(replacement) => {
let hir_id = self.lower_node_id(l.id);
self.replace_elided_lifetime(hir_id, span, replacement)
}
},
ident => {
self.maybe_collect_in_band_lifetime(ident);
let param_name = ParamName::Plain(ident);
self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(param_name))
}
}
}
fn new_named_lifetime(
&mut self,
id: NodeId,
span: Span,
name: hir::LifetimeName,
) -> hir::Lifetime {
hir::Lifetime {
hir_id: self.lower_node_id(id),
span,
name: name,
}
}
/// Replace a return-position elided lifetime with the elided lifetime
/// from the arguments.
fn replace_elided_lifetime(
&mut self,
hir_id: hir::HirId,
span: Span,
replacement: LtReplacement,
) -> hir::Lifetime {
let multiple_or_none = match replacement {
LtReplacement::Some(name) => {
return hir::Lifetime {
hir_id,
span,
name: hir::LifetimeName::Param(name),
};
}
LtReplacement::MultipleLifetimes => "multiple",
LtReplacement::NoLifetimes => "none",
};
let mut err = crate::middle::resolve_lifetime::report_missing_lifetime_specifiers(
self.sess,
span,
1,
);
err.note(&format!(
"return-position elided lifetimes require exactly one \
input-position elided lifetime, found {}.", multiple_or_none));
err.emit();
hir::Lifetime { hir_id, span, name: hir::LifetimeName::Error }
}
fn lower_generic_params(
&mut self,
params: &[GenericParam],
add_bounds: &NodeMap<Vec<GenericBound>>,
mut itctx: ImplTraitContext<'_>,
) -> hir::HirVec<hir::GenericParam> {
params.iter().map(|param| {
self.lower_generic_param(param, add_bounds, itctx.reborrow())
}).collect()
}
fn lower_generic_param(&mut self,
param: &GenericParam,
add_bounds: &NodeMap<Vec<GenericBound>>,
mut itctx: ImplTraitContext<'_>)
-> hir::GenericParam {
let mut bounds = self.with_anonymous_lifetime_mode(
AnonymousLifetimeMode::ReportError,
|this| this.lower_param_bounds(&param.bounds, itctx.reborrow()),
);
let (name, kind) = match param.kind {
GenericParamKind::Lifetime => {
let was_collecting_in_band = self.is_collecting_in_band_lifetimes;
self.is_collecting_in_band_lifetimes = false;
let lt = self.with_anonymous_lifetime_mode(
AnonymousLifetimeMode::ReportError,
|this| this.lower_lifetime(&Lifetime { id: param.id, ident: param.ident }),
);
let param_name = match lt.name {
hir::LifetimeName::Param(param_name) => param_name,
hir::LifetimeName::Implicit
| hir::LifetimeName::Underscore
| hir::LifetimeName::Static => hir::ParamName::Plain(lt.name.ident()),
hir::LifetimeName::Error => ParamName::Error,
};
let kind = hir::GenericParamKind::Lifetime {
kind: hir::LifetimeParamKind::Explicit
};
self.is_collecting_in_band_lifetimes = was_collecting_in_band;
(param_name, kind)
}
GenericParamKind::Type { ref default, .. } => {
// Don't expose `Self` (recovered "keyword used as ident" parse error).
// `rustc::ty` expects `Self` to be only used for a trait's `Self`.
// Instead, use `gensym("Self")` to create a distinct name that looks the same.
let ident = if param.ident.name == kw::SelfUpper {
param.ident.gensym()
} else {
param.ident
};
let add_bounds = add_bounds.get(&param.id).map_or(&[][..], |x| &x);
if !add_bounds.is_empty() {
let params = self.lower_param_bounds(add_bounds, itctx.reborrow()).into_iter();
bounds = bounds.into_iter()
.chain(params)
.collect();
}
let kind = hir::GenericParamKind::Type {
default: default.as_ref().map(|x| {
self.lower_ty(x, ImplTraitContext::Existential(None))
}),
synthetic: param.attrs.iter()
.filter(|attr| attr.check_name(sym::rustc_synthetic))
.map(|_| hir::SyntheticTyParamKind::ImplTrait)
.next(),
};
(hir::ParamName::Plain(ident), kind)
}
GenericParamKind::Const { ref ty } => {
(hir::ParamName::Plain(param.ident), hir::GenericParamKind::Const {
ty: self.lower_ty(&ty, ImplTraitContext::disallowed()),
})
}
};
hir::GenericParam {
hir_id: self.lower_node_id(param.id),
name,
span: param.ident.span,
pure_wrt_drop: attr::contains_name(&param.attrs, sym::may_dangle),
attrs: self.lower_attrs(&param.attrs),
bounds,
kind,
}
}
fn lower_generics(
&mut self,
generics: &Generics,
itctx: ImplTraitContext<'_>)
-> hir::Generics
{
// Collect `?Trait` bounds in where clause and move them to parameter definitions.
// FIXME: this could probably be done with less rightward drift. It also looks like two
// control paths where `report_error` is called are the only paths that advance to after the
// match statement, so the error reporting could probably just be moved there.
let mut add_bounds: NodeMap<Vec<_>> = Default::default();
for pred in &generics.where_clause.predicates {
if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
'next_bound: for bound in &bound_pred.bounds {
if let GenericBound::Trait(_, TraitBoundModifier::Maybe) = *bound {
let report_error = |this: &mut Self| {
this.diagnostic().span_err(
bound_pred.bounded_ty.span,
"`?Trait` bounds are only permitted at the \
point where a type parameter is declared",
);
};
// Check if the where clause type is a plain type parameter.
match bound_pred.bounded_ty.node {
TyKind::Path(None, ref path)
if path.segments.len() == 1
&& bound_pred.bound_generic_params.is_empty() =>
{
if let Some(Res::Def(DefKind::TyParam, def_id)) = self.resolver
.get_partial_res(bound_pred.bounded_ty.id)
.map(|d| d.base_res())
{
if let Some(node_id) =
self.resolver.definitions().as_local_node_id(def_id)
{
for param in &generics.params {
match param.kind {
GenericParamKind::Type { .. } => {
if node_id == param.id {
add_bounds.entry(param.id)
.or_default()
.push(bound.clone());
continue 'next_bound;
}
}
_ => {}
}
}
}
}
report_error(self)
}
_ => report_error(self),
}
}
}
}
}
hir::Generics {
params: self.lower_generic_params(&generics.params, &add_bounds, itctx),
where_clause: self.lower_where_clause(&generics.where_clause),
span: generics.span,
}
}
fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause {
self.with_anonymous_lifetime_mode(
AnonymousLifetimeMode::ReportError,
|this| {
hir::WhereClause {
predicates: wc.predicates
.iter()
.map(|predicate| this.lower_where_predicate(predicate))
.collect(),
span: wc.span,
}
},
)
}
fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate {
match *pred {
WherePredicate::BoundPredicate(WhereBoundPredicate {
ref bound_generic_params,
ref bounded_ty,
ref bounds,
span,
}) => {
self.with_in_scope_lifetime_defs(
&bound_generic_params,
|this| {
hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
bound_generic_params: this.lower_generic_params(
bound_generic_params,
&NodeMap::default(),
ImplTraitContext::disallowed(),
),
bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
bounds: bounds
.iter()
.filter_map(|bound| match *bound {
// Ignore `?Trait` bounds.
// They were copied into type parameters already.
GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
_ => Some(this.lower_param_bound(
bound,
ImplTraitContext::disallowed(),
)),
})
.collect(),
span,
})
},
)
}
WherePredicate::RegionPredicate(WhereRegionPredicate {
ref lifetime,
ref bounds,
span,
}) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
span,
lifetime: self.lower_lifetime(lifetime),
bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
}),
WherePredicate::EqPredicate(WhereEqPredicate {
id,
ref lhs_ty,
ref rhs_ty,
span,
}) => {
hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
hir_id: self.lower_node_id(id),
lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::disallowed()),
rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::disallowed()),
span,
})
},
}
}
fn lower_variant_data(&mut self, vdata: &VariantData) -> hir::VariantData {
match *vdata {
VariantData::Struct(ref fields, recovered) => hir::VariantData::Struct(
fields.iter().enumerate().map(|f| self.lower_struct_field(f)).collect(),
recovered,
),
VariantData::Tuple(ref fields, id) => {
hir::VariantData::Tuple(
fields
.iter()
.enumerate()
.map(|f| self.lower_struct_field(f))
.collect(),
self.lower_node_id(id),
)
},
VariantData::Unit(id) => {
hir::VariantData::Unit(self.lower_node_id(id))
},
}
}
fn lower_trait_ref(&mut self, p: &TraitRef, itctx: ImplTraitContext<'_>) -> hir::TraitRef {
let path = match self.lower_qpath(p.ref_id, &None, &p.path, ParamMode::Explicit, itctx) {
hir::QPath::Resolved(None, path) => path.and_then(|path| path),
qpath => bug!("lower_trait_ref: unexpected QPath `{:?}`", qpath),
};
hir::TraitRef {
path,
hir_ref_id: self.lower_node_id(p.ref_id),
}
}
fn lower_poly_trait_ref(
&mut self,
p: &PolyTraitRef,
mut itctx: ImplTraitContext<'_>,
) -> hir::PolyTraitRef {
let bound_generic_params = self.lower_generic_params(
&p.bound_generic_params,
&NodeMap::default(),
itctx.reborrow(),
);
let trait_ref = self.with_in_scope_lifetime_defs(
&p.bound_generic_params,
|this| this.lower_trait_ref(&p.trait_ref, itctx),
);
hir::PolyTraitRef {
bound_generic_params,
trait_ref,
span: p.span,
}
}
fn lower_struct_field(&mut self, (index, f): (usize, &StructField)) -> hir::StructField {
let ty = if let TyKind::Path(ref qself, ref path) = f.ty.node {
let t = self.lower_path_ty(
&f.ty,
qself,
path,
ParamMode::ExplicitNamed, // no `'_` in declarations (Issue #61124)
ImplTraitContext::disallowed()
);
P(t)
} else {
self.lower_ty(&f.ty, ImplTraitContext::disallowed())
};
hir::StructField {
span: f.span,
hir_id: self.lower_node_id(f.id),
ident: match f.ident {
Some(ident) => ident,
// FIXME(jseyfried): positional field hygiene.
None => Ident::new(sym::integer(index), f.span),
},
vis: self.lower_visibility(&f.vis, None),
ty,
attrs: self.lower_attrs(&f.attrs),
}
}
fn lower_field(&mut self, f: &Field) -> hir::Field {
hir::Field {
hir_id: self.next_id(),
ident: f.ident,
expr: P(self.lower_expr(&f.expr)),
span: f.span,
is_shorthand: f.is_shorthand,
}
}
fn lower_mt(&mut self, mt: &MutTy, itctx: ImplTraitContext<'_>) -> hir::MutTy {
hir::MutTy {
ty: self.lower_ty(&mt.ty, itctx),
mutbl: self.lower_mutability(mt.mutbl),
}
}
fn lower_param_bounds(&mut self, bounds: &[GenericBound], mut itctx: ImplTraitContext<'_>)
-> hir::GenericBounds {
bounds.iter().map(|bound| self.lower_param_bound(bound, itctx.reborrow())).collect()
}
fn lower_block_with_stmts(
&mut self,
b: &Block,
targeted_by_break: bool,
mut stmts: Vec<hir::Stmt>,
) -> P<hir::Block> {
let mut expr = None;
for (index, stmt) in b.stmts.iter().enumerate() {
if index == b.stmts.len() - 1 {
if let StmtKind::Expr(ref e) = stmt.node {
expr = Some(P(self.lower_expr(e)));
} else {
stmts.extend(self.lower_stmt(stmt));
}
} else {
stmts.extend(self.lower_stmt(stmt));
}
}
P(hir::Block {
hir_id: self.lower_node_id(b.id),
stmts: stmts.into(),
expr,
rules: self.lower_block_check_mode(&b.rules),
span: b.span,
targeted_by_break,
})
}
fn lower_block(&mut self, b: &Block, targeted_by_break: bool) -> P<hir::Block> {
self.lower_block_with_stmts(b, targeted_by_break, vec![])
}
fn lower_maybe_async_body(
&mut self,
decl: &FnDecl,
asyncness: IsAsync,
body: &Block,
) -> hir::BodyId {
let closure_id = match asyncness {
IsAsync::Async { closure_id, .. } => closure_id,
IsAsync::NotAsync => return self.lower_fn_body(&decl, |this| {
let body = this.lower_block(body, false);
this.expr_block(body, ThinVec::new())
}),
};
self.lower_body(|this| {
let mut arguments: Vec<hir::Arg> = Vec::new();
let mut statements: Vec<hir::Stmt> = Vec::new();
// Async function arguments are lowered into the closure body so that they are
// captured and so that the drop order matches the equivalent non-async functions.
//
// from:
//
// async fn foo(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
// async move {
// }
// }
//
// into:
//
// fn foo(__arg0: <ty>, __arg1: <ty>, __arg2: <ty>) {
// async move {
// let __arg2 = __arg2;
// let <pattern> = __arg2;
// let __arg1 = __arg1;
// let <pattern> = __arg1;
// let __arg0 = __arg0;
// let <pattern> = __arg0;
// }
// }
//
// If `<pattern>` is a simple ident, then it is lowered to a single
// `let <pattern> = <pattern>;` statement as an optimization.
for (index, argument) in decl.inputs.iter().enumerate() {
let argument = this.lower_arg(argument);
let span = argument.pat.span;
// Check if this is a binding pattern, if so, we can optimize and avoid adding a
// `let <pat> = __argN;` statement. In this case, we do not rename the argument.
let (ident, is_simple_argument) = match argument.pat.node {
hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, ident, _) =>
(ident, true),
_ => {
// Replace the ident for bindings that aren't simple.
let name = format!("__arg{}", index);
let ident = Ident::from_str(&name);
(ident, false)
},
};
let desugared_span =
this.mark_span_with_reason(CompilerDesugaringKind::Async, span, None);
// Construct an argument representing `__argN: <ty>` to replace the argument of the
// async function.
//
// If this is the simple case, this argument will end up being the same as the
// original argument, but with a different pattern id.
let (new_argument_pat, new_argument_id) = this.pat_ident(desugared_span, ident);
let new_argument = hir::Arg {
hir_id: argument.hir_id,
pat: new_argument_pat,
};
if is_simple_argument {
// If this is the simple case, then we only insert one statement that is
// `let <pat> = <pat>;`. We re-use the original argument's pattern so that
// `HirId`s are densely assigned.
let expr = this.expr_ident(desugared_span, ident, new_argument_id);
let stmt = this.stmt_let_pat(
desugared_span, Some(P(expr)), argument.pat, hir::LocalSource::AsyncFn);
statements.push(stmt);
} else {
// If this is not the simple case, then we construct two statements:
//
// ```
// let __argN = __argN;
// let <pat> = __argN;
// ```
//
// The first statement moves the argument into the closure and thus ensures
// that the drop order is correct.
//
// The second statement creates the bindings that the user wrote.
// Construct the `let mut __argN = __argN;` statement. It must be a mut binding
// because the user may have specified a `ref mut` binding in the next
// statement.
let (move_pat, move_id) = this.pat_ident_binding_mode(
desugared_span, ident, hir::BindingAnnotation::Mutable);
let move_expr = this.expr_ident(desugared_span, ident, new_argument_id);
let move_stmt = this.stmt_let_pat(
desugared_span, Some(P(move_expr)), move_pat, hir::LocalSource::AsyncFn);
// Construct the `let <pat> = __argN;` statement. We re-use the original
// argument's pattern so that `HirId`s are densely assigned.
let pattern_expr = this.expr_ident(desugared_span, ident, move_id);
let pattern_stmt = this.stmt_let_pat(
desugared_span, Some(P(pattern_expr)), argument.pat,
hir::LocalSource::AsyncFn);
statements.push(move_stmt);
statements.push(pattern_stmt);
};
arguments.push(new_argument);
}
let async_expr = this.make_async_expr(
CaptureBy::Value, closure_id, None, body.span,
|this| {
let body = this.lower_block_with_stmts(body, false, statements);
this.expr_block(body, ThinVec::new())
});
(HirVec::from(arguments), this.expr(body.span, async_expr, ThinVec::new()))
})
}
fn lower_item_kind(
&mut self,
id: NodeId,
ident: &mut Ident,
attrs: &hir::HirVec<Attribute>,
vis: &mut hir::Visibility,
i: &ItemKind,
) -> hir::ItemKind {
match *i {
ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name),
ItemKind::Use(ref use_tree) => {
// Start with an empty prefix.
let prefix = Path {
segments: vec![],
span: use_tree.span,
};
self.lower_use_tree(use_tree, &prefix, id, vis, ident, attrs)
}
ItemKind::Static(ref t, m, ref e) => {
hir::ItemKind::Static(
self.lower_ty(
t,
if self.sess.features_untracked().impl_trait_in_bindings {
ImplTraitContext::Existential(None)
} else {
ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
}
),
self.lower_mutability(m),
self.lower_const_body(e),
)
}
ItemKind::Const(ref t, ref e) => {
hir::ItemKind::Const(
self.lower_ty(
t,
if self.sess.features_untracked().impl_trait_in_bindings {
ImplTraitContext::Existential(None)
} else {
ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
}
),
self.lower_const_body(e)
)
}
ItemKind::Fn(ref decl, header, ref generics, ref body) => {
let fn_def_id = self.resolver.definitions().local_def_id(id);
self.with_new_scopes(|this| {
this.current_item = Some(ident.span);
// Note: we don't need to change the return type from `T` to
// `impl Future<Output = T>` here because lower_body
// only cares about the input argument patterns in the function
// declaration (decl), not the return types.
let body_id = this.lower_maybe_async_body(&decl, header.asyncness.node, body);
let (generics, fn_decl) = this.add_in_band_defs(
generics,
fn_def_id,
AnonymousLifetimeMode::PassThrough,
|this, idty| this.lower_fn_decl(
&decl,
Some((fn_def_id, idty)),
true,
header.asyncness.node.opt_return_id()
),
);
hir::ItemKind::Fn(
fn_decl,
this.lower_fn_header(header),
generics,
body_id,
)
})
}
ItemKind::Mod(ref m) => hir::ItemKind::Mod(self.lower_mod(m)),
ItemKind::ForeignMod(ref nm) => hir::ItemKind::ForeignMod(self.lower_foreign_mod(nm)),
ItemKind::GlobalAsm(ref ga) => hir::ItemKind::GlobalAsm(self.lower_global_asm(ga)),
ItemKind::Ty(ref t, ref generics) => hir::ItemKind::Ty(
self.lower_ty(t, ImplTraitContext::disallowed()),
self.lower_generics(generics, ImplTraitContext::disallowed()),
),
ItemKind::Existential(ref b, ref generics) => hir::ItemKind::Existential(
hir::ExistTy {
generics: self.lower_generics(generics,
ImplTraitContext::Existential(None)),
bounds: self.lower_param_bounds(b,
ImplTraitContext::Existential(None)),
impl_trait_fn: None,
origin: hir::ExistTyOrigin::ExistentialType,
},
),
ItemKind::Enum(ref enum_definition, ref generics) => {
hir::ItemKind::Enum(
hir::EnumDef {
variants: enum_definition
.variants
.iter()
.map(|x| self.lower_variant(x))
.collect(),
},
self.lower_generics(generics, ImplTraitContext::disallowed()),
)
},
ItemKind::Struct(ref struct_def, ref generics) => {
let struct_def = self.lower_variant_data(struct_def);
hir::ItemKind::Struct(
struct_def,
self.lower_generics(generics, ImplTraitContext::disallowed()),
)
}
ItemKind::Union(ref vdata, ref generics) => {
let vdata = self.lower_variant_data(vdata);
hir::ItemKind::Union(
vdata,
self.lower_generics(generics, ImplTraitContext::disallowed()),
)
}
ItemKind::Impl(
unsafety,
polarity,
defaultness,
ref ast_generics,
ref trait_ref,
ref ty,
ref impl_items,
) => {
let def_id = self.resolver.definitions().local_def_id(id);
// Lower the "impl header" first. This ordering is important
// for in-band lifetimes! Consider `'a` here:
//
// impl Foo<'a> for u32 {
// fn method(&'a self) { .. }
// }
//
// Because we start by lowering the `Foo<'a> for u32`
// part, we will add `'a` to the list of generics on
// the impl. When we then encounter it later in the
// method, it will not be considered an in-band
// lifetime to be added, but rather a reference to a
// parent lifetime.
let lowered_trait_impl_id = self.lower_node_id(id);
let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
ast_generics,
def_id,
AnonymousLifetimeMode::CreateParameter,
|this, _| {
let trait_ref = trait_ref.as_ref().map(|trait_ref| {
this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
});
if let Some(ref trait_ref) = trait_ref {
if let Res::Def(DefKind::Trait, def_id) = trait_ref.path.res {
this.trait_impls.entry(def_id).or_default().push(
lowered_trait_impl_id);
}
}
let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());
(trait_ref, lowered_ty)
},
);
let new_impl_items = self.with_in_scope_lifetime_defs(
&ast_generics.params,
|this| {
impl_items
.iter()
.map(|item| this.lower_impl_item_ref(item))
.collect()
},
);
hir::ItemKind::Impl(
self.lower_unsafety(unsafety),
self.lower_impl_polarity(polarity),
self.lower_defaultness(defaultness, true /* [1] */),
generics,
trait_ref,
lowered_ty,
new_impl_items,
)
}
ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref items) => {
let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
let items = items
.iter()
.map(|item| self.lower_trait_item_ref(item))
.collect();
hir::ItemKind::Trait(
self.lower_is_auto(is_auto),
self.lower_unsafety(unsafety),
self.lower_generics(generics, ImplTraitContext::disallowed()),
bounds,
items,
)
}
ItemKind::TraitAlias(ref generics, ref bounds) => hir::ItemKind::TraitAlias(
self.lower_generics(generics, ImplTraitContext::disallowed()),
self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
),
ItemKind::MacroDef(..)
| ItemKind::Mac(..) => bug!("`TyMac` should have been expanded by now"),
}
// [1] `defaultness.has_value()` is never called for an `impl`, always `true` in order to
// not cause an assertion failure inside the `lower_defaultness` function.
}
fn lower_use_tree(
&mut self,
tree: &UseTree,
prefix: &Path,
id: NodeId,
vis: &mut hir::Visibility,
ident: &mut Ident,
attrs: &hir::HirVec<Attribute>,
) -> hir::ItemKind {
debug!("lower_use_tree(tree={:?})", tree);
debug!("lower_use_tree: vis = {:?}", vis);
let path = &tree.prefix;
let segments = prefix
.segments
.iter()
.chain(path.segments.iter())
.cloned()
.collect();
match tree.kind {
UseTreeKind::Simple(rename, id1, id2) => {
*ident = tree.ident();
// First, apply the prefix to the path.
let mut path = Path {
segments,
span: path.span,
};
// Correctly resolve `self` imports.
if path.segments.len() > 1
&& path.segments.last().unwrap().ident.name == kw::SelfLower
{
let _ = path.segments.pop();
if rename.is_none() {
*ident = path.segments.last().unwrap().ident;
}
}
let mut resolutions = self.expect_full_res_from_use(id);
// We want to return *something* from this function, so hold onto the first item
// for later.
let ret_res = self.lower_res(resolutions.next().unwrap_or(Res::Err));
// Here, we are looping over namespaces, if they exist for the definition
// being imported. We only handle type and value namespaces because we
// won't be dealing with macros in the rest of the compiler.
// Essentially a single `use` which imports two names is desugared into
// two imports.
for (res, &new_node_id) in resolutions.zip([id1, id2].iter()) {
let ident = *ident;
let mut path = path.clone();
for seg in &mut path.segments {
seg.id = self.sess.next_node_id();
}
let span = path.span;
self.with_hir_id_owner(new_node_id, |this| {
let new_id = this.lower_node_id(new_node_id);
let res = this.lower_res(res);
let path =
this.lower_path_extra(res, &path, ParamMode::Explicit, None);
let item = hir::ItemKind::Use(P(path), hir::UseKind::Single);
let vis = this.rebuild_vis(&vis);
this.insert_item(
hir::Item {
hir_id: new_id,
ident,
attrs: attrs.clone(),
node: item,
vis,
span,
},
);
});
}
let path =
P(self.lower_path_extra(ret_res, &path, ParamMode::Explicit, None));
hir::ItemKind::Use(path, hir::UseKind::Single)
}
UseTreeKind::Glob => {
let path = P(self.lower_path(
id,
&Path {
segments,
span: path.span,
},
ParamMode::Explicit,
));
hir::ItemKind::Use(path, hir::UseKind::Glob)
}
UseTreeKind::Nested(ref trees) => {
// Nested imports are desugared into simple imports.
// So, if we start with
//
// ```
// pub(x) use foo::{a, b};
// ```
//
// we will create three items:
//
// ```
// pub(x) use foo::a;
// pub(x) use foo::b;
// pub(x) use foo::{}; // <-- this is called the `ListStem`
// ```
//
// The first two are produced by recursively invoking
// `lower_use_tree` (and indeed there may be things
// like `use foo::{a::{b, c}}` and so forth). They
// wind up being directly added to
// `self.items`. However, the structure of this
// function also requires us to return one item, and
// for that we return the `{}` import (called the
// `ListStem`).
let prefix = Path {
segments,
span: prefix.span.to(path.span),
};
// Add all the nested `PathListItem`s to the HIR.
for &(ref use_tree, id) in trees {
let new_hir_id = self.lower_node_id(id);
let mut prefix = prefix.clone();
// Give the segments new node-ids since they are being cloned.
for seg in &mut prefix.segments {
seg.id = self.sess.next_node_id();
}
// Each `use` import is an item and thus are owners of the
// names in the path. Up to this point the nested import is
// the current owner, since we want each desugared import to
// own its own names, we have to adjust the owner before
// lowering the rest of the import.
self.with_hir_id_owner(id, |this| {
let mut vis = this.rebuild_vis(&vis);
let mut ident = *ident;
let item = this.lower_use_tree(use_tree,
&prefix,
id,
&mut vis,
&mut ident,
attrs);
this.insert_item(
hir::Item {
hir_id: new_hir_id,
ident,
attrs: attrs.clone(),
node: item,
vis,
span: use_tree.span,
},
);
});
}
// Subtle and a bit hacky: we lower the privacy level
// of the list stem to "private" most of the time, but
// not for "restricted" paths. The key thing is that
// we don't want it to stay as `pub` (with no caveats)
// because that affects rustdoc and also the lints
// about `pub` items. But we can't *always* make it
// private -- particularly not for restricted paths --
// because it contains node-ids that would then be
// unused, failing the check that HirIds are "densely
// assigned".
match vis.node {
hir::VisibilityKind::Public |
hir::VisibilityKind::Crate(_) |
hir::VisibilityKind::Inherited => {
*vis = respan(prefix.span.shrink_to_lo(), hir::VisibilityKind::Inherited);
}
hir::VisibilityKind::Restricted { .. } => {
// Do nothing here, as described in the comment on the match.
}
}
let res = self.expect_full_res_from_use(id).next().unwrap_or(Res::Err);
let res = self.lower_res(res);
let path = P(self.lower_path_extra(res, &prefix, ParamMode::Explicit, None));
hir::ItemKind::Use(path, hir::UseKind::ListStem)
}
}
}
/// Paths like the visibility path in `pub(super) use foo::{bar, baz}` are repeated
/// many times in the HIR tree; for each occurrence, we need to assign distinct
/// `NodeId`s. (See, e.g., #56128.)
fn rebuild_use_path(&mut self, path: &hir::Path) -> hir::Path {
debug!("rebuild_use_path(path = {:?})", path);
let segments = path.segments.iter().map(|seg| hir::PathSegment {
ident: seg.ident,
hir_id: seg.hir_id.map(|_| self.next_id()),
res: seg.res,
args: None,
infer_args: seg.infer_args,
}).collect();
hir::Path {
span: path.span,
res: path.res,
segments,
}
}
fn rebuild_vis(&mut self, vis: &hir::Visibility) -> hir::Visibility {
let vis_kind = match vis.node {
hir::VisibilityKind::Public => hir::VisibilityKind::Public,
hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
hir::VisibilityKind::Restricted {
path: P(self.rebuild_use_path(path)),
hir_id: self.next_id(),
}
}
};
respan(vis.span, vis_kind)
}
fn lower_trait_item(&mut self, i: &TraitItem) -> hir::TraitItem {
let trait_item_def_id = self.resolver.definitions().local_def_id(i.id);
let (generics, node) = match i.node {
TraitItemKind::Const(ref ty, ref default) => (
self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
hir::TraitItemKind::Const(
self.lower_ty(ty, ImplTraitContext::disallowed()),
default
.as_ref()
.map(|x| self.lower_const_body(x)),
),
),
TraitItemKind::Method(ref sig, None) => {
let names = self.lower_fn_args_to_names(&sig.decl);
let (generics, sig) = self.lower_method_sig(
&i.generics,
sig,
trait_item_def_id,
false,
None,
);
(generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Required(names)))
}
TraitItemKind::Method(ref sig, Some(ref body)) => {
let body_id = self.lower_fn_body(&sig.decl, |this| {
let body = this.lower_block(body, false);
this.expr_block(body, ThinVec::new())
});
let (generics, sig) = self.lower_method_sig(
&i.generics,
sig,
trait_item_def_id,
false,
None,
);
(generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Provided(body_id)))
}
TraitItemKind::Type(ref bounds, ref default) => {
let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
let node = hir::TraitItemKind::Type(
self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
default
.as_ref()
.map(|x| self.lower_ty(x, ImplTraitContext::disallowed())),
);
(generics, node)
},
TraitItemKind::Macro(..) => bug!("macro item shouldn't exist at this point"),
};
hir::TraitItem {
hir_id: self.lower_node_id(i.id),
ident: i.ident,
attrs: self.lower_attrs(&i.attrs),
generics,
node,
span: i.span,
}
}
fn lower_trait_item_ref(&mut self, i: &TraitItem) -> hir::TraitItemRef {
let (kind, has_default) = match i.node {
TraitItemKind::Const(_, ref default) => {
(hir::AssocItemKind::Const, default.is_some())
}
TraitItemKind::Type(_, ref default) => {
(hir::AssocItemKind::Type, default.is_some())
}
TraitItemKind::Method(ref sig, ref default) => (
hir::AssocItemKind::Method {
has_self: sig.decl.has_self(),
},
default.is_some(),
),
TraitItemKind::Macro(..) => unimplemented!(),
};
hir::TraitItemRef {
id: hir::TraitItemId { hir_id: self.lower_node_id(i.id) },
ident: i.ident,
span: i.span,
defaultness: self.lower_defaultness(Defaultness::Default, has_default),
kind,
}
}
fn lower_impl_item(&mut self, i: &ImplItem) -> hir::ImplItem {
let impl_item_def_id = self.resolver.definitions().local_def_id(i.id);
let (generics, node) = match i.node {
ImplItemKind::Const(ref ty, ref expr) => (
self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
hir::ImplItemKind::Const(
self.lower_ty(ty, ImplTraitContext::disallowed()),
self.lower_const_body(expr),
),
),
ImplItemKind::Method(ref sig, ref body) => {
self.current_item = Some(i.span);
let body_id = self.lower_maybe_async_body(
&sig.decl, sig.header.asyncness.node, body
);
let impl_trait_return_allow = !self.is_in_trait_impl;
let (generics, sig) = self.lower_method_sig(
&i.generics,
sig,
impl_item_def_id,
impl_trait_return_allow,
sig.header.asyncness.node.opt_return_id(),
);
(generics, hir::ImplItemKind::Method(sig, body_id))
}
ImplItemKind::Type(ref ty) => (
self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
hir::ImplItemKind::Type(self.lower_ty(ty, ImplTraitContext::disallowed())),
),
ImplItemKind::Existential(ref bounds) => (
self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
hir::ImplItemKind::Existential(
self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
),
),
ImplItemKind::Macro(..) => bug!("`TyMac` should have been expanded by now"),
};
hir::ImplItem {
hir_id: self.lower_node_id(i.id),
ident: i.ident,
attrs: self.lower_attrs(&i.attrs),
generics,
vis: self.lower_visibility(&i.vis, None),
defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
node,
span: i.span,
}
// [1] since `default impl` is not yet implemented, this is always true in impls
}
fn lower_impl_item_ref(&mut self, i: &ImplItem) -> hir::ImplItemRef {
hir::ImplItemRef {
id: hir::ImplItemId { hir_id: self.lower_node_id(i.id) },
ident: i.ident,
span: i.span,
vis: self.lower_visibility(&i.vis, Some(i.id)),
defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
kind: match i.node {
ImplItemKind::Const(..) => hir::AssocItemKind::Const,
ImplItemKind::Type(..) => hir::AssocItemKind::Type,
ImplItemKind::Existential(..) => hir::AssocItemKind::Existential,
ImplItemKind::Method(ref sig, _) => hir::AssocItemKind::Method {
has_self: sig.decl.has_self(),
},
ImplItemKind::Macro(..) => unimplemented!(),
},
}
// [1] since `default impl` is not yet implemented, this is always true in impls
}
fn lower_mod(&mut self, m: &Mod) -> hir::Mod {
hir::Mod {
inner: m.inner,
item_ids: m.items.iter().flat_map(|x| self.lower_item_id(x)).collect(),
}
}
fn lower_item_id(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> {
let node_ids = match i.node {
ItemKind::Use(ref use_tree) => {
let mut vec = smallvec![i.id];
self.lower_item_id_use_tree(use_tree, i.id, &mut vec);
vec
}
ItemKind::MacroDef(..) => SmallVec::new(),
ItemKind::Fn(..) |
ItemKind::Impl(.., None, _, _) => smallvec![i.id],
ItemKind::Static(ref ty, ..) => {
let mut ids = smallvec![i.id];
if self.sess.features_untracked().impl_trait_in_bindings {
let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
visitor.visit_ty(ty);
}
ids
},
ItemKind::Const(ref ty, ..) => {
let mut ids = smallvec![i.id];
if self.sess.features_untracked().impl_trait_in_bindings {
let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
visitor.visit_ty(ty);
}
ids
},
_ => smallvec![i.id],
};
node_ids.into_iter().map(|node_id| hir::ItemId {
id: self.allocate_hir_id_counter(node_id)
}).collect()
}
fn lower_item_id_use_tree(&mut self,
tree: &UseTree,
base_id: NodeId,
vec: &mut SmallVec<[NodeId; 1]>)
{
match tree.kind {
UseTreeKind::Nested(ref nested_vec) => for &(ref nested, id) in nested_vec {
vec.push(id);
self.lower_item_id_use_tree(nested, id, vec);
},
UseTreeKind::Glob => {}
UseTreeKind::Simple(_, id1, id2) => {
for (_, &id) in self.expect_full_res_from_use(base_id)
.skip(1)
.zip([id1, id2].iter())
{
vec.push(id);
}
},
}
}
pub fn lower_item(&mut self, i: &Item) -> Option<hir::Item> {
let mut ident = i.ident;
let mut vis = self.lower_visibility(&i.vis, None);
let attrs = self.lower_attrs(&i.attrs);
if let ItemKind::MacroDef(ref def) = i.node {
if !def.legacy || attr::contains_name(&i.attrs, sym::macro_export) ||
attr::contains_name(&i.attrs, sym::rustc_doc_only_macro) {
let body = self.lower_token_stream(def.stream());
let hir_id = self.lower_node_id(i.id);
self.exported_macros.push(hir::MacroDef {
name: ident.name,
vis,
attrs,
hir_id,
span: i.span,
body,
legacy: def.legacy,
});
}
return None;
}
let node = self.lower_item_kind(i.id, &mut ident, &attrs, &mut vis, &i.node);
Some(hir::Item {
hir_id: self.lower_node_id(i.id),
ident,
attrs,
node,
vis,
span: i.span,
})
}
fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem {
let def_id = self.resolver.definitions().local_def_id(i.id);
hir::ForeignItem {
hir_id: self.lower_node_id(i.id),
ident: i.ident,
attrs: self.lower_attrs(&i.attrs),
node: match i.node {
ForeignItemKind::Fn(ref fdec, ref generics) => {
let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
generics,
def_id,
AnonymousLifetimeMode::PassThrough,
|this, _| {
(
// Disallow impl Trait in foreign items
this.lower_fn_decl(fdec, None, false, None),
this.lower_fn_args_to_names(fdec),
)
},
);
hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
}
ForeignItemKind::Static(ref t, m) => {
hir::ForeignItemKind::Static(
self.lower_ty(t, ImplTraitContext::disallowed()), self.lower_mutability(m))
}
ForeignItemKind::Ty => hir::ForeignItemKind::Type,
ForeignItemKind::Macro(_) => panic!("shouldn't exist here"),
},
vis: self.lower_visibility(&i.vis, None),
span: i.span,
}
}
fn lower_method_sig(
&mut self,
generics: &Generics,
sig: &MethodSig,
fn_def_id: DefId,
impl_trait_return_allow: bool,
is_async: Option<NodeId>,
) -> (hir::Generics, hir::MethodSig) {
let header = self.lower_fn_header(sig.header);
let (generics, decl) = self.add_in_band_defs(
generics,
fn_def_id,
AnonymousLifetimeMode::PassThrough,
|this, idty| this.lower_fn_decl(
&sig.decl,
Some((fn_def_id, idty)),
impl_trait_return_allow,
is_async,
),
);
(generics, hir::MethodSig { header, decl })
}
fn lower_is_auto(&mut self, a: IsAuto) -> hir::IsAuto {
match a {
IsAuto::Yes => hir::IsAuto::Yes,
IsAuto::No => hir::IsAuto::No,
}
}
fn lower_fn_header(&mut self, h: FnHeader) -> hir::FnHeader {
hir::FnHeader {
unsafety: self.lower_unsafety(h.unsafety),
asyncness: self.lower_asyncness(h.asyncness.node),
constness: self.lower_constness(h.constness),
abi: h.abi,
}
}
fn lower_unsafety(&mut self, u: Unsafety) -> hir::Unsafety {
match u {
Unsafety::Unsafe => hir::Unsafety::Unsafe,
Unsafety::Normal => hir::Unsafety::Normal,
}
}
fn lower_constness(&mut self, c: Spanned<Constness>) -> hir::Constness {
match c.node {
Constness::Const => hir::Constness::Const,
Constness::NotConst => hir::Constness::NotConst,
}
}
fn lower_asyncness(&mut self, a: IsAsync) -> hir::IsAsync {
match a {
IsAsync::Async { .. } => hir::IsAsync::Async,
IsAsync::NotAsync => hir::IsAsync::NotAsync,
}
}
fn lower_unop(&mut self, u: UnOp) -> hir::UnOp {
match u {
UnOp::Deref => hir::UnDeref,
UnOp::Not => hir::UnNot,
UnOp::Neg => hir::UnNeg,
}
}
fn lower_binop(&mut self, b: BinOp) -> hir::BinOp {
Spanned {
node: match b.node {
BinOpKind::Add => hir::BinOpKind::Add,
BinOpKind::Sub => hir::BinOpKind::Sub,
BinOpKind::Mul => hir::BinOpKind::Mul,
BinOpKind::Div => hir::BinOpKind::Div,
BinOpKind::Rem => hir::BinOpKind::Rem,
BinOpKind::And => hir::BinOpKind::And,
BinOpKind::Or => hir::BinOpKind::Or,
BinOpKind::BitXor => hir::BinOpKind::BitXor,
BinOpKind::BitAnd => hir::BinOpKind::BitAnd,
BinOpKind::BitOr => hir::BinOpKind::BitOr,
BinOpKind::Shl => hir::BinOpKind::Shl,
BinOpKind::Shr => hir::BinOpKind::Shr,
BinOpKind::Eq => hir::BinOpKind::Eq,
BinOpKind::Lt => hir::BinOpKind::Lt,
BinOpKind::Le => hir::BinOpKind::Le,
BinOpKind::Ne => hir::BinOpKind::Ne,
BinOpKind::Ge => hir::BinOpKind::Ge,
BinOpKind::Gt => hir::BinOpKind::Gt,
},
span: b.span,
}
}
fn lower_pat(&mut self, p: &Pat) -> P<hir::Pat> {
let node = match p.node {
PatKind::Wild => hir::PatKind::Wild,
PatKind::Ident(ref binding_mode, ident, ref sub) => {
match self.resolver.get_partial_res(p.id).map(|d| d.base_res()) {
// `None` can occur in body-less function signatures
res @ None | res @ Some(Res::Local(_)) => {
let canonical_id = match res {
Some(Res::Local(id)) => id,
_ => p.id,
};
hir::PatKind::Binding(
self.lower_binding_mode(binding_mode),
self.lower_node_id(canonical_id),
ident,
sub.as_ref().map(|x| self.lower_pat(x)),
)
}
Some(res) => hir::PatKind::Path(hir::QPath::Resolved(
None,
P(hir::Path {
span: ident.span,
res: self.lower_res(res),
segments: hir_vec![hir::PathSegment::from_ident(ident)],
}),
)),
}
}
PatKind::Lit(ref e) => hir::PatKind::Lit(P(self.lower_expr(e))),
PatKind::TupleStruct(ref path, ref pats, ddpos) => {
let qpath = self.lower_qpath(
p.id,
&None,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
);
hir::PatKind::TupleStruct(
qpath,
pats.iter().map(|x| self.lower_pat(x)).collect(),
ddpos,
)
}
PatKind::Path(ref qself, ref path) => {
let qpath = self.lower_qpath(
p.id,
qself,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
);
hir::PatKind::Path(qpath)
}
PatKind::Struct(ref path, ref fields, etc) => {
let qpath = self.lower_qpath(
p.id,
&None,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
);
let fs = fields
.iter()
.map(|f| {
Spanned {
span: f.span,
node: hir::FieldPat {
hir_id: self.next_id(),
ident: f.node.ident,
pat: self.lower_pat(&f.node.pat),
is_shorthand: f.node.is_shorthand,
},
}
})
.collect();
hir::PatKind::Struct(qpath, fs, etc)
}
PatKind::Tuple(ref elts, ddpos) => {
hir::PatKind::Tuple(elts.iter().map(|x| self.lower_pat(x)).collect(), ddpos)
}
PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
PatKind::Ref(ref inner, mutbl) => {
hir::PatKind::Ref(self.lower_pat(inner), self.lower_mutability(mutbl))
}
PatKind::Range(ref e1, ref e2, Spanned { node: ref end, .. }) => hir::PatKind::Range(
P(self.lower_expr(e1)),
P(self.lower_expr(e2)),
self.lower_range_end(end),
),
PatKind::Slice(ref before, ref slice, ref after) => hir::PatKind::Slice(
before.iter().map(|x| self.lower_pat(x)).collect(),
slice.as_ref().map(|x| self.lower_pat(x)),
after.iter().map(|x| self.lower_pat(x)).collect(),
),
PatKind::Paren(ref inner) => return self.lower_pat(inner),
PatKind::Mac(_) => panic!("Shouldn't exist here"),
};
P(hir::Pat {
hir_id: self.lower_node_id(p.id),
node,
span: p.span,
})
}
fn lower_range_end(&mut self, e: &RangeEnd) -> hir::RangeEnd {
match *e {
RangeEnd::Included(_) => hir::RangeEnd::Included,
RangeEnd::Excluded => hir::RangeEnd::Excluded,
}
}
fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst {
self.with_new_scopes(|this| {
hir::AnonConst {
hir_id: this.lower_node_id(c.id),
body: this.lower_const_body(&c.value),
}
})
}
fn lower_expr(&mut self, e: &Expr) -> hir::Expr {
let kind = match e.node {
ExprKind::Box(ref inner) => hir::ExprKind::Box(P(self.lower_expr(inner))),
ExprKind::Array(ref exprs) => {
hir::ExprKind::Array(exprs.iter().map(|x| self.lower_expr(x)).collect())
}
ExprKind::Repeat(ref expr, ref count) => {
let expr = P(self.lower_expr(expr));
let count = self.lower_anon_const(count);
hir::ExprKind::Repeat(expr, count)
}
ExprKind::Tup(ref elts) => {
hir::ExprKind::Tup(elts.iter().map(|x| self.lower_expr(x)).collect())
}
ExprKind::Call(ref f, ref args) => {
let f = P(self.lower_expr(f));
hir::ExprKind::Call(f, args.iter().map(|x| self.lower_expr(x)).collect())
}
ExprKind::MethodCall(ref seg, ref args) => {
let hir_seg = P(self.lower_path_segment(
e.span,
seg,
ParamMode::Optional,
0,
ParenthesizedGenericArgs::Err,
ImplTraitContext::disallowed(),
None,
));
let args = args.iter().map(|x| self.lower_expr(x)).collect();
hir::ExprKind::MethodCall(hir_seg, seg.ident.span, args)
}
ExprKind::Binary(binop, ref lhs, ref rhs) => {
let binop = self.lower_binop(binop);
let lhs = P(self.lower_expr(lhs));
let rhs = P(self.lower_expr(rhs));
hir::ExprKind::Binary(binop, lhs, rhs)
}
ExprKind::Unary(op, ref ohs) => {
let op = self.lower_unop(op);
let ohs = P(self.lower_expr(ohs));
hir::ExprKind::Unary(op, ohs)
}
ExprKind::Lit(ref l) => hir::ExprKind::Lit(respan(l.span, l.node.clone())),
ExprKind::Cast(ref expr, ref ty) => {
let expr = P(self.lower_expr(expr));
hir::ExprKind::Cast(expr, self.lower_ty(ty, ImplTraitContext::disallowed()))
}
ExprKind::Type(ref expr, ref ty) => {
let expr = P(self.lower_expr(expr));
hir::ExprKind::Type(expr, self.lower_ty(ty, ImplTraitContext::disallowed()))
}
ExprKind::AddrOf(m, ref ohs) => {
let m = self.lower_mutability(m);
let ohs = P(self.lower_expr(ohs));
hir::ExprKind::AddrOf(m, ohs)
}
ExprKind::Let(ref pats, ref scrutinee) => {
// If we got here, the `let` expression is not allowed.
self.sess
.struct_span_err(e.span, "`let` expressions are not supported here")
.note("only supported directly in conditions of `if`- and `while`-expressions")
.note("as well as when nested within `&&` and parenthesis in those conditions")
.emit();
// For better recovery, we emit:
// ```
// match scrutinee { pats => true, _ => false }
// ```
// While this doesn't fully match the user's intent, it has key advantages:
// 1. We can avoid using `abort_if_errors`.
// 2. We can typeck both `pats` and `scrutinee`.
// 3. `pats` is allowed to be refutable.
// 4. The return type of the block is `bool` which seems like what the user wanted.
let scrutinee = self.lower_expr(scrutinee);
let then_arm = {
let pats = pats.iter().map(|pat| self.lower_pat(pat)).collect();
let expr = self.expr_bool(e.span, true);
self.arm(pats, P(expr))
};
let else_arm = {
let pats = hir_vec![self.pat_wild(e.span)];
let expr = self.expr_bool(e.span, false);
self.arm(pats, P(expr))
};
hir::ExprKind::Match(
P(scrutinee),
vec![then_arm, else_arm].into(),
hir::MatchSource::Normal,
)
}
// FIXME(#53667): handle lowering of && and parens.
ExprKind::If(ref cond, ref then, ref else_opt) => {
// `_ => else_block` where `else_block` is `{}` if there's `None`:
let else_pat = self.pat_wild(e.span);
let (else_expr, contains_else_clause) = match else_opt {
None => (self.expr_block_empty(e.span), false),
Some(els) => (self.lower_expr(els), true),
};
let else_arm = self.arm(hir_vec![else_pat], P(else_expr));
// Handle then + scrutinee:
let then_blk = self.lower_block(then, false);
let then_expr = self.expr_block(then_blk, ThinVec::new());
let (then_pats, scrutinee, desugar) = match cond.node {
// `<pat> => <then>`
ExprKind::Let(ref pats, ref scrutinee) => {
let scrutinee = self.lower_expr(scrutinee);
let pats = pats.iter().map(|pat| self.lower_pat(pat)).collect();
let desugar = hir::MatchSource::IfLetDesugar { contains_else_clause };
(pats, scrutinee, desugar)
}
// `true => then`:
_ => {
// Lower condition:
let cond = self.lower_expr(cond);
// Wrap in a construct equivalent to `{ let _t = $cond; _t }`
// to preserve drop semantics since `if cond { ... }`
// don't let temporaries live outside of `cond`.
let span_block = self.mark_span_with_reason(IfTemporary, cond.span, None);
// Wrap in a construct equivalent to `{ let _t = $cond; _t }`
// to preserve drop semantics since `if cond { ... }` does not
// let temporaries live outside of `cond`.
let cond = self.expr_drop_temps(span_block, P(cond), ThinVec::new());
let desugar = hir::MatchSource::IfDesugar { contains_else_clause };
let pats = hir_vec![self.pat_bool(e.span, true)];
(pats, cond, desugar)
}
};
let then_arm = self.arm(then_pats, P(then_expr));
hir::ExprKind::Match(P(scrutinee), vec![then_arm, else_arm].into(), desugar)
}
// FIXME(#53667): handle lowering of && and parens.
ExprKind::While(ref cond, ref body, opt_label) => {
// Desugar `ExprWhileLet`
// from: `[opt_ident]: while let <pat> = <sub_expr> <body>`
if let ExprKind::Let(ref pats, ref sub_expr) = cond.node {
// to:
//
// [opt_ident]: loop {
// match <sub_expr> {
// <pat> => <body>,
// _ => break
// }
// }
// Note that the block AND the condition are evaluated in the loop scope.
// This is done to allow `break` from inside the condition of the loop.
let (body, break_expr, sub_expr) = self.with_loop_scope(e.id, |this| {
(
this.lower_block(body, false),
this.expr_break(e.span, ThinVec::new()),
this.with_loop_condition_scope(|this| P(this.lower_expr(sub_expr))),
)
});
// `<pat> => <body>`
let pat_arm = {
let body_expr = P(self.expr_block(body, ThinVec::new()));
let pats = pats.iter().map(|pat| self.lower_pat(pat)).collect();
self.arm(pats, body_expr)
};
// `_ => break`
let break_arm = {
let pat_under = self.pat_wild(e.span);
self.arm(hir_vec![pat_under], break_expr)
};
// `match <sub_expr> { ... }`
let arms = hir_vec![pat_arm, break_arm];
let match_expr = self.expr(
sub_expr.span,
hir::ExprKind::Match(sub_expr, arms, hir::MatchSource::WhileLetDesugar),
ThinVec::new(),
);
// `[opt_ident]: loop { ... }`
let loop_block = P(self.block_expr(P(match_expr)));
let loop_expr = hir::ExprKind::Loop(
loop_block,
self.lower_label(opt_label),
hir::LoopSource::WhileLet,
);
// Add attributes to the outer returned expr node.
loop_expr
} else {
self.with_loop_scope(e.id, |this| {
hir::ExprKind::While(
this.with_loop_condition_scope(|this| P(this.lower_expr(cond))),
this.lower_block(body, false),
this.lower_label(opt_label),
)
})
}
}
ExprKind::Loop(ref body, opt_label) => self.with_loop_scope(e.id, |this| {
hir::ExprKind::Loop(
this.lower_block(body, false),
this.lower_label(opt_label),
hir::LoopSource::Loop,
)
}),
ExprKind::TryBlock(ref body) => {
self.with_catch_scope(body.id, |this| {
let unstable_span = this.mark_span_with_reason(
CompilerDesugaringKind::TryBlock,
body.span,
this.allow_try_trait.clone(),
);
let mut block = this.lower_block(body, true).into_inner();
let tail = block.expr.take().map_or_else(
|| {
let span = this.sess.source_map().end_point(unstable_span);
hir::Expr {
span,
node: hir::ExprKind::Tup(hir_vec![]),
attrs: ThinVec::new(),
hir_id: this.next_id(),
}
},
|x: P<hir::Expr>| x.into_inner(),
);
block.expr = Some(this.wrap_in_try_constructor(
sym::from_ok, tail, unstable_span));
hir::ExprKind::Block(P(block), None)
})
}
ExprKind::Match(ref expr, ref arms) => hir::ExprKind::Match(
P(self.lower_expr(expr)),
arms.iter().map(|x| self.lower_arm(x)).collect(),
hir::MatchSource::Normal,
),
ExprKind::Async(capture_clause, closure_node_id, ref block) => {
self.make_async_expr(capture_clause, closure_node_id, None, block.span, |this| {
this.with_new_scopes(|this| {
let block = this.lower_block(block, false);
this.expr_block(block, ThinVec::new())
})
})
}
ExprKind::Await(_origin, ref expr) => self.lower_await(e.span, expr),
ExprKind::Closure(
capture_clause, asyncness, movability, ref decl, ref body, fn_decl_span
) => {
if let IsAsync::Async { closure_id, .. } = asyncness {
let outer_decl = FnDecl {
inputs: decl.inputs.clone(),
output: FunctionRetTy::Default(fn_decl_span),
c_variadic: false,
};
// We need to lower the declaration outside the new scope, because we
// have to conserve the state of being inside a loop condition for the
// closure argument types.
let fn_decl = self.lower_fn_decl(&outer_decl, None, false, None);
self.with_new_scopes(|this| {
// FIXME(cramertj): allow `async` non-`move` closures with arguments.
if capture_clause == CaptureBy::Ref &&
!decl.inputs.is_empty()
{
struct_span_err!(
this.sess,
fn_decl_span,
E0708,
"`async` non-`move` closures with arguments \
are not currently supported",
)
.help("consider using `let` statements to manually capture \
variables by reference before entering an \
`async move` closure")
.emit();
}
// Transform `async |x: u8| -> X { ... }` into
// `|x: u8| future_from_generator(|| -> X { ... })`.
let body_id = this.lower_fn_body(&outer_decl, |this| {
let async_ret_ty = if let FunctionRetTy::Ty(ty) = &decl.output {
Some(&**ty)
} else { None };
let async_body = this.make_async_expr(
capture_clause, closure_id, async_ret_ty, body.span,
|this| {
this.with_new_scopes(|this| this.lower_expr(body))
});
this.expr(fn_decl_span, async_body, ThinVec::new())
});
hir::ExprKind::Closure(
this.lower_capture_clause(capture_clause),
fn_decl,
body_id,
fn_decl_span,
None,
)
})
} else {
// Lower outside new scope to preserve `is_in_loop_condition`.
let fn_decl = self.lower_fn_decl(decl, None, false, None);
self.with_new_scopes(|this| {
this.current_item = Some(fn_decl_span);
let mut generator_kind = None;
let body_id = this.lower_fn_body(decl, |this| {
let e = this.lower_expr(body);
generator_kind = this.generator_kind;
e
});
let generator_option = this.generator_movability_for_fn(
&decl,
fn_decl_span,
generator_kind,
movability,
);
hir::ExprKind::Closure(
this.lower_capture_clause(capture_clause),
fn_decl,
body_id,
fn_decl_span,
generator_option,
)
})
}
}
ExprKind::Block(ref blk, opt_label) => {
hir::ExprKind::Block(self.lower_block(blk,
opt_label.is_some()),
self.lower_label(opt_label))
}
ExprKind::Assign(ref el, ref er) => {
hir::ExprKind::Assign(P(self.lower_expr(el)), P(self.lower_expr(er)))
}
ExprKind::AssignOp(op, ref el, ref er) => hir::ExprKind::AssignOp(
self.lower_binop(op),
P(self.lower_expr(el)),
P(self.lower_expr(er)),
),
ExprKind::Field(ref el, ident) => hir::ExprKind::Field(P(self.lower_expr(el)), ident),
ExprKind::Index(ref el, ref er) => {
hir::ExprKind::Index(P(self.lower_expr(el)), P(self.lower_expr(er)))
}
// Desugar `<start>..=<end>` into `std::ops::RangeInclusive::new(<start>, <end>)`.
ExprKind::Range(Some(ref e1), Some(ref e2), RangeLimits::Closed) => {
let id = self.next_id();
let e1 = self.lower_expr(e1);
let e2 = self.lower_expr(e2);
self.expr_call_std_assoc_fn(
id,
e.span,
&[sym::ops, sym::RangeInclusive],
"new",
hir_vec![e1, e2],
)
}
ExprKind::Range(ref e1, ref e2, lims) => {
use syntax::ast::RangeLimits::*;
let path = match (e1, e2, lims) {
(&None, &None, HalfOpen) => sym::RangeFull,
(&Some(..), &None, HalfOpen) => sym::RangeFrom,
(&None, &Some(..), HalfOpen) => sym::RangeTo,
(&Some(..), &Some(..), HalfOpen) => sym::Range,
(&None, &Some(..), Closed) => sym::RangeToInclusive,
(&Some(..), &Some(..), Closed) => unreachable!(),
(_, &None, Closed) => self.diagnostic()
.span_fatal(e.span, "inclusive range with no end")
.raise(),
};
let fields = e1.iter()
.map(|e| ("start", e))
.chain(e2.iter().map(|e| ("end", e)))
.map(|(s, e)| {
let expr = P(self.lower_expr(&e));
let ident = Ident::new(Symbol::intern(s), e.span);
self.field(ident, expr, e.span)
})
.collect::<P<[hir::Field]>>();
let is_unit = fields.is_empty();
let struct_path = [sym::ops, path];
let struct_path = self.std_path(e.span, &struct_path, None, is_unit);
let struct_path = hir::QPath::Resolved(None, P(struct_path));
return hir::Expr {
hir_id: self.lower_node_id(e.id),
node: if is_unit {
hir::ExprKind::Path(struct_path)
} else {
hir::ExprKind::Struct(P(struct_path), fields, None)
},
span: e.span,
attrs: e.attrs.clone(),
};
}
ExprKind::Path(ref qself, ref path) => {
let qpath = self.lower_qpath(
e.id,
qself,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
);
hir::ExprKind::Path(qpath)
}
ExprKind::Break(opt_label, ref opt_expr) => {
let destination = if self.is_in_loop_condition && opt_label.is_none() {
hir::Destination {
label: None,
target_id: Err(hir::LoopIdError::UnlabeledCfInWhileCondition).into(),
}
} else {
self.lower_loop_destination(opt_label.map(|label| (e.id, label)))
};
hir::ExprKind::Break(
destination,
opt_expr.as_ref().map(|x| P(self.lower_expr(x))),
)
}
ExprKind::Continue(opt_label) => {
hir::ExprKind::Continue(if self.is_in_loop_condition && opt_label.is_none() {
hir::Destination {
label: None,
target_id: Err(hir::LoopIdError::UnlabeledCfInWhileCondition).into(),
}
} else {
self.lower_loop_destination(opt_label.map(|label| (e.id, label)))
})
}
ExprKind::Ret(ref e) => hir::ExprKind::Ret(e.as_ref().map(|x| P(self.lower_expr(x)))),
ExprKind::InlineAsm(ref asm) => {
let hir_asm = hir::InlineAsm {
inputs: asm.inputs.iter().map(|&(ref c, _)| c.clone()).collect(),
outputs: asm.outputs
.iter()
.map(|out| hir::InlineAsmOutput {
constraint: out.constraint.clone(),
is_rw: out.is_rw,
is_indirect: out.is_indirect,
span: out.expr.span,
})
.collect(),
asm: asm.asm.clone(),
asm_str_style: asm.asm_str_style,
clobbers: asm.clobbers.clone().into(),
volatile: asm.volatile,
alignstack: asm.alignstack,
dialect: asm.dialect,
ctxt: asm.ctxt,
};
let outputs = asm.outputs
.iter()
.map(|out| self.lower_expr(&out.expr))
.collect();
let inputs = asm.inputs
.iter()
.map(|&(_, ref input)| self.lower_expr(input))
.collect();
hir::ExprKind::InlineAsm(P(hir_asm), outputs, inputs)
}
ExprKind::Struct(ref path, ref fields, ref maybe_expr) => hir::ExprKind::Struct(
P(self.lower_qpath(
e.id,
&None,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
)),
fields.iter().map(|x| self.lower_field(x)).collect(),
maybe_expr.as_ref().map(|x| P(self.lower_expr(x))),
),
ExprKind::Paren(ref ex) => {
let mut ex = self.lower_expr(ex);
// Include parens in span, but only if it is a super-span.
if e.span.contains(ex.span) {
ex.span = e.span;
}
// Merge attributes into the inner expression.
let mut attrs = e.attrs.clone();
attrs.extend::<Vec<_>>(ex.attrs.into());
ex.attrs = attrs;
return ex;
}
ExprKind::Yield(ref opt_expr) => {
match self.generator_kind {
Some(hir::GeneratorKind::Gen) => {},
Some(hir::GeneratorKind::Async) => {
span_err!(
self.sess,
e.span,
E0727,
"`async` generators are not yet supported",
);
self.sess.abort_if_errors();
},
None => {
self.generator_kind = Some(hir::GeneratorKind::Gen);
}
}
let expr = opt_expr
.as_ref()
.map(|x| self.lower_expr(x))
.unwrap_or_else(|| self.expr_unit(e.span));
hir::ExprKind::Yield(P(expr), hir::YieldSource::Yield)
}
ExprKind::Err => hir::ExprKind::Err,
// Desugar `ExprForLoop`
// from: `[opt_ident]: for <pat> in <head> <body>`
ExprKind::ForLoop(ref pat, ref head, ref body, opt_label) => {
// to:
//
// {
// let result = match ::std::iter::IntoIterator::into_iter(<head>) {
// mut iter => {
// [opt_ident]: loop {
// let mut __next;
// match ::std::iter::Iterator::next(&mut iter) {
// ::std::option::Option::Some(val) => __next = val,
// ::std::option::Option::None => break
// };
// let <pat> = __next;
// StmtKind::Expr(<body>);
// }
// }
// };
// result
// }
// expand <head>
let mut head = self.lower_expr(head);
let head_sp = head.span;
let desugared_span = self.mark_span_with_reason(
CompilerDesugaringKind::ForLoop,
head_sp,
None,
);
head.span = desugared_span;
let iter = Ident::with_empty_ctxt(sym::iter);
let next_ident = Ident::with_empty_ctxt(sym::__next);
let (next_pat, next_pat_hid) = self.pat_ident_binding_mode(
desugared_span,
next_ident,
hir::BindingAnnotation::Mutable,
);
// `::std::option::Option::Some(val) => __next = val`
let pat_arm = {
let val_ident = Ident::with_empty_ctxt(sym::val);
let (val_pat, val_pat_hid) = self.pat_ident(pat.span, val_ident);
let val_expr = P(self.expr_ident(pat.span, val_ident, val_pat_hid));
let next_expr = P(self.expr_ident(pat.span, next_ident, next_pat_hid));
let assign = P(self.expr(
pat.span,
hir::ExprKind::Assign(next_expr, val_expr),
ThinVec::new(),
));
let some_pat = self.pat_some(pat.span, val_pat);
self.arm(hir_vec![some_pat], assign)
};
// `::std::option::Option::None => break`
let break_arm = {
let break_expr =
self.with_loop_scope(e.id, |this| this.expr_break(e.span, ThinVec::new()));
let pat = self.pat_none(e.span);
self.arm(hir_vec![pat], break_expr)
};
// `mut iter`
let (iter_pat, iter_pat_nid) = self.pat_ident_binding_mode(
desugared_span,
iter,
hir::BindingAnnotation::Mutable
);
// `match ::std::iter::Iterator::next(&mut iter) { ... }`
let match_expr = {
let iter = P(self.expr_ident(head_sp, iter, iter_pat_nid));
let ref_mut_iter = self.expr_mut_addr_of(head_sp, iter);
let next_path = &[sym::iter, sym::Iterator, sym::next];
let next_expr = P(self.expr_call_std_path(
head_sp,
next_path,
hir_vec![ref_mut_iter],
));
let arms = hir_vec![pat_arm, break_arm];
P(self.expr(
head_sp,
hir::ExprKind::Match(
next_expr,
arms,
hir::MatchSource::ForLoopDesugar
),
ThinVec::new(),
))
};
let match_stmt = self.stmt(head_sp, hir::StmtKind::Expr(match_expr));
let next_expr = P(self.expr_ident(head_sp, next_ident, next_pat_hid));
// `let mut __next`
let next_let = self.stmt_let_pat(
desugared_span,
None,
next_pat,
hir::LocalSource::ForLoopDesugar,
);
// `let <pat> = __next`
let pat = self.lower_pat(pat);
let pat_let = self.stmt_let_pat(
head_sp,
Some(next_expr),
pat,
hir::LocalSource::ForLoopDesugar,
);
let body_block = self.with_loop_scope(e.id, |this| this.lower_block(body, false));
let body_expr = P(self.expr_block(body_block, ThinVec::new()));
let body_stmt = self.stmt(body.span, hir::StmtKind::Expr(body_expr));
let loop_block = P(self.block_all(
e.span,
hir_vec![next_let, match_stmt, pat_let, body_stmt],
None,
));
// `[opt_ident]: loop { ... }`
let loop_expr = hir::ExprKind::Loop(
loop_block,
self.lower_label(opt_label),
hir::LoopSource::ForLoop,
);
let loop_expr = P(hir::Expr {
hir_id: self.lower_node_id(e.id),
node: loop_expr,
span: e.span,
attrs: ThinVec::new(),
});
// `mut iter => { ... }`
let iter_arm = self.arm(hir_vec![iter_pat], loop_expr);
// `match ::std::iter::IntoIterator::into_iter(<head>) { ... }`
let into_iter_expr = {
let into_iter_path =
&[sym::iter, sym::IntoIterator, sym::into_iter];
P(self.expr_call_std_path(
head_sp,
into_iter_path,
hir_vec![head],
))
};
let match_expr = P(self.expr_match(
head_sp,
into_iter_expr,
hir_vec![iter_arm],
hir::MatchSource::ForLoopDesugar,
));
// This is effectively `{ let _result = ...; _result }`.
// The construct was introduced in #21984.
// FIXME(60253): Is this still necessary?
// Also, add the attributes to the outer returned expr node.
return self.expr_drop_temps(head_sp, match_expr, e.attrs.clone())
}
// Desugar `ExprKind::Try`
// from: `<expr>?`
ExprKind::Try(ref sub_expr) => {
// into:
//
// match Try::into_result(<expr>) {
// Ok(val) => #[allow(unreachable_code)] val,
// Err(err) => #[allow(unreachable_code)]
// // If there is an enclosing `catch {...}`
// break 'catch_target Try::from_error(From::from(err)),
// // Otherwise
// return Try::from_error(From::from(err)),
// }
let unstable_span = self.mark_span_with_reason(
CompilerDesugaringKind::QuestionMark,
e.span,
self.allow_try_trait.clone(),
);
let try_span = self.sess.source_map().end_point(e.span);
let try_span = self.mark_span_with_reason(
CompilerDesugaringKind::QuestionMark,
try_span,
self.allow_try_trait.clone(),
);
// `Try::into_result(<expr>)`
let discr = {
// expand <expr>
let sub_expr = self.lower_expr(sub_expr);
let path = &[sym::ops, sym::Try, sym::into_result];
P(self.expr_call_std_path(
unstable_span,
path,
hir_vec![sub_expr],
))
};
// `#[allow(unreachable_code)]`
let attr = {
// `allow(unreachable_code)`
let allow = {
let allow_ident = Ident::with_empty_ctxt(sym::allow).with_span_pos(e.span);
let uc_ident = Ident::with_empty_ctxt(sym::unreachable_code)
.with_span_pos(e.span);
let uc_nested = attr::mk_nested_word_item(uc_ident);
attr::mk_list_item(e.span, allow_ident, vec![uc_nested])
};
attr::mk_spanned_attr_outer(e.span, attr::mk_attr_id(), allow)
};
let attrs = vec![attr];
// `Ok(val) => #[allow(unreachable_code)] val,`
let ok_arm = {
let val_ident = Ident::with_empty_ctxt(sym::val);
let (val_pat, val_pat_nid) = self.pat_ident(e.span, val_ident);
let val_expr = P(self.expr_ident_with_attrs(
e.span,
val_ident,
val_pat_nid,
ThinVec::from(attrs.clone()),
));
let ok_pat = self.pat_ok(e.span, val_pat);
self.arm(hir_vec![ok_pat], val_expr)
};
// `Err(err) => #[allow(unreachable_code)]
// return Try::from_error(From::from(err)),`
let err_arm = {
let err_ident = Ident::with_empty_ctxt(sym::err);
let (err_local, err_local_nid) = self.pat_ident(try_span, err_ident);
let from_expr = {
let from_path = &[sym::convert, sym::From, sym::from];
let err_expr = self.expr_ident(try_span, err_ident, err_local_nid);
self.expr_call_std_path(try_span, from_path, hir_vec![err_expr])
};
let from_err_expr =
self.wrap_in_try_constructor(sym::from_error, from_expr, unstable_span);
let thin_attrs = ThinVec::from(attrs);
let catch_scope = self.catch_scopes.last().map(|x| *x);
let ret_expr = if let Some(catch_node) = catch_scope {
let target_id = Ok(self.lower_node_id(catch_node));
P(self.expr(
try_span,
hir::ExprKind::Break(
hir::Destination {
label: None,
target_id,
},
Some(from_err_expr),
),
thin_attrs,
))
} else {
P(self.expr(try_span, hir::ExprKind::Ret(Some(from_err_expr)), thin_attrs))
};
let err_pat = self.pat_err(try_span, err_local);
self.arm(hir_vec![err_pat], ret_expr)
};
hir::ExprKind::Match(
discr,
hir_vec![err_arm, ok_arm],
hir::MatchSource::TryDesugar,
)
}
ExprKind::Mac(_) => panic!("Shouldn't exist here"),
};
hir::Expr {
hir_id: self.lower_node_id(e.id),
node: kind,
span: e.span,
attrs: e.attrs.clone(),
}
}
fn lower_stmt(&mut self, s: &Stmt) -> SmallVec<[hir::Stmt; 1]> {
smallvec![match s.node {
StmtKind::Local(ref l) => {
let (l, item_ids) = self.lower_local(l);
let mut ids: SmallVec<[hir::Stmt; 1]> = item_ids
.into_iter()
.map(|item_id| {
let item_id = hir::ItemId { id: self.lower_node_id(item_id) };
self.stmt(s.span, hir::StmtKind::Item(item_id))
})
.collect();
ids.push({
hir::Stmt {
hir_id: self.lower_node_id(s.id),
node: hir::StmtKind::Local(P(l)),
span: s.span,
}
});
return ids;
},
StmtKind::Item(ref it) => {
// Can only use the ID once.
let mut id = Some(s.id);
return self.lower_item_id(it)
.into_iter()
.map(|item_id| {
let hir_id = id.take()
.map(|id| self.lower_node_id(id))
.unwrap_or_else(|| self.next_id());
hir::Stmt {
hir_id,
node: hir::StmtKind::Item(item_id),
span: s.span,
}
})
.collect();
}
StmtKind::Expr(ref e) => {
hir::Stmt {
hir_id: self.lower_node_id(s.id),
node: hir::StmtKind::Expr(P(self.lower_expr(e))),
span: s.span,
}
},
StmtKind::Semi(ref e) => {
hir::Stmt {
hir_id: self.lower_node_id(s.id),
node: hir::StmtKind::Semi(P(self.lower_expr(e))),
span: s.span,
}
},
StmtKind::Mac(..) => panic!("Shouldn't exist here"),
}]
}
fn lower_capture_clause(&mut self, c: CaptureBy) -> hir::CaptureClause {
match c {
CaptureBy::Value => hir::CaptureByValue,
CaptureBy::Ref => hir::CaptureByRef,
}
}
/// If an `explicit_owner` is given, this method allocates the `HirId` in
/// the address space of that item instead of the item currently being
/// lowered. This can happen during `lower_impl_item_ref()` where we need to
/// lower a `Visibility` value although we haven't lowered the owning
/// `ImplItem` in question yet.
fn lower_visibility(
&mut self,
v: &Visibility,
explicit_owner: Option<NodeId>,
) -> hir::Visibility {
let node = match v.node {
VisibilityKind::Public => hir::VisibilityKind::Public,
VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
VisibilityKind::Restricted { ref path, id } => {
debug!("lower_visibility: restricted path id = {:?}", id);
let lowered_id = if let Some(owner) = explicit_owner {
self.lower_node_id_with_owner(id, owner)
} else {
self.lower_node_id(id)
};
let res = self.expect_full_res(id);
let res = self.lower_res(res);
hir::VisibilityKind::Restricted {
path: P(self.lower_path_extra(
res,
path,
ParamMode::Explicit,
explicit_owner,
)),
hir_id: lowered_id,
}
},
VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
};
respan(v.span, node)
}
fn lower_defaultness(&self, d: Defaultness, has_value: bool) -> hir::Defaultness {
match d {
Defaultness::Default => hir::Defaultness::Default {
has_value: has_value,
},
Defaultness::Final => {
assert!(has_value);
hir::Defaultness::Final
}
}
}
fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
match *b {
BlockCheckMode::Default => hir::DefaultBlock,
BlockCheckMode::Unsafe(u) => hir::UnsafeBlock(self.lower_unsafe_source(u)),
}
}
fn lower_binding_mode(&mut self, b: &BindingMode) -> hir::BindingAnnotation {
match *b {
BindingMode::ByValue(Mutability::Immutable) => hir::BindingAnnotation::Unannotated,
BindingMode::ByRef(Mutability::Immutable) => hir::BindingAnnotation::Ref,
BindingMode::ByValue(Mutability::Mutable) => hir::BindingAnnotation::Mutable,
BindingMode::ByRef(Mutability::Mutable) => hir::BindingAnnotation::RefMut,
}
}
fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
match u {
CompilerGenerated => hir::CompilerGenerated,
UserProvided => hir::UserProvided,
}
}
fn lower_impl_polarity(&mut self, i: ImplPolarity) -> hir::ImplPolarity {
match i {
ImplPolarity::Positive => hir::ImplPolarity::Positive,
ImplPolarity::Negative => hir::ImplPolarity::Negative,
}
}
fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
match f {
TraitBoundModifier::None => hir::TraitBoundModifier::None,
TraitBoundModifier::Maybe => hir::TraitBoundModifier::Maybe,
}
}
// Helper methods for building HIR.
fn arm(&mut self, pats: hir::HirVec<P<hir::Pat>>, expr: P<hir::Expr>) -> hir::Arm {
hir::Arm {
hir_id: self.next_id(),
attrs: hir_vec![],
pats,
guard: None,
span: expr.span,
body: expr,
}
}
fn field(&mut self, ident: Ident, expr: P<hir::Expr>, span: Span) -> hir::Field {
hir::Field {
hir_id: self.next_id(),
ident,
span,
expr,
is_shorthand: false,
}
}
fn expr_break(&mut self, span: Span, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
let expr_break = hir::ExprKind::Break(self.lower_loop_destination(None), None);
P(self.expr(span, expr_break, attrs))
}
fn expr_call(
&mut self,
span: Span,
e: P<hir::Expr>,
args: hir::HirVec<hir::Expr>,
) -> hir::Expr {
self.expr(span, hir::ExprKind::Call(e, args), ThinVec::new())
}
// Note: associated functions must use `expr_call_std_path`.
fn expr_call_std_path(
&mut self,
span: Span,
path_components: &[Symbol],
args: hir::HirVec<hir::Expr>,
) -> hir::Expr {
let path = P(self.expr_std_path(span, path_components, None, ThinVec::new()));
self.expr_call(span, path, args)
}
// Create an expression calling an associated function of an std type.
//
// Associated functions cannot be resolved through the normal `std_path` function,
// as they are resolved differently and so cannot use `expr_call_std_path`.
//
// This function accepts the path component (`ty_path_components`) separately from
// the name of the associated function (`assoc_fn_name`) in order to facilitate
// separate resolution of the type and creation of a path referring to its associated
// function.
fn expr_call_std_assoc_fn(
&mut self,
ty_path_id: hir::HirId,
span: Span,
ty_path_components: &[Symbol],
assoc_fn_name: &str,
args: hir::HirVec<hir::Expr>,
) -> hir::ExprKind {
let ty_path = P(self.std_path(span, ty_path_components, None, false));
let ty = P(self.ty_path(ty_path_id, span, hir::QPath::Resolved(None, ty_path)));
let fn_seg = P(hir::PathSegment::from_ident(Ident::from_str(assoc_fn_name)));
let fn_path = hir::QPath::TypeRelative(ty, fn_seg);
let fn_expr = P(self.expr(span, hir::ExprKind::Path(fn_path), ThinVec::new()));
hir::ExprKind::Call(fn_expr, args)
}
fn expr_ident(&mut self, span: Span, ident: Ident, binding: hir::HirId) -> hir::Expr {
self.expr_ident_with_attrs(span, ident, binding, ThinVec::new())
}
fn expr_ident_with_attrs(
&mut self,
span: Span,
ident: Ident,
binding: hir::HirId,
attrs: ThinVec<Attribute>,
) -> hir::Expr {
let expr_path = hir::ExprKind::Path(hir::QPath::Resolved(
None,
P(hir::Path {
span,
res: Res::Local(binding),
segments: hir_vec![hir::PathSegment::from_ident(ident)],
}),
));
self.expr(span, expr_path, attrs)
}
fn expr_mut_addr_of(&mut self, span: Span, e: P<hir::Expr>) -> hir::Expr {
self.expr(span, hir::ExprKind::AddrOf(hir::MutMutable, e), ThinVec::new())
}
fn expr_std_path(
&mut self,
span: Span,
components: &[Symbol],
params: Option<P<hir::GenericArgs>>,
attrs: ThinVec<Attribute>,
) -> hir::Expr {
let path = self.std_path(span, components, params, true);
self.expr(
span,
hir::ExprKind::Path(hir::QPath::Resolved(None, P(path))),
attrs,
)
}
/// Wrap the given `expr` in a terminating scope using `hir::ExprKind::DropTemps`.
///
/// In terms of drop order, it has the same effect as wrapping `expr` in
/// `{ let _t = $expr; _t }` but should provide better compile-time performance.
///
/// The drop order can be important in e.g. `if expr { .. }`.
fn expr_drop_temps(
&mut self,
span: Span,
expr: P<hir::Expr>,
attrs: ThinVec<Attribute>
) -> hir::Expr {
self.expr(span, hir::ExprKind::DropTemps(expr), attrs)
}
fn expr_match(
&mut self,
span: Span,
arg: P<hir::Expr>,
arms: hir::HirVec<hir::Arm>,
source: hir::MatchSource,
) -> hir::Expr {
self.expr(span, hir::ExprKind::Match(arg, arms, source), ThinVec::new())
}
fn expr_block(&mut self, b: P<hir::Block>, attrs: ThinVec<Attribute>) -> hir::Expr {
self.expr(b.span, hir::ExprKind::Block(b, None), attrs)
}
fn expr_unit(&mut self, sp: Span) -> hir::Expr {
self.expr_tuple(sp, hir_vec![])
}
fn expr_tuple(&mut self, sp: Span, exprs: hir::HirVec<hir::Expr>) -> hir::Expr {
self.expr(sp, hir::ExprKind::Tup(exprs), ThinVec::new())
}
fn expr(&mut self, span: Span, node: hir::ExprKind, attrs: ThinVec<Attribute>) -> hir::Expr {
hir::Expr {
hir_id: self.next_id(),
node,
span,
attrs,
}
}
fn stmt(&mut self, span: Span, node: hir::StmtKind) -> hir::Stmt {
hir::Stmt { span, node, hir_id: self.next_id() }
}
fn stmt_let_pat(
&mut self,
span: Span,
init: Option<P<hir::Expr>>,
pat: P<hir::Pat>,
source: hir::LocalSource,
) -> hir::Stmt {
let local = hir::Local {
pat,
ty: None,
init,
hir_id: self.next_id(),
span,
source,
attrs: ThinVec::new()
};
self.stmt(span, hir::StmtKind::Local(P(local)))
}
fn expr_block_empty(&mut self, span: Span) -> hir::Expr {
let blk = self.block_all(span, hir_vec![], None);
self.expr_block(P(blk), ThinVec::new())
}
fn block_expr(&mut self, expr: P<hir::Expr>) -> hir::Block {
self.block_all(expr.span, hir::HirVec::new(), Some(expr))
}
fn block_all(
&mut self,
span: Span,
stmts: hir::HirVec<hir::Stmt>,
expr: Option<P<hir::Expr>>,
) -> hir::Block {
hir::Block {
stmts,
expr,
hir_id: self.next_id(),
rules: hir::DefaultBlock,
span,
targeted_by_break: false,
}
}
fn expr_unsafe(&mut self, expr: P<hir::Expr>) -> hir::Expr {
let hir_id = self.next_id();
let span = expr.span;
self.expr(
span,
hir::ExprKind::Block(P(hir::Block {
stmts: hir_vec![],
expr: Some(expr),
hir_id,
rules: hir::UnsafeBlock(hir::CompilerGenerated),
span,
targeted_by_break: false,
}), None),
ThinVec::new(),
)
}
/// Constructs a `true` or `false` literal expression.
fn expr_bool(&mut self, span: Span, val: bool) -> hir::Expr {
let lit = Spanned { span, node: LitKind::Bool(val) };
self.expr(span, hir::ExprKind::Lit(lit), ThinVec::new())
}
/// Constructs a `true` or `false` literal pattern.
fn pat_bool(&mut self, span: Span, val: bool) -> P<hir::Pat> {
let expr = self.expr_bool(span, val);
self.pat(span, hir::PatKind::Lit(P(expr)))
}
fn pat_ok(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
self.pat_std_enum(span, &[sym::result, sym::Result, sym::Ok], hir_vec![pat])
}
fn pat_err(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
self.pat_std_enum(span, &[sym::result, sym::Result, sym::Err], hir_vec![pat])
}
fn pat_some(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
self.pat_std_enum(span, &[sym::option, sym::Option, sym::Some], hir_vec![pat])
}
fn pat_none(&mut self, span: Span) -> P<hir::Pat> {
self.pat_std_enum(span, &[sym::option, sym::Option, sym::None], hir_vec![])
}
fn pat_std_enum(
&mut self,
span: Span,
components: &[Symbol],
subpats: hir::HirVec<P<hir::Pat>>,
) -> P<hir::Pat> {
let path = self.std_path(span, components, None, true);
let qpath = hir::QPath::Resolved(None, P(path));
let pt = if subpats.is_empty() {
hir::PatKind::Path(qpath)
} else {
hir::PatKind::TupleStruct(qpath, subpats, None)
};
self.pat(span, pt)
}
fn pat_ident(&mut self, span: Span, ident: Ident) -> (P<hir::Pat>, hir::HirId) {
self.pat_ident_binding_mode(span, ident, hir::BindingAnnotation::Unannotated)
}
fn pat_ident_binding_mode(
&mut self,
span: Span,
ident: Ident,
bm: hir::BindingAnnotation,
) -> (P<hir::Pat>, hir::HirId) {
let hir_id = self.next_id();
(
P(hir::Pat {
hir_id,
node: hir::PatKind::Binding(bm, hir_id, ident.with_span_pos(span), None),
span,
}),
hir_id
)
}
fn pat_wild(&mut self, span: Span) -> P<hir::Pat> {
self.pat(span, hir::PatKind::Wild)
}
fn pat(&mut self, span: Span, pat: hir::PatKind) -> P<hir::Pat> {
P(hir::Pat {
hir_id: self.next_id(),
node: pat,
span,
})
}
/// Given a suffix `["b", "c", "d"]`, returns path `::std::b::c::d` when
/// `fld.cx.use_std`, and `::core::b::c::d` otherwise.
/// The path is also resolved according to `is_value`.
fn std_path(
&mut self,
span: Span,
components: &[Symbol],
params: Option<P<hir::GenericArgs>>,
is_value: bool,
) -> hir::Path {
let (path, res) = self.resolver
.resolve_str_path(span, self.crate_root, components, is_value);
let mut segments: Vec<_> = path.segments.iter().map(|segment| {
let res = self.expect_full_res(segment.id);
hir::PathSegment {
ident: segment.ident,
hir_id: Some(self.lower_node_id(segment.id)),
res: Some(self.lower_res(res)),
infer_args: true,
args: None,
}
}).collect();
segments.last_mut().unwrap().args = params;
hir::Path {
span,
res: res.map_id(|_| panic!("unexpected node_id")),
segments: segments.into(),
}
}
fn ty_path(&mut self, mut hir_id: hir::HirId, span: Span, qpath: hir::QPath) -> hir::Ty {
let node = match qpath {
hir::QPath::Resolved(None, path) => {
// Turn trait object paths into `TyKind::TraitObject` instead.
match path.res {
Res::Def(DefKind::Trait, _) | Res::Def(DefKind::TraitAlias, _) => {
let principal = hir::PolyTraitRef {
bound_generic_params: hir::HirVec::new(),
trait_ref: hir::TraitRef {
path: path.and_then(|path| path),
hir_ref_id: hir_id,
},
span,
};
// The original ID is taken by the `PolyTraitRef`,
// so the `Ty` itself needs a different one.
hir_id = self.next_id();
hir::TyKind::TraitObject(hir_vec![principal], self.elided_dyn_bound(span))
}
_ => hir::TyKind::Path(hir::QPath::Resolved(None, path)),
}
}
_ => hir::TyKind::Path(qpath),
};
hir::Ty {
hir_id,
node,
span,
}
}
/// Invoked to create the lifetime argument for a type `&T`
/// with no explicit lifetime.
fn elided_ref_lifetime(&mut self, span: Span) -> hir::Lifetime {
match self.anonymous_lifetime_mode {
// Intercept when we are in an impl header or async fn and introduce an in-band
// lifetime.
// Hence `impl Foo for &u32` becomes `impl<'f> Foo for &'f u32` for some fresh
// `'f`.
AnonymousLifetimeMode::CreateParameter => {
let fresh_name = self.collect_fresh_in_band_lifetime(span);
hir::Lifetime {
hir_id: self.next_id(),
span,
name: hir::LifetimeName::Param(fresh_name),
}
}
AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
AnonymousLifetimeMode::Replace(replacement) => {
self.new_replacement_lifetime(replacement, span)
}
}
}
/// Report an error on illegal use of `'_` or a `&T` with no explicit lifetime;
/// return a "error lifetime".
fn new_error_lifetime(&mut self, id: Option<NodeId>, span: Span) -> hir::Lifetime {
let (id, msg, label) = match id {
Some(id) => (id, "`'_` cannot be used here", "`'_` is a reserved lifetime name"),
None => (
self.sess.next_node_id(),
"`&` without an explicit lifetime name cannot be used here",
"explicit lifetime name needed here",
),
};
let mut err = struct_span_err!(
self.sess,
span,
E0637,
"{}",
msg,
);
err.span_label(span, label);
err.emit();
self.new_named_lifetime(id, span, hir::LifetimeName::Error)
}
/// Invoked to create the lifetime argument(s) for a path like
/// `std::cell::Ref<T>`; note that implicit lifetimes in these
/// sorts of cases are deprecated. This may therefore report a warning or an
/// error, depending on the mode.
fn elided_path_lifetimes(&mut self, span: Span, count: usize) -> P<[hir::Lifetime]> {
(0..count)
.map(|_| self.elided_path_lifetime(span))
.collect()
}
fn elided_path_lifetime(&mut self, span: Span) -> hir::Lifetime {
match self.anonymous_lifetime_mode {
AnonymousLifetimeMode::CreateParameter => {
// We should have emitted E0726 when processing this path above
self.sess.delay_span_bug(
span,
"expected 'implicit elided lifetime not allowed' error",
);
let id = self.sess.next_node_id();
self.new_named_lifetime(id, span, hir::LifetimeName::Error)
}
// This is the normal case.
AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
AnonymousLifetimeMode::Replace(replacement) => {
self.new_replacement_lifetime(replacement, span)
}
AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
}
}
/// Invoked to create the lifetime argument(s) for an elided trait object
/// bound, like the bound in `Box<dyn Debug>`. This method is not invoked
/// when the bound is written, even if it is written with `'_` like in
/// `Box<dyn Debug + '_>`. In those cases, `lower_lifetime` is invoked.
fn elided_dyn_bound(&mut self, span: Span) -> hir::Lifetime {
match self.anonymous_lifetime_mode {
// NB. We intentionally ignore the create-parameter mode here.
// and instead "pass through" to resolve-lifetimes, which will apply
// the object-lifetime-defaulting rules. Elided object lifetime defaults
// do not act like other elided lifetimes. In other words, given this:
//
// impl Foo for Box<dyn Debug>
//
// we do not introduce a fresh `'_` to serve as the bound, but instead
// ultimately translate to the equivalent of:
//
// impl Foo for Box<dyn Debug + 'static>
//
// `resolve_lifetime` has the code to make that happen.
AnonymousLifetimeMode::CreateParameter => {}
AnonymousLifetimeMode::ReportError => {
// ReportError applies to explicit use of `'_`.
}
// This is the normal case.
AnonymousLifetimeMode::PassThrough => {}
// We don't need to do any replacement here as this lifetime
// doesn't refer to an elided lifetime elsewhere in the function
// signature.
AnonymousLifetimeMode::Replace(_) => {}
}
self.new_implicit_lifetime(span)
}
fn new_replacement_lifetime(
&mut self,
replacement: LtReplacement,
span: Span,
) -> hir::Lifetime {
let hir_id = self.next_id();
self.replace_elided_lifetime(hir_id, span, replacement)
}
fn new_implicit_lifetime(&mut self, span: Span) -> hir::Lifetime {
hir::Lifetime {
hir_id: self.next_id(),
span,
name: hir::LifetimeName::Implicit,
}
}
fn maybe_lint_bare_trait(&self, span: Span, id: NodeId, is_global: bool) {
self.sess.buffer_lint_with_diagnostic(
builtin::BARE_TRAIT_OBJECTS,
id,
span,
"trait objects without an explicit `dyn` are deprecated",
builtin::BuiltinLintDiagnostics::BareTraitObject(span, is_global),
)
}
fn wrap_in_try_constructor(
&mut self,
method: Symbol,
e: hir::Expr,
unstable_span: Span,
) -> P<hir::Expr> {
let path = &[sym::ops, sym::Try, method];
let from_err = P(self.expr_std_path(unstable_span, path, None,
ThinVec::new()));
P(self.expr_call(e.span, from_err, hir_vec![e]))
}
fn lower_await(
&mut self,
await_span: Span,
expr: &ast::Expr,
) -> hir::ExprKind {
// to:
//
// {
// let mut pinned = <expr>;
// loop {
// match ::std::future::poll_with_tls_context(unsafe {
// ::std::pin::Pin::new_unchecked(&mut pinned)
// }) {
// ::std::task::Poll::Ready(result) => break result,
// ::std::task::Poll::Pending => {},
// }
// yield ();
// }
// }
match self.generator_kind {
Some(hir::GeneratorKind::Async) => {},
Some(hir::GeneratorKind::Gen) |
None => {
let mut err = struct_span_err!(
self.sess,
await_span,
E0728,
"`await` is only allowed inside `async` functions and blocks"
);
err.span_label(await_span, "only allowed inside `async` functions and blocks");
if let Some(item_sp) = self.current_item {
err.span_label(item_sp, "this is not `async`");
}
err.emit();
return hir::ExprKind::Err;
}
}
let span = self.mark_span_with_reason(
CompilerDesugaringKind::Await,
await_span,
None,
);
let gen_future_span = self.mark_span_with_reason(
CompilerDesugaringKind::Await,
await_span,
self.allow_gen_future.clone(),
);
// let mut pinned = <expr>;
let expr = P(self.lower_expr(expr));
let pinned_ident = Ident::with_empty_ctxt(sym::pinned);
let (pinned_pat, pinned_pat_hid) = self.pat_ident_binding_mode(
span,
pinned_ident,
hir::BindingAnnotation::Mutable,
);
let pinned_let = self.stmt_let_pat(
span,
Some(expr),
pinned_pat,
hir::LocalSource::AwaitDesugar,
);
// ::std::future::poll_with_tls_context(unsafe {
// ::std::pin::Pin::new_unchecked(&mut pinned)
// })`
let poll_expr = {
let pinned = P(self.expr_ident(span, pinned_ident, pinned_pat_hid));
let ref_mut_pinned = self.expr_mut_addr_of(span, pinned);
let pin_ty_id = self.next_id();
let new_unchecked_expr_kind = self.expr_call_std_assoc_fn(
pin_ty_id,
span,
&[sym::pin, sym::Pin],
"new_unchecked",
hir_vec![ref_mut_pinned],
);
let new_unchecked = P(self.expr(span, new_unchecked_expr_kind, ThinVec::new()));
let unsafe_expr = self.expr_unsafe(new_unchecked);
P(self.expr_call_std_path(
gen_future_span,
&[sym::future, sym::poll_with_tls_context],
hir_vec![unsafe_expr],
))
};
// `::std::task::Poll::Ready(result) => break result`
let loop_node_id = self.sess.next_node_id();
let loop_hir_id = self.lower_node_id(loop_node_id);
let ready_arm = {
let x_ident = Ident::with_empty_ctxt(sym::result);
let (x_pat, x_pat_hid) = self.pat_ident(span, x_ident);
let x_expr = P(self.expr_ident(span, x_ident, x_pat_hid));
let ready_pat = self.pat_std_enum(
span,
&[sym::task, sym::Poll, sym::Ready],
hir_vec![x_pat],
);
let break_x = self.with_loop_scope(loop_node_id, |this| {
let expr_break = hir::ExprKind::Break(
this.lower_loop_destination(None),
Some(x_expr),
);
P(this.expr(await_span, expr_break, ThinVec::new()))
});
self.arm(hir_vec![ready_pat], break_x)
};
// `::std::task::Poll::Pending => {}`
let pending_arm = {
let pending_pat = self.pat_std_enum(
span,
&[sym::task, sym::Poll, sym::Pending],
hir_vec![],
);
let empty_block = P(self.expr_block_empty(span));
self.arm(hir_vec![pending_pat], empty_block)
};
let match_stmt = {
let match_expr = P(self.expr_match(
span,
poll_expr,
hir_vec![ready_arm, pending_arm],
hir::MatchSource::AwaitDesugar,
));
self.stmt(span, hir::StmtKind::Expr(match_expr))
};
let yield_stmt = {
let unit = self.expr_unit(span);
let yield_expr = P(self.expr(
span,
hir::ExprKind::Yield(P(unit), hir::YieldSource::Await),
ThinVec::new(),
));
self.stmt(span, hir::StmtKind::Expr(yield_expr))
};
let loop_block = P(self.block_all(
span,
hir_vec![match_stmt, yield_stmt],
None,
));
let loop_expr = P(hir::Expr {
hir_id: loop_hir_id,
node: hir::ExprKind::Loop(
loop_block,
None,
hir::LoopSource::Loop,
),
span,
attrs: ThinVec::new(),
});
hir::ExprKind::Block(
P(self.block_all(span, hir_vec![pinned_let], Some(loop_expr))),
None,
)
}
}
fn body_ids(bodies: &BTreeMap<hir::BodyId, hir::Body>) -> Vec<hir::BodyId> {
// Sorting by span ensures that we get things in order within a
// file, and also puts the files in a sensible order.
let mut body_ids: Vec<_> = bodies.keys().cloned().collect();
body_ids.sort_by_key(|b| bodies[b].value.span);
body_ids
}
/// Checks if the specified expression is a built-in range literal.
/// (See: `LoweringContext::lower_expr()`).
pub fn is_range_literal(sess: &Session, expr: &hir::Expr) -> bool {
use hir::{Path, QPath, ExprKind, TyKind};
// Returns whether the given path represents a (desugared) range,
// either in std or core, i.e. has either a `::std::ops::Range` or
// `::core::ops::Range` prefix.
fn is_range_path(path: &Path) -> bool {
let segs: Vec<_> = path.segments.iter().map(|seg| seg.ident.as_str().to_string()).collect();
let segs: Vec<_> = segs.iter().map(|seg| &**seg).collect();
// "{{root}}" is the equivalent of `::` prefix in `Path`.
if let ["{{root}}", std_core, "ops", range] = segs.as_slice() {
(*std_core == "std" || *std_core == "core") && range.starts_with("Range")
} else {
false
}
};
// Check whether a span corresponding to a range expression is a
// range literal, rather than an explicit struct or `new()` call.
fn is_lit(sess: &Session, span: &Span) -> bool {
let source_map = sess.source_map();
let end_point = source_map.end_point(*span);
if let Ok(end_string) = source_map.span_to_snippet(end_point) {
!(end_string.ends_with("}") || end_string.ends_with(")"))
} else {
false
}
};
match expr.node {
// All built-in range literals but `..=` and `..` desugar to `Struct`s.
ExprKind::Struct(ref qpath, _, _) => {
if let QPath::Resolved(None, ref path) = **qpath {
return is_range_path(&path) && is_lit(sess, &expr.span);
}
}
// `..` desugars to its struct path.
ExprKind::Path(QPath::Resolved(None, ref path)) => {
return is_range_path(&path) && is_lit(sess, &expr.span);
}
// `..=` desugars into `::std::ops::RangeInclusive::new(...)`.
ExprKind::Call(ref func, _) => {
if let ExprKind::Path(QPath::TypeRelative(ref ty, ref segment)) = func.node {
if let TyKind::Path(QPath::Resolved(None, ref path)) = ty.node {
let new_call = segment.ident.as_str() == "new";
return is_range_path(&path) && is_lit(sess, &expr.span) && new_call;
}
}
}
_ => {}
}
false
}