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fuchsia / third_party / rust / 00d159095adbb14c7dfaa6a77177be1b58600dc9 / . / src / librustc / hir / lowering.rs
blob: 492029eed05706adbcb1ff8f872bca13a5e0b300 [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.
mod expr;
mod item;
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::{Namespace, Res, DefKind, PartialRes, PerNS};
use crate::hir::{GenericArg, ConstArg};
use crate::hir::ptr::P;
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::BTreeMap;
use std::mem;
use smallvec::SmallVec;
use syntax::attr;
use syntax::ast;
use syntax::ptr::P as AstP;
use syntax::ast::*;
use syntax::errors;
use syntax::ext::base::SpecialDerives;
use syntax::ext::hygiene::ExpnId;
use syntax::print::pprust;
use syntax::source_map::{respan, ExpnData, ExpnKind, DesugaringKind, Spanned};
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::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 AST nodes.
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>,
non_exported_macro_attrs: Vec<ast::Attribute>,
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)>,
/// `true` if 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.
///
/// We always store a `modern()` version of the param-name in this
/// vector.
in_scope_lifetimes: Vec<ParamName>,
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 {
/// Obtains resolution for a `NodeId` with a single resolution.
fn get_partial_res(&mut self, id: NodeId) -> Option<PartialRes>;
/// Obtains per-namespace resolutions for `use` statement with the given `NodeId`.
fn get_import_res(&mut self, id: NodeId) -> PerNS<Option<Res<NodeId>>>;
/// Obtains 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],
ns: Namespace,
) -> (ast::Path, Res<NodeId>);
fn has_derives(&self, node_id: NodeId, derives: SpecialDerives) -> bool;
}
/// 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 opaque type.
/// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually
/// equivalent to a new opaque type like `type T = impl Debug; 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).
OpaqueTy(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),
OpaqueTy(fn_def_id) => OpaqueTy(*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: sess.parse_sess.injected_crate_name.try_get().copied(),
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(),
non_exported_macro_attrs: 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, Debug)]
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,
}
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,
ExpnId::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) {
if let PatKind::Paren(..) | PatKind::Rest = p.node {
// Doesn't generate a HIR node
} else if let Some(owner) = self.hir_id_owner {
self.lctx.lower_node_id_with_owner(p.id, owner);
}
visit::walk_pat(self, p)
}
// HACK(or_patterns; Centril | dlrobertson): Avoid creating
// HIR nodes for `PatKind::Or` for the top level of a `ast::Arm`.
// This is a temporary hack that should go away once we push down
// `arm.pats: HirVec<P<Pat>>` -> `arm.pat: P<Pat>` to HIR. // Centril
fn visit_arm(&mut self, arm: &'tcx Arm) {
match &arm.pat.node {
PatKind::Or(pats) => pats.iter().for_each(|p| self.visit_pat(p)),
_ => self.visit_pat(&arm.pat),
}
walk_list!(self, visit_expr, &arm.guard);
self.visit_expr(&arm.body);
walk_list!(self, visit_attribute, &arm.attrs);
}
// HACK(or_patterns; Centril | dlrobertson): Same as above. // Centril
fn visit_expr(&mut self, e: &'tcx Expr) {
if let ExprKind::Let(pat, scrutinee) = &e.node {
walk_list!(self, visit_attribute, e.attrs.iter());
match &pat.node {
PatKind::Or(pats) => pats.iter().for_each(|p| self.visit_pat(p)),
_ => self.visit_pat(&pat),
}
self.visit_expr(scrutinee);
self.visit_expr_post(e);
return;
}
visit::walk_expr(self, e)
}
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::TyAlias(_, ref generics)
| ItemKind::OpaqueTy(_, 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 parameter in &f.decl.inputs {
// We don't lower the ids of argument patterns
self.with_hir_id_owner(None, |this| {
this.visit_pat(&parameter.pat);
});
self.visit_ty(&parameter.ty)
}
self.visit_fn_ret_ty(&f.decl.output)
}
_ => visit::walk_ty(self, t),
}
}
}
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 item::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),
non_exported_macro_attrs: hir::HirVec::from(self.non_exported_macro_attrs),
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 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 `NodeId` 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: DesugaringKind,
span: Span,
allow_internal_unstable: Option<Lrc<[Symbol]>>,
) -> Span {
span.fresh_expansion(ExpnData {
allow_internal_unstable,
..ExpnData::default(ExpnKind::Desugaring(reason), span, self.sess.edition())
})
}
fn with_anonymous_lifetime_mode<R>(
&mut self,
anonymous_lifetime_mode: AnonymousLifetimeMode,
op: impl FnOnce(&mut Self) -> R,
) -> R {
debug!(
"with_anonymous_lifetime_mode(anonymous_lifetime_mode={:?})",
anonymous_lifetime_mode,
);
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;
debug!("with_anonymous_lifetime_mode: restoring 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
/// parameter 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),
ExpnId::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(&ParamName::Plain(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(ParamName::Plain(param.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
/// parameter 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))
})
},
);
let mut lowered_params: Vec<_> = 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_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.params = lowered_params.into();
(lowered_generics, res)
}
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::take(&mut self.catch_scopes);
let loop_scopes = mem::take(&mut self.loop_scopes);
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_attrs_extendable(&mut self, attrs: &[Attribute]) -> Vec<Attribute> {
attrs
.iter()
.map(|a| self.lower_attr(a))
.collect()
}
fn lower_attrs(&mut self, attrs: &[Attribute]) -> hir::HirVec<Attribute> {
self.lower_attrs_extendable(attrs).into()
}
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(),
}
}
/// 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,
constraint: &AssocTyConstraint,
itctx: ImplTraitContext<'_>,
) -> hir::TypeBinding {
debug!("lower_assoc_ty_constraint(constraint={:?}, itctx={:?})", constraint, itctx);
let kind = match constraint.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::OpaqueTy(_) => (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 opaque type).
//
// FIXME: this is only needed until `impl Trait` is allowed in type aliases.
ImplTraitContext::Disallowed(_) if self.is_in_dyn_type =>
(true, ImplTraitContext::OpaqueTy(None)),
// We are in the parameter 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,
ExpnId::root(),
constraint.span,
);
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: constraint.span,
},
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(constraint.id),
ident: constraint.ident,
kind,
span: constraint.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),
param_names: this.lower_fn_params_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_dummy_span(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::OpaqueTy(fn_def_id) => {
self.lower_opaque_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_and_span(&pprust::ty_to_string(t), 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_opaque_impl_trait(
&mut self,
span: Span,
fn_def_id: Option<DefId>,
opaque_ty_node_id: NodeId,
lower_bounds: impl FnOnce(&mut LoweringContext<'_>) -> hir::GenericBounds,
) -> hir::TyKind {
debug!(
"lower_opaque_impl_trait(fn_def_id={:?}, opaque_ty_node_id={:?}, span={:?})",
fn_def_id,
opaque_ty_node_id,
span,
);
// 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 opaque_ty_span = self.mark_span_with_reason(
DesugaringKind::OpaqueTy,
span,
None,
);
let opaque_ty_def_index = self
.resolver
.definitions()
.opt_def_index(opaque_ty_node_id)
.unwrap();
self.allocate_hir_id_counter(opaque_ty_node_id);
let hir_bounds = self.with_hir_id_owner(opaque_ty_node_id, lower_bounds);
let (lifetimes, lifetime_defs) = self.lifetimes_from_impl_trait_bounds(
opaque_ty_node_id,
opaque_ty_def_index,
&hir_bounds,
);
debug!(
"lower_opaque_impl_trait: lifetimes={:#?}", lifetimes,
);
debug!(
"lower_opaque_impl_trait: lifetime_defs={:#?}", lifetime_defs,
);
self.with_hir_id_owner(opaque_ty_node_id, |lctx| {
let opaque_ty_item = hir::OpaqueTy {
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::OpaqueTyOrigin::FnReturn,
};
trace!("lower_opaque_impl_trait: {:#?}", opaque_ty_def_index);
let opaque_ty_id = lctx.generate_opaque_type(
opaque_ty_node_id,
opaque_ty_item,
span,
opaque_ty_span,
);
// `impl Trait` now just becomes `Foo<'a, 'b, ..>`.
hir::TyKind::Def(hir::ItemId { id: opaque_ty_id }, lifetimes)
})
}
/// Registers a new opaque type with the proper `NodeId`s and
/// returns the lowered node-ID for the opaque type.
fn generate_opaque_type(
&mut self,
opaque_ty_node_id: NodeId,
opaque_ty_item: hir::OpaqueTy,
span: Span,
opaque_ty_span: Span,
) -> hir::HirId {
let opaque_ty_item_kind = hir::ItemKind::OpaqueTy(opaque_ty_item);
let opaque_ty_id = self.lower_node_id(opaque_ty_node_id);
// Generate an `type Foo = impl Trait;` declaration.
trace!("registering opaque type with id {:#?}", opaque_ty_id);
let opaque_ty_item = hir::Item {
hir_id: opaque_ty_id,
ident: Ident::invalid(),
attrs: Default::default(),
node: opaque_ty_item_kind,
vis: respan(span.shrink_to_lo(), hir::VisibilityKind::Inherited),
span: opaque_ty_span,
};
// Insert the item into the global item list. This usually happens
// automatically for all AST items. But this opaque type item
// does not actually exist in the AST.
self.insert_item(opaque_ty_item);
opaque_ty_id
}
fn lifetimes_from_impl_trait_bounds(
&mut self,
opaque_ty_id: NodeId,
parent_index: DefIndex,
bounds: &hir::GenericBounds,
) -> (HirVec<hir::GenericArg>, HirVec<hir::GenericParam>) {
debug!(
"lifetimes_from_impl_trait_bounds(opaque_ty_id={:?}, \
parent_index={:?}, \
bounds={:#?})",
opaque_ty_id, parent_index, bounds,
);
// 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,
opaque_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
// `type Foo<'_> = impl SomeTrait<'_>;`.
hir::LifetimeName::Underscore
} else {
return;
}
}
hir::LifetimeName::Param(_) => lifetime.name,
// Refers to some other lifetime that is "in
// scope" within the type.
hir::LifetimeName::ImplicitObjectLifetimeDefault => return,
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.opaque_ty_id);
self.context.resolver.definitions().create_def_with_parent(
self.parent,
def_node_id,
DefPathData::LifetimeNs(name.ident().as_interned_str()),
ExpnId::root(),
lifetime.span);
let (name, kind) = match name {
hir::LifetimeName::Underscore => (
hir::ParamName::Plain(Ident::with_dummy_span(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,
opaque_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_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 => {
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_dummy_span(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::OpaqueTy(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_fn_params_to_names(&mut self, decl: &FnDecl) -> hir::HirVec<Ident> {
decl.inputs
.iter()
.map(|param| match param.pat.node {
PatKind::Ident(_, ident, _) => ident,
_ => Ident::new(kw::Invalid, param.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 opaque `impl Trait` 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 inputs = self.with_anonymous_lifetime_mode(lt_mode, |this| {
decl.inputs
.iter()
.map(|param| {
if let Some((_, ibty)) = &mut in_band_ty_params {
this.lower_ty_direct(&param.ty, ImplTraitContext::Universal(ibty))
} else {
this.lower_ty_direct(&param.ty, ImplTraitContext::disallowed())
}
})
.collect::<HirVec<_>>()
});
let output = if let Some(ret_id) = make_ret_async {
self.lower_async_fn_ret_ty(
&decl.output,
in_band_ty_params.expect("`make_ret_async` but no `fn_def_id`").0,
ret_id,
)
} 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::OpaqueTy(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 `-> OpaqueTy { .. }`
// combined with the following definition of `OpaqueTy`:
//
// type OpaqueTy<generics_from_parent_fn> = impl Future<Output = T>;
//
// `inputs`: lowered types of parameters 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)
// `opaque_ty_node_id`: `NodeId` of the opaque `impl Trait` 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,
opaque_ty_node_id: NodeId,
) -> hir::FunctionRetTy {
debug!(
"lower_async_fn_ret_ty(\
output={:?}, \
fn_def_id={:?}, \
opaque_ty_node_id={:?})",
output, fn_def_id, opaque_ty_node_id,
);
let span = output.span();
let opaque_ty_span = self.mark_span_with_reason(
DesugaringKind::Async,
span,
None,
);
let opaque_ty_def_index = self
.resolver
.definitions()
.opt_def_index(opaque_ty_node_id)
.unwrap();
self.allocate_hir_id_counter(opaque_ty_node_id);
// When we create the opaque type for this async fn, it is going to have
// to capture all the lifetimes involved in the signature (including in the
// return type). This is done by introducing lifetime parameters for:
//
// - all the explicitly declared lifetimes from the impl and function itself;
// - all the elided lifetimes in the fn arguments;
// - all the elided lifetimes in the return type.
//
// So for example in this snippet:
//
// ```rust
// impl<'a> Foo<'a> {
// async fn bar<'b>(&self, x: &'b Vec<f64>, y: &str) -> &u32 {
// // ^ '0 ^ '1 ^ '2
// // elided lifetimes used below
// }
// }
// ```
//
// we would create an opaque type like:
//
// ```
// type Bar<'a, 'b, '0, '1, '2> = impl Future<Output = &'2 u32>;
// ```
//
// and we would then desugar `bar` to the equivalent of:
//
// ```rust
// impl<'a> Foo<'a> {
// fn bar<'b, '0, '1>(&'0 self, x: &'b Vec<f64>, y: &'1 str) -> Bar<'a, 'b, '0, '1, '_>
// }
// ```
//
// Note that the final parameter to `Bar` is `'_`, not `'2` --
// this is because the elided lifetimes from the return type
// should be figured out using the ordinary elision rules, and
// this desugaring achieves that.
//
// The variable `input_lifetimes_count` tracks the number of
// lifetime parameters to the opaque type *not counting* those
// lifetimes elided in the return type. This includes those
// that are explicitly declared (`in_scope_lifetimes`) and
// those elided lifetimes we found in the arguments (current
// content of `lifetimes_to_define`). Next, we will process
// the return type, which will cause `lifetimes_to_define` to
// grow.
let input_lifetimes_count = self.in_scope_lifetimes.len() + self.lifetimes_to_define.len();
let (opaque_ty_id, lifetime_params) = self.with_hir_id_owner(opaque_ty_node_id, |this| {
// We have to be careful to get elision right here. The
// idea is that we create a lifetime parameter for each
// lifetime in the return type. So, given a return type
// like `async fn foo(..) -> &[&u32]`, we lower to `impl
// Future<Output = &'1 [ &'2 u32 ]>`.
//
// Then, we will create `fn foo(..) -> Foo<'_, '_>`, and
// hence the elision takes place at the fn site.
let future_bound = this.with_anonymous_lifetime_mode(
AnonymousLifetimeMode::CreateParameter,
|this| this.lower_async_fn_output_type_to_future_bound(
output,
fn_def_id,
span,
),
);
debug!("lower_async_fn_ret_ty: future_bound={:#?}", future_bound);
// Calculate all the lifetimes that should be captured
// by the opaque 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(|name| (name.ident().span, name))
.chain(this.lifetimes_to_define.iter().cloned())
.collect();
debug!("lower_async_fn_ret_ty: in_scope_lifetimes={:#?}", this.in_scope_lifetimes);
debug!("lower_async_fn_ret_ty: lifetimes_to_define={:#?}", this.lifetimes_to_define);
debug!("lower_async_fn_ret_ty: lifetime_params={:#?}", lifetime_params);
let generic_params =
lifetime_params
.iter().cloned()
.map(|(span, hir_name)| {
this.lifetime_to_generic_param(span, hir_name, opaque_ty_def_index)
})
.collect();
let opaque_ty_item = hir::OpaqueTy {
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::OpaqueTyOrigin::AsyncFn,
};
trace!("exist ty from async fn def index: {:#?}", opaque_ty_def_index);
let opaque_ty_id = this.generate_opaque_type(
opaque_ty_node_id,
opaque_ty_item,
span,
opaque_ty_span,
);
(opaque_ty_id, lifetime_params)
});
// As documented above on the variable
// `input_lifetimes_count`, we need to create the lifetime
// arguments to our opaque type. Continuing with our example,
// we're creating the type arguments for the return type:
//
// ```
// Bar<'a, 'b, '0, '1, '_>
// ```
//
// For the "input" lifetime parameters, we wish to create
// references to the parameters themselves, including the
// "implicit" ones created from parameter types (`'a`, `'b`,
// '`0`, `'1`).
//
// For the "output" lifetime parameters, we just want to
// generate `'_`.
let mut generic_args: Vec<_> =
lifetime_params[..input_lifetimes_count]
.iter()
.map(|&(span, hir_name)| {
// Input lifetime like `'a` or `'1`:
GenericArg::Lifetime(hir::Lifetime {
hir_id: self.next_id(),
span,
name: hir::LifetimeName::Param(hir_name),
})
})
.collect();
generic_args.extend(
lifetime_params[input_lifetimes_count..]
.iter()
.map(|&(span, _)| {
// Output lifetime like `'_`.
GenericArg::Lifetime(hir::Lifetime {
hir_id: self.next_id(),
span,
name: hir::LifetimeName::Implicit,
})
})
);
// Create the `Foo<...>` refernece itself. Note that the `type
// Foo = impl Trait` is, internally, created as a child of the
// async fn, so the *type parameters* are inherited. It's
// only the lifetime parameters that we must supply.
let opaque_ty_ref = hir::TyKind::Def(hir::ItemId { id: opaque_ty_id }, generic_args.into());
hir::FunctionRetTy::Return(P(hir::Ty {
node: opaque_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::OpaqueTy(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_dummy_span(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 =
P(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),
},
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,
}
}
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::ImplicitObjectLifetimeDefault => {
span_bug!(
param.ident.span,
"object-lifetime-default should not occur here",
);
}
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, .. } => {
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::OpaqueTy(None))
}),
synthetic: param.attrs.iter()
.filter(|attr| attr.check_name(sym::rustc_synthetic))
.map(|_| hir::SyntheticTyParamKind::ImplTrait)
.next(),
};
(hir::ParamName::Plain(param.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_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,
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_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(&mut self, b: &Block, targeted_by_break: bool) -> P<hir::Block> {
let mut stmts = vec![];
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_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) => {
let lower_sub = |this: &mut Self| sub.as_ref().map(|x| this.lower_pat(x));
self.lower_pat_ident(p, binding_mode, ident, lower_sub)
}
PatKind::Lit(ref e) => hir::PatKind::Lit(P(self.lower_expr(e))),
PatKind::TupleStruct(ref path, ref pats) => {
let qpath = self.lower_qpath(
p.id,
&None,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
);
let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple struct");
hir::PatKind::TupleStruct(qpath, pats, ddpos)
}
PatKind::Or(ref pats) => {
hir::PatKind::Or(pats.iter().map(|x| self.lower_pat(x)).collect())
}
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| hir::FieldPat {
hir_id: self.next_id(),
ident: f.ident,
pat: self.lower_pat(&f.pat),
is_shorthand: f.is_shorthand,
span: f.span,
})
.collect();
hir::PatKind::Struct(qpath, fs, etc)
}
PatKind::Tuple(ref pats) => {
let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple");
hir::PatKind::Tuple(pats, 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 pats) => self.lower_pat_slice(pats),
PatKind::Rest => {
// If we reach here the `..` pattern is not semantically allowed.
self.ban_illegal_rest_pat(p.span)
}
PatKind::Paren(ref inner) => return self.lower_pat(inner),
PatKind::Mac(_) => panic!("Shouldn't exist here"),
};
self.pat_with_node_id_of(p, node)
}
fn lower_pat_tuple(
&mut self,
pats: &[AstP<Pat>],
ctx: &str,
) -> (HirVec<P<hir::Pat>>, Option<usize>) {
let mut elems = Vec::with_capacity(pats.len());
let mut rest = None;
let mut iter = pats.iter().enumerate();
while let Some((idx, pat)) = iter.next() {
// Interpret the first `..` pattern as a subtuple pattern.
if pat.is_rest() {
rest = Some((idx, pat.span));
break;
}
// It was not a subslice pattern so lower it normally.
elems.push(self.lower_pat(pat));
}
while let Some((_, pat)) = iter.next() {
// There was a previous subtuple pattern; make sure we don't allow more.
if pat.is_rest() {
self.ban_extra_rest_pat(pat.span, rest.unwrap().1, ctx);
} else {
elems.push(self.lower_pat(pat));
}
}
(elems.into(), rest.map(|(ddpos, _)| ddpos))
}
fn lower_pat_slice(&mut self, pats: &[AstP<Pat>]) -> hir::PatKind {
let mut before = Vec::new();
let mut after = Vec::new();
let mut slice = None;
let mut prev_rest_span = None;
let mut iter = pats.iter();
while let Some(pat) = iter.next() {
// Interpret the first `((ref mut?)? x @)? ..` pattern as a subslice pattern.
match pat.node {
PatKind::Rest => {
prev_rest_span = Some(pat.span);
slice = Some(self.pat_wild_with_node_id_of(pat));
break;
},
PatKind::Ident(ref bm, ident, Some(ref sub)) if sub.is_rest() => {
prev_rest_span = Some(sub.span);
let lower_sub = |this: &mut Self| Some(this.pat_wild_with_node_id_of(sub));
let node = self.lower_pat_ident(pat, bm, ident, lower_sub);
slice = Some(self.pat_with_node_id_of(pat, node));
break;
},
_ => {}
}
// It was not a subslice pattern so lower it normally.
before.push(self.lower_pat(pat));
}
while let Some(pat) = iter.next() {
// There was a previous subslice pattern; make sure we don't allow more.
let rest_span = match pat.node {
PatKind::Rest => Some(pat.span),
PatKind::Ident(.., Some(ref sub)) if sub.is_rest() => {
// The `HirValidator` is merciless; add a `_` pattern to avoid ICEs.
after.push(self.pat_wild_with_node_id_of(pat));
Some(sub.span)
},
_ => None,
};
if let Some(rest_span) = rest_span {
self.ban_extra_rest_pat(rest_span, prev_rest_span.unwrap(), "slice");
} else {
after.push(self.lower_pat(pat));
}
}
hir::PatKind::Slice(before.into(), slice, after.into())
}
fn lower_pat_ident(
&mut self,
p: &Pat,
binding_mode: &BindingMode,
ident: Ident,
lower_sub: impl FnOnce(&mut Self) -> Option<P<hir::Pat>>,
) -> hir::PatKind {
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,
lower_sub(self),
)
}
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)],
}),
)),
}
}
fn pat_wild_with_node_id_of(&mut self, p: &Pat) -> P<hir::Pat> {
self.pat_with_node_id_of(p, hir::PatKind::Wild)
}
/// Construct a `Pat` with the `HirId` of `p.id` lowered.
fn pat_with_node_id_of(&mut self, p: &Pat, node: hir::PatKind) -> P<hir::Pat> {
P(hir::Pat {
hir_id: self.lower_node_id(p.id),
node,
span: p.span,
})
}
/// Emit a friendly error for extra `..` patterns in a tuple/tuple struct/slice pattern.
fn ban_extra_rest_pat(&self, sp: Span, prev_sp: Span, ctx: &str) {
self.diagnostic()
.struct_span_err(sp, &format!("`..` can only be used once per {} pattern", ctx))
.span_label(sp, &format!("can only be used once per {} pattern", ctx))
.span_label(prev_sp, "previously used here")
.emit();
}
/// Used to ban the `..` pattern in places it shouldn't be semantically.
fn ban_illegal_rest_pat(&self, sp: Span) -> hir::PatKind {
self.diagnostic()
.struct_span_err(sp, "`..` patterns are not allowed here")
.note("only allowed in tuple, tuple struct, and slice patterns")
.emit();
// We're not in a list context so `..` can be reasonably treated
// as `_` because it should always be valid and roughly matches the
// intent of `..` (notice that the rest of a single slot is that slot).
hir::PatKind::Wild
}
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_stmt(&mut self, s: &Stmt) -> SmallVec<[hir::Stmt; 1]> {
let node = 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::StmtKind::Expr(P(self.lower_expr(e))),
StmtKind::Semi(ref e) => hir::StmtKind::Semi(P(self.lower_expr(e))),
StmtKind::Mac(..) => panic!("shouldn't exist here"),
};
smallvec![hir::Stmt {
hir_id: self.lower_node_id(s.id),
node,
span: s.span,
}]
}
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_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 stmt(&mut self, span: Span, node: hir::StmtKind) -> hir::Stmt {
hir::Stmt { span, node, hir_id: self.next_id() }
}
fn stmt_expr(&mut self, span: Span, expr: hir::Expr) -> hir::Stmt {
self.stmt(span, hir::StmtKind::Expr(P(expr)))
}
fn stmt_let_pat(
&mut self,
attrs: ThinVec<Attribute>,
span: Span,
init: Option<P<hir::Expr>>,
pat: P<hir::Pat>,
source: hir::LocalSource,
) -> hir::Stmt {
let local = hir::Local {
attrs,
hir_id: self.next_id(),
init,
pat,
source,
span,
ty: None,
};
self.stmt(span, hir::StmtKind::Local(P(local)))
}
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,
}
}
/// 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 ns = if is_value { Namespace::ValueNS } else { Namespace::TypeNS };
let (path, res) = self.resolver.resolve_str_path(span, self.crate_root, components, ns);
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 `NodeId`")),
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,
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),
}
}
/// 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::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 => {}
}
let r = hir::Lifetime {
hir_id: self.next_id(),
span,
name: hir::LifetimeName::ImplicitObjectLifetimeDefault,
};
debug!("elided_dyn_bound: r={:?}", r);
r
}
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) {
// FIXME(davidtwco): This is a hack to detect macros which produce spans of the
// call site which do not have a macro backtrace. See #61963.
let is_macro_callsite = self.sess.source_map()
.span_to_snippet(span)
.map(|snippet| snippet.starts_with("#["))
.unwrap_or(true);
if !is_macro_callsite {
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 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
}