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fuchsia / third_party / rust / 20d43d03dd27568f609d621ce44673393e838892 / . / src / librustc_typeck / astconv.rs
blob: 09e6b76900396de821f7010af30c52db6186a7dc [file] [log] [blame]
//! Conversion from AST representation of types to the `ty.rs` representation.
//! The main routine here is `ast_ty_to_ty()`; each use is parameterized by an
//! instance of `AstConv`.
use errors::{Applicability, DiagnosticId};
use crate::hir::{self, GenericArg, GenericArgs, ExprKind};
use crate::hir::def::{CtorOf, Res, DefKind};
use crate::hir::def_id::DefId;
use crate::hir::HirVec;
use crate::hir::ptr::P;
use crate::lint;
use crate::middle::lang_items::SizedTraitLangItem;
use crate::middle::resolve_lifetime as rl;
use crate::namespace::Namespace;
use rustc::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
use rustc::traits;
use rustc::ty::{self, DefIdTree, Ty, TyCtxt, Const, ToPredicate, TypeFoldable};
use rustc::ty::{GenericParamDef, GenericParamDefKind};
use rustc::ty::subst::{Kind, Subst, InternalSubsts, SubstsRef};
use rustc::ty::wf::object_region_bounds;
use rustc::mir::interpret::ConstValue;
use rustc_target::spec::abi;
use crate::require_c_abi_if_c_variadic;
use smallvec::SmallVec;
use syntax::ast;
use syntax::errors::pluralise;
use syntax::feature_gate::{GateIssue, emit_feature_err};
use syntax::util::lev_distance::find_best_match_for_name;
use syntax::symbol::sym;
use syntax_pos::{DUMMY_SP, Span, MultiSpan};
use crate::util::common::ErrorReported;
use crate::util::nodemap::FxHashMap;
use std::collections::BTreeSet;
use std::iter;
use std::slice;
use rustc_data_structures::fx::FxHashSet;
#[derive(Debug)]
pub struct PathSeg(pub DefId, pub usize);
pub trait AstConv<'tcx> {
fn tcx<'a>(&'a self) -> TyCtxt<'tcx>;
/// Returns predicates in scope of the form `X: Foo`, where `X` is
/// a type parameter `X` with the given id `def_id`. This is a
/// subset of the full set of predicates.
///
/// This is used for one specific purpose: resolving "short-hand"
/// associated type references like `T::Item`. In principle, we
/// would do that by first getting the full set of predicates in
/// scope and then filtering down to find those that apply to `T`,
/// but this can lead to cycle errors. The problem is that we have
/// to do this resolution *in order to create the predicates in
/// the first place*. Hence, we have this "special pass".
fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
-> &'tcx ty::GenericPredicates<'tcx>;
/// Returns the lifetime to use when a lifetime is omitted (and not elided).
fn re_infer(
&self,
param: Option<&ty::GenericParamDef>,
span: Span,
)
-> Option<ty::Region<'tcx>>;
/// Returns the type to use when a type is omitted.
fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx>;
/// Returns the const to use when a const is omitted.
fn ct_infer(
&self,
ty: Ty<'tcx>,
param: Option<&ty::GenericParamDef>,
span: Span,
) -> &'tcx Const<'tcx>;
/// Projecting an associated type from a (potentially)
/// higher-ranked trait reference is more complicated, because of
/// the possibility of late-bound regions appearing in the
/// associated type binding. This is not legal in function
/// signatures for that reason. In a function body, we can always
/// handle it because we can use inference variables to remove the
/// late-bound regions.
fn projected_ty_from_poly_trait_ref(&self,
span: Span,
item_def_id: DefId,
poly_trait_ref: ty::PolyTraitRef<'tcx>)
-> Ty<'tcx>;
/// Normalize an associated type coming from the user.
fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx>;
/// Invoked when we encounter an error from some prior pass
/// (e.g., resolve) that is translated into a ty-error. This is
/// used to help suppress derived errors typeck might otherwise
/// report.
fn set_tainted_by_errors(&self);
fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
}
pub enum SizedByDefault {
Yes,
No,
}
struct ConvertedBinding<'a, 'tcx> {
item_name: ast::Ident,
kind: ConvertedBindingKind<'a, 'tcx>,
span: Span,
}
enum ConvertedBindingKind<'a, 'tcx> {
Equality(Ty<'tcx>),
Constraint(&'a [hir::GenericBound]),
}
#[derive(PartialEq)]
enum GenericArgPosition {
Type,
Value, // e.g., functions
MethodCall,
}
impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
pub fn ast_region_to_region(&self,
lifetime: &hir::Lifetime,
def: Option<&ty::GenericParamDef>)
-> ty::Region<'tcx>
{
let tcx = self.tcx();
let lifetime_name = |def_id| {
tcx.hir().name(tcx.hir().as_local_hir_id(def_id).unwrap()).as_interned_str()
};
let r = match tcx.named_region(lifetime.hir_id) {
Some(rl::Region::Static) => {
tcx.lifetimes.re_static
}
Some(rl::Region::LateBound(debruijn, id, _)) => {
let name = lifetime_name(id);
tcx.mk_region(ty::ReLateBound(debruijn,
ty::BrNamed(id, name)))
}
Some(rl::Region::LateBoundAnon(debruijn, index)) => {
tcx.mk_region(ty::ReLateBound(debruijn, ty::BrAnon(index)))
}
Some(rl::Region::EarlyBound(index, id, _)) => {
let name = lifetime_name(id);
tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
def_id: id,
index,
name,
}))
}
Some(rl::Region::Free(scope, id)) => {
let name = lifetime_name(id);
tcx.mk_region(ty::ReFree(ty::FreeRegion {
scope,
bound_region: ty::BrNamed(id, name)
}))
// (*) -- not late-bound, won't change
}
None => {
self.re_infer(def, lifetime.span)
.unwrap_or_else(|| {
// This indicates an illegal lifetime
// elision. `resolve_lifetime` should have
// reported an error in this case -- but if
// not, let's error out.
tcx.sess.delay_span_bug(lifetime.span, "unelided lifetime in signature");
// Supply some dummy value. We don't have an
// `re_error`, annoyingly, so use `'static`.
tcx.lifetimes.re_static
})
}
};
debug!("ast_region_to_region(lifetime={:?}) yields {:?}",
lifetime,
r);
r
}
/// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
/// returns an appropriate set of substitutions for this particular reference to `I`.
pub fn ast_path_substs_for_ty(&self,
span: Span,
def_id: DefId,
item_segment: &hir::PathSegment)
-> SubstsRef<'tcx>
{
let (substs, assoc_bindings, _) = self.create_substs_for_ast_path(
span,
def_id,
item_segment.generic_args(),
item_segment.infer_args,
None,
);
assoc_bindings.first().map(|b| Self::prohibit_assoc_ty_binding(self.tcx(), b.span));
substs
}
/// Report error if there is an explicit type parameter when using `impl Trait`.
fn check_impl_trait(
tcx: TyCtxt<'_>,
span: Span,
seg: &hir::PathSegment,
generics: &ty::Generics,
) -> bool {
let explicit = !seg.infer_args;
let impl_trait = generics.params.iter().any(|param| match param.kind {
ty::GenericParamDefKind::Type {
synthetic: Some(hir::SyntheticTyParamKind::ImplTrait), ..
} => true,
_ => false,
});
if explicit && impl_trait {
let mut err = struct_span_err! {
tcx.sess,
span,
E0632,
"cannot provide explicit type parameters when `impl Trait` is \
used in argument position."
};
err.emit();
}
impl_trait
}
/// Checks that the correct number of generic arguments have been provided.
/// Used specifically for function calls.
pub fn check_generic_arg_count_for_call(
tcx: TyCtxt<'_>,
span: Span,
def: &ty::Generics,
seg: &hir::PathSegment,
is_method_call: bool,
) -> bool {
let empty_args = P(hir::GenericArgs {
args: HirVec::new(), bindings: HirVec::new(), parenthesized: false,
});
let suppress_mismatch = Self::check_impl_trait(tcx, span, seg, &def);
Self::check_generic_arg_count(
tcx,
span,
def,
if let Some(ref args) = seg.args {
args
} else {
&empty_args
},
if is_method_call {
GenericArgPosition::MethodCall
} else {
GenericArgPosition::Value
},
def.parent.is_none() && def.has_self, // `has_self`
seg.infer_args || suppress_mismatch, // `infer_args`
).0
}
/// Checks that the correct number of generic arguments have been provided.
/// This is used both for datatypes and function calls.
fn check_generic_arg_count(
tcx: TyCtxt<'_>,
span: Span,
def: &ty::Generics,
args: &hir::GenericArgs,
position: GenericArgPosition,
has_self: bool,
infer_args: bool,
) -> (bool, Option<Vec<Span>>) {
// At this stage we are guaranteed that the generic arguments are in the correct order, e.g.
// that lifetimes will proceed types. So it suffices to check the number of each generic
// arguments in order to validate them with respect to the generic parameters.
let param_counts = def.own_counts();
let arg_counts = args.own_counts();
let infer_lifetimes = position != GenericArgPosition::Type && arg_counts.lifetimes == 0;
let mut defaults: ty::GenericParamCount = Default::default();
for param in &def.params {
match param.kind {
GenericParamDefKind::Lifetime => {}
GenericParamDefKind::Type { has_default, .. } => {
defaults.types += has_default as usize
}
GenericParamDefKind::Const => {
// FIXME(const_generics:defaults)
}
};
}
if position != GenericArgPosition::Type && !args.bindings.is_empty() {
AstConv::prohibit_assoc_ty_binding(tcx, args.bindings[0].span);
}
// Prohibit explicit lifetime arguments if late-bound lifetime parameters are present.
let mut reported_late_bound_region_err = None;
if !infer_lifetimes {
if let Some(span_late) = def.has_late_bound_regions {
let msg = "cannot specify lifetime arguments explicitly \
if late bound lifetime parameters are present";
let note = "the late bound lifetime parameter is introduced here";
let span = args.args[0].span();
if position == GenericArgPosition::Value
&& arg_counts.lifetimes != param_counts.lifetimes {
let mut err = tcx.sess.struct_span_err(span, msg);
err.span_note(span_late, note);
err.emit();
reported_late_bound_region_err = Some(true);
} else {
let mut multispan = MultiSpan::from_span(span);
multispan.push_span_label(span_late, note.to_string());
tcx.lint_hir(lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS,
args.args[0].id(), multispan, msg);
reported_late_bound_region_err = Some(false);
}
}
}
let check_kind_count = |kind, required, permitted, provided, offset| {
debug!(
"check_kind_count: kind: {} required: {} permitted: {} provided: {} offset: {}",
kind,
required,
permitted,
provided,
offset
);
// We enforce the following: `required` <= `provided` <= `permitted`.
// For kinds without defaults (e.g.., lifetimes), `required == permitted`.
// For other kinds (i.e., types), `permitted` may be greater than `required`.
if required <= provided && provided <= permitted {
return (reported_late_bound_region_err.unwrap_or(false), None);
}
// Unfortunately lifetime and type parameter mismatches are typically styled
// differently in diagnostics, which means we have a few cases to consider here.
let (bound, quantifier) = if required != permitted {
if provided < required {
(required, "at least ")
} else { // provided > permitted
(permitted, "at most ")
}
} else {
(required, "")
};
let mut potential_assoc_types: Option<Vec<Span>> = None;
let (spans, label) = if required == permitted && provided > permitted {
// In the case when the user has provided too many arguments,
// we want to point to the unexpected arguments.
let spans: Vec<Span> = args.args[offset+permitted .. offset+provided]
.iter()
.map(|arg| arg.span())
.collect();
potential_assoc_types = Some(spans.clone());
(spans, format!( "unexpected {} argument", kind))
} else {
(vec![span], format!(
"expected {}{} {} argument{}",
quantifier,
bound,
kind,
pluralise!(bound),
))
};
let mut err = tcx.sess.struct_span_err_with_code(
spans.clone(),
&format!(
"wrong number of {} arguments: expected {}{}, found {}",
kind,
quantifier,
bound,
provided,
),
DiagnosticId::Error("E0107".into())
);
for span in spans {
err.span_label(span, label.as_str());
}
err.emit();
(
provided > required, // `suppress_error`
potential_assoc_types,
)
};
if reported_late_bound_region_err.is_none()
&& (!infer_lifetimes || arg_counts.lifetimes > param_counts.lifetimes) {
check_kind_count(
"lifetime",
param_counts.lifetimes,
param_counts.lifetimes,
arg_counts.lifetimes,
0,
);
}
// FIXME(const_generics:defaults)
if !infer_args || arg_counts.consts > param_counts.consts {
check_kind_count(
"const",
param_counts.consts,
param_counts.consts,
arg_counts.consts,
arg_counts.lifetimes + arg_counts.types,
);
}
// Note that type errors are currently be emitted *after* const errors.
if !infer_args
|| arg_counts.types > param_counts.types - defaults.types - has_self as usize {
check_kind_count(
"type",
param_counts.types - defaults.types - has_self as usize,
param_counts.types - has_self as usize,
arg_counts.types,
arg_counts.lifetimes,
)
} else {
(reported_late_bound_region_err.unwrap_or(false), None)
}
}
/// Creates the relevant generic argument substitutions
/// corresponding to a set of generic parameters. This is a
/// rather complex function. Let us try to explain the role
/// of each of its parameters:
///
/// To start, we are given the `def_id` of the thing we are
/// creating the substitutions for, and a partial set of
/// substitutions `parent_substs`. In general, the substitutions
/// for an item begin with substitutions for all the "parents" of
/// that item -- e.g., for a method it might include the
/// parameters from the impl.
///
/// Therefore, the method begins by walking down these parents,
/// starting with the outermost parent and proceed inwards until
/// it reaches `def_id`. For each parent `P`, it will check `parent_substs`
/// first to see if the parent's substitutions are listed in there. If so,
/// we can append those and move on. Otherwise, it invokes the
/// three callback functions:
///
/// - `args_for_def_id`: given the `DefId` `P`, supplies back the
/// generic arguments that were given to that parent from within
/// the path; so e.g., if you have `<T as Foo>::Bar`, the `DefId`
/// might refer to the trait `Foo`, and the arguments might be
/// `[T]`. The boolean value indicates whether to infer values
/// for arguments whose values were not explicitly provided.
/// - `provided_kind`: given the generic parameter and the value from `args_for_def_id`,
/// instantiate a `Kind`.
/// - `inferred_kind`: if no parameter was provided, and inference is enabled, then
/// creates a suitable inference variable.
pub fn create_substs_for_generic_args<'b>(
tcx: TyCtxt<'tcx>,
def_id: DefId,
parent_substs: &[Kind<'tcx>],
has_self: bool,
self_ty: Option<Ty<'tcx>>,
args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs>, bool),
provided_kind: impl Fn(&GenericParamDef, &GenericArg) -> Kind<'tcx>,
inferred_kind: impl Fn(Option<&[Kind<'tcx>]>, &GenericParamDef, bool) -> Kind<'tcx>,
) -> SubstsRef<'tcx> {
// Collect the segments of the path; we need to substitute arguments
// for parameters throughout the entire path (wherever there are
// generic parameters).
let mut parent_defs = tcx.generics_of(def_id);
let count = parent_defs.count();
let mut stack = vec![(def_id, parent_defs)];
while let Some(def_id) = parent_defs.parent {
parent_defs = tcx.generics_of(def_id);
stack.push((def_id, parent_defs));
}
// We manually build up the substitution, rather than using convenience
// methods in `subst.rs`, so that we can iterate over the arguments and
// parameters in lock-step linearly, instead of trying to match each pair.
let mut substs: SmallVec<[Kind<'tcx>; 8]> = SmallVec::with_capacity(count);
// Iterate over each segment of the path.
while let Some((def_id, defs)) = stack.pop() {
let mut params = defs.params.iter().peekable();
// If we have already computed substitutions for parents, we can use those directly.
while let Some(&param) = params.peek() {
if let Some(&kind) = parent_substs.get(param.index as usize) {
substs.push(kind);
params.next();
} else {
break;
}
}
// `Self` is handled first, unless it's been handled in `parent_substs`.
if has_self {
if let Some(&param) = params.peek() {
if param.index == 0 {
if let GenericParamDefKind::Type { .. } = param.kind {
substs.push(self_ty.map(|ty| ty.into())
.unwrap_or_else(|| inferred_kind(None, param, true)));
params.next();
}
}
}
}
// Check whether this segment takes generic arguments and the user has provided any.
let (generic_args, infer_args) = args_for_def_id(def_id);
let mut args = generic_args.iter().flat_map(|generic_args| generic_args.args.iter())
.peekable();
loop {
// We're going to iterate through the generic arguments that the user
// provided, matching them with the generic parameters we expect.
// Mismatches can occur as a result of elided lifetimes, or for malformed
// input. We try to handle both sensibly.
match (args.peek(), params.peek()) {
(Some(&arg), Some(&param)) => {
match (arg, &param.kind) {
(GenericArg::Lifetime(_), GenericParamDefKind::Lifetime)
| (GenericArg::Type(_), GenericParamDefKind::Type { .. })
| (GenericArg::Const(_), GenericParamDefKind::Const) => {
substs.push(provided_kind(param, arg));
args.next();
params.next();
}
(GenericArg::Type(_), GenericParamDefKind::Lifetime)
| (GenericArg::Const(_), GenericParamDefKind::Lifetime) => {
// We expected a lifetime argument, but got a type or const
// argument. That means we're inferring the lifetimes.
substs.push(inferred_kind(None, param, infer_args));
params.next();
}
(_, _) => {
// We expected one kind of parameter, but the user provided
// another. This is an error, but we need to handle it
// gracefully so we can report sensible errors.
// In this case, we're simply going to infer this argument.
args.next();
}
}
}
(Some(_), None) => {
// We should never be able to reach this point with well-formed input.
// Getting to this point means the user supplied more arguments than
// there are parameters.
args.next();
}
(None, Some(&param)) => {
// If there are fewer arguments than parameters, it means
// we're inferring the remaining arguments.
substs.push(inferred_kind(Some(&substs), param, infer_args));
args.next();
params.next();
}
(None, None) => break,
}
}
}
tcx.intern_substs(&substs)
}
/// Given the type/lifetime/const arguments provided to some path (along with
/// an implicit `Self`, if this is a trait reference), returns the complete
/// set of substitutions. This may involve applying defaulted type parameters.
/// Also returns back constriants on associated types.
///
/// Example:
///
/// ```
/// T: std::ops::Index<usize, Output = u32>
/// ^1 ^^^^^^^^^^^^^^2 ^^^^3 ^^^^^^^^^^^4
/// ```
///
/// 1. The `self_ty` here would refer to the type `T`.
/// 2. The path in question is the path to the trait `std::ops::Index`,
/// which will have been resolved to a `def_id`
/// 3. The `generic_args` contains info on the `<...>` contents. The `usize` type
/// parameters are returned in the `SubstsRef`, the associated type bindings like
/// `Output = u32` are returned in the `Vec<ConvertedBinding...>` result.
///
/// Note that the type listing given here is *exactly* what the user provided.
fn create_substs_for_ast_path<'a>(&self,
span: Span,
def_id: DefId,
generic_args: &'a hir::GenericArgs,
infer_args: bool,
self_ty: Option<Ty<'tcx>>)
-> (SubstsRef<'tcx>, Vec<ConvertedBinding<'a, 'tcx>>, Option<Vec<Span>>)
{
// If the type is parameterized by this region, then replace this
// region with the current anon region binding (in other words,
// whatever & would get replaced with).
debug!("create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \
generic_args={:?})",
def_id, self_ty, generic_args);
let tcx = self.tcx();
let generic_params = tcx.generics_of(def_id);
// If a self-type was declared, one should be provided.
assert_eq!(generic_params.has_self, self_ty.is_some());
let has_self = generic_params.has_self;
let (_, potential_assoc_types) = Self::check_generic_arg_count(
tcx,
span,
&generic_params,
&generic_args,
GenericArgPosition::Type,
has_self,
infer_args,
);
let is_object = self_ty.map_or(false, |ty| {
ty == self.tcx().types.trait_object_dummy_self
});
let default_needs_object_self = |param: &ty::GenericParamDef| {
if let GenericParamDefKind::Type { has_default, .. } = param.kind {
if is_object && has_default && has_self {
let self_param = tcx.types.self_param;
if tcx.at(span).type_of(param.def_id).walk().any(|ty| ty == self_param) {
// There is no suitable inference default for a type parameter
// that references self, in an object type.
return true;
}
}
}
false
};
let substs = Self::create_substs_for_generic_args(
tcx,
def_id,
&[][..],
self_ty.is_some(),
self_ty,
// Provide the generic args, and whether types should be inferred.
|_| (Some(generic_args), infer_args),
// Provide substitutions for parameters for which (valid) arguments have been provided.
|param, arg| {
match (&param.kind, arg) {
(GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
self.ast_region_to_region(&lt, Some(param)).into()
}
(GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
self.ast_ty_to_ty(&ty).into()
}
(GenericParamDefKind::Const, GenericArg::Const(ct)) => {
self.ast_const_to_const(&ct.value, tcx.type_of(param.def_id)).into()
}
_ => unreachable!(),
}
},
// Provide substitutions for parameters for which arguments are inferred.
|substs, param, infer_args| {
match param.kind {
GenericParamDefKind::Lifetime => tcx.lifetimes.re_static.into(),
GenericParamDefKind::Type { has_default, .. } => {
if !infer_args && has_default {
// No type parameter provided, but a default exists.
// If we are converting an object type, then the
// `Self` parameter is unknown. However, some of the
// other type parameters may reference `Self` in their
// defaults. This will lead to an ICE if we are not
// careful!
if default_needs_object_self(param) {
struct_span_err!(tcx.sess, span, E0393,
"the type parameter `{}` must be explicitly specified",
param.name
)
.span_label(span, format!(
"missing reference to `{}`", param.name))
.note(&format!(
"because of the default `Self` reference, type parameters \
must be specified on object types"))
.emit();
tcx.types.err.into()
} else {
// This is a default type parameter.
self.normalize_ty(
span,
tcx.at(span).type_of(param.def_id)
.subst_spanned(tcx, substs.unwrap(), Some(span))
).into()
}
} else if infer_args {
// No type parameters were provided, we can infer all.
let param = if !default_needs_object_self(param) {
Some(param)
} else {
None
};
self.ty_infer(param, span).into()
} else {
// We've already errored above about the mismatch.
tcx.types.err.into()
}
}
GenericParamDefKind::Const => {
// FIXME(const_generics:defaults)
if infer_args {
// No const parameters were provided, we can infer all.
let ty = tcx.at(span).type_of(param.def_id);
self.ct_infer(ty, Some(param), span).into()
} else {
// We've already errored above about the mismatch.
tcx.consts.err.into()
}
}
}
},
);
// Convert associated-type bindings or constraints into a separate vector.
// Example: Given this:
//
// T: Iterator<Item = u32>
//
// The `T` is passed in as a self-type; the `Item = u32` is
// not a "type parameter" of the `Iterator` trait, but rather
// a restriction on `<T as Iterator>::Item`, so it is passed
// back separately.
let assoc_bindings = generic_args.bindings.iter()
.map(|binding| {
let kind = match binding.kind {
hir::TypeBindingKind::Equality { ref ty } =>
ConvertedBindingKind::Equality(self.ast_ty_to_ty(ty)),
hir::TypeBindingKind::Constraint { ref bounds } =>
ConvertedBindingKind::Constraint(bounds),
};
ConvertedBinding {
item_name: binding.ident,
kind,
span: binding.span,
}
})
.collect();
debug!("create_substs_for_ast_path(generic_params={:?}, self_ty={:?}) -> {:?}",
generic_params, self_ty, substs);
(substs, assoc_bindings, potential_assoc_types)
}
/// Instantiates the path for the given trait reference, assuming that it's
/// bound to a valid trait type. Returns the `DefId` of the defining trait.
/// The type _cannot_ be a type other than a trait type.
///
/// If the `projections` argument is `None`, then assoc type bindings like `Foo<T = X>`
/// are disallowed. Otherwise, they are pushed onto the vector given.
pub fn instantiate_mono_trait_ref(&self,
trait_ref: &hir::TraitRef,
self_ty: Ty<'tcx>
) -> ty::TraitRef<'tcx>
{
self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
self.ast_path_to_mono_trait_ref(trait_ref.path.span,
trait_ref.trait_def_id(),
self_ty,
trait_ref.path.segments.last().unwrap())
}
/// The given trait-ref must actually be a trait.
pub(super) fn instantiate_poly_trait_ref_inner(&self,
trait_ref: &hir::TraitRef,
span: Span,
self_ty: Ty<'tcx>,
bounds: &mut Bounds<'tcx>,
speculative: bool,
) -> Option<Vec<Span>> {
let trait_def_id = trait_ref.trait_def_id();
debug!("instantiate_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id);
self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
let (substs, assoc_bindings, potential_assoc_types) = self.create_substs_for_ast_trait_ref(
trait_ref.path.span,
trait_def_id,
self_ty,
trait_ref.path.segments.last().unwrap(),
);
let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs));
bounds.trait_bounds.push((poly_trait_ref, span));
let mut dup_bindings = FxHashMap::default();
for binding in &assoc_bindings {
// Specify type to assert that error was already reported in `Err` case.
let _: Result<_, ErrorReported> =
self.add_predicates_for_ast_type_binding(
trait_ref.hir_ref_id,
poly_trait_ref,
binding,
bounds,
speculative,
&mut dup_bindings,
);
// Okay to ignore `Err` because of `ErrorReported` (see above).
}
debug!("instantiate_poly_trait_ref({:?}, bounds={:?}) -> {:?}",
trait_ref, bounds, poly_trait_ref);
potential_assoc_types
}
/// Given a trait bound like `Debug`, applies that trait bound the given self-type to construct
/// a full trait reference. The resulting trait reference is returned. This may also generate
/// auxiliary bounds, which are added to `bounds`.
///
/// Example:
///
/// ```
/// poly_trait_ref = Iterator<Item = u32>
/// self_ty = Foo
/// ```
///
/// this would return `Foo: Iterator` and add `<Foo as Iterator>::Item = u32` into `bounds`.
///
/// **A note on binders:** against our usual convention, there is an implied bounder around
/// the `self_ty` and `poly_trait_ref` parameters here. So they may reference bound regions.
/// If for example you had `for<'a> Foo<'a>: Bar<'a>`, then the `self_ty` would be `Foo<'a>`
/// where `'a` is a bound region at depth 0. Similarly, the `poly_trait_ref` would be
/// `Bar<'a>`. The returned poly-trait-ref will have this binder instantiated explicitly,
/// however.
pub fn instantiate_poly_trait_ref(&self,
poly_trait_ref: &hir::PolyTraitRef,
self_ty: Ty<'tcx>,
bounds: &mut Bounds<'tcx>,
) -> Option<Vec<Span>> {
self.instantiate_poly_trait_ref_inner(
&poly_trait_ref.trait_ref,
poly_trait_ref.span,
self_ty,
bounds,
false,
)
}
fn ast_path_to_mono_trait_ref(&self,
span: Span,
trait_def_id: DefId,
self_ty: Ty<'tcx>,
trait_segment: &hir::PathSegment
) -> ty::TraitRef<'tcx>
{
let (substs, assoc_bindings, _) =
self.create_substs_for_ast_trait_ref(span,
trait_def_id,
self_ty,
trait_segment);
assoc_bindings.first().map(|b| AstConv::prohibit_assoc_ty_binding(self.tcx(), b.span));
ty::TraitRef::new(trait_def_id, substs)
}
fn create_substs_for_ast_trait_ref<'a>(
&self,
span: Span,
trait_def_id: DefId,
self_ty: Ty<'tcx>,
trait_segment: &'a hir::PathSegment,
) -> (SubstsRef<'tcx>, Vec<ConvertedBinding<'a, 'tcx>>, Option<Vec<Span>>) {
debug!("create_substs_for_ast_trait_ref(trait_segment={:?})",
trait_segment);
let trait_def = self.tcx().trait_def(trait_def_id);
if !self.tcx().features().unboxed_closures &&
trait_segment.generic_args().parenthesized != trait_def.paren_sugar
{
// For now, require that parenthetical notation be used only with `Fn()` etc.
let msg = if trait_def.paren_sugar {
"the precise format of `Fn`-family traits' type parameters is subject to change. \
Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead"
} else {
"parenthetical notation is only stable when used with `Fn`-family traits"
};
emit_feature_err(&self.tcx().sess.parse_sess, sym::unboxed_closures,
span, GateIssue::Language, msg);
}
self.create_substs_for_ast_path(span,
trait_def_id,
trait_segment.generic_args(),
trait_segment.infer_args,
Some(self_ty))
}
fn trait_defines_associated_type_named(&self,
trait_def_id: DefId,
assoc_name: ast::Ident)
-> bool
{
self.tcx().associated_items(trait_def_id).any(|item| {
item.kind == ty::AssocKind::Type &&
self.tcx().hygienic_eq(assoc_name, item.ident, trait_def_id)
})
}
// Returns `true` if a bounds list includes `?Sized`.
pub fn is_unsized(&self, ast_bounds: &[hir::GenericBound], span: Span) -> bool {
let tcx = self.tcx();
// Try to find an unbound in bounds.
let mut unbound = None;
for ab in ast_bounds {
if let &hir::GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = ab {
if unbound.is_none() {
unbound = Some(&ptr.trait_ref);
} else {
span_err!(
tcx.sess,
span,
E0203,
"type parameter has more than one relaxed default \
bound, only one is supported"
);
}
}
}
let kind_id = tcx.lang_items().require(SizedTraitLangItem);
match unbound {
Some(tpb) => {
// FIXME(#8559) currently requires the unbound to be built-in.
if let Ok(kind_id) = kind_id {
if tpb.path.res != Res::Def(DefKind::Trait, kind_id) {
tcx.sess.span_warn(
span,
"default bound relaxed for a type parameter, but \
this does nothing because the given bound is not \
a default. Only `?Sized` is supported",
);
}
}
}
_ if kind_id.is_ok() => {
return false;
}
// No lang item for `Sized`, so we can't add it as a bound.
None => {}
}
true
}
/// This helper takes a *converted* parameter type (`param_ty`)
/// and an *unconverted* list of bounds:
///
/// ```
/// fn foo<T: Debug>
/// ^ ^^^^^ `ast_bounds` parameter, in HIR form
/// |
/// `param_ty`, in ty form
/// ```
///
/// It adds these `ast_bounds` into the `bounds` structure.
///
/// **A note on binders:** there is an implied binder around
/// `param_ty` and `ast_bounds`. See `instantiate_poly_trait_ref`
/// for more details.
fn add_bounds(&self,
param_ty: Ty<'tcx>,
ast_bounds: &[hir::GenericBound],
bounds: &mut Bounds<'tcx>,
) {
let mut trait_bounds = Vec::new();
let mut region_bounds = Vec::new();
for ast_bound in ast_bounds {
match *ast_bound {
hir::GenericBound::Trait(ref b, hir::TraitBoundModifier::None) =>
trait_bounds.push(b),
hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => {}
hir::GenericBound::Outlives(ref l) =>
region_bounds.push(l),
}
}
for bound in trait_bounds {
let _ = self.instantiate_poly_trait_ref(
bound,
param_ty,
bounds,
);
}
bounds.region_bounds.extend(region_bounds
.into_iter()
.map(|r| (self.ast_region_to_region(r, None), r.span))
);
}
/// Translates a list of bounds from the HIR into the `Bounds` data structure.
/// The self-type for the bounds is given by `param_ty`.
///
/// Example:
///
/// ```
/// fn foo<T: Bar + Baz>() { }
/// ^ ^^^^^^^^^ ast_bounds
/// param_ty
/// ```
///
/// The `sized_by_default` parameter indicates if, in this context, the `param_ty` should be
/// considered `Sized` unless there is an explicit `?Sized` bound. This would be true in the
/// example above, but is not true in supertrait listings like `trait Foo: Bar + Baz`.
///
/// `span` should be the declaration size of the parameter.
pub fn compute_bounds(&self,
param_ty: Ty<'tcx>,
ast_bounds: &[hir::GenericBound],
sized_by_default: SizedByDefault,
span: Span,
) -> Bounds<'tcx> {
let mut bounds = Bounds::default();
self.add_bounds(param_ty, ast_bounds, &mut bounds);
bounds.trait_bounds.sort_by_key(|(t, _)| t.def_id());
bounds.implicitly_sized = if let SizedByDefault::Yes = sized_by_default {
if !self.is_unsized(ast_bounds, span) {
Some(span)
} else {
None
}
} else {
None
};
bounds
}
/// Given an HIR binding like `Item = Foo` or `Item: Foo`, pushes the corresponding predicates
/// onto `bounds`.
///
/// **A note on binders:** given something like `T: for<'a> Iterator<Item = &'a u32>`, the
/// `trait_ref` here will be `for<'a> T: Iterator`. The `binding` data however is from *inside*
/// the binder (e.g., `&'a u32`) and hence may reference bound regions.
fn add_predicates_for_ast_type_binding(
&self,
hir_ref_id: hir::HirId,
trait_ref: ty::PolyTraitRef<'tcx>,
binding: &ConvertedBinding<'_, 'tcx>,
bounds: &mut Bounds<'tcx>,
speculative: bool,
dup_bindings: &mut FxHashMap<DefId, Span>,
) -> Result<(), ErrorReported> {
let tcx = self.tcx();
if !speculative {
// Given something like `U: SomeTrait<T = X>`, we want to produce a
// predicate like `<U as SomeTrait>::T = X`. This is somewhat
// subtle in the event that `T` is defined in a supertrait of
// `SomeTrait`, because in that case we need to upcast.
//
// That is, consider this case:
//
// ```
// trait SubTrait: SuperTrait<int> { }
// trait SuperTrait<A> { type T; }
//
// ... B: SubTrait<T = foo> ...
// ```
//
// We want to produce `<B as SuperTrait<int>>::T == foo`.
// Find any late-bound regions declared in `ty` that are not
// declared in the trait-ref. These are not well-formed.
//
// Example:
//
// for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
// for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
if let ConvertedBindingKind::Equality(ty) = binding.kind {
let late_bound_in_trait_ref =
tcx.collect_constrained_late_bound_regions(&trait_ref);
let late_bound_in_ty =
tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(ty));
debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
let br_name = match *br {
ty::BrNamed(_, name) => name,
_ => {
span_bug!(
binding.span,
"anonymous bound region {:?} in binding but not trait ref",
br);
}
};
struct_span_err!(tcx.sess,
binding.span,
E0582,
"binding for associated type `{}` references lifetime `{}`, \
which does not appear in the trait input types",
binding.item_name, br_name)
.emit();
}
}
}
let candidate = if self.trait_defines_associated_type_named(trait_ref.def_id(),
binding.item_name) {
// Simple case: X is defined in the current trait.
Ok(trait_ref)
} else {
// Otherwise, we have to walk through the supertraits to find
// those that do.
let candidates = traits::supertraits(tcx, trait_ref).filter(|r| {
self.trait_defines_associated_type_named(r.def_id(), binding.item_name)
});
self.one_bound_for_assoc_type(candidates, &trait_ref.to_string(),
binding.item_name, binding.span)
}?;
let (assoc_ident, def_scope) =
tcx.adjust_ident_and_get_scope(binding.item_name, candidate.def_id(), hir_ref_id);
let assoc_ty = tcx.associated_items(candidate.def_id()).find(|i| {
i.kind == ty::AssocKind::Type && i.ident.modern() == assoc_ident
}).expect("missing associated type");
if !assoc_ty.vis.is_accessible_from(def_scope, tcx) {
let msg = format!("associated type `{}` is private", binding.item_name);
tcx.sess.span_err(binding.span, &msg);
}
tcx.check_stability(assoc_ty.def_id, Some(hir_ref_id), binding.span);
if !speculative {
dup_bindings.entry(assoc_ty.def_id)
.and_modify(|prev_span| {
struct_span_err!(self.tcx().sess, binding.span, E0719,
"the value of the associated type `{}` (from the trait `{}`) \
is already specified",
binding.item_name,
tcx.def_path_str(assoc_ty.container.id()))
.span_label(binding.span, "re-bound here")
.span_label(*prev_span, format!("`{}` bound here first", binding.item_name))
.emit();
})
.or_insert(binding.span);
}
match binding.kind {
ConvertedBindingKind::Equality(ref ty) => {
// "Desugar" a constraint like `T: Iterator<Item = u32>` this to
// the "projection predicate" for:
//
// `<T as Iterator>::Item = u32`
bounds.projection_bounds.push((candidate.map_bound(|trait_ref| {
ty::ProjectionPredicate {
projection_ty: ty::ProjectionTy::from_ref_and_name(
tcx,
trait_ref,
binding.item_name,
),
ty,
}
}), binding.span));
}
ConvertedBindingKind::Constraint(ast_bounds) => {
// "Desugar" a constraint like `T: Iterator<Item: Debug>` to
//
// `<T as Iterator>::Item: Debug`
//
// Calling `skip_binder` is okay, because `add_bounds` expects the `param_ty`
// parameter to have a skipped binder.
let param_ty = tcx.mk_projection(assoc_ty.def_id, candidate.skip_binder().substs);
self.add_bounds(param_ty, ast_bounds, bounds);
}
}
Ok(())
}
fn ast_path_to_ty(&self,
span: Span,
did: DefId,
item_segment: &hir::PathSegment)
-> Ty<'tcx>
{
let substs = self.ast_path_substs_for_ty(span, did, item_segment);
self.normalize_ty(
span,
self.tcx().at(span).type_of(did).subst(self.tcx(), substs)
)
}
/// Transform a `PolyTraitRef` into a `PolyExistentialTraitRef` by
/// removing the dummy `Self` type (`trait_object_dummy_self`).
fn trait_ref_to_existential(&self, trait_ref: ty::TraitRef<'tcx>)
-> ty::ExistentialTraitRef<'tcx> {
if trait_ref.self_ty() != self.tcx().types.trait_object_dummy_self {
bug!("trait_ref_to_existential called on {:?} with non-dummy Self", trait_ref);
}
ty::ExistentialTraitRef::erase_self_ty(self.tcx(), trait_ref)
}
fn conv_object_ty_poly_trait_ref(&self,
span: Span,
trait_bounds: &[hir::PolyTraitRef],
lifetime: &hir::Lifetime)
-> Ty<'tcx>
{
let tcx = self.tcx();
let mut bounds = Bounds::default();
let mut potential_assoc_types = Vec::new();
let dummy_self = self.tcx().types.trait_object_dummy_self;
for trait_bound in trait_bounds.iter().rev() {
let cur_potential_assoc_types = self.instantiate_poly_trait_ref(
trait_bound,
dummy_self,
&mut bounds,
);
potential_assoc_types.extend(cur_potential_assoc_types.into_iter().flatten());
}
// Expand trait aliases recursively and check that only one regular (non-auto) trait
// is used and no 'maybe' bounds are used.
let expanded_traits =
traits::expand_trait_aliases(tcx, bounds.trait_bounds.iter().cloned());
let (mut auto_traits, regular_traits): (Vec<_>, Vec<_>) =
expanded_traits.partition(|i| tcx.trait_is_auto(i.trait_ref().def_id()));
if regular_traits.len() > 1 {
let first_trait = &regular_traits[0];
let additional_trait = &regular_traits[1];
let mut err = struct_span_err!(tcx.sess, additional_trait.bottom().1, E0225,
"only auto traits can be used as additional traits in a trait object"
);
additional_trait.label_with_exp_info(&mut err,
"additional non-auto trait", "additional use");
first_trait.label_with_exp_info(&mut err,
"first non-auto trait", "first use");
err.emit();
}
if regular_traits.is_empty() && auto_traits.is_empty() {
span_err!(tcx.sess, span, E0224,
"at least one trait is required for an object type");
return tcx.types.err;
}
// Check that there are no gross object safety violations;
// most importantly, that the supertraits don't contain `Self`,
// to avoid ICEs.
for item in &regular_traits {
let object_safety_violations =
tcx.global_tcx().astconv_object_safety_violations(item.trait_ref().def_id());
if !object_safety_violations.is_empty() {
tcx.report_object_safety_error(
span,
item.trait_ref().def_id(),
object_safety_violations
)
.map(|mut err| err.emit());
return tcx.types.err;
}
}
// Use a `BTreeSet` to keep output in a more consistent order.
let mut associated_types = BTreeSet::default();
let regular_traits_refs = bounds.trait_bounds
.into_iter()
.filter(|(trait_ref, _)| !tcx.trait_is_auto(trait_ref.def_id()))
.map(|(trait_ref, _)| trait_ref);
for trait_ref in traits::elaborate_trait_refs(tcx, regular_traits_refs) {
debug!("conv_object_ty_poly_trait_ref: observing object predicate `{:?}`", trait_ref);
match trait_ref {
ty::Predicate::Trait(pred) => {
associated_types
.extend(tcx.associated_items(pred.def_id())
.filter(|item| item.kind == ty::AssocKind::Type)
.map(|item| item.def_id));
}
ty::Predicate::Projection(pred) => {
// A `Self` within the original bound will be substituted with a
// `trait_object_dummy_self`, so check for that.
let references_self =
pred.skip_binder().ty.walk().any(|t| t == dummy_self);
// If the projection output contains `Self`, force the user to
// elaborate it explicitly to avoid a lot of complexity.
//
// The "classicaly useful" case is the following:
// ```
// trait MyTrait: FnMut() -> <Self as MyTrait>::MyOutput {
// type MyOutput;
// }
// ```
//
// Here, the user could theoretically write `dyn MyTrait<Output = X>`,
// but actually supporting that would "expand" to an infinitely-long type
// `fix $ τ → dyn MyTrait<MyOutput = X, Output = <τ as MyTrait>::MyOutput`.
//
// Instead, we force the user to write `dyn MyTrait<MyOutput = X, Output = X>`,
// which is uglier but works. See the discussion in #56288 for alternatives.
if !references_self {
// Include projections defined on supertraits.
bounds.projection_bounds.push((pred, DUMMY_SP))
}
}
_ => ()
}
}
for (projection_bound, _) in &bounds.projection_bounds {
associated_types.remove(&projection_bound.projection_def_id());
}
if !associated_types.is_empty() {
let names = associated_types.iter().map(|item_def_id| {
let assoc_item = tcx.associated_item(*item_def_id);
let trait_def_id = assoc_item.container.id();
format!(
"`{}` (from the trait `{}`)",
assoc_item.ident,
tcx.def_path_str(trait_def_id),
)
}).collect::<Vec<_>>().join(", ");
let mut err = struct_span_err!(
tcx.sess,
span,
E0191,
"the value of the associated type{} {} must be specified",
if associated_types.len() == 1 { "" } else { "s" },
names,
);
let (suggest, potential_assoc_types_spans) =
if potential_assoc_types.len() == associated_types.len() {
// Only suggest when the amount of missing associated types equals the number of
// extra type arguments present, as that gives us a relatively high confidence
// that the user forgot to give the associtated type's name. The canonical
// example would be trying to use `Iterator<isize>` instead of
// `Iterator<Item = isize>`.
(true, potential_assoc_types)
} else {
(false, Vec::new())
};
let mut suggestions = Vec::new();
for (i, item_def_id) in associated_types.iter().enumerate() {
let assoc_item = tcx.associated_item(*item_def_id);
err.span_label(
span,
format!("associated type `{}` must be specified", assoc_item.ident),
);
if item_def_id.is_local() {
err.span_label(
tcx.def_span(*item_def_id),
format!("`{}` defined here", assoc_item.ident),
);
}
if suggest {
if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(
potential_assoc_types_spans[i],
) {
suggestions.push((
potential_assoc_types_spans[i],
format!("{} = {}", assoc_item.ident, snippet),
));
}
}
}
if !suggestions.is_empty() {
let msg = format!("if you meant to specify the associated {}, write",
if suggestions.len() == 1 { "type" } else { "types" });
err.multipart_suggestion(
&msg,
suggestions,
Applicability::MaybeIncorrect,
);
}
err.emit();
}
// De-duplicate auto traits so that, e.g., `dyn Trait + Send + Send` is the same as
// `dyn Trait + Send`.
auto_traits.sort_by_key(|i| i.trait_ref().def_id());
auto_traits.dedup_by_key(|i| i.trait_ref().def_id());
debug!("regular_traits: {:?}", regular_traits);
debug!("auto_traits: {:?}", auto_traits);
// Erase the `dummy_self` (`trait_object_dummy_self`) used above.
let existential_trait_refs = regular_traits.iter().map(|i| {
i.trait_ref().map_bound(|trait_ref| self.trait_ref_to_existential(trait_ref))
});
let existential_projections = bounds.projection_bounds.iter().map(|(bound, _)| {
bound.map_bound(|b| {
let trait_ref = self.trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
ty::ExistentialProjection {
ty: b.ty,
item_def_id: b.projection_ty.item_def_id,
substs: trait_ref.substs,
}
})
});
// Calling `skip_binder` is okay because the predicates are re-bound.
let regular_trait_predicates = existential_trait_refs.map(
|trait_ref| ty::ExistentialPredicate::Trait(*trait_ref.skip_binder()));
let auto_trait_predicates = auto_traits.into_iter().map(
|trait_ref| ty::ExistentialPredicate::AutoTrait(trait_ref.trait_ref().def_id()));
let mut v =
regular_trait_predicates
.chain(auto_trait_predicates)
.chain(existential_projections
.map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
.collect::<SmallVec<[_; 8]>>();
v.sort_by(|a, b| a.stable_cmp(tcx, b));
v.dedup();
let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
// Use explicitly-specified region bound.
let region_bound = if !lifetime.is_elided() {
self.ast_region_to_region(lifetime, None)
} else {
self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
if tcx.named_region(lifetime.hir_id).is_some() {
self.ast_region_to_region(lifetime, None)
} else {
self.re_infer(None, span).unwrap_or_else(|| {
span_err!(tcx.sess, span, E0228,
"the lifetime bound for this object type cannot be deduced \
from context; please supply an explicit bound");
tcx.lifetimes.re_static
})
}
})
};
debug!("region_bound: {:?}", region_bound);
let ty = tcx.mk_dynamic(existential_predicates, region_bound);
debug!("trait_object_type: {:?}", ty);
ty
}
fn report_ambiguous_associated_type(
&self,
span: Span,
type_str: &str,
trait_str: &str,
name: ast::Name,
) {
let mut err = struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type");
if let (Some(_), Ok(snippet)) = (
self.tcx().sess.confused_type_with_std_module.borrow().get(&span),
self.tcx().sess.source_map().span_to_snippet(span),
) {
err.span_suggestion(
span,
"you are looking for the module in `std`, not the primitive type",
format!("std::{}", snippet),
Applicability::MachineApplicable,
);
} else {
err.span_suggestion(
span,
"use fully-qualified syntax",
format!("<{} as {}>::{}", type_str, trait_str, name),
Applicability::HasPlaceholders
);
}
err.emit();
}
// Search for a bound on a type parameter which includes the associated item
// given by `assoc_name`. `ty_param_def_id` is the `DefId` of the type parameter
// This function will fail if there are no suitable bounds or there is
// any ambiguity.
fn find_bound_for_assoc_item(&self,
ty_param_def_id: DefId,
assoc_name: ast::Ident,
span: Span)
-> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
{
let tcx = self.tcx();
debug!(
"find_bound_for_assoc_item(ty_param_def_id={:?}, assoc_name={:?}, span={:?})",
ty_param_def_id,
assoc_name,
span,
);
let predicates = &self.get_type_parameter_bounds(span, ty_param_def_id).predicates;
debug!("find_bound_for_assoc_item: predicates={:#?}", predicates);
let bounds = predicates.iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref());
// Check that there is exactly one way to find an associated type with the
// correct name.
let suitable_bounds = traits::transitive_bounds(tcx, bounds)
.filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
let param_hir_id = tcx.hir().as_local_hir_id(ty_param_def_id).unwrap();
let param_name = tcx.hir().ty_param_name(param_hir_id);
self.one_bound_for_assoc_type(suitable_bounds,
&param_name.as_str(),
assoc_name,
span)
}
// Checks that `bounds` contains exactly one element and reports appropriate
// errors otherwise.
fn one_bound_for_assoc_type<I>(&self,
mut bounds: I,
ty_param_name: &str,
assoc_name: ast::Ident,
span: Span)
-> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
where I: Iterator<Item = ty::PolyTraitRef<'tcx>>
{
let bound = match bounds.next() {
Some(bound) => bound,
None => {
struct_span_err!(self.tcx().sess, span, E0220,
"associated type `{}` not found for `{}`",
assoc_name,
ty_param_name)
.span_label(span, format!("associated type `{}` not found", assoc_name))
.emit();
return Err(ErrorReported);
}
};
debug!("one_bound_for_assoc_type: bound = {:?}", bound);
if let Some(bound2) = bounds.next() {
debug!("one_bound_for_assoc_type: bound2 = {:?}", bound2);
let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
let mut err = struct_span_err!(
self.tcx().sess, span, E0221,
"ambiguous associated type `{}` in bounds of `{}`",
assoc_name,
ty_param_name);
err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
for bound in bounds {
let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
item.kind == ty::AssocKind::Type &&
self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id())
})
.and_then(|item| self.tcx().hir().span_if_local(item.def_id));
if let Some(span) = bound_span {
err.span_label(span, format!("ambiguous `{}` from `{}`",
assoc_name,
bound));
} else {
span_note!(&mut err, span,
"associated type `{}` could derive from `{}`",
ty_param_name,
bound);
}
}
err.emit();
}
return Ok(bound);
}
// Create a type from a path to an associated type.
// For a path `A::B::C::D`, `qself_ty` and `qself_def` are the type and def for `A::B::C`
// and item_segment is the path segment for `D`. We return a type and a def for
// the whole path.
// Will fail except for `T::A` and `Self::A`; i.e., if `qself_ty`/`qself_def` are not a type
// parameter or `Self`.
pub fn associated_path_to_ty(
&self,
hir_ref_id: hir::HirId,
span: Span,
qself_ty: Ty<'tcx>,
qself_res: Res,
assoc_segment: &hir::PathSegment,
permit_variants: bool,
) -> Result<(Ty<'tcx>, DefKind, DefId), ErrorReported> {
let tcx = self.tcx();
let assoc_ident = assoc_segment.ident;
debug!("associated_path_to_ty: {:?}::{}", qself_ty, assoc_ident);
self.prohibit_generics(slice::from_ref(assoc_segment));
// Check if we have an enum variant.
let mut variant_resolution = None;
if let ty::Adt(adt_def, _) = qself_ty.sty {
if adt_def.is_enum() {
let variant_def = adt_def.variants.iter().find(|vd| {
tcx.hygienic_eq(assoc_ident, vd.ident, adt_def.did)
});
if let Some(variant_def) = variant_def {
if permit_variants {
tcx.check_stability(variant_def.def_id, Some(hir_ref_id), span);
return Ok((qself_ty, DefKind::Variant, variant_def.def_id));
} else {
variant_resolution = Some(variant_def.def_id);
}
}
}
}
// Find the type of the associated item, and the trait where the associated
// item is declared.
let bound = match (&qself_ty.sty, qself_res) {
(_, Res::SelfTy(Some(_), Some(impl_def_id))) => {
// `Self` in an impl of a trait -- we have a concrete self type and a
// trait reference.
let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
Some(trait_ref) => trait_ref,
None => {
// A cycle error occurred, most likely.
return Err(ErrorReported);
}
};
let candidates = traits::supertraits(tcx, ty::Binder::bind(trait_ref))
.filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_ident));
self.one_bound_for_assoc_type(candidates, "Self", assoc_ident, span)?
}
(&ty::Param(_), Res::SelfTy(Some(param_did), None)) |
(&ty::Param(_), Res::Def(DefKind::TyParam, param_did)) => {
self.find_bound_for_assoc_item(param_did, assoc_ident, span)?
}
_ => {
if variant_resolution.is_some() {
// Variant in type position
let msg = format!("expected type, found variant `{}`", assoc_ident);
tcx.sess.span_err(span, &msg);
} else if qself_ty.is_enum() {
let mut err = tcx.sess.struct_span_err(
assoc_ident.span,
&format!("no variant `{}` in enum `{}`", assoc_ident, qself_ty),
);
let adt_def = qself_ty.ty_adt_def().expect("enum is not an ADT");
if let Some(suggested_name) = find_best_match_for_name(
adt_def.variants.iter().map(|variant| &variant.ident.name),
&assoc_ident.as_str(),
None,
) {
err.span_suggestion(
assoc_ident.span,
"there is a variant with a similar name",
suggested_name.to_string(),
Applicability::MaybeIncorrect,
);
} else {
err.span_label(
assoc_ident.span,
format!("variant not found in `{}`", qself_ty),
);
}
if let Some(sp) = tcx.hir().span_if_local(adt_def.did) {
let sp = tcx.sess.source_map().def_span(sp);
err.span_label(sp, format!("variant `{}` not found here", assoc_ident));
}
err.emit();
} else if !qself_ty.references_error() {
// Don't print `TyErr` to the user.
self.report_ambiguous_associated_type(
span,
&qself_ty.to_string(),
"Trait",
assoc_ident.name,
);
}
return Err(ErrorReported);
}
};
let trait_did = bound.def_id();
let (assoc_ident, def_scope) =
tcx.adjust_ident_and_get_scope(assoc_ident, trait_did, hir_ref_id);
let item = tcx.associated_items(trait_did).find(|i| {
Namespace::from(i.kind) == Namespace::Type &&
i.ident.modern() == assoc_ident
}).expect("missing associated type");
let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
let ty = self.normalize_ty(span, ty);
let kind = DefKind::AssocTy;
if !item.vis.is_accessible_from(def_scope, tcx) {
let msg = format!("{} `{}` is private", kind.descr(item.def_id), assoc_ident);
tcx.sess.span_err(span, &msg);
}
tcx.check_stability(item.def_id, Some(hir_ref_id), span);
if let Some(variant_def_id) = variant_resolution {
let mut err = tcx.struct_span_lint_hir(
AMBIGUOUS_ASSOCIATED_ITEMS,
hir_ref_id,
span,
"ambiguous associated item",
);
let mut could_refer_to = |kind: DefKind, def_id, also| {
let note_msg = format!("`{}` could{} refer to {} defined here",
assoc_ident, also, kind.descr(def_id));
err.span_note(tcx.def_span(def_id), &note_msg);
};
could_refer_to(DefKind::Variant, variant_def_id, "");
could_refer_to(kind, item.def_id, " also");
err.span_suggestion(
span,
"use fully-qualified syntax",
format!("<{} as {}>::{}", qself_ty, tcx.item_name(trait_did), assoc_ident),
Applicability::MachineApplicable,
).emit();
}
Ok((ty, kind, item.def_id))
}
fn qpath_to_ty(&self,
span: Span,
opt_self_ty: Option<Ty<'tcx>>,
item_def_id: DefId,
trait_segment: &hir::PathSegment,
item_segment: &hir::PathSegment)
-> Ty<'tcx>
{
let tcx = self.tcx();
let trait_def_id = tcx.parent(item_def_id).unwrap();
self.prohibit_generics(slice::from_ref(item_segment));
let self_ty = if let Some(ty) = opt_self_ty {
ty
} else {
let path_str = tcx.def_path_str(trait_def_id);
self.report_ambiguous_associated_type(
span,
"Type",
&path_str,
item_segment.ident.name,
);
return tcx.types.err;
};
debug!("qpath_to_ty: self_type={:?}", self_ty);
let trait_ref = self.ast_path_to_mono_trait_ref(span,
trait_def_id,
self_ty,
trait_segment);
debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
self.normalize_ty(span, tcx.mk_projection(item_def_id, trait_ref.substs))
}
pub fn prohibit_generics<'a, T: IntoIterator<Item = &'a hir::PathSegment>>(
&self, segments: T) -> bool {
let mut has_err = false;
for segment in segments {
let (mut err_for_lt, mut err_for_ty, mut err_for_ct) = (false, false, false);
for arg in &segment.generic_args().args {
let (span, kind) = match arg {
hir::GenericArg::Lifetime(lt) => {
if err_for_lt { continue }
err_for_lt = true;
has_err = true;
(lt.span, "lifetime")
}
hir::GenericArg::Type(ty) => {
if err_for_ty { continue }
err_for_ty = true;
has_err = true;
(ty.span, "type")
}
hir::GenericArg::Const(ct) => {
if err_for_ct { continue }
err_for_ct = true;
(ct.span, "const")
}
};
let mut err = struct_span_err!(
self.tcx().sess,
span,
E0109,
"{} arguments are not allowed for this type",
kind,
);
err.span_label(span, format!("{} argument not allowed", kind));
err.emit();
if err_for_lt && err_for_ty && err_for_ct {
break;
}
}
for binding in &segment.generic_args().bindings {
has_err = true;
Self::prohibit_assoc_ty_binding(self.tcx(), binding.span);
break;
}
}
has_err
}
pub fn prohibit_assoc_ty_binding(tcx: TyCtxt<'_>, span: Span) {
let mut err = struct_span_err!(tcx.sess, span, E0229,
"associated type bindings are not allowed here");
err.span_label(span, "associated type not allowed here").emit();
}
// FIXME(eddyb, varkor) handle type paths here too, not just value ones.
pub fn def_ids_for_value_path_segments(
&self,
segments: &[hir::PathSegment],
self_ty: Option<Ty<'tcx>>,
kind: DefKind,
def_id: DefId,
) -> Vec<PathSeg> {
// We need to extract the type parameters supplied by the user in
// the path `path`. Due to the current setup, this is a bit of a
// tricky-process; the problem is that resolve only tells us the
// end-point of the path resolution, and not the intermediate steps.
// Luckily, we can (at least for now) deduce the intermediate steps
// just from the end-point.
//
// There are basically five cases to consider:
//
// 1. Reference to a constructor of a struct:
//
// struct Foo<T>(...)
//
// In this case, the parameters are declared in the type space.
//
// 2. Reference to a constructor of an enum variant:
//
// enum E<T> { Foo(...) }
//
// In this case, the parameters are defined in the type space,
// but may be specified either on the type or the variant.
//
// 3. Reference to a fn item or a free constant:
//
// fn foo<T>() { }
//
// In this case, the path will again always have the form
// `a::b::foo::<T>` where only the final segment should have
// type parameters. However, in this case, those parameters are
// declared on a value, and hence are in the `FnSpace`.
//
// 4. Reference to a method or an associated constant:
//
// impl<A> SomeStruct<A> {
// fn foo<B>(...)
// }
//
// Here we can have a path like
// `a::b::SomeStruct::<A>::foo::<B>`, in which case parameters
// may appear in two places. The penultimate segment,
// `SomeStruct::<A>`, contains parameters in TypeSpace, and the
// final segment, `foo::<B>` contains parameters in fn space.
//
// The first step then is to categorize the segments appropriately.
let tcx = self.tcx();
assert!(!segments.is_empty());
let last = segments.len() - 1;
let mut path_segs = vec![];
match kind {
// Case 1. Reference to a struct constructor.
DefKind::Ctor(CtorOf::Struct, ..) => {
// Everything but the final segment should have no
// parameters at all.
let generics = tcx.generics_of(def_id);
// Variant and struct constructors use the
// generics of their parent type definition.
let generics_def_id = generics.parent.unwrap_or(def_id);
path_segs.push(PathSeg(generics_def_id, last));
}
// Case 2. Reference to a variant constructor.
DefKind::Ctor(CtorOf::Variant, ..)
| DefKind::Variant => {
let adt_def = self_ty.map(|t| t.ty_adt_def().unwrap());
let (generics_def_id, index) = if let Some(adt_def) = adt_def {
debug_assert!(adt_def.is_enum());
(adt_def.did, last)
} else if last >= 1 && segments[last - 1].args.is_some() {
// Everything but the penultimate segment should have no
// parameters at all.
let mut def_id = def_id;
// `DefKind::Ctor` -> `DefKind::Variant`
if let DefKind::Ctor(..) = kind {
def_id = tcx.parent(def_id).unwrap()
}
// `DefKind::Variant` -> `DefKind::Enum`
let enum_def_id = tcx.parent(def_id).unwrap();
(enum_def_id, last - 1)
} else {
// FIXME: lint here recommending `Enum::<...>::Variant` form
// instead of `Enum::Variant::<...>` form.
// Everything but the final segment should have no
// parameters at all.
let generics = tcx.generics_of(def_id);
// Variant and struct constructors use the
// generics of their parent type definition.
(generics.parent.unwrap_or(def_id), last)
};
path_segs.push(PathSeg(generics_def_id, index));
}
// Case 3. Reference to a top-level value.
DefKind::Fn
| DefKind::Const
| DefKind::ConstParam
| DefKind::Static => {
path_segs.push(PathSeg(def_id, last));
}
// Case 4. Reference to a method or associated const.
DefKind::Method
| DefKind::AssocConst => {
if segments.len() >= 2 {
let generics = tcx.generics_of(def_id);
path_segs.push(PathSeg(generics.parent.unwrap(), last - 1));
}
path_segs.push(PathSeg(def_id, last));
}
kind => bug!("unexpected definition kind {:?} for {:?}", kind, def_id),
}
debug!("path_segs = {:?}", path_segs);
path_segs
}
// Check a type `Path` and convert it to a `Ty`.
pub fn res_to_ty(&self,
opt_self_ty: Option<Ty<'tcx>>,
path: &hir::Path,
permit_variants: bool)
-> Ty<'tcx> {
let tcx = self.tcx();
debug!("res_to_ty(res={:?}, opt_self_ty={:?}, path_segments={:?})",
path.res, opt_self_ty, path.segments);
let span = path.span;
match path.res {
Res::Def(DefKind::OpaqueTy, did) => {
// Check for desugared `impl Trait`.
assert!(ty::is_impl_trait_defn(tcx, did).is_none());
let item_segment = path.segments.split_last().unwrap();
self.prohibit_generics(item_segment.1);
let substs = self.ast_path_substs_for_ty(span, did, item_segment.0);
self.normalize_ty(
span,
tcx.mk_opaque(did, substs),
)
}
Res::Def(DefKind::Enum, did)
| Res::Def(DefKind::TyAlias, did)
| Res::Def(DefKind::Struct, did)
| Res::Def(DefKind::Union, did)
| Res::Def(DefKind::ForeignTy, did) => {
assert_eq!(opt_self_ty, None);
self.prohibit_generics(path.segments.split_last().unwrap().1);
self.ast_path_to_ty(span, did, path.segments.last().unwrap())
}
Res::Def(kind @ DefKind::Variant, def_id) if permit_variants => {
// Convert "variant type" as if it were a real type.
// The resulting `Ty` is type of the variant's enum for now.
assert_eq!(opt_self_ty, None);
let path_segs =
self.def_ids_for_value_path_segments(&path.segments, None, kind, def_id);
let generic_segs: FxHashSet<_> =
path_segs.iter().map(|PathSeg(_, index)| index).collect();
self.prohibit_generics(path.segments.iter().enumerate().filter_map(|(index, seg)| {
if !generic_segs.contains(&index) {
Some(seg)
} else {
None
}
}));
let PathSeg(def_id, index) = path_segs.last().unwrap();
self.ast_path_to_ty(span, *def_id, &path.segments[*index])
}
Res::Def(DefKind::TyParam, def_id) => {
assert_eq!(opt_self_ty, None);
self.prohibit_generics(&path.segments);
let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
let item_id = tcx.hir().get_parent_node(hir_id);
let item_def_id = tcx.hir().local_def_id(item_id);
let generics = tcx.generics_of(item_def_id);
let index = generics.param_def_id_to_index[&def_id];
tcx.mk_ty_param(index, tcx.hir().name(hir_id).as_interned_str())
}
Res::SelfTy(Some(_), None) => {
// `Self` in trait or type alias.
assert_eq!(opt_self_ty, None);
self.prohibit_generics(&path.segments);
tcx.types.self_param
}
Res::SelfTy(_, Some(def_id)) => {
// `Self` in impl (we know the concrete type).
assert_eq!(opt_self_ty, None);
self.prohibit_generics(&path.segments);
// Try to evaluate any array length constants.
self.normalize_ty(span, tcx.at(span).type_of(def_id))
}
Res::Def(DefKind::AssocTy, def_id) => {
debug_assert!(path.segments.len() >= 2);
self.prohibit_generics(&path.segments[..path.segments.len() - 2]);
self.qpath_to_ty(span,
opt_self_ty,
def_id,
&path.segments[path.segments.len() - 2],
path.segments.last().unwrap())
}
Res::PrimTy(prim_ty) => {
assert_eq!(opt_self_ty, None);
self.prohibit_generics(&path.segments);
match prim_ty {
hir::Bool => tcx.types.bool,
hir::Char => tcx.types.char,
hir::Int(it) => tcx.mk_mach_int(it),
hir::Uint(uit) => tcx.mk_mach_uint(uit),
hir::Float(ft) => tcx.mk_mach_float(ft),
hir::Str => tcx.mk_str()
}
}
Res::Err => {
self.set_tainted_by_errors();
return self.tcx().types.err;
}
_ => span_bug!(span, "unexpected resolution: {:?}", path.res)
}
}
/// Parses the programmer's textual representation of a type into our
/// internal notion of a type.
pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
debug!("ast_ty_to_ty(id={:?}, ast_ty={:?} ty_ty={:?})",
ast_ty.hir_id, ast_ty, ast_ty.node);
let tcx = self.tcx();
let result_ty = match ast_ty.node {
hir::TyKind::Slice(ref ty) => {
tcx.mk_slice(self.ast_ty_to_ty(&ty))
}
hir::TyKind::Ptr(ref mt) => {
tcx.mk_ptr(ty::TypeAndMut {
ty: self.ast_ty_to_ty(&mt.ty),
mutbl: mt.mutbl
})
}
hir::TyKind::Rptr(ref region, ref mt) => {
let r = self.ast_region_to_region(region, None);
debug!("ast_ty_to_ty: r={:?}", r);
let t = self.ast_ty_to_ty(&mt.ty);
tcx.mk_ref(r, ty::TypeAndMut {ty: t, mutbl: mt.mutbl})
}
hir::TyKind::Never => {
tcx.types.never
},
hir::TyKind::Tup(ref fields) => {
tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
}
hir::TyKind::BareFn(ref bf) => {
require_c_abi_if_c_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
}
hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
}
hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
let opt_self_ty = maybe_qself.as_ref().map(|qself| {
self.ast_ty_to_ty(qself)
});
self.res_to_ty(opt_self_ty, path, false)
}
hir::TyKind::Def(item_id, ref lifetimes) => {
let did = tcx.hir().local_def_id(item_id.id);
self.impl_trait_ty_to_ty(did, lifetimes)
}
hir::TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => {
debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
let ty = self.ast_ty_to_ty(qself);
let res = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.node {
path.res
} else {
Res::Err
};
self.associated_path_to_ty(ast_ty.hir_id, ast_ty.span, ty, res, segment, false)
.map(|(ty, _, _)| ty).unwrap_or(tcx.types.err)
}
hir::TyKind::Array(ref ty, ref length) => {
let length = self.ast_const_to_const(length, tcx.types.usize);
let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length));
self.normalize_ty(ast_ty.span, array_ty)
}
hir::TyKind::Typeof(ref _e) => {
struct_span_err!(tcx.sess, ast_ty.span, E0516,
"`typeof` is a reserved keyword but unimplemented")
.span_label(ast_ty.span, "reserved keyword")
.emit();
tcx.types.err
}
hir::TyKind::Infer => {
// Infer also appears as the type of arguments or return
// values in a ExprKind::Closure, or as
// the type of local variables. Both of these cases are
// handled specially and will not descend into this routine.
self.ty_infer(None, ast_ty.span)
}
hir::TyKind::CVarArgs(lt) => {
let va_list_did = match tcx.lang_items().va_list() {
Some(did) => did,
None => span_bug!(ast_ty.span,
"`va_list` lang item required for variadics"),
};
let region = self.ast_region_to_region(&lt, None);
tcx.type_of(va_list_did).subst(tcx, &[region.into()])
}
hir::TyKind::Err => {
tcx.types.err
}
};
debug!("ast_ty_to_ty: result_ty={:?}", result_ty);
self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
result_ty
}
/// Returns the `DefId` of the constant parameter that the provided expression is a path to.
pub fn const_param_def_id(&self, expr: &hir::Expr) -> Option<DefId> {
// Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
// currently have to be wrapped in curly brackets, so it's necessary to special-case.
let expr = match &expr.node {
ExprKind::Block(block, _) if block.stmts.is_empty() && block.expr.is_some() =>
block.expr.as_ref().unwrap(),
_ => expr,
};
match &expr.node {
ExprKind::Path(hir::QPath::Resolved(_, path)) => match path.res {
Res::Def(DefKind::ConstParam, did) => Some(did),
_ => None,
},
_ => None,
}
}
pub fn ast_const_to_const(
&self,
ast_const: &hir::AnonConst,
ty: Ty<'tcx>
) -> &'tcx ty::Const<'tcx> {
debug!("ast_const_to_const(id={:?}, ast_const={:?})", ast_const.hir_id, ast_const);
let tcx = self.tcx();
let def_id = tcx.hir().local_def_id(ast_const.hir_id);
let mut const_ = ty::Const {
val: ConstValue::Unevaluated(
def_id,
InternalSubsts::identity_for_item(tcx, def_id),
),
ty,
};
let expr = &tcx.hir().body(ast_const.body).value;
if let Some(def_id) = self.const_param_def_id(expr) {
// Find the name and index of the const parameter by indexing the generics of the
// parent item and construct a `ParamConst`.
let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
let item_id = tcx.hir().get_parent_node(hir_id);
let item_def_id = tcx.hir().local_def_id(item_id);
let generics = tcx.generics_of(item_def_id);
let index = generics.param_def_id_to_index[&tcx.hir().local_def_id(hir_id)];
let name = tcx.hir().name(hir_id).as_interned_str();
const_.val = ConstValue::Param(ty::ParamConst::new(index, name));
}
tcx.mk_const(const_)
}
pub fn impl_trait_ty_to_ty(
&self,
def_id: DefId,
lifetimes: &[hir::GenericArg],
) -> Ty<'tcx> {
debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
let tcx = self.tcx();
let generics = tcx.generics_of(def_id);
debug!("impl_trait_ty_to_ty: generics={:?}", generics);
let substs = InternalSubsts::for_item(tcx, def_id, |param, _| {
if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
// Our own parameters are the resolved lifetimes.
match param.kind {
GenericParamDefKind::Lifetime => {
if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
self.ast_region_to_region(lifetime, None).into()
} else {
bug!()
}
}
_ => bug!()
}
} else {
// Replace all parent lifetimes with `'static`.
match param.kind {
GenericParamDefKind::Lifetime => {
tcx.lifetimes.re_static.into()
}
_ => tcx.mk_param_from_def(param)
}
}
});
debug!("impl_trait_ty_to_ty: substs={:?}", substs);
let ty = tcx.mk_opaque(def_id, substs);
debug!("impl_trait_ty_to_ty: {}", ty);
ty
}
pub fn ty_of_arg(&self,
ty: &hir::Ty,
expected_ty: Option<Ty<'tcx>>)
-> Ty<'tcx>
{
match ty.node {
hir::TyKind::Infer if expected_ty.is_some() => {
self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
expected_ty.unwrap()
}
_ => self.ast_ty_to_ty(ty),
}
}
pub fn ty_of_fn(&self,
unsafety: hir::Unsafety,
abi: abi::Abi,
decl: &hir::FnDecl)
-> ty::PolyFnSig<'tcx> {
debug!("ty_of_fn");
let tcx = self.tcx();
let input_tys =
decl.inputs.iter().map(|a| self.ty_of_arg(a, None));
let output_ty = match decl.output {
hir::Return(ref output) => self.ast_ty_to_ty(output),
hir::DefaultReturn(..) => tcx.mk_unit(),
};
debug!("ty_of_fn: output_ty={:?}", output_ty);
let bare_fn_ty = ty::Binder::bind(tcx.mk_fn_sig(
input_tys,
output_ty,
decl.c_variadic,
unsafety,
abi
));
// Find any late-bound regions declared in return type that do
// not appear in the arguments. These are not well-formed.
//
// Example:
// for<'a> fn() -> &'a str <-- 'a is bad
// for<'a> fn(&'a String) -> &'a str <-- 'a is ok
let inputs = bare_fn_ty.inputs();
let late_bound_in_args = tcx.collect_constrained_late_bound_regions(
&inputs.map_bound(|i| i.to_owned()));
let output = bare_fn_ty.output();
let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
for br in late_bound_in_ret.difference(&late_bound_in_args) {
let lifetime_name = match *br {
ty::BrNamed(_, name) => format!("lifetime `{}`,", name),
ty::BrAnon(_) | ty::BrEnv => "an anonymous lifetime".to_string(),
};
let mut err = struct_span_err!(tcx.sess,
decl.output.span(),
E0581,
"return type references {} \
which is not constrained by the fn input types",
lifetime_name);
if let ty::BrAnon(_) = *br {
// The only way for an anonymous lifetime to wind up
// in the return type but **also** be unconstrained is
// if it only appears in "associated types" in the
// input. See #47511 for an example. In this case,
// though we can easily give a hint that ought to be
// relevant.
err.note("lifetimes appearing in an associated type \
are not considered constrained");
}
err.emit();
}
bare_fn_ty
}
/// Given the bounds on an object, determines what single region bound (if any) we can
/// use to summarize this type. The basic idea is that we will use the bound the user
/// provided, if they provided one, and otherwise search the supertypes of trait bounds
/// for region bounds. It may be that we can derive no bound at all, in which case
/// we return `None`.
fn compute_object_lifetime_bound(&self,
span: Span,
existential_predicates: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>)
-> Option<ty::Region<'tcx>> // if None, use the default
{
let tcx = self.tcx();
debug!("compute_opt_region_bound(existential_predicates={:?})",
existential_predicates);
// No explicit region bound specified. Therefore, examine trait
// bounds and see if we can derive region bounds from those.
let derived_region_bounds =
object_region_bounds(tcx, existential_predicates);
// If there are no derived region bounds, then report back that we
// can find no region bound. The caller will use the default.
if derived_region_bounds.is_empty() {
return None;
}
// If any of the derived region bounds are 'static, that is always
// the best choice.
if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
return Some(tcx.lifetimes.re_static);
}
// Determine whether there is exactly one unique region in the set
// of derived region bounds. If so, use that. Otherwise, report an
// error.
let r = derived_region_bounds[0];
if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
span_err!(tcx.sess, span, E0227,
"ambiguous lifetime bound, explicit lifetime bound required");
}
return Some(r);
}
}
/// Collects together a list of bounds that are applied to some type,
/// after they've been converted into `ty` form (from the HIR
/// representations). These lists of bounds occur in many places in
/// Rust's syntax:
///
/// ```
/// trait Foo: Bar + Baz { }
/// ^^^^^^^^^ supertrait list bounding the `Self` type parameter
///
/// fn foo<T: Bar + Baz>() { }
/// ^^^^^^^^^ bounding the type parameter `T`
///
/// impl dyn Bar + Baz
/// ^^^^^^^^^ bounding the forgotten dynamic type
/// ```
///
/// Our representation is a bit mixed here -- in some cases, we
/// include the self type (e.g., `trait_bounds`) but in others we do
#[derive(Default, PartialEq, Eq, Clone, Debug)]
pub struct Bounds<'tcx> {
/// A list of region bounds on the (implicit) self type. So if you
/// had `T: 'a + 'b` this might would be a list `['a, 'b]` (but
/// the `T` is not explicitly included).
pub region_bounds: Vec<(ty::Region<'tcx>, Span)>,
/// A list of trait bounds. So if you had `T: Debug` this would be
/// `T: Debug`. Note that the self-type is explicit here.
pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span)>,
/// A list of projection equality bounds. So if you had `T:
/// Iterator<Item = u32>` this would include `<T as
/// Iterator>::Item => u32`. Note that the self-type is explicit
/// here.
pub projection_bounds: Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
/// `Some` if there is *no* `?Sized` predicate. The `span`
/// is the location in the source of the `T` declaration which can
/// be cited as the source of the `T: Sized` requirement.
pub implicitly_sized: Option<Span>,
}
impl<'tcx> Bounds<'tcx> {
/// Converts a bounds list into a flat set of predicates (like
/// where-clauses). Because some of our bounds listings (e.g.,
/// regions) don't include the self-type, you must supply the
/// self-type here (the `param_ty` parameter).
pub fn predicates(
&self,
tcx: TyCtxt<'tcx>,
param_ty: Ty<'tcx>,
) -> Vec<(ty::Predicate<'tcx>, Span)> {
// If it could be sized, and is, add the `Sized` predicate.
let sized_predicate = self.implicitly_sized.and_then(|span| {
tcx.lang_items().sized_trait().map(|sized| {
let trait_ref = ty::TraitRef {
def_id: sized,
substs: tcx.mk_substs_trait(param_ty, &[])
};
(trait_ref.to_predicate(), span)
})
});
sized_predicate.into_iter().chain(
self.region_bounds.iter().map(|&(region_bound, span)| {
// Account for the binder being introduced below; no need to shift `param_ty`
// because, at present at least, it can only refer to early-bound regions.
let region_bound = ty::fold::shift_region(tcx, region_bound, 1);
let outlives = ty::OutlivesPredicate(param_ty, region_bound);
(ty::Binder::dummy(outlives).to_predicate(), span)
}).chain(
self.trait_bounds.iter().map(|&(bound_trait_ref, span)| {
(bound_trait_ref.to_predicate(), span)
})
).chain(
self.projection_bounds.iter().map(|&(projection, span)| {
(projection.to_predicate(), span)
})
)
).collect()
}
}