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android / toolchain / rustc / 87880447cc5437c45a3562596a9766d9797e7318 / . / compiler / rustc_hir_analysis / src / astconv / mod.rs
blob: 668763f9bf60d342d8f10b832a07a4491a883252 [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`.
mod bounds;
mod errors;
pub mod generics;
mod lint;
mod object_safety;
use crate::astconv::errors::prohibit_assoc_ty_binding;
use crate::astconv::generics::{check_generic_arg_count, create_args_for_parent_generic_args};
use crate::bounds::Bounds;
use crate::collect::HirPlaceholderCollector;
use crate::errors::{AmbiguousLifetimeBound, TypeofReservedKeywordUsed};
use crate::middle::resolve_bound_vars as rbv;
use crate::require_c_abi_if_c_variadic;
use rustc_ast::TraitObjectSyntax;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_errors::{
struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, FatalError,
MultiSpan,
};
use rustc_hir as hir;
use rustc_hir::def::{CtorOf, DefKind, Namespace, Res};
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_hir::intravisit::{walk_generics, Visitor as _};
use rustc_hir::{GenericArg, GenericArgs, OpaqueTyOrigin};
use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
use rustc_infer::traits::ObligationCause;
use rustc_middle::middle::stability::AllowUnstable;
use rustc_middle::ty::GenericParamDefKind;
use rustc_middle::ty::{
self, Const, GenericArgKind, GenericArgsRef, IsSuggestable, Ty, TyCtxt, TypeVisitableExt,
};
use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
use rustc_span::edit_distance::find_best_match_for_name;
use rustc_span::symbol::{kw, Ident, Symbol};
use rustc_span::{sym, Span, DUMMY_SP};
use rustc_target::spec::abi;
use rustc_trait_selection::traits::wf::object_region_bounds;
use rustc_trait_selection::traits::{self, NormalizeExt, ObligationCtxt};
use rustc_type_ir::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
use std::fmt::Display;
use std::slice;
#[derive(Debug)]
pub struct PathSeg(pub DefId, pub usize);
#[derive(Copy, Clone, Debug)]
pub struct OnlySelfBounds(pub bool);
#[derive(Copy, Clone, Debug)]
pub enum PredicateFilter {
/// All predicates may be implied by the trait.
All,
/// Only traits that reference `Self: ..` are implied by the trait.
SelfOnly,
/// Only traits that reference `Self: ..` and define an associated type
/// with the given ident are implied by the trait.
SelfThatDefines(Ident),
/// Only traits that reference `Self: ..` and their associated type bounds.
/// For example, given `Self: Tr<A: B>`, this would expand to `Self: Tr`
/// and `<Self as Tr>::A: B`.
SelfAndAssociatedTypeBounds,
}
pub trait AstConv<'tcx> {
fn tcx(&self) -> TyCtxt<'tcx>;
fn item_def_id(&self) -> DefId;
/// Returns predicates in scope of the form `X: Foo<T>`, where `X`
/// is a type parameter `X` with the given id `def_id` and T
/// matches `assoc_name`. 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: LocalDefId,
assoc_name: Ident,
) -> 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 `true` if `_` is allowed in type signatures in the current context.
fn allow_ty_infer(&self) -> bool;
/// Returns the const to use when a const is omitted.
fn ct_infer(
&self,
ty: Ty<'tcx>,
param: Option<&ty::GenericParamDef>,
span: Span,
) -> 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,
item_segment: &hir::PathSegment<'_>,
poly_trait_ref: ty::PolyTraitRef<'tcx>,
) -> Ty<'tcx>;
/// Returns `AdtDef` if `ty` is an ADT.
/// Note that `ty` might be a projection type that needs normalization.
/// This used to get the enum variants in scope of the type.
/// For example, `Self::A` could refer to an associated type
/// or to an enum variant depending on the result of this function.
fn probe_adt(&self, span: Span, ty: Ty<'tcx>) -> Option<ty::AdtDef<'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, e: ErrorGuaranteed);
fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
fn astconv(&self) -> &dyn AstConv<'tcx>
where
Self: Sized,
{
self
}
fn infcx(&self) -> Option<&InferCtxt<'tcx>>;
}
#[derive(Debug)]
struct ConvertedBinding<'a, 'tcx> {
hir_id: hir::HirId,
item_name: Ident,
kind: ConvertedBindingKind<'a, 'tcx>,
gen_args: &'a GenericArgs<'a>,
span: Span,
}
#[derive(Debug)]
enum ConvertedBindingKind<'a, 'tcx> {
Equality(ty::Term<'tcx>),
Constraint(&'a [hir::GenericBound<'a>]),
}
/// New-typed boolean indicating whether explicit late-bound lifetimes
/// are present in a set of generic arguments.
///
/// For example if we have some method `fn f<'a>(&'a self)` implemented
/// for some type `T`, although `f` is generic in the lifetime `'a`, `'a`
/// is late-bound so should not be provided explicitly. Thus, if `f` is
/// instantiated with some generic arguments providing `'a` explicitly,
/// we taint those arguments with `ExplicitLateBound::Yes` so that we
/// can provide an appropriate diagnostic later.
#[derive(Copy, Clone, PartialEq, Debug)]
pub enum ExplicitLateBound {
Yes,
No,
}
#[derive(Copy, Clone, PartialEq)]
pub enum IsMethodCall {
Yes,
No,
}
/// Denotes the "position" of a generic argument, indicating if it is a generic type,
/// generic function or generic method call.
#[derive(Copy, Clone, PartialEq)]
pub(crate) enum GenericArgPosition {
Type,
Value, // e.g., functions
MethodCall,
}
/// A marker denoting that the generic arguments that were
/// provided did not match the respective generic parameters.
#[derive(Clone, Default, Debug)]
pub struct GenericArgCountMismatch {
/// Indicates whether a fatal error was reported (`Some`), or just a lint (`None`).
pub reported: Option<ErrorGuaranteed>,
/// A list of spans of arguments provided that were not valid.
pub invalid_args: Vec<Span>,
}
/// Decorates the result of a generic argument count mismatch
/// check with whether explicit late bounds were provided.
#[derive(Clone, Debug)]
pub struct GenericArgCountResult {
pub explicit_late_bound: ExplicitLateBound,
pub correct: Result<(), GenericArgCountMismatch>,
}
pub trait CreateSubstsForGenericArgsCtxt<'a, 'tcx> {
fn args_for_def_id(&mut self, def_id: DefId) -> (Option<&'a GenericArgs<'a>>, bool);
fn provided_kind(
&mut self,
param: &ty::GenericParamDef,
arg: &GenericArg<'_>,
) -> ty::GenericArg<'tcx>;
fn inferred_kind(
&mut self,
args: Option<&[ty::GenericArg<'tcx>]>,
param: &ty::GenericParamDef,
infer_args: bool,
) -> ty::GenericArg<'tcx>;
}
impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
#[instrument(level = "debug", skip(self), ret)]
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().local_def_id_to_hir_id(def_id));
match tcx.named_bound_var(lifetime.hir_id) {
Some(rbv::ResolvedArg::StaticLifetime) => tcx.lifetimes.re_static,
Some(rbv::ResolvedArg::LateBound(debruijn, index, def_id)) => {
let name = lifetime_name(def_id.expect_local());
let br = ty::BoundRegion {
var: ty::BoundVar::from_u32(index),
kind: ty::BrNamed(def_id, name),
};
ty::Region::new_late_bound(tcx, debruijn, br)
}
Some(rbv::ResolvedArg::EarlyBound(def_id)) => {
let name = tcx.hir().ty_param_name(def_id.expect_local());
let item_def_id = tcx.hir().ty_param_owner(def_id.expect_local());
let generics = tcx.generics_of(item_def_id);
let index = generics.param_def_id_to_index[&def_id];
ty::Region::new_early_bound(tcx, ty::EarlyBoundRegion { def_id, index, name })
}
Some(rbv::ResolvedArg::Free(scope, id)) => {
let name = lifetime_name(id.expect_local());
ty::Region::new_free(tcx, scope, ty::BrNamed(id, name))
// (*) -- not late-bound, won't change
}
Some(rbv::ResolvedArg::Error(_)) => {
bug!("only ty/ct should resolve as ResolvedArg::Error")
}
None => {
self.re_infer(def, lifetime.ident.span).unwrap_or_else(|| {
debug!(?lifetime, "unelided lifetime in signature");
// This indicates an illegal lifetime
// elision. `resolve_lifetime` should have
// reported an error in this case -- but if
// not, let's error out.
ty::Region::new_error_with_message(
tcx,
lifetime.ident.span,
"unelided lifetime in signature",
)
})
}
}
}
/// 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_args_for_ty(
&self,
span: Span,
def_id: DefId,
item_segment: &hir::PathSegment<'_>,
) -> GenericArgsRef<'tcx> {
let (args, _) = self.create_args_for_ast_path(
span,
def_id,
&[],
item_segment,
item_segment.args(),
item_segment.infer_args,
None,
ty::BoundConstness::NotConst,
);
if let Some(b) = item_segment.args().bindings.first() {
prohibit_assoc_ty_binding(self.tcx(), b.span, Some((item_segment, span)));
}
args
}
/// 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.
/// Constraints on associated types are created from `create_assoc_bindings_for_generic_args`.
///
/// Example:
///
/// ```ignore (illustrative)
/// 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 `GenericArgsRef`, the associated type bindings like
/// `Output = u32` are returned from `create_assoc_bindings_for_generic_args`.
///
/// Note that the type listing given here is *exactly* what the user provided.
///
/// For (generic) associated types
///
/// ```ignore (illustrative)
/// <Vec<u8> as Iterable<u8>>::Iter::<'a>
/// ```
///
/// We have the parent args are the args for the parent trait:
/// `[Vec<u8>, u8]` and `generic_args` are the arguments for the associated
/// type itself: `['a]`. The returned `GenericArgsRef` concatenates these two
/// lists: `[Vec<u8>, u8, 'a]`.
#[instrument(level = "debug", skip(self, span), ret)]
fn create_args_for_ast_path<'a>(
&self,
span: Span,
def_id: DefId,
parent_args: &[ty::GenericArg<'tcx>],
seg: &hir::PathSegment<'_>,
generic_args: &'a hir::GenericArgs<'_>,
infer_args: bool,
self_ty: Option<Ty<'tcx>>,
constness: ty::BoundConstness,
) -> (GenericArgsRef<'tcx>, GenericArgCountResult) {
// 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).
let tcx = self.tcx();
let generics = tcx.generics_of(def_id);
debug!("generics: {:?}", generics);
if generics.has_self {
if generics.parent.is_some() {
// The parent is a trait so it should have at least one subst
// for the `Self` type.
assert!(!parent_args.is_empty())
} else {
// This item (presumably a trait) needs a self-type.
assert!(self_ty.is_some());
}
} else {
assert!(self_ty.is_none());
}
let arg_count = check_generic_arg_count(
tcx,
span,
def_id,
seg,
generics,
generic_args,
GenericArgPosition::Type,
self_ty.is_some(),
infer_args,
);
// Skip processing if type has no generic parameters.
// Traits always have `Self` as a generic parameter, which means they will not return early
// here and so associated type bindings will be handled regardless of whether there are any
// non-`Self` generic parameters.
if generics.params.is_empty() {
return (tcx.mk_args(parent_args), arg_count);
}
struct SubstsForAstPathCtxt<'a, 'tcx> {
astconv: &'a (dyn AstConv<'tcx> + 'a),
def_id: DefId,
generic_args: &'a GenericArgs<'a>,
span: Span,
inferred_params: Vec<Span>,
infer_args: bool,
}
impl<'a, 'tcx> CreateSubstsForGenericArgsCtxt<'a, 'tcx> for SubstsForAstPathCtxt<'a, 'tcx> {
fn args_for_def_id(&mut self, did: DefId) -> (Option<&'a GenericArgs<'a>>, bool) {
if did == self.def_id {
(Some(self.generic_args), self.infer_args)
} else {
// The last component of this tuple is unimportant.
(None, false)
}
}
fn provided_kind(
&mut self,
param: &ty::GenericParamDef,
arg: &GenericArg<'_>,
) -> ty::GenericArg<'tcx> {
let tcx = self.astconv.tcx();
let mut handle_ty_args = |has_default, ty: &hir::Ty<'_>| {
if has_default {
tcx.check_optional_stability(
param.def_id,
Some(arg.hir_id()),
arg.span(),
None,
AllowUnstable::No,
|_, _| {
// Default generic parameters may not be marked
// with stability attributes, i.e. when the
// default parameter was defined at the same time
// as the rest of the type. As such, we ignore missing
// stability attributes.
},
);
}
if let (hir::TyKind::Infer, false) = (&ty.kind, self.astconv.allow_ty_infer()) {
self.inferred_params.push(ty.span);
Ty::new_misc_error(tcx).into()
} else {
self.astconv.ast_ty_to_ty(ty).into()
}
};
match (&param.kind, arg) {
(GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
self.astconv.ast_region_to_region(lt, Some(param)).into()
}
(&GenericParamDefKind::Type { has_default, .. }, GenericArg::Type(ty)) => {
handle_ty_args(has_default, ty)
}
(&GenericParamDefKind::Type { has_default, .. }, GenericArg::Infer(inf)) => {
handle_ty_args(has_default, &inf.to_ty())
}
(GenericParamDefKind::Const { .. }, GenericArg::Const(ct)) => {
let did = ct.value.def_id;
tcx.feed_anon_const_type(did, tcx.type_of(param.def_id));
ty::Const::from_anon_const(tcx, did).into()
}
(&GenericParamDefKind::Const { .. }, hir::GenericArg::Infer(inf)) => {
let ty = tcx
.at(self.span)
.type_of(param.def_id)
.no_bound_vars()
.expect("const parameter types cannot be generic");
if self.astconv.allow_ty_infer() {
self.astconv.ct_infer(ty, Some(param), inf.span).into()
} else {
self.inferred_params.push(inf.span);
ty::Const::new_misc_error(tcx, ty).into()
}
}
_ => unreachable!(),
}
}
fn inferred_kind(
&mut self,
args: Option<&[ty::GenericArg<'tcx>]>,
param: &ty::GenericParamDef,
infer_args: bool,
) -> ty::GenericArg<'tcx> {
let tcx = self.astconv.tcx();
match param.kind {
GenericParamDefKind::Lifetime => self
.astconv
.re_infer(Some(param), self.span)
.unwrap_or_else(|| {
debug!(?param, "unelided lifetime in signature");
// This indicates an illegal lifetime in a non-assoc-trait position
ty::Region::new_error_with_message(
tcx,
self.span,
"unelided lifetime in signature",
)
})
.into(),
GenericParamDefKind::Type { has_default, .. } => {
if !infer_args && has_default {
// No type parameter provided, but a default exists.
let args = args.unwrap();
if args.iter().any(|arg| match arg.unpack() {
GenericArgKind::Type(ty) => ty.references_error(),
_ => false,
}) {
// Avoid ICE #86756 when type error recovery goes awry.
return Ty::new_misc_error(tcx).into();
}
tcx.at(self.span).type_of(param.def_id).instantiate(tcx, args).into()
} else if infer_args {
self.astconv.ty_infer(Some(param), self.span).into()
} else {
// We've already errored above about the mismatch.
Ty::new_misc_error(tcx).into()
}
}
GenericParamDefKind::Const { has_default } => {
let ty = tcx
.at(self.span)
.type_of(param.def_id)
.no_bound_vars()
.expect("const parameter types cannot be generic");
if let Err(guar) = ty.error_reported() {
return ty::Const::new_error(tcx, guar, ty).into();
}
// FIXME(effects) see if we should special case effect params here
if !infer_args && has_default {
tcx.const_param_default(param.def_id)
.instantiate(tcx, args.unwrap())
.into()
} else {
if infer_args {
self.astconv.ct_infer(ty, Some(param), self.span).into()
} else {
// We've already errored above about the mismatch.
ty::Const::new_misc_error(tcx, ty).into()
}
}
}
}
}
}
let mut args_ctx = SubstsForAstPathCtxt {
astconv: self,
def_id,
span,
generic_args,
inferred_params: vec![],
infer_args,
};
let args = create_args_for_parent_generic_args(
tcx,
def_id,
parent_args,
self_ty.is_some(),
self_ty,
&arg_count,
&mut args_ctx,
);
if let ty::BoundConstness::ConstIfConst = constness
&& generics.has_self && !tcx.has_attr(def_id, sym::const_trait)
{
tcx.sess.emit_err(crate::errors::ConstBoundForNonConstTrait { span } );
}
(args, arg_count)
}
fn create_assoc_bindings_for_generic_args<'a>(
&self,
generic_args: &'a hir::GenericArgs<'_>,
) -> Vec<ConvertedBinding<'a, 'tcx>> {
// 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 { term } => match term {
hir::Term::Ty(ty) => {
ConvertedBindingKind::Equality(self.ast_ty_to_ty(ty).into())
}
hir::Term::Const(c) => {
let c = Const::from_anon_const(self.tcx(), c.def_id);
ConvertedBindingKind::Equality(c.into())
}
},
hir::TypeBindingKind::Constraint { bounds } => {
ConvertedBindingKind::Constraint(bounds)
}
};
ConvertedBinding {
hir_id: binding.hir_id,
item_name: binding.ident,
kind,
gen_args: binding.gen_args,
span: binding.span,
}
})
.collect();
assoc_bindings
}
pub fn create_args_for_associated_item(
&self,
span: Span,
item_def_id: DefId,
item_segment: &hir::PathSegment<'_>,
parent_args: GenericArgsRef<'tcx>,
) -> GenericArgsRef<'tcx> {
debug!(
"create_args_for_associated_item(span: {:?}, item_def_id: {:?}, item_segment: {:?}",
span, item_def_id, item_segment
);
let (args, _) = self.create_args_for_ast_path(
span,
item_def_id,
parent_args,
item_segment,
item_segment.args(),
item_segment.infer_args,
None,
ty::BoundConstness::NotConst,
);
if let Some(b) = item_segment.args().bindings.first() {
prohibit_assoc_ty_binding(self.tcx(), b.span, Some((item_segment, span)));
}
args
}
/// 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.iter(), |_| {});
self.ast_path_to_mono_trait_ref(
trait_ref.path.span,
trait_ref.trait_def_id().unwrap_or_else(|| FatalError.raise()),
self_ty,
trait_ref.path.segments.last().unwrap(),
true,
ty::BoundConstness::NotConst,
)
}
fn instantiate_poly_trait_ref_inner(
&self,
hir_id: hir::HirId,
span: Span,
binding_span: Option<Span>,
constness: ty::BoundConstness,
polarity: ty::ImplPolarity,
bounds: &mut Bounds<'tcx>,
speculative: bool,
trait_ref_span: Span,
trait_def_id: DefId,
trait_segment: &hir::PathSegment<'_>,
args: &GenericArgs<'_>,
infer_args: bool,
self_ty: Ty<'tcx>,
only_self_bounds: OnlySelfBounds,
) -> GenericArgCountResult {
let (generic_args, arg_count) = self.create_args_for_ast_path(
trait_ref_span,
trait_def_id,
&[],
trait_segment,
args,
infer_args,
Some(self_ty),
constness,
);
let tcx = self.tcx();
let bound_vars = tcx.late_bound_vars(hir_id);
debug!(?bound_vars);
let assoc_bindings = self.create_assoc_bindings_for_generic_args(args);
let poly_trait_ref = ty::Binder::bind_with_vars(
ty::TraitRef::new(tcx, trait_def_id, generic_args),
bound_vars,
);
debug!(?poly_trait_ref, ?assoc_bindings);
bounds.push_trait_bound(tcx, poly_trait_ref, span, polarity);
let mut dup_bindings = FxHashMap::default();
for binding in &assoc_bindings {
// Don't register additional associated type bounds for negative bounds,
// since we should have emitten an error for them earlier, and they will
// not be well-formed!
if polarity == ty::ImplPolarity::Negative {
self.tcx()
.sess
.delay_span_bug(binding.span, "negative trait bounds should not have bindings");
continue;
}
// Specify type to assert that error was already reported in `Err` case.
let _: Result<_, ErrorGuaranteed> = self.add_predicates_for_ast_type_binding(
hir_id,
poly_trait_ref,
binding,
bounds,
speculative,
&mut dup_bindings,
binding_span.unwrap_or(binding.span),
constness,
only_self_bounds,
polarity,
);
// Okay to ignore `Err` because of `ErrorGuaranteed` (see above).
}
arg_count
}
/// 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:
///
/// ```ignore (illustrative)
/// 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.
#[instrument(level = "debug", skip(self, span, constness, bounds, speculative))]
pub(crate) fn instantiate_poly_trait_ref(
&self,
trait_ref: &hir::TraitRef<'_>,
span: Span,
constness: ty::BoundConstness,
polarity: ty::ImplPolarity,
self_ty: Ty<'tcx>,
bounds: &mut Bounds<'tcx>,
speculative: bool,
only_self_bounds: OnlySelfBounds,
) -> GenericArgCountResult {
let hir_id = trait_ref.hir_ref_id;
let binding_span = None;
let trait_ref_span = trait_ref.path.span;
let trait_def_id = trait_ref.trait_def_id().unwrap_or_else(|| FatalError.raise());
let trait_segment = trait_ref.path.segments.last().unwrap();
let args = trait_segment.args();
let infer_args = trait_segment.infer_args;
self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1.iter(), |_| {});
self.complain_about_internal_fn_trait(span, trait_def_id, trait_segment, false);
self.instantiate_poly_trait_ref_inner(
hir_id,
span,
binding_span,
constness,
polarity,
bounds,
speculative,
trait_ref_span,
trait_def_id,
trait_segment,
args,
infer_args,
self_ty,
only_self_bounds,
)
}
pub(crate) fn instantiate_lang_item_trait_ref(
&self,
lang_item: hir::LangItem,
span: Span,
hir_id: hir::HirId,
args: &GenericArgs<'_>,
self_ty: Ty<'tcx>,
bounds: &mut Bounds<'tcx>,
only_self_bounds: OnlySelfBounds,
) {
let binding_span = Some(span);
let constness = ty::BoundConstness::NotConst;
let speculative = false;
let trait_ref_span = span;
let trait_def_id = self.tcx().require_lang_item(lang_item, Some(span));
let trait_segment = &hir::PathSegment::invalid();
let infer_args = false;
self.instantiate_poly_trait_ref_inner(
hir_id,
span,
binding_span,
constness,
ty::ImplPolarity::Positive,
bounds,
speculative,
trait_ref_span,
trait_def_id,
trait_segment,
args,
infer_args,
self_ty,
only_self_bounds,
);
}
fn ast_path_to_mono_trait_ref(
&self,
span: Span,
trait_def_id: DefId,
self_ty: Ty<'tcx>,
trait_segment: &hir::PathSegment<'_>,
is_impl: bool,
// FIXME(effects) move all host param things in astconv to hir lowering
constness: ty::BoundConstness,
) -> ty::TraitRef<'tcx> {
let (generic_args, _) = self.create_args_for_ast_trait_ref(
span,
trait_def_id,
self_ty,
trait_segment,
is_impl,
constness,
);
if let Some(b) = trait_segment.args().bindings.first() {
prohibit_assoc_ty_binding(self.tcx(), b.span, Some((trait_segment, span)));
}
ty::TraitRef::new(self.tcx(), trait_def_id, generic_args)
}
#[instrument(level = "debug", skip(self, span))]
fn create_args_for_ast_trait_ref<'a>(
&self,
span: Span,
trait_def_id: DefId,
self_ty: Ty<'tcx>,
trait_segment: &'a hir::PathSegment<'a>,
is_impl: bool,
constness: ty::BoundConstness,
) -> (GenericArgsRef<'tcx>, GenericArgCountResult) {
self.complain_about_internal_fn_trait(span, trait_def_id, trait_segment, is_impl);
self.create_args_for_ast_path(
span,
trait_def_id,
&[],
trait_segment,
trait_segment.args(),
trait_segment.infer_args,
Some(self_ty),
constness,
)
}
fn trait_defines_associated_item_named(
&self,
trait_def_id: DefId,
assoc_kind: ty::AssocKind,
assoc_name: Ident,
) -> bool {
self.tcx()
.associated_items(trait_def_id)
.find_by_name_and_kind(self.tcx(), assoc_name, assoc_kind, trait_def_id)
.is_some()
}
fn ast_path_to_ty(
&self,
span: Span,
did: DefId,
item_segment: &hir::PathSegment<'_>,
) -> Ty<'tcx> {
let tcx = self.tcx();
let args = self.ast_path_args_for_ty(span, did, item_segment);
let ty = tcx.at(span).type_of(did);
if let DefKind::TyAlias { lazy } = tcx.def_kind(did)
&& (lazy || ty.skip_binder().has_opaque_types())
{
// Type aliases referring to types that contain opaque types (but aren't just directly
// referencing a single opaque type) as well as those defined in crates that have the
// feature `lazy_type_alias` enabled get encoded as a type alias that normalization will
// then actually instantiate the where bounds of.
let alias_ty = tcx.mk_alias_ty(did, args);
Ty::new_alias(tcx, ty::Weak, alias_ty)
} else {
ty.instantiate(tcx, args)
}
}
fn report_ambiguous_associated_type(
&self,
span: Span,
types: &[String],
traits: &[String],
name: Symbol,
) -> ErrorGuaranteed {
let mut err = struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type");
if self
.tcx()
.resolutions(())
.confused_type_with_std_module
.keys()
.any(|full_span| full_span.contains(span))
{
err.span_suggestion_verbose(
span.shrink_to_lo(),
"you are looking for the module in `std`, not the primitive type",
"std::",
Applicability::MachineApplicable,
);
} else {
match (types, traits) {
([], []) => {
err.span_suggestion_verbose(
span,
format!(
"if there were a type named `Type` that implements a trait named \
`Trait` with associated type `{name}`, you could use the \
fully-qualified path",
),
format!("<Type as Trait>::{name}"),
Applicability::HasPlaceholders,
);
}
([], [trait_str]) => {
err.span_suggestion_verbose(
span,
format!(
"if there were a type named `Example` that implemented `{trait_str}`, \
you could use the fully-qualified path",
),
format!("<Example as {trait_str}>::{name}"),
Applicability::HasPlaceholders,
);
}
([], traits) => {
err.span_suggestions(
span,
format!(
"if there were a type named `Example` that implemented one of the \
traits with associated type `{name}`, you could use the \
fully-qualified path",
),
traits
.iter()
.map(|trait_str| format!("<Example as {trait_str}>::{name}"))
.collect::<Vec<_>>(),
Applicability::HasPlaceholders,
);
}
([type_str], []) => {
err.span_suggestion_verbose(
span,
format!(
"if there were a trait named `Example` with associated type `{name}` \
implemented for `{type_str}`, you could use the fully-qualified path",
),
format!("<{type_str} as Example>::{name}"),
Applicability::HasPlaceholders,
);
}
(types, []) => {
err.span_suggestions(
span,
format!(
"if there were a trait named `Example` with associated type `{name}` \
implemented for one of the types, you could use the fully-qualified \
path",
),
types
.into_iter()
.map(|type_str| format!("<{type_str} as Example>::{name}")),
Applicability::HasPlaceholders,
);
}
(types, traits) => {
let mut suggestions = vec![];
for type_str in types {
for trait_str in traits {
suggestions.push(format!("<{type_str} as {trait_str}>::{name}"));
}
}
err.span_suggestions(
span,
"use the fully-qualified path",
suggestions,
Applicability::MachineApplicable,
);
}
}
}
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: LocalDefId,
assoc_name: Ident,
span: Span,
) -> Result<ty::PolyTraitRef<'tcx>, ErrorGuaranteed> {
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, assoc_name).predicates;
debug!("find_bound_for_assoc_item: predicates={:#?}", predicates);
let param_name = tcx.hir().ty_param_name(ty_param_def_id);
self.one_bound_for_assoc_type(
|| {
traits::transitive_bounds_that_define_assoc_item(
tcx,
predicates
.iter()
.filter_map(|(p, _)| Some(p.as_trait_clause()?.map_bound(|t| t.trait_ref))),
assoc_name,
)
},
param_name,
assoc_name,
span,
None,
)
}
// Checks that `bounds` contains exactly one element and reports appropriate
// errors otherwise.
#[instrument(level = "debug", skip(self, all_candidates, ty_param_name, is_equality), ret)]
fn one_bound_for_assoc_type<I>(
&self,
all_candidates: impl Fn() -> I,
ty_param_name: impl Display,
assoc_name: Ident,
span: Span,
is_equality: Option<ty::Term<'tcx>>,
) -> Result<ty::PolyTraitRef<'tcx>, ErrorGuaranteed>
where
I: Iterator<Item = ty::PolyTraitRef<'tcx>>,
{
let mut matching_candidates = all_candidates().filter(|r| {
self.trait_defines_associated_item_named(r.def_id(), ty::AssocKind::Type, assoc_name)
});
let mut const_candidates = all_candidates().filter(|r| {
self.trait_defines_associated_item_named(r.def_id(), ty::AssocKind::Const, assoc_name)
});
let (bound, next_cand) = match (matching_candidates.next(), const_candidates.next()) {
(Some(bound), _) => (bound, matching_candidates.next()),
(None, Some(bound)) => (bound, const_candidates.next()),
(None, None) => {
let reported = self.complain_about_assoc_type_not_found(
all_candidates,
&ty_param_name.to_string(),
assoc_name,
span,
);
return Err(reported);
}
};
debug!(?bound);
if let Some(bound2) = next_cand {
debug!(?bound2);
let bounds = IntoIterator::into_iter([bound, bound2]).chain(matching_candidates);
let mut err = if is_equality.is_some() {
// More specific Error Index entry.
struct_span_err!(
self.tcx().sess,
span,
E0222,
"ambiguous associated type `{}` in bounds of `{}`",
assoc_name,
ty_param_name
)
} else {
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}`"));
let mut where_bounds = vec![];
for bound in bounds {
let bound_id = bound.def_id();
let bound_span = self
.tcx()
.associated_items(bound_id)
.find_by_name_and_kind(self.tcx(), assoc_name, ty::AssocKind::Type, bound_id)
.and_then(|item| self.tcx().hir().span_if_local(item.def_id));
if let Some(bound_span) = bound_span {
err.span_label(
bound_span,
format!(
"ambiguous `{}` from `{}`",
assoc_name,
bound.print_only_trait_path(),
),
);
if let Some(constraint) = &is_equality {
where_bounds.push(format!(
" T: {trait}::{assoc} = {constraint}",
trait=bound.print_only_trait_path(),
assoc=assoc_name,
constraint=constraint,
));
} else {
err.span_suggestion_verbose(
span.with_hi(assoc_name.span.lo()),
"use fully qualified syntax to disambiguate",
format!("<{} as {}>::", ty_param_name, bound.print_only_trait_path()),
Applicability::MaybeIncorrect,
);
}
} else {
err.note(format!(
"associated type `{}` could derive from `{}`",
ty_param_name,
bound.print_only_trait_path(),
));
}
}
if !where_bounds.is_empty() {
err.help(format!(
"consider introducing a new type parameter `T` and adding `where` constraints:\
\n where\n T: {},\n{}",
ty_param_name,
where_bounds.join(",\n"),
));
}
let reported = err.emit();
if !where_bounds.is_empty() {
return Err(reported);
}
}
Ok(bound)
}
#[instrument(level = "debug", skip(self, all_candidates, ty_name), ret)]
fn one_bound_for_assoc_method(
&self,
all_candidates: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
ty_name: impl Display,
assoc_name: Ident,
span: Span,
) -> Result<ty::PolyTraitRef<'tcx>, ErrorGuaranteed> {
let mut matching_candidates = all_candidates.filter(|r| {
self.trait_defines_associated_item_named(r.def_id(), ty::AssocKind::Fn, assoc_name)
});
let candidate = match matching_candidates.next() {
Some(candidate) => candidate,
None => {
return Err(self.tcx().sess.emit_err(
crate::errors::ReturnTypeNotationMissingMethod {
span,
ty_name: ty_name.to_string(),
assoc_name: assoc_name.name,
},
));
}
};
if let Some(conflicting_candidate) = matching_candidates.next() {
return Err(self.tcx().sess.emit_err(
crate::errors::ReturnTypeNotationConflictingBound {
span,
ty_name: ty_name.to_string(),
assoc_name: assoc_name.name,
first_bound: candidate.print_only_trait_path(),
second_bound: conflicting_candidate.print_only_trait_path(),
},
));
}
Ok(candidate)
}
// Create a type from a path to an associated type or to an enum variant.
// 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`.
// NOTE: When this function starts resolving `Trait::AssocTy` successfully
// it should also start reporting the `BARE_TRAIT_OBJECTS` lint.
#[instrument(level = "debug", skip(self, hir_ref_id, span, qself, assoc_segment), fields(assoc_ident=?assoc_segment.ident), ret)]
pub fn associated_path_to_ty(
&self,
hir_ref_id: hir::HirId,
span: Span,
qself_ty: Ty<'tcx>,
qself: &hir::Ty<'_>,
assoc_segment: &hir::PathSegment<'_>,
permit_variants: bool,
) -> Result<(Ty<'tcx>, DefKind, DefId), ErrorGuaranteed> {
let tcx = self.tcx();
let assoc_ident = assoc_segment.ident;
let qself_res = if let hir::TyKind::Path(hir::QPath::Resolved(_, path)) = &qself.kind {
path.res
} else {
Res::Err
};
// Check if we have an enum variant or an inherent associated type.
let mut variant_resolution = None;
if let Some(adt_def) = self.probe_adt(span, qself_ty) {
if adt_def.is_enum() {
let variant_def = adt_def
.variants()
.iter()
.find(|vd| tcx.hygienic_eq(assoc_ident, vd.ident(tcx), 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, None);
self.prohibit_generics(slice::from_ref(assoc_segment).iter(), |err| {
err.note("enum variants can't have type parameters");
let type_name = tcx.item_name(adt_def.did());
let msg = format!(
"you might have meant to specify type parameters on enum \
`{type_name}`"
);
let Some(args) = assoc_segment.args else {
return;
};
// Get the span of the generics args *including* the leading `::`.
let args_span =
assoc_segment.ident.span.shrink_to_hi().to(args.span_ext);
if tcx.generics_of(adt_def.did()).count() == 0 {
// FIXME(estebank): we could also verify that the arguments being
// work for the `enum`, instead of just looking if it takes *any*.
err.span_suggestion_verbose(
args_span,
format!("{type_name} doesn't have generic parameters"),
"",
Applicability::MachineApplicable,
);
return;
}
let Ok(snippet) = tcx.sess.source_map().span_to_snippet(args_span)
else {
err.note(msg);
return;
};
let (qself_sugg_span, is_self) =
if let hir::TyKind::Path(hir::QPath::Resolved(_, path)) =
&qself.kind
{
// If the path segment already has type params, we want to overwrite
// them.
match &path.segments {
// `segment` is the previous to last element on the path,
// which would normally be the `enum` itself, while the last
// `_` `PathSegment` corresponds to the variant.
[
..,
hir::PathSegment {
ident,
args,
res: Res::Def(DefKind::Enum, _),
..
},
_,
] => (
// We need to include the `::` in `Type::Variant::<Args>`
// to point the span to `::<Args>`, not just `<Args>`.
ident.span.shrink_to_hi().to(args
.map_or(ident.span.shrink_to_hi(), |a| a.span_ext)),
false,
),
[segment] => (
// We need to include the `::` in `Type::Variant::<Args>`
// to point the span to `::<Args>`, not just `<Args>`.
segment.ident.span.shrink_to_hi().to(segment
.args
.map_or(segment.ident.span.shrink_to_hi(), |a| {
a.span_ext
})),
kw::SelfUpper == segment.ident.name,
),
_ => {
err.note(msg);
return;
}
}
} else {
err.note(msg);
return;
};
let suggestion = vec![
if is_self {
// Account for people writing `Self::Variant::<Args>`, where
// `Self` is the enum, and suggest replacing `Self` with the
// appropriate type: `Type::<Args>::Variant`.
(qself.span, format!("{type_name}{snippet}"))
} else {
(qself_sugg_span, snippet)
},
(args_span, String::new()),
];
err.multipart_suggestion_verbose(
msg,
suggestion,
Applicability::MaybeIncorrect,
);
});
return Ok((qself_ty, DefKind::Variant, variant_def.def_id));
} else {
variant_resolution = Some(variant_def.def_id);
}
}
}
if let Some((ty, did)) = self.lookup_inherent_assoc_ty(
assoc_ident,
assoc_segment,
adt_def.did(),
qself_ty,
hir_ref_id,
span,
)? {
return Ok((ty, DefKind::AssocTy, did));
}
}
// Find the type of the associated item, and the trait where the associated
// item is declared.
let bound = match (&qself_ty.kind(), qself_res) {
(_, Res::SelfTyAlias { alias_to: impl_def_id, is_trait_impl: true, .. }) => {
// `Self` in an impl of a trait -- we have a concrete self type and a
// trait reference.
let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) else {
// A cycle error occurred, most likely.
let guar = tcx.sess.delay_span_bug(span, "expected cycle error");
return Err(guar);
};
self.one_bound_for_assoc_type(
|| {
traits::supertraits(
tcx,
ty::Binder::dummy(trait_ref.instantiate_identity()),
)
},
kw::SelfUpper,
assoc_ident,
span,
None,
)?
}
(
&ty::Param(_),
Res::SelfTyParam { trait_: param_did } | Res::Def(DefKind::TyParam, param_did),
) => self.find_bound_for_assoc_item(param_did.expect_local(), assoc_ident, span)?,
_ => {
let reported = 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 = struct_span_err!(
tcx.sess,
assoc_ident.span,
E0599,
"no variant named `{}` found for 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.name)
.collect::<Vec<Symbol>>(),
assoc_ident.name,
None,
) {
err.span_suggestion(
assoc_ident.span,
"there is a variant with a similar name",
suggested_name,
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()) {
err.span_label(sp, format!("variant `{assoc_ident}` not found here"));
}
err.emit()
} else if let Err(reported) = qself_ty.error_reported() {
reported
} else if let ty::Alias(ty::Opaque, alias_ty) = qself_ty.kind() {
// `<impl Trait as OtherTrait>::Assoc` makes no sense.
struct_span_err!(
tcx.sess,
tcx.def_span(alias_ty.def_id),
E0667,
"`impl Trait` is not allowed in path parameters"
)
.emit() // Already reported in an earlier stage.
} else {
let traits: Vec<_> =
self.probe_traits_that_match_assoc_ty(qself_ty, assoc_ident);
// Don't print `ty::Error` to the user.
self.report_ambiguous_associated_type(
span,
&[qself_ty.to_string()],
&traits,
assoc_ident.name,
)
};
return Err(reported);
}
};
let trait_did = bound.def_id();
let Some(assoc_ty_did) = self.lookup_assoc_ty(assoc_ident, hir_ref_id, span, trait_did)
else {
// Assume that if it's not matched, there must be a const defined with the same name
// but it was used in a type position.
let msg = format!("found associated const `{assoc_ident}` when type was expected");
let guar = tcx.sess.struct_span_err(span, msg).emit();
return Err(guar);
};
let ty = self.projected_ty_from_poly_trait_ref(span, assoc_ty_did, assoc_segment, bound);
if let Some(variant_def_id) = variant_resolution {
tcx.struct_span_lint_hir(
AMBIGUOUS_ASSOCIATED_ITEMS,
hir_ref_id,
span,
"ambiguous associated item",
|lint| {
let mut could_refer_to = |kind: DefKind, def_id, also| {
let note_msg = format!(
"`{}` could{} refer to the {} defined here",
assoc_ident,
also,
tcx.def_kind_descr(kind, def_id)
);
lint.span_note(tcx.def_span(def_id), note_msg);
};
could_refer_to(DefKind::Variant, variant_def_id, "");
could_refer_to(DefKind::AssocTy, assoc_ty_did, " also");
lint.span_suggestion(
span,
"use fully-qualified syntax",
format!("<{} as {}>::{}", qself_ty, tcx.item_name(trait_did), assoc_ident),
Applicability::MachineApplicable,
);
lint
},
);
}
Ok((ty, DefKind::AssocTy, assoc_ty_did))
}
fn lookup_inherent_assoc_ty(
&self,
name: Ident,
segment: &hir::PathSegment<'_>,
adt_did: DefId,
self_ty: Ty<'tcx>,
block: hir::HirId,
span: Span,
) -> Result<Option<(Ty<'tcx>, DefId)>, ErrorGuaranteed> {
let tcx = self.tcx();
// Don't attempt to look up inherent associated types when the feature is not enabled.
// Theoretically it'd be fine to do so since we feature-gate their definition site.
// However, due to current limitations of the implementation (caused by us performing
// selection in AstConv), IATs can lead to cycle errors (#108491, #110106) which mask the
// feature-gate error, needlessly confusing users that use IATs by accident (#113265).
if !tcx.features().inherent_associated_types {
return Ok(None);
}
let candidates: Vec<_> = tcx
.inherent_impls(adt_did)
.iter()
.filter_map(|&impl_| Some((impl_, self.lookup_assoc_ty_unchecked(name, block, impl_)?)))
.collect();
if candidates.is_empty() {
return Ok(None);
}
//
// Select applicable inherent associated type candidates modulo regions.
//
// In contexts that have no inference context, just make a new one.
// We do need a local variable to store it, though.
let infcx_;
let infcx = match self.infcx() {
Some(infcx) => infcx,
None => {
assert!(!self_ty.has_infer());
infcx_ = tcx.infer_ctxt().ignoring_regions().build();
&infcx_
}
};
// FIXME(inherent_associated_types): Acquiring the ParamEnv this early leads to cycle errors
// when inside of an ADT (#108491) or where clause.
let param_env = tcx.param_env(block.owner);
let cause = ObligationCause::misc(span, block.owner.def_id);
let mut fulfillment_errors = Vec::new();
let mut applicable_candidates: Vec<_> = infcx.probe(|_| {
// Regions are not considered during selection.
let self_ty = self_ty
.fold_with(&mut BoundVarEraser { tcx, universe: infcx.create_next_universe() });
struct BoundVarEraser<'tcx> {
tcx: TyCtxt<'tcx>,
universe: ty::UniverseIndex,
}
// FIXME(non_lifetime_binders): Don't assign the same universe to each placeholder.
impl<'tcx> TypeFolder<TyCtxt<'tcx>> for BoundVarEraser<'tcx> {
fn interner(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
if r.is_late_bound() { self.tcx.lifetimes.re_erased } else { r }
}
fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
match *ty.kind() {
ty::Bound(_, bv) => Ty::new_placeholder(
self.tcx,
ty::PlaceholderType { universe: self.universe, bound: bv },
),
_ => ty.super_fold_with(self),
}
}
fn fold_const(
&mut self,
ct: ty::Const<'tcx>,
) -> <TyCtxt<'tcx> as rustc_type_ir::Interner>::Const {
assert!(!ct.ty().has_escaping_bound_vars());
match ct.kind() {
ty::ConstKind::Bound(_, bv) => ty::Const::new_placeholder(
self.tcx,
ty::PlaceholderConst { universe: self.universe, bound: bv },
ct.ty(),
),
_ => ct.super_fold_with(self),
}
}
}
let InferOk { value: self_ty, obligations } =
infcx.at(&cause, param_env).normalize(self_ty);
candidates
.iter()
.copied()
.filter(|&(impl_, _)| {
infcx.probe(|_| {
let ocx = ObligationCtxt::new(&infcx);
ocx.register_obligations(obligations.clone());
let impl_args = infcx.fresh_args_for_item(span, impl_);
let impl_ty = tcx.type_of(impl_).instantiate(tcx, impl_args);
let impl_ty = ocx.normalize(&cause, param_env, impl_ty);
// Check that the self types can be related.
// FIXME(inherent_associated_types): Should we use `eq` here? Method probing uses
// `sup` for this situtation, too. What for? To constrain inference variables?
if ocx.sup(&ObligationCause::dummy(), param_env, impl_ty, self_ty).is_err()
{
return false;
}
// Check whether the impl imposes obligations we have to worry about.
let impl_bounds = tcx.predicates_of(impl_).instantiate(tcx, impl_args);
let impl_bounds = ocx.normalize(&cause, param_env, impl_bounds);
let impl_obligations = traits::predicates_for_generics(
|_, _| cause.clone(),
param_env,
impl_bounds,
);
ocx.register_obligations(impl_obligations);
let mut errors = ocx.select_where_possible();
if !errors.is_empty() {
fulfillment_errors.append(&mut errors);
return false;
}
true
})
})
.collect()
});
if applicable_candidates.len() > 1 {
return Err(self.complain_about_ambiguous_inherent_assoc_type(
name,
applicable_candidates.into_iter().map(|(_, (candidate, _))| candidate).collect(),
span,
));
}
if let Some((impl_, (assoc_item, def_scope))) = applicable_candidates.pop() {
self.check_assoc_ty(assoc_item, name, def_scope, block, span);
// FIXME(fmease): Currently creating throwaway `parent_args` to please
// `create_args_for_associated_item`. Modify the latter instead (or sth. similar) to
// not require the parent args logic.
let parent_args = ty::GenericArgs::identity_for_item(tcx, impl_);
let args = self.create_args_for_associated_item(span, assoc_item, segment, parent_args);
let args = tcx.mk_args_from_iter(
std::iter::once(ty::GenericArg::from(self_ty))
.chain(args.into_iter().skip(parent_args.len())),
);
let ty = Ty::new_alias(tcx, ty::Inherent, tcx.mk_alias_ty(assoc_item, args));
return Ok(Some((ty, assoc_item)));
}
Err(self.complain_about_inherent_assoc_type_not_found(
name,
self_ty,
candidates,
fulfillment_errors,
span,
))
}
fn lookup_assoc_ty(
&self,
name: Ident,
block: hir::HirId,
span: Span,
scope: DefId,
) -> Option<DefId> {
let (item, def_scope) = self.lookup_assoc_ty_unchecked(name, block, scope)?;
self.check_assoc_ty(item, name, def_scope, block, span);
Some(item)
}
fn lookup_assoc_ty_unchecked(
&self,
name: Ident,
block: hir::HirId,
scope: DefId,
) -> Option<(DefId, DefId)> {
let tcx = self.tcx();
let (ident, def_scope) = tcx.adjust_ident_and_get_scope(name, scope, block);
// We have already adjusted the item name above, so compare with `ident.normalize_to_macros_2_0()` instead
// of calling `find_by_name_and_kind`.
let item = tcx.associated_items(scope).in_definition_order().find(|i| {
i.kind.namespace() == Namespace::TypeNS
&& i.ident(tcx).normalize_to_macros_2_0() == ident
})?;
Some((item.def_id, def_scope))
}
fn check_assoc_ty(
&self,
item: DefId,
name: Ident,
def_scope: DefId,
block: hir::HirId,
span: Span,
) {
let tcx = self.tcx();
let kind = DefKind::AssocTy;
if !tcx.visibility(item).is_accessible_from(def_scope, tcx) {
let kind = tcx.def_kind_descr(kind, item);
let msg = format!("{kind} `{name}` is private");
let def_span = tcx.def_span(item);
tcx.sess
.struct_span_err_with_code(span, msg, rustc_errors::error_code!(E0624))
.span_label(span, format!("private {kind}"))
.span_label(def_span, format!("{kind} defined here"))
.emit();
}
tcx.check_stability(item, Some(block), span, None);
}
fn probe_traits_that_match_assoc_ty(
&self,
qself_ty: Ty<'tcx>,
assoc_ident: Ident,
) -> Vec<String> {
let tcx = self.tcx();
// In contexts that have no inference context, just make a new one.
// We do need a local variable to store it, though.
let infcx_;
let infcx = if let Some(infcx) = self.infcx() {
infcx
} else {
assert!(!qself_ty.has_infer());
infcx_ = tcx.infer_ctxt().build();
&infcx_
};
tcx.all_traits()
.filter(|trait_def_id| {
// Consider only traits with the associated type
tcx.associated_items(*trait_def_id)
.in_definition_order()
.any(|i| {
i.kind.namespace() == Namespace::TypeNS
&& i.ident(tcx).normalize_to_macros_2_0() == assoc_ident
&& matches!(i.kind, ty::AssocKind::Type)
})
// Consider only accessible traits
&& tcx.visibility(*trait_def_id)
.is_accessible_from(self.item_def_id(), tcx)
&& tcx.all_impls(*trait_def_id)
.any(|impl_def_id| {
let trait_ref = tcx.impl_trait_ref(impl_def_id);
trait_ref.is_some_and(|trait_ref| {
let impl_ = trait_ref.instantiate(
tcx,
infcx.fresh_args_for_item(DUMMY_SP, impl_def_id),
);
let value = tcx.fold_regions(qself_ty, |_, _| tcx.lifetimes.re_erased);
// FIXME: Don't bother dealing with non-lifetime binders here...
if value.has_escaping_bound_vars() {
return false;
}
infcx
.can_eq(
ty::ParamEnv::empty(),
impl_.self_ty(),
value,
)
})
&& tcx.impl_polarity(impl_def_id) != ty::ImplPolarity::Negative
})
})
.map(|trait_def_id| tcx.def_path_str(trait_def_id))
.collect()
}
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<'_>,
constness: ty::BoundConstness,
) -> Ty<'tcx> {
let tcx = self.tcx();
let trait_def_id = tcx.parent(item_def_id);
debug!("qpath_to_ty: trait_def_id={:?}", trait_def_id);
let Some(self_ty) = opt_self_ty else {
let path_str = tcx.def_path_str(trait_def_id);
let def_id = self.item_def_id();
debug!("qpath_to_ty: self.item_def_id()={:?}", def_id);
let parent_def_id = def_id
.as_local()
.map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id))
.map(|hir_id| tcx.hir().get_parent_item(hir_id).to_def_id());
debug!("qpath_to_ty: parent_def_id={:?}", parent_def_id);
// If the trait in segment is the same as the trait defining the item,
// use the `<Self as ..>` syntax in the error.
let is_part_of_self_trait_constraints = def_id == trait_def_id;
let is_part_of_fn_in_self_trait = parent_def_id == Some(trait_def_id);
let type_names = if is_part_of_self_trait_constraints || is_part_of_fn_in_self_trait {
vec!["Self".to_string()]
} else {
// Find all the types that have an `impl` for the trait.
tcx.all_impls(trait_def_id)
.filter(|impl_def_id| {
// Consider only accessible traits
tcx.visibility(trait_def_id).is_accessible_from(self.item_def_id(), tcx)
&& tcx.impl_polarity(impl_def_id) != ty::ImplPolarity::Negative
})
.filter_map(|impl_def_id| tcx.impl_trait_ref(impl_def_id))
.map(|impl_| impl_.instantiate_identity().self_ty())
// We don't care about blanket impls.
.filter(|self_ty| !self_ty.has_non_region_param())
.map(|self_ty| tcx.erase_regions(self_ty).to_string())
.collect()
};
// FIXME: also look at `tcx.generics_of(self.item_def_id()).params` any that
// references the trait. Relevant for the first case in
// `src/test/ui/associated-types/associated-types-in-ambiguous-context.rs`
let reported = self.report_ambiguous_associated_type(
span,
&type_names,
&[path_str],
item_segment.ident.name,
);
return Ty::new_error(tcx, reported);
};
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,
false,
constness,
);
let item_args =
self.create_args_for_associated_item(span, item_def_id, item_segment, trait_ref.args);
debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
Ty::new_projection(tcx, item_def_id, item_args)
}
pub fn prohibit_generics<'a>(
&self,
segments: impl Iterator<Item = &'a hir::PathSegment<'a>> + Clone,
extend: impl Fn(&mut Diagnostic),
) -> bool {
let args = segments.clone().flat_map(|segment| segment.args().args);
let (lt, ty, ct, inf) =
args.clone().fold((false, false, false, false), |(lt, ty, ct, inf), arg| match arg {
hir::GenericArg::Lifetime(_) => (true, ty, ct, inf),
hir::GenericArg::Type(_) => (lt, true, ct, inf),
hir::GenericArg::Const(_) => (lt, ty, true, inf),
hir::GenericArg::Infer(_) => (lt, ty, ct, true),
});
let mut emitted = false;
if lt || ty || ct || inf {
let types_and_spans: Vec<_> = segments
.clone()
.flat_map(|segment| {
if segment.args().args.is_empty() {
None
} else {
Some((
match segment.res {
Res::PrimTy(ty) => format!("{} `{}`", segment.res.descr(), ty.name()),
Res::Def(_, def_id)
if let Some(name) = self.tcx().opt_item_name(def_id) => {
format!("{} `{name}`", segment.res.descr())
}
Res::Err => "this type".to_string(),
_ => segment.res.descr().to_string(),
},
segment.ident.span,
))
}
})
.collect();
let this_type = match &types_and_spans[..] {
[.., _, (last, _)] => format!(
"{} and {last}",
types_and_spans[..types_and_spans.len() - 1]
.iter()
.map(|(x, _)| x.as_str())
.intersperse(&", ")
.collect::<String>()
),
[(only, _)] => only.to_string(),
[] => "this type".to_string(),
};
let arg_spans: Vec<Span> = args.map(|arg| arg.span()).collect();
let mut kinds = Vec::with_capacity(4);
if lt {
kinds.push("lifetime");
}
if ty {
kinds.push("type");
}
if ct {
kinds.push("const");
}
if inf {
kinds.push("generic");
}
let (kind, s) = match kinds[..] {
[.., _, last] => (
format!(
"{} and {last}",
kinds[..kinds.len() - 1]
.iter()
.map(|&x| x)
.intersperse(", ")
.collect::<String>()
),
"s",
),
[only] => (only.to_string(), ""),
[] => unreachable!(),
};
let last_span = *arg_spans.last().unwrap();
let span: MultiSpan = arg_spans.into();
let mut err = struct_span_err!(
self.tcx().sess,
span,
E0109,
"{kind} arguments are not allowed on {this_type}",
);
err.span_label(last_span, format!("{kind} argument{s} not allowed"));
for (what, span) in types_and_spans {
err.span_label(span, format!("not allowed on {what}"));
}
extend(&mut err);
err.emit();
emitted = true;
}
for segment in segments {
// Only emit the first error to avoid overloading the user with error messages.
if let Some(b) = segment.args().bindings.first() {
prohibit_assoc_ty_binding(self.tcx(), b.span, None);
return true;
}
}
emitted
}
// 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,
span: Span,
) -> 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 (generics_def_id, index) = if let Some(self_ty) = self_ty {
let adt_def = self.probe_adt(span, self_ty).unwrap();
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);
}
// `DefKind::Variant` -> `DefKind::Enum`
let enum_def_id = tcx.parent(def_id);
(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::AssocFn | 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<'_>,
hir_id: hir::HirId,
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!(tcx.is_type_alias_impl_trait(did));
let item_segment = path.segments.split_last().unwrap();
self.prohibit_generics(item_segment.1.iter(), |err| {
err.note("`impl Trait` types can't have type parameters");
});
let args = self.ast_path_args_for_ty(span, did, item_segment.0);
Ty::new_opaque(tcx, did, args)
}
Res::Def(
DefKind::Enum
| DefKind::TyAlias { .. }
| DefKind::Struct
| DefKind::Union
| DefKind::ForeignTy,
did,
) => {
assert_eq!(opt_self_ty, None);
self.prohibit_generics(path.segments.split_last().unwrap().1.iter(), |_| {});
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, span);
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 }
}),
|err| {
err.note("enum variants can't have type parameters");
},
);
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.iter(), |err| {
if let Some(span) = tcx.def_ident_span(def_id) {
let name = tcx.item_name(def_id);
err.span_note(span, format!("type parameter `{name}` defined here"));
}
});
match tcx.named_bound_var(hir_id) {
Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => {
let name =
tcx.hir().name(tcx.hir().local_def_id_to_hir_id(def_id.expect_local()));
let br = ty::BoundTy {
var: ty::BoundVar::from_u32(index),
kind: ty::BoundTyKind::Param(def_id, name),
};
Ty::new_bound(tcx, debruijn, br)
}
Some(rbv::ResolvedArg::EarlyBound(_)) => {
let def_id = def_id.expect_local();
let item_def_id = tcx.hir().ty_param_owner(def_id);
let generics = tcx.generics_of(item_def_id);
let index = generics.param_def_id_to_index[&def_id.to_def_id()];
Ty::new_param(tcx, index, tcx.hir().ty_param_name(def_id))
}
Some(rbv::ResolvedArg::Error(guar)) => Ty::new_error(tcx, guar),
arg => bug!("unexpected bound var resolution for {hir_id:?}: {arg:?}"),
}
}
Res::SelfTyParam { .. } => {
// `Self` in trait or type alias.
assert_eq!(opt_self_ty, None);
self.prohibit_generics(path.segments.iter(), |err| {
if let [hir::PathSegment { args: Some(args), ident, .. }] = &path.segments {
err.span_suggestion_verbose(
ident.span.shrink_to_hi().to(args.span_ext),
"the `Self` type doesn't accept type parameters",
"",
Applicability::MaybeIncorrect,
);
}
});
tcx.types.self_param
}
Res::SelfTyAlias { alias_to: def_id, forbid_generic, .. } => {
// `Self` in impl (we know the concrete type).
assert_eq!(opt_self_ty, None);
// Try to evaluate any array length constants.
let ty = tcx.at(span).type_of(def_id).instantiate_identity();
let span_of_impl = tcx.span_of_impl(def_id);
self.prohibit_generics(path.segments.iter(), |err| {
let def_id = match *ty.kind() {
ty::Adt(self_def, _) => self_def.did(),
_ => return,
};
let type_name = tcx.item_name(def_id);
let span_of_ty = tcx.def_ident_span(def_id);
let generics = tcx.generics_of(def_id).count();
let msg = format!("`Self` is of type `{ty}`");
if let (Ok(i_sp), Some(t_sp)) = (span_of_impl, span_of_ty) {
let mut span: MultiSpan = vec![t_sp].into();
span.push_span_label(
i_sp,
format!("`Self` is on type `{type_name}` in this `impl`"),
);
let mut postfix = "";
if generics == 0 {
postfix = ", which doesn't have generic parameters";
}
span.push_span_label(
t_sp,
format!("`Self` corresponds to this type{postfix}"),
);
err.span_note(span, msg);
} else {
err.note(msg);
}
for segment in path.segments {
if let Some(args) = segment.args && segment.ident.name == kw::SelfUpper {
if generics == 0 {
// FIXME(estebank): we could also verify that the arguments being
// work for the `enum`, instead of just looking if it takes *any*.
err.span_suggestion_verbose(
segment.ident.span.shrink_to_hi().to(args.span_ext),
"the `Self` type doesn't accept type parameters",
"",
Applicability::MachineApplicable,
);
return;
} else {
err.span_suggestion_verbose(
segment.ident.span,
format!(
"the `Self` type doesn't accept type parameters, use the \
concrete type's name `{type_name}` instead if you want to \
specify its type parameters"
),
type_name,
Applicability::MaybeIncorrect,
);
}
}
}
});
// HACK(min_const_generics): Forbid generic `Self` types
// here as we can't easily do that during nameres.
//
// We do this before normalization as we otherwise allow
// ```rust
// trait AlwaysApplicable { type Assoc; }
// impl<T: ?Sized> AlwaysApplicable for T { type Assoc = usize; }
//
// trait BindsParam<T> {
// type ArrayTy;
// }
// impl<T> BindsParam<T> for <T as AlwaysApplicable>::Assoc {
// type ArrayTy = [u8; Self::MAX];
// }
// ```
// Note that the normalization happens in the param env of
// the anon const, which is empty. This is why the
// `AlwaysApplicable` impl needs a `T: ?Sized` bound for
// this to compile if we were to normalize here.
if forbid_generic && ty.has_param() {
let mut err = tcx.sess.struct_span_err(
path.span,
"generic `Self` types are currently not permitted in anonymous constants",
);
if let Some(hir::Node::Item(&hir::Item {
kind: hir::ItemKind::Impl(impl_),
..
})) = tcx.hir().get_if_local(def_id)
{
err.span_note(impl_.self_ty.span, "not a concrete type");
}
Ty::new_error(tcx, err.emit())
} else {
ty
}
}
Res::Def(DefKind::AssocTy, def_id) => {
debug_assert!(path.segments.len() >= 2);
self.prohibit_generics(path.segments[..path.segments.len() - 2].iter(), |_| {});
// HACK: until we support `<Type as ~const Trait>`, assume all of them are.
let constness = if tcx.has_attr(tcx.parent(def_id), sym::const_trait) {
ty::BoundConstness::ConstIfConst
} else {
ty::BoundConstness::NotConst
};
self.qpath_to_ty(
span,
opt_self_ty,
def_id,
&path.segments[path.segments.len() - 2],
path.segments.last().unwrap(),
constness,
)
}
Res::PrimTy(prim_ty) => {
assert_eq!(opt_self_ty, None);
self.prohibit_generics(path.segments.iter(), |err| {
let name = prim_ty.name_str();
for segment in path.segments {
if let Some(args) = segment.args {
err.span_suggestion_verbose(
segment.ident.span.shrink_to_hi().to(args.span_ext),
format!("primitive type `{name}` doesn't have generic parameters"),
"",
Applicability::MaybeIncorrect,
);
}
}
});
match prim_ty {
hir::PrimTy::Bool => tcx.types.bool,
hir::PrimTy::Char => tcx.types.char,
hir::PrimTy::Int(it) => Ty::new_int(tcx, ty::int_ty(it)),
hir::PrimTy::Uint(uit) => Ty::new_uint(tcx, ty::uint_ty(uit)),
hir::PrimTy::Float(ft) => Ty::new_float(tcx, ty::float_ty(ft)),
hir::PrimTy::Str => tcx.types.str_,
}
}
Res::Err => {
let e = self
.tcx()
.sess
.delay_span_bug(path.span, "path with `Res::Err` but no error emitted");
self.set_tainted_by_errors(e);
Ty::new_error(self.tcx(), e)
}
_ => 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> {
self.ast_ty_to_ty_inner(ast_ty, false, false)
}
/// Parses the programmer's textual representation of a type into our
/// internal notion of a type. This is meant to be used within a path.
pub fn ast_ty_to_ty_in_path(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
self.ast_ty_to_ty_inner(ast_ty, false, true)
}
/// Turns a `hir::Ty` into a `Ty`. For diagnostics' purposes we keep track of whether trait
/// objects are borrowed like `&dyn Trait` to avoid emitting redundant errors.
#[instrument(level = "debug", skip(self), ret)]
fn ast_ty_to_ty_inner(&self, ast_ty: &hir::Ty<'_>, borrowed: bool, in_path: bool) -> Ty<'tcx> {
let tcx = self.tcx();
let result_ty = match &ast_ty.kind {
hir::TyKind::Slice(ty) => Ty::new_slice(tcx, self.ast_ty_to_ty(ty)),
hir::TyKind::Ptr(mt) => {
Ty::new_ptr(tcx, ty::TypeAndMut { ty: self.ast_ty_to_ty(mt.ty), mutbl: mt.mutbl })
}
hir::TyKind::Ref(region, mt) => {
let r = self.ast_region_to_region(region, None);
debug!(?r);
let t = self.ast_ty_to_ty_inner(mt.ty, true, false);
Ty::new_ref(tcx, r, ty::TypeAndMut { ty: t, mutbl: mt.mutbl })
}
hir::TyKind::Never => tcx.types.never,
hir::TyKind::Tup(fields) => {
Ty::new_tup_from_iter(tcx, fields.iter().map(|t| self.ast_ty_to_ty(t)))
}
hir::TyKind::BareFn(bf) => {
require_c_abi_if_c_variadic(tcx, bf.decl, bf.abi, ast_ty.span);
Ty::new_fn_ptr(
tcx,
self.ty_of_fn(ast_ty.hir_id, bf.unsafety, bf.abi, bf.decl, None, Some(ast_ty)),
)
}
hir::TyKind::TraitObject(bounds, lifetime, repr) => {
self.maybe_lint_bare_trait(ast_ty, in_path);
let repr = match repr {
TraitObjectSyntax::Dyn | TraitObjectSyntax::None => ty::Dyn,
TraitObjectSyntax::DynStar => ty::DynStar,
};
self.conv_object_ty_poly_trait_ref(
ast_ty.span,
ast_ty.hir_id,
bounds,
lifetime,
borrowed,
repr,
)
}
hir::TyKind::Path(hir::QPath::Resolved(maybe_qself, path)) => {
debug!(?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, ast_ty.hir_id, false)
}
&hir::TyKind::OpaqueDef(item_id, lifetimes, in_trait) => {
let opaque_ty = tcx.hir().item(item_id);
match opaque_ty.kind {
hir::ItemKind::OpaqueTy(&hir::OpaqueTy { origin, .. }) => {
let local_def_id = item_id.owner_id.def_id;
// If this is an RPITIT and we are using the new RPITIT lowering scheme, we
// generate the def_id of an associated type for the trait and return as
// type a projection.
let def_id = if in_trait {
tcx.associated_type_for_impl_trait_in_trait(local_def_id).to_def_id()
} else {
local_def_id.to_def_id()
};
self.impl_trait_ty_to_ty(def_id, lifetimes, origin, in_trait)
}
ref i => bug!("`impl Trait` pointed to non-opaque type?? {:#?}", i),
}
}
hir::TyKind::Path(hir::QPath::TypeRelative(qself, segment)) => {
debug!(?qself, ?segment);
let ty = self.ast_ty_to_ty_inner(qself, false, true);
self.associated_path_to_ty(ast_ty.hir_id, ast_ty.span, ty, qself, segment, false)
.map(|(ty, _, _)| ty)
.unwrap_or_else(|guar| Ty::new_error(tcx, guar))
}
&hir::TyKind::Path(hir::QPath::LangItem(lang_item, span, _)) => {
let def_id = tcx.require_lang_item(lang_item, Some(span));
let (args, _) = self.create_args_for_ast_path(
span,
def_id,
&[],
&hir::PathSegment::invalid(),
&GenericArgs::none(),
true,
None,
ty::BoundConstness::NotConst,
);
tcx.at(span).type_of(def_id).instantiate(tcx, args)
}
hir::TyKind::Array(ty, length) => {
let length = match length {
&hir::ArrayLen::Infer(_, span) => self.ct_infer(tcx.types.usize, None, span),
hir::ArrayLen::Body(constant) => {
ty::Const::from_anon_const(tcx, constant.def_id)
}
};
Ty::new_array_with_const_len(tcx, self.ast_ty_to_ty(ty), length)
}
hir::TyKind::Typeof(e) => {
let ty_erased = tcx.type_of(e.def_id).instantiate_identity();
let ty = tcx.fold_regions(ty_erased, |r, _| {
if r.is_erased() { tcx.lifetimes.re_static } else { r }
});
let span = ast_ty.span;
let (ty, opt_sugg) = if let Some(ty) = ty.make_suggestable(tcx, false) {
(ty, Some((span, Applicability::MachineApplicable)))
} else {
(ty, None)
};
tcx.sess.emit_err(TypeofReservedKeywordUsed { span, ty, opt_sugg });
ty
}
hir::TyKind::Infer => {
// Infer also appears as the type of arguments or return
// values in an 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::Err(guar) => Ty::new_error(tcx, *guar),
};
self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
result_ty
}
#[instrument(level = "debug", skip(self), ret)]
fn impl_trait_ty_to_ty(
&self,
def_id: DefId,
lifetimes: &[hir::GenericArg<'_>],
origin: OpaqueTyOrigin,
in_trait: bool,
) -> 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 args = ty::GenericArgs::for_item(tcx, def_id, |param, _| {
// We use `generics.count() - lifetimes.len()` here instead of `generics.parent_count`
// since return-position impl trait in trait squashes all of the generics from its source fn
// into its own generics, so the opaque's "own" params isn't always just lifetimes.
if let Some(i) = (param.index as usize).checked_sub(generics.count() - lifetimes.len())
{
// Resolve our own lifetime parameters.
let GenericParamDefKind::Lifetime { .. } = param.kind else { bug!() };
let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] else { bug!() };
self.ast_region_to_region(lifetime, None).into()
} else {
tcx.mk_param_from_def(param)
}
});
debug!("impl_trait_ty_to_ty: args={:?}", args);
if in_trait {
Ty::new_projection(tcx, def_id, args)
} else {
Ty::new_opaque(tcx, def_id, args)
}
}
pub fn ty_of_arg(&self, ty: &hir::Ty<'_>, expected_ty: Option<Ty<'tcx>>) -> Ty<'tcx> {
match ty.kind {
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),
}
}
#[instrument(level = "debug", skip(self, hir_id, unsafety, abi, decl, generics, hir_ty), ret)]
pub fn ty_of_fn(
&self,
hir_id: hir::HirId,
unsafety: hir::Unsafety,
abi: abi::Abi,
decl: &hir::FnDecl<'_>,
generics: Option<&hir::Generics<'_>>,
hir_ty: Option<&hir::Ty<'_>>,
) -> ty::PolyFnSig<'tcx> {
let tcx = self.tcx();
let bound_vars = tcx.late_bound_vars(hir_id);
debug!(?bound_vars);
// We proactively collect all the inferred type params to emit a single error per fn def.
let mut visitor = HirPlaceholderCollector::default();
let mut infer_replacements = vec![];
if let Some(generics) = generics {
walk_generics(&mut visitor, generics);
}
let input_tys: Vec<_> = decl
.inputs
.iter()
.enumerate()
.map(|(i, a)| {
if let hir::TyKind::Infer = a.kind && !self.allow_ty_infer() {
if let Some(suggested_ty) =
self.suggest_trait_fn_ty_for_impl_fn_infer(hir_id, Some(i))
{
infer_replacements.push((a.span, suggested_ty.to_string()));
return suggested_ty;
}
}
// Only visit the type looking for `_` if we didn't fix the type above
visitor.visit_ty(a);
self.ty_of_arg(a, None)
})
.collect();
let output_ty = match decl.output {
hir::FnRetTy::Return(output) => {
if let hir::TyKind::Infer = output.kind
&& !self.allow_ty_infer()
&& let Some(suggested_ty) =
self.suggest_trait_fn_ty_for_impl_fn_infer(hir_id, None)
{
infer_replacements.push((output.span, suggested_ty.to_string()));
suggested_ty
} else {
visitor.visit_ty(output);
self.ast_ty_to_ty(output)
}
}
hir::FnRetTy::DefaultReturn(..) => Ty::new_unit(tcx,),
};
debug!(?output_ty);
let fn_ty = tcx.mk_fn_sig(input_tys, output_ty, decl.c_variadic, unsafety, abi);
let bare_fn_ty = ty::Binder::bind_with_vars(fn_ty, bound_vars);
if !self.allow_ty_infer() && !(visitor.0.is_empty() && infer_replacements.is_empty()) {
// We always collect the spans for placeholder types when evaluating `fn`s, but we
// only want to emit an error complaining about them if infer types (`_`) are not
// allowed. `allow_ty_infer` gates this behavior. We check for the presence of
// `ident_span` to not emit an error twice when we have `fn foo(_: fn() -> _)`.
let mut diag = crate::collect::placeholder_type_error_diag(
tcx,
generics,
visitor.0,
infer_replacements.iter().map(|(s, _)| *s).collect(),
true,
hir_ty,
"function",
);
if !infer_replacements.is_empty() {
diag.multipart_suggestion(
format!(
"try replacing `_` with the type{} in the corresponding trait method signature",
rustc_errors::pluralize!(infer_replacements.len()),
),
infer_replacements,
Applicability::MachineApplicable,
);
}
diag.emit();
}
// 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);
self.validate_late_bound_regions(late_bound_in_args, late_bound_in_ret, |br_name| {
struct_span_err!(
tcx.sess,
decl.output.span(),
E0581,
"return type references {}, which is not constrained by the fn input types",
br_name
)
});
bare_fn_ty
}
/// Given a fn_hir_id for a impl function, suggest the type that is found on the
/// corresponding function in the trait that the impl implements, if it exists.
/// If arg_idx is Some, then it corresponds to an input type index, otherwise it
/// corresponds to the return type.
fn suggest_trait_fn_ty_for_impl_fn_infer(
&self,
fn_hir_id: hir::HirId,
arg_idx: Option<usize>,
) -> Option<Ty<'tcx>> {
let tcx = self.tcx();
let hir = tcx.hir();
let hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), ident, .. }) =
hir.get(fn_hir_id)
else {
return None;
};
let i = hir.get_parent(fn_hir_id).expect_item().expect_impl();
let trait_ref =
self.instantiate_mono_trait_ref(i.of_trait.as_ref()?, self.ast_ty_to_ty(i.self_ty));
let assoc = tcx.associated_items(trait_ref.def_id).find_by_name_and_kind(
tcx,
*ident,
ty::AssocKind::Fn,
trait_ref.def_id,
)?;
let fn_sig = tcx.fn_sig(assoc.def_id).instantiate(
tcx,
trait_ref.args.extend_to(tcx, assoc.def_id, |param, _| tcx.mk_param_from_def(param)),
);
let fn_sig = tcx.liberate_late_bound_regions(fn_hir_id.expect_owner().to_def_id(), fn_sig);
Some(if let Some(arg_idx) = arg_idx {
*fn_sig.inputs().get(arg_idx)?
} else {
fn_sig.output()
})
}
#[instrument(level = "trace", skip(self, generate_err))]
fn validate_late_bound_regions(
&self,
constrained_regions: FxHashSet<ty::BoundRegionKind>,
referenced_regions: FxHashSet<ty::BoundRegionKind>,
generate_err: impl Fn(&str) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>,
) {
for br in referenced_regions.difference(&constrained_regions) {
let br_name = match *br {
ty::BrNamed(_, kw::UnderscoreLifetime) | ty::BrAnon(..) | ty::BrEnv => {
"an anonymous lifetime".to_string()
}
ty::BrNamed(_, name) => format!("lifetime `{name}`"),
};
let mut err = generate_err(&br_name);
if let ty::BrNamed(_, kw::UnderscoreLifetime) | 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 and #62200 for examples. In this case,
// though we can easily give a hint that ought to be
// relevant.
err.note(
"lifetimes appearing in an associated or opaque type are not considered constrained",
);
err.note("consider introducing a named lifetime parameter");
}
err.emit();
}
}
/// 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: &'tcx ty::List<ty::PolyExistentialPredicate<'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| r.is_static()) {
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) {
tcx.sess.emit_err(AmbiguousLifetimeBound { span });
}
Some(r)
}
}