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android / toolchain / rustc / 89a0a0cd9cbd0a0138a09bd877bbc73859a8c330 / . / compiler / rustc_hir_analysis / src / astconv / mod.rs
blob: 38f195dabb90428cac239c1103fd115b2a473874 [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 errors;
mod generics;
use crate::bounds::Bounds;
use crate::collect::HirPlaceholderCollector;
use crate::errors::{
AmbiguousLifetimeBound, MultipleRelaxedDefaultBounds, TraitObjectDeclaredWithNoTraits,
TypeofReservedKeywordUsed, ValueOfAssociatedStructAlreadySpecified,
};
use crate::middle::resolve_lifetime as rl;
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::lang_items::LangItem;
use rustc_hir::{GenericArg, GenericArgs, OpaqueTyOrigin};
use rustc_middle::middle::stability::AllowUnstable;
use rustc_middle::ty::subst::{self, GenericArgKind, InternalSubsts, SubstsRef};
use rustc_middle::ty::DynKind;
use rustc_middle::ty::GenericParamDefKind;
use rustc_middle::ty::{
self, Const, DefIdTree, EarlyBinder, IsSuggestable, Ty, TyCtxt, TypeVisitable,
};
use rustc_session::lint::builtin::{AMBIGUOUS_ASSOCIATED_ITEMS, BARE_TRAIT_OBJECTS};
use rustc_span::edition::Edition;
use rustc_span::lev_distance::find_best_match_for_name;
use rustc_span::symbol::{kw, Ident, Symbol};
use rustc_span::{sym, Span};
use rustc_target::spec::abi;
use rustc_trait_selection::traits;
use rustc_trait_selection::traits::astconv_object_safety_violations;
use rustc_trait_selection::traits::error_reporting::{
report_object_safety_error, suggestions::NextTypeParamName,
};
use rustc_trait_selection::traits::wf::object_region_bounds;
use smallvec::{smallvec, SmallVec};
use std::collections::BTreeSet;
use std::slice;
#[derive(Debug)]
pub struct PathSeg(pub DefId, pub usize);
pub trait AstConv<'tcx> {
fn tcx<'a>(&'a self) -> TyCtxt<'tcx>;
fn item_def_id(&self) -> Option<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: DefId,
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>;
/// 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);
}
#[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<'_>,
) -> subst::GenericArg<'tcx>;
fn inferred_kind(
&mut self,
substs: Option<&[subst::GenericArg<'tcx>]>,
param: &ty::GenericParamDef,
infer_args: bool,
) -> subst::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_region(lifetime.hir_id) {
Some(rl::Region::Static) => tcx.lifetimes.re_static,
Some(rl::Region::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),
};
tcx.mk_region(ty::ReLateBound(debruijn, br))
}
Some(rl::Region::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];
tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion { def_id, index, name }))
}
Some(rl::Region::Free(scope, id)) => {
let name = lifetime_name(id.expect_local());
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(|| {
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.
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
})
}
}
}
/// 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, _) = self.create_substs_for_ast_path(
span,
def_id,
&[],
item_segment,
item_segment.args(),
item_segment.infer_args,
None,
None,
);
if let Some(b) = item_segment.args().bindings.first() {
Self::prohibit_assoc_ty_binding(self.tcx(), b.span);
}
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.
/// 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 `SubstsRef`, 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 substs are the substs for the parent trait:
/// `[Vec<u8>, u8]` and `generic_args` are the arguments for the associated
/// type itself: `['a]`. The returned `SubstsRef` concatenates these two
/// lists: `[Vec<u8>, u8, 'a]`.
#[instrument(level = "debug", skip(self, span), ret)]
fn create_substs_for_ast_path<'a>(
&self,
span: Span,
def_id: DefId,
parent_substs: &[subst::GenericArg<'tcx>],
seg: &hir::PathSegment<'_>,
generic_args: &'a hir::GenericArgs<'_>,
infer_args: bool,
self_ty: Option<Ty<'tcx>>,
constness: Option<ty::BoundConstness>,
) -> (SubstsRef<'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_substs.is_empty())
} else {
// This item (presumably a trait) needs a self-type.
assert!(self_ty.is_some());
}
} else {
assert!(self_ty.is_none() && parent_substs.is_empty());
}
let arg_count = Self::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.intern_substs(parent_substs), 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<'_>,
) -> subst::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);
tcx.ty_error().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)) => {
ty::Const::from_opt_const_arg_anon_const(
tcx,
ty::WithOptConstParam {
did: tcx.hir().local_def_id(ct.value.hir_id),
const_param_did: Some(param.def_id),
},
)
.into()
}
(&GenericParamDefKind::Const { .. }, hir::GenericArg::Infer(inf)) => {
let ty = tcx.at(self.span).type_of(param.def_id);
if self.astconv.allow_ty_infer() {
self.astconv.ct_infer(ty, Some(param), inf.span).into()
} else {
self.inferred_params.push(inf.span);
tcx.const_error(ty).into()
}
}
_ => unreachable!(),
}
}
fn inferred_kind(
&mut self,
substs: Option<&[subst::GenericArg<'tcx>]>,
param: &ty::GenericParamDef,
infer_args: bool,
) -> subst::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
tcx.sess.delay_span_bug(self.span, "unelided lifetime in signature");
// Supply some dummy value. We don't have an
// `re_error`, annoyingly, so use `'static`.
tcx.lifetimes.re_static
})
.into(),
GenericParamDefKind::Type { has_default, .. } => {
if !infer_args && has_default {
// No type parameter provided, but a default exists.
let substs = substs.unwrap();
if substs.iter().any(|arg| match arg.unpack() {
GenericArgKind::Type(ty) => ty.references_error(),
_ => false,
}) {
// Avoid ICE #86756 when type error recovery goes awry.
return tcx.ty_error().into();
}
self.astconv
.normalize_ty(
self.span,
EarlyBinder(tcx.at(self.span).type_of(param.def_id))
.subst(tcx, substs),
)
.into()
} else if infer_args {
self.astconv.ty_infer(Some(param), self.span).into()
} else {
// We've already errored above about the mismatch.
tcx.ty_error().into()
}
}
GenericParamDefKind::Const { has_default } => {
let ty = tcx.at(self.span).type_of(param.def_id);
if !infer_args && has_default {
tcx.bound_const_param_default(param.def_id)
.subst(tcx, substs.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.
tcx.const_error(ty).into()
}
}
}
}
}
}
let mut substs_ctx = SubstsForAstPathCtxt {
astconv: self,
def_id,
span,
generic_args,
inferred_params: vec![],
infer_args,
};
let substs = Self::create_substs_for_generic_args(
tcx,
def_id,
parent_substs,
self_ty.is_some(),
self_ty,
&arg_count,
&mut substs_ctx,
);
if let Some(ty::BoundConstness::ConstIfConst) = constness
&& generics.has_self && !tcx.has_attr(def_id, sym::const_trait)
{
tcx.sess.emit_err(crate::errors::ConstBoundForNonConstTrait { span } );
}
(substs, 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 { ref term } => match term {
hir::Term::Ty(ref ty) => {
ConvertedBindingKind::Equality(self.ast_ty_to_ty(ty).into())
}
hir::Term::Const(ref c) => {
let local_did = self.tcx().hir().local_def_id(c.hir_id);
let c = Const::from_anon_const(self.tcx(), local_did);
ConvertedBindingKind::Equality(c.into())
}
},
hir::TypeBindingKind::Constraint { ref 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_substs_for_associated_item(
&self,
span: Span,
item_def_id: DefId,
item_segment: &hir::PathSegment<'_>,
parent_substs: SubstsRef<'tcx>,
) -> SubstsRef<'tcx> {
debug!(
"create_substs_for_associated_item(span: {:?}, item_def_id: {:?}, item_segment: {:?}",
span, item_def_id, item_segment
);
let (args, _) = self.create_substs_for_ast_path(
span,
item_def_id,
parent_substs,
item_segment,
item_segment.args(),
item_segment.infer_args,
None,
None,
);
if let Some(b) = item_segment.args().bindings.first() {
Self::prohibit_assoc_ty_binding(self.tcx(), b.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>,
constness: ty::BoundConstness,
) -> 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,
Some(constness),
)
}
fn instantiate_poly_trait_ref_inner(
&self,
hir_id: hir::HirId,
span: Span,
binding_span: Option<Span>,
constness: ty::BoundConstness,
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>,
) -> GenericArgCountResult {
let (substs, arg_count) = self.create_substs_for_ast_path(
trait_ref_span,
trait_def_id,
&[],
trait_segment,
args,
infer_args,
Some(self_ty),
Some(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(trait_def_id, substs), bound_vars);
debug!(?poly_trait_ref, ?assoc_bindings);
bounds.trait_bounds.push((poly_trait_ref, span, constness));
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<_, 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,
);
// 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,
self_ty: Ty<'tcx>,
bounds: &mut Bounds<'tcx>,
speculative: bool,
) -> 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,
bounds,
speculative,
trait_ref_span,
trait_def_id,
trait_segment,
args,
infer_args,
self_ty,
)
}
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>,
) {
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,
bounds,
speculative,
trait_ref_span,
trait_def_id,
trait_segment,
args,
infer_args,
self_ty,
);
}
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,
constness: Option<ty::BoundConstness>,
) -> ty::TraitRef<'tcx> {
let (substs, _) = self.create_substs_for_ast_trait_ref(
span,
trait_def_id,
self_ty,
trait_segment,
is_impl,
constness,
);
if let Some(b) = trait_segment.args().bindings.first() {
Self::prohibit_assoc_ty_binding(self.tcx(), b.span);
}
ty::TraitRef::new(trait_def_id, substs)
}
#[instrument(level = "debug", skip(self, span))]
fn create_substs_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: Option<ty::BoundConstness>,
) -> (SubstsRef<'tcx>, GenericArgCountResult) {
self.complain_about_internal_fn_trait(span, trait_def_id, trait_segment, is_impl);
self.create_substs_for_ast_path(
span,
trait_def_id,
&[],
trait_segment,
trait_segment.args(),
trait_segment.infer_args,
Some(self_ty),
constness,
)
}
fn trait_defines_associated_type_named(&self, trait_def_id: DefId, assoc_name: Ident) -> bool {
self.tcx()
.associated_items(trait_def_id)
.find_by_name_and_kind(self.tcx(), assoc_name, ty::AssocKind::Type, trait_def_id)
.is_some()
}
fn trait_defines_associated_const_named(&self, trait_def_id: DefId, assoc_name: Ident) -> bool {
self.tcx()
.associated_items(trait_def_id)
.find_by_name_and_kind(self.tcx(), assoc_name, ty::AssocKind::Const, trait_def_id)
.is_some()
}
// Sets `implicitly_sized` to true on `Bounds` if necessary
pub(crate) fn add_implicitly_sized<'hir>(
&self,
bounds: &mut Bounds<'hir>,
ast_bounds: &'hir [hir::GenericBound<'hir>],
self_ty_where_predicates: Option<(hir::HirId, &'hir [hir::WherePredicate<'hir>])>,
span: Span,
) {
let tcx = self.tcx();
// Try to find an unbound in bounds.
let mut unbound = None;
let mut search_bounds = |ast_bounds: &'hir [hir::GenericBound<'hir>]| {
for ab in ast_bounds {
if let hir::GenericBound::Trait(ptr, hir::TraitBoundModifier::Maybe) = ab {
if unbound.is_none() {
unbound = Some(&ptr.trait_ref);
} else {
tcx.sess.emit_err(MultipleRelaxedDefaultBounds { span });
}
}
}
};
search_bounds(ast_bounds);
if let Some((self_ty, where_clause)) = self_ty_where_predicates {
let self_ty_def_id = tcx.hir().local_def_id(self_ty).to_def_id();
for clause in where_clause {
if let hir::WherePredicate::BoundPredicate(pred) = clause {
if pred.is_param_bound(self_ty_def_id) {
search_bounds(pred.bounds);
}
}
}
}
let sized_def_id = tcx.lang_items().require(LangItem::Sized);
match (&sized_def_id, unbound) {
(Ok(sized_def_id), Some(tpb))
if tpb.path.res == Res::Def(DefKind::Trait, *sized_def_id) =>
{
// There was in fact a `?Sized` bound, return without doing anything
return;
}
(_, Some(_)) => {
// There was a `?Trait` bound, but it was not `?Sized`; warn.
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",
);
// Otherwise, add implicitly sized if `Sized` is available.
}
_ => {
// There was no `?Sized` bound; add implicitly sized if `Sized` is available.
}
}
if sized_def_id.is_err() {
// No lang item for `Sized`, so we can't add it as a bound.
return;
}
bounds.implicitly_sized = Some(span);
}
/// This helper takes a *converted* parameter type (`param_ty`)
/// and an *unconverted* list of bounds:
///
/// ```text
/// 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.
#[instrument(level = "debug", skip(self, ast_bounds, bounds))]
pub(crate) fn add_bounds<'hir, I: Iterator<Item = &'hir hir::GenericBound<'hir>>>(
&self,
param_ty: Ty<'tcx>,
ast_bounds: I,
bounds: &mut Bounds<'tcx>,
bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
) {
for ast_bound in ast_bounds {
match ast_bound {
hir::GenericBound::Trait(poly_trait_ref, modifier) => {
let constness = match modifier {
hir::TraitBoundModifier::MaybeConst => ty::BoundConstness::ConstIfConst,
hir::TraitBoundModifier::None => ty::BoundConstness::NotConst,
hir::TraitBoundModifier::Maybe => continue,
};
let _ = self.instantiate_poly_trait_ref(
&poly_trait_ref.trait_ref,
poly_trait_ref.span,
constness,
param_ty,
bounds,
false,
);
}
&hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => {
self.instantiate_lang_item_trait_ref(
lang_item, span, hir_id, args, param_ty, bounds,
);
}
hir::GenericBound::Outlives(lifetime) => {
let region = self.ast_region_to_region(lifetime, None);
bounds
.region_bounds
.push((ty::Binder::bind_with_vars(region, bound_vars), lifetime.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:
///
/// ```ignore (illustrative)
/// 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(crate) fn compute_bounds(
&self,
param_ty: Ty<'tcx>,
ast_bounds: &[hir::GenericBound<'_>],
) -> Bounds<'tcx> {
self.compute_bounds_inner(param_ty, ast_bounds)
}
/// Convert the bounds in `ast_bounds` that refer to traits which define an associated type
/// named `assoc_name` into ty::Bounds. Ignore the rest.
pub(crate) fn compute_bounds_that_match_assoc_type(
&self,
param_ty: Ty<'tcx>,
ast_bounds: &[hir::GenericBound<'_>],
assoc_name: Ident,
) -> Bounds<'tcx> {
let mut result = Vec::new();
for ast_bound in ast_bounds {
if let Some(trait_ref) = ast_bound.trait_ref()
&& let Some(trait_did) = trait_ref.trait_def_id()
&& self.tcx().trait_may_define_assoc_type(trait_did, assoc_name)
{
result.push(ast_bound.clone());
}
}
self.compute_bounds_inner(param_ty, &result)
}
fn compute_bounds_inner(
&self,
param_ty: Ty<'tcx>,
ast_bounds: &[hir::GenericBound<'_>],
) -> Bounds<'tcx> {
let mut bounds = Bounds::default();
self.add_bounds(param_ty, ast_bounds.iter(), &mut bounds, ty::List::empty());
debug!(?bounds);
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.
#[instrument(level = "debug", skip(self, bounds, speculative, dup_bindings, path_span))]
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>,
path_span: Span,
constness: ty::BoundConstness,
) -> Result<(), ErrorGuaranteed> {
// 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<i32> { }
// trait SuperTrait<A> { type T; }
//
// ... B: SubTrait<T = foo> ...
// ```
//
// We want to produce `<B as SuperTrait<i32>>::T == foo`.
let tcx = self.tcx();
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.
trait_ref
} else {
// Otherwise, we have to walk through the supertraits to find
// those that do.
self.one_bound_for_assoc_type(
|| traits::supertraits(tcx, trait_ref),
|| trait_ref.print_only_trait_path().to_string(),
binding.item_name,
path_span,
|| match binding.kind {
ConvertedBindingKind::Equality(ty) => Some(ty.to_string()),
_ => None,
},
)?
};
let (assoc_ident, def_scope) =
tcx.adjust_ident_and_get_scope(binding.item_name, candidate.def_id(), hir_ref_id);
// We have already adjusted the item name above, so compare with `ident.normalize_to_macros_2_0()` instead
// of calling `filter_by_name_and_kind`.
let find_item_of_kind = |kind| {
tcx.associated_items(candidate.def_id())
.filter_by_name_unhygienic(assoc_ident.name)
.find(|i| i.kind == kind && i.ident(tcx).normalize_to_macros_2_0() == assoc_ident)
};
let assoc_item = find_item_of_kind(ty::AssocKind::Type)
.or_else(|| find_item_of_kind(ty::AssocKind::Const))
.expect("missing associated type");
if !assoc_item.visibility(tcx).is_accessible_from(def_scope, tcx) {
tcx.sess
.struct_span_err(
binding.span,
&format!("{} `{}` is private", assoc_item.kind, binding.item_name),
)
.span_label(binding.span, &format!("private {}", assoc_item.kind))
.emit();
}
tcx.check_stability(assoc_item.def_id, Some(hir_ref_id), binding.span, None);
if !speculative {
dup_bindings
.entry(assoc_item.def_id)
.and_modify(|prev_span| {
self.tcx().sess.emit_err(ValueOfAssociatedStructAlreadySpecified {
span: binding.span,
prev_span: *prev_span,
item_name: binding.item_name,
def_path: tcx.def_path_str(assoc_item.container_id(tcx)),
});
})
.or_insert(binding.span);
}
// Include substitutions for generic parameters of associated types
let projection_ty = candidate.map_bound(|trait_ref| {
let ident = Ident::new(assoc_item.name, binding.item_name.span);
let item_segment = hir::PathSegment {
ident,
hir_id: binding.hir_id,
res: Res::Err,
args: Some(binding.gen_args),
infer_args: false,
};
let substs_trait_ref_and_assoc_item = self.create_substs_for_associated_item(
path_span,
assoc_item.def_id,
&item_segment,
trait_ref.substs,
);
debug!(?substs_trait_ref_and_assoc_item);
ty::ProjectionTy {
item_def_id: assoc_item.def_id,
substs: substs_trait_ref_and_assoc_item,
}
});
if !speculative {
// Find any late-bound regions declared in `ty` that are not
// declared in the trait-ref or assoc_item. 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(&projection_ty);
let late_bound_in_ty =
tcx.collect_referenced_late_bound_regions(&trait_ref.rebind(ty));
debug!(?late_bound_in_trait_ref);
debug!(?late_bound_in_ty);
// FIXME: point at the type params that don't have appropriate lifetimes:
// struct S1<F: for<'a> Fn(&i32, &i32) -> &'a i32>(F);
// ---- ---- ^^^^^^^
self.validate_late_bound_regions(
late_bound_in_trait_ref,
late_bound_in_ty,
|br_name| {
struct_span_err!(
tcx.sess,
binding.span,
E0582,
"binding for associated type `{}` references {}, \
which does not appear in the trait input types",
binding.item_name,
br_name
)
},
);
}
}
match binding.kind {
ConvertedBindingKind::Equality(mut term) => {
// "Desugar" a constraint like `T: Iterator<Item = u32>` this to
// the "projection predicate" for:
//
// `<T as Iterator>::Item = u32`
let assoc_item_def_id = projection_ty.skip_binder().item_def_id;
let def_kind = tcx.def_kind(assoc_item_def_id);
match (def_kind, term.unpack()) {
(hir::def::DefKind::AssocTy, ty::TermKind::Ty(_))
| (hir::def::DefKind::AssocConst, ty::TermKind::Const(_)) => (),
(_, _) => {
let got = if let Some(_) = term.ty() { "type" } else { "constant" };
let expected = def_kind.descr(assoc_item_def_id);
tcx.sess
.struct_span_err(
binding.span,
&format!("expected {expected} bound, found {got}"),
)
.span_note(
tcx.def_span(assoc_item_def_id),
&format!("{expected} defined here"),
)
.emit();
term = match def_kind {
hir::def::DefKind::AssocTy => tcx.ty_error().into(),
hir::def::DefKind::AssocConst => tcx
.const_error(
tcx.bound_type_of(assoc_item_def_id)
.subst(tcx, projection_ty.skip_binder().substs),
)
.into(),
_ => unreachable!(),
};
}
}
bounds.projection_bounds.push((
projection_ty.map_bound(|projection_ty| ty::ProjectionPredicate {
projection_ty,
term: term,
}),
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_ty(ty::Projection(projection_ty.skip_binder()));
self.add_bounds(param_ty, ast_bounds.iter(), bounds, candidate.bound_vars());
}
}
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,
EarlyBinder(self.tcx().at(span).type_of(did)).subst(self.tcx(), substs),
)
}
fn conv_object_ty_poly_trait_ref(
&self,
span: Span,
trait_bounds: &[hir::PolyTraitRef<'_>],
lifetime: &hir::Lifetime,
borrowed: bool,
representation: DynKind,
) -> 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() {
if let GenericArgCountResult {
correct:
Err(GenericArgCountMismatch { invalid_args: cur_potential_assoc_types, .. }),
..
} = self.instantiate_poly_trait_ref(
&trait_bound.trait_ref,
trait_bound.span,
ty::BoundConstness::NotConst,
dummy_self,
&mut bounds,
false,
) {
potential_assoc_types.extend(cur_potential_assoc_types);
}
}
// 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().map(|&(a, b, _)| (a, b)));
let (mut auto_traits, regular_traits): (Vec<_>, Vec<_>) = expanded_traits
.filter(|i| i.trait_ref().self_ty().skip_binder() == dummy_self)
.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.help(&format!(
"consider creating a new trait with all of these as supertraits and using that \
trait here instead: `trait NewTrait: {} {{}}`",
regular_traits
.iter()
.map(|t| t.trait_ref().print_only_trait_path().to_string())
.collect::<Vec<_>>()
.join(" + "),
));
err.note(
"auto-traits like `Send` and `Sync` are traits that have special properties; \
for more information on them, visit \
<https://doc.rust-lang.org/reference/special-types-and-traits.html#auto-traits>",
);
err.emit();
}
if regular_traits.is_empty() && auto_traits.is_empty() {
let trait_alias_span = bounds
.trait_bounds
.iter()
.map(|&(trait_ref, _, _)| trait_ref.def_id())
.find(|&trait_ref| tcx.is_trait_alias(trait_ref))
.map(|trait_ref| tcx.def_span(trait_ref));
tcx.sess.emit_err(TraitObjectDeclaredWithNoTraits { span, trait_alias_span });
return tcx.ty_error();
}
// 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 =
astconv_object_safety_violations(tcx, item.trait_ref().def_id());
if !object_safety_violations.is_empty() {
report_object_safety_error(
tcx,
span,
item.trait_ref().def_id(),
&object_safety_violations,
)
.emit();
return tcx.ty_error();
}
}
// Use a `BTreeSet` to keep output in a more consistent order.
let mut associated_types: FxHashMap<Span, BTreeSet<DefId>> = FxHashMap::default();
let regular_traits_refs_spans = bounds
.trait_bounds
.into_iter()
.filter(|(trait_ref, _, _)| !tcx.trait_is_auto(trait_ref.def_id()));
for (base_trait_ref, span, constness) in regular_traits_refs_spans {
assert_eq!(constness, ty::BoundConstness::NotConst);
for obligation in traits::elaborate_trait_ref(tcx, base_trait_ref) {
debug!(
"conv_object_ty_poly_trait_ref: observing object predicate `{:?}`",
obligation.predicate
);
let bound_predicate = obligation.predicate.kind();
match bound_predicate.skip_binder() {
ty::PredicateKind::Trait(pred) => {
let pred = bound_predicate.rebind(pred);
associated_types.entry(span).or_default().extend(
tcx.associated_items(pred.def_id())
.in_definition_order()
.filter(|item| item.kind == ty::AssocKind::Type)
.map(|item| item.def_id),
);
}
ty::PredicateKind::Projection(pred) => {
let pred = bound_predicate.rebind(pred);
// A `Self` within the original bound will be substituted with a
// `trait_object_dummy_self`, so check for that.
let references_self = match pred.skip_binder().term.unpack() {
ty::TermKind::Ty(ty) => ty.walk().any(|arg| arg == dummy_self.into()),
ty::TermKind::Const(c) => {
c.ty().walk().any(|arg| arg == dummy_self.into())
}
};
// If the projection output contains `Self`, force the user to
// elaborate it explicitly to avoid a lot of complexity.
//
// The "classically 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, span));
}
}
_ => (),
}
}
}
for (projection_bound, _) in &bounds.projection_bounds {
for def_ids in associated_types.values_mut() {
def_ids.remove(&projection_bound.projection_def_id());
}
}
self.complain_about_missing_associated_types(
associated_types,
potential_assoc_types,
trait_bounds,
);
// De-duplicate auto traits so that, e.g., `dyn Trait + Send + Send` is the same as
// `dyn Trait + Send`.
// We remove duplicates by inserting into a `FxHashSet` to avoid re-ordering
// the bounds
let mut duplicates = FxHashSet::default();
auto_traits.retain(|i| duplicates.insert(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: ty::TraitRef<'tcx>| {
assert_eq!(trait_ref.self_ty(), dummy_self);
// Verify that `dummy_self` did not leak inside default type parameters. This
// could not be done at path creation, since we need to see through trait aliases.
let mut missing_type_params = vec![];
let mut references_self = false;
let generics = tcx.generics_of(trait_ref.def_id);
let substs: Vec<_> = trait_ref
.substs
.iter()
.enumerate()
.skip(1) // Remove `Self` for `ExistentialPredicate`.
.map(|(index, arg)| {
if arg == dummy_self.into() {
let param = &generics.params[index];
missing_type_params.push(param.name);
return tcx.ty_error().into();
} else if arg.walk().any(|arg| arg == dummy_self.into()) {
references_self = true;
return tcx.ty_error().into();
}
arg
})
.collect();
let substs = tcx.intern_substs(&substs[..]);
let span = i.bottom().1;
let empty_generic_args = trait_bounds.iter().any(|hir_bound| {
hir_bound.trait_ref.path.res == Res::Def(DefKind::Trait, trait_ref.def_id)
&& hir_bound.span.contains(span)
});
self.complain_about_missing_type_params(
missing_type_params,
trait_ref.def_id,
span,
empty_generic_args,
);
if references_self {
let def_id = i.bottom().0.def_id();
let mut err = struct_span_err!(
tcx.sess,
i.bottom().1,
E0038,
"the {} `{}` cannot be made into an object",
tcx.def_kind(def_id).descr(def_id),
tcx.item_name(def_id),
);
err.note(
rustc_middle::traits::ObjectSafetyViolation::SupertraitSelf(smallvec![])
.error_msg(),
);
err.emit();
}
ty::ExistentialTraitRef { def_id: trait_ref.def_id, substs }
})
});
let existential_projections = bounds.projection_bounds.iter().map(|(bound, _)| {
bound.map_bound(|mut b| {
assert_eq!(b.projection_ty.self_ty(), dummy_self);
// Like for trait refs, verify that `dummy_self` did not leak inside default type
// parameters.
let references_self = b.projection_ty.substs.iter().skip(1).any(|arg| {
if arg.walk().any(|arg| arg == dummy_self.into()) {
return true;
}
false
});
if references_self {
tcx.sess
.delay_span_bug(span, "trait object projection bounds reference `Self`");
let substs: Vec<_> = b
.projection_ty
.substs
.iter()
.map(|arg| {
if arg.walk().any(|arg| arg == dummy_self.into()) {
return tcx.ty_error().into();
}
arg
})
.collect();
b.projection_ty.substs = tcx.intern_substs(&substs[..]);
}
ty::ExistentialProjection::erase_self_ty(tcx, b)
})
});
let regular_trait_predicates = existential_trait_refs
.map(|trait_ref| trait_ref.map_bound(ty::ExistentialPredicate::Trait));
let auto_trait_predicates = auto_traits.into_iter().map(|trait_ref| {
ty::Binder::dummy(ty::ExistentialPredicate::AutoTrait(trait_ref.trait_ref().def_id()))
});
// N.b. principal, projections, auto traits
// FIXME: This is actually wrong with multiple principals in regards to symbol mangling
let mut v = regular_trait_predicates
.chain(
existential_projections.map(|x| x.map_bound(ty::ExistentialPredicate::Projection)),
)
.chain(auto_trait_predicates)
.collect::<SmallVec<[_; 8]>>();
v.sort_by(|a, b| a.skip_binder().stable_cmp(tcx, &b.skip_binder()));
v.dedup();
let existential_predicates = tcx.mk_poly_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(|| {
let mut err = struct_span_err!(
tcx.sess,
span,
E0228,
"the lifetime bound for this object type cannot be deduced \
from context; please supply an explicit bound"
);
if borrowed {
// We will have already emitted an error E0106 complaining about a
// missing named lifetime in `&dyn Trait`, so we elide this one.
err.delay_as_bug();
} else {
err.emit();
}
tcx.lifetimes.re_static
})
}
})
};
debug!("region_bound: {:?}", region_bound);
let ty = tcx.mk_dynamic(existential_predicates, region_bound, representation);
debug!("trait_object_type: {:?}", ty);
ty
}
fn report_ambiguous_associated_type(
&self,
span: Span,
type_str: &str,
trait_str: &str,
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(
span.shrink_to_lo(),
"you are looking for the module in `std`, not the primitive type",
"std::",
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: 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.to_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_type(
tcx,
predicates.iter().filter_map(|(p, _)| {
Some(p.to_opt_poly_trait_pred()?.map_bound(|t| t.trait_ref))
}),
assoc_name,
)
},
|| param_name.to_string(),
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 Fn() -> String,
assoc_name: Ident,
span: Span,
is_equality: impl Fn() -> Option<String>,
) -> Result<ty::PolyTraitRef<'tcx>, ErrorGuaranteed>
where
I: Iterator<Item = ty::PolyTraitRef<'tcx>>,
{
let mut matching_candidates = all_candidates()
.filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_name));
let mut const_candidates = all_candidates()
.filter(|r| self.trait_defines_associated_const_named(r.def_id(), 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(),
assoc_name,
span,
);
return Err(reported);
}
};
debug!(?bound);
if let Some(bound2) = next_cand {
debug!(?bound2);
let is_equality = is_equality();
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)
}
// 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`.
// 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(_, ref path)) = qself.kind {
path.res
} else {
Res::Err
};
// Check if we have an enum variant.
let mut variant_resolution = None;
if let ty::Adt(adt_def, _) = qself_ty.kind() {
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 specity 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(_, ref 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);
}
}
}
}
// 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)),
|| "Self".to_string(),
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 `{}` not found here", assoc_ident));
}
err.emit()
} else if let Some(reported) = qself_ty.error_reported() {
reported
} else {
// Don't print `TyErr` to the user.
self.report_ambiguous_associated_type(
span,
&qself_ty.to_string(),
"Trait",
assoc_ident.name,
)
};
return Err(reported);
}
};
let trait_did = bound.def_id();
let (assoc_ident, def_scope) =
tcx.adjust_ident_and_get_scope(assoc_ident, trait_did, hir_ref_id);
// We have already adjusted the item name above, so compare with `ident.normalize_to_macros_2_0()` instead
// of calling `filter_by_name_and_kind`.
let item = tcx.associated_items(trait_did).in_definition_order().find(|i| {
i.kind.namespace() == Namespace::TypeNS
&& i.ident(tcx).normalize_to_macros_2_0() == assoc_ident
});
// 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 Some(item) = item else {
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, item.def_id, assoc_segment, bound);
let ty = self.normalize_ty(span, ty);
let kind = DefKind::AssocTy;
if !item.visibility(tcx).is_accessible_from(def_scope, tcx) {
let kind = kind.descr(item.def_id);
let msg = format!("{} `{}` is private", kind, assoc_ident);
tcx.sess
.struct_span_err(span, &msg)
.span_label(span, &format!("private {}", kind))
.emit();
}
tcx.check_stability(item.def_id, Some(hir_ref_id), span, None);
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,
kind.descr(def_id)
);
lint.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");
lint.span_suggestion(
span,
"use fully-qualified syntax",
format!("<{} as {}>::{}", qself_ty, tcx.item_name(trait_did), assoc_ident),
Applicability::MachineApplicable,
);
lint
},
);
}
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<'_>,
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
.and_then(|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 == Some(trait_def_id);
let is_part_of_fn_in_self_trait = parent_def_id == Some(trait_def_id);
let type_name = if is_part_of_self_trait_constraints || is_part_of_fn_in_self_trait {
"Self"
} else {
"Type"
};
self.report_ambiguous_associated_type(
span,
type_name,
&path_str,
item_segment.ident.name,
);
return tcx.ty_error();
};
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,
Some(constness),
);
let item_substs = self.create_substs_for_associated_item(
span,
item_def_id,
item_segment,
trait_ref.substs,
);
debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
self.normalize_ty(span, tcx.mk_projection(item_def_id, item_substs))
}
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] => (format!("{only}"), ""),
[] => 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() {
Self::prohibit_assoc_ty_binding(self.tcx(), b.span);
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,
) -> 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);
}
// `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<'_>,
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 | DefKind::ImplTraitPlaceholder, 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.iter(), |err| {
err.note("`impl Trait` types can't have type parameters");
});
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
| 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);
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"));
}
});
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()];
tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id))
}
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);
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.needs_subst() {
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(ref impl_),
..
})) = tcx.hir().get_if_local(def_id)
{
err.span_note(impl_.self_ty.span, "not a concrete type");
}
err.emit();
tcx.ty_error()
} else {
self.normalize_ty(span, 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) => tcx.mk_mach_int(ty::int_ty(it)),
hir::PrimTy::Uint(uit) => tcx.mk_mach_uint(ty::uint_ty(uit)),
hir::PrimTy::Float(ft) => tcx.mk_mach_float(ty::float_ty(ft)),
hir::PrimTy::Str => tcx.types.str_,
}
}
Res::Err => {
self.set_tainted_by_errors();
self.tcx().ty_error()
}
_ => 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(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!(?r);
let t = self.ast_ty_to_ty_inner(mt.ty, true, false);
tcx.mk_ref(r, ty::TypeAndMut { ty: t, mutbl: mt.mutbl })
}
hir::TyKind::Never => tcx.types.never,
hir::TyKind::Tup(fields) => tcx.mk_tup(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);
tcx.mk_fn_ptr(self.ty_of_fn(
ast_ty.hir_id,
bf.unsafety,
bf.abi,
bf.decl,
None,
Some(ast_ty),
))
}
hir::TyKind::TraitObject(bounds, ref 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, bounds, lifetime, borrowed, repr)
}
hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref 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, false)
}
hir::TyKind::OpaqueDef(item_id, lifetimes, in_trait) => {
let opaque_ty = tcx.hir().item(item_id);
let def_id = item_id.owner_id.to_def_id();
match opaque_ty.kind {
hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
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(ref qself, ref 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(|_| tcx.ty_error())
}
hir::TyKind::Path(hir::QPath::LangItem(lang_item, span, _)) => {
let def_id = tcx.require_lang_item(lang_item, Some(span));
let (substs, _) = self.create_substs_for_ast_path(
span,
def_id,
&[],
&hir::PathSegment::invalid(),
&GenericArgs::none(),
true,
None,
None,
);
EarlyBinder(self.normalize_ty(span, tcx.at(span).type_of(def_id)))
.subst(tcx, substs)
}
hir::TyKind::Array(ref ty, ref length) => {
let length = match length {
&hir::ArrayLen::Infer(_, span) => self.ct_infer(tcx.types.usize, None, span),
hir::ArrayLen::Body(constant) => {
let length_def_id = tcx.hir().local_def_id(constant.hir_id);
ty::Const::from_anon_const(tcx, length_def_id)
}
};
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) => {
let ty_erased = tcx.type_of(tcx.hir().local_def_id(e.hir_id));
let ty = tcx.fold_regions(ty_erased, |r, _| {
if r.is_erased() { tcx.lifetimes.re_static } else { r }
});
let span = ast_ty.span;
tcx.sess.emit_err(TypeofReservedKeywordUsed {
span,
ty,
opt_sugg: Some((span, Applicability::MachineApplicable))
.filter(|_| ty.is_suggestable(tcx, false)),
});
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 => tcx.ty_error(),
};
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 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.
if let GenericParamDefKind::Lifetime = param.kind {
if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
self.ast_region_to_region(lifetime, None).into()
} else {
bug!()
}
} else {
bug!()
}
} else {
match param.kind {
// For RPIT (return position impl trait), only lifetimes
// mentioned in the impl Trait predicate are captured by
// the opaque type, so the lifetime parameters from the
// parent item need to be replaced with `'static`.
//
// For `impl Trait` in the types of statics, constants,
// locals and type aliases. These capture all parent
// lifetimes, so they can use their identity subst.
GenericParamDefKind::Lifetime
if matches!(
origin,
hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..)
) =>
{
tcx.lifetimes.re_static.into()
}
_ => tcx.mk_param_from_def(param),
}
}
});
debug!("impl_trait_ty_to_ty: substs={:?}", substs);
if in_trait { tcx.mk_projection(def_id, substs) } else { tcx.mk_opaque(def_id, substs) }
}
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(..) => tcx.mk_unit(),
};
debug!(?output_ty);
let fn_ty = tcx.mk_fn_sig(input_tys.into_iter(), 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 hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(i), .. }) =
hir.get(hir.get_parent_node(fn_hir_id)) else { bug!("ImplItem should have Impl parent") };
let trait_ref = self.instantiate_mono_trait_ref(
i.of_trait.as_ref()?,
self.ast_ty_to_ty(i.self_ty),
ty::BoundConstness::NotConst,
);
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.bound_fn_sig(assoc.def_id).subst(
tcx,
trait_ref.substs.extend_to(tcx, assoc.def_id, |param, _| tcx.mk_param_from_def(param)),
);
let ty = if let Some(arg_idx) = arg_idx { fn_sig.input(arg_idx) } else { fn_sig.output() };
Some(tcx.liberate_late_bound_regions(fn_hir_id.expect_owner().to_def_id(), ty))
}
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::Binder<'tcx, 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| 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)
}
/// Make sure that we are in the condition to suggest the blanket implementation.
fn maybe_lint_blanket_trait_impl(&self, self_ty: &hir::Ty<'_>, diag: &mut Diagnostic) {
let tcx = self.tcx();
let parent_id = tcx.hir().get_parent_item(self_ty.hir_id).def_id;
if let hir::Node::Item(hir::Item {
kind:
hir::ItemKind::Impl(hir::Impl {
self_ty: impl_self_ty, of_trait: Some(of_trait_ref), generics, ..
}),
..
}) = tcx.hir().get_by_def_id(parent_id) && self_ty.hir_id == impl_self_ty.hir_id
{
if !of_trait_ref.trait_def_id().map_or(false, |def_id| def_id.is_local()) {
return;
}
let of_trait_span = of_trait_ref.path.span;
// make sure that we are not calling unwrap to abort during the compilation
let Ok(impl_trait_name) = tcx.sess.source_map().span_to_snippet(self_ty.span) else { return; };
let Ok(of_trait_name) = tcx.sess.source_map().span_to_snippet(of_trait_span) else { return; };
// check if the trait has generics, to make a correct suggestion
let param_name = generics.params.next_type_param_name(None);
let add_generic_sugg = if let Some(span) = generics.span_for_param_suggestion() {
(span, format!(", {}: {}", param_name, impl_trait_name))
} else {
(generics.span, format!("<{}: {}>", param_name, impl_trait_name))
};
diag.multipart_suggestion(
format!("alternatively use a blanket \
implementation to implement `{of_trait_name}` for \
all types that also implement `{impl_trait_name}`"),
vec![
(self_ty.span, param_name),
add_generic_sugg,
],
Applicability::MaybeIncorrect,
);
}
}
fn maybe_lint_bare_trait(&self, self_ty: &hir::Ty<'_>, in_path: bool) {
let tcx = self.tcx();
if let hir::TyKind::TraitObject([poly_trait_ref, ..], _, TraitObjectSyntax::None) =
self_ty.kind
{
let needs_bracket = in_path
&& !tcx
.sess
.source_map()
.span_to_prev_source(self_ty.span)
.ok()
.map_or(false, |s| s.trim_end().ends_with('<'));
let is_global = poly_trait_ref.trait_ref.path.is_global();
let mut sugg = Vec::from_iter([(
self_ty.span.shrink_to_lo(),
format!(
"{}dyn {}",
if needs_bracket { "<" } else { "" },
if is_global { "(" } else { "" },
),
)]);
if is_global || needs_bracket {
sugg.push((
self_ty.span.shrink_to_hi(),
format!(
"{}{}",
if is_global { ")" } else { "" },
if needs_bracket { ">" } else { "" },
),
));
}
if self_ty.span.edition() >= Edition::Edition2021 {
let msg = "trait objects must include the `dyn` keyword";
let label = "add `dyn` keyword before this trait";
let mut diag =
rustc_errors::struct_span_err!(tcx.sess, self_ty.span, E0782, "{}", msg);
diag.multipart_suggestion_verbose(label, sugg, Applicability::MachineApplicable);
// check if the impl trait that we are considering is a impl of a local trait
self.maybe_lint_blanket_trait_impl(&self_ty, &mut diag);
diag.emit();
} else {
let msg = "trait objects without an explicit `dyn` are deprecated";
tcx.struct_span_lint_hir(
BARE_TRAIT_OBJECTS,
self_ty.hir_id,
self_ty.span,
msg,
|lint| {
lint.multipart_suggestion_verbose(
"use `dyn`",
sugg,
Applicability::MachineApplicable,
);
self.maybe_lint_blanket_trait_impl(&self_ty, lint);
lint
},
);
}
}
}
}