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Diffstat (limited to 'compiler/rustc_middle/src/ty/error.rs')
| -rw-r--r-- | compiler/rustc_middle/src/ty/error.rs | 897 |
1 files changed, 897 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/ty/error.rs b/compiler/rustc_middle/src/ty/error.rs new file mode 100644 index 00000000000..1963881626e --- /dev/null +++ b/compiler/rustc_middle/src/ty/error.rs @@ -0,0 +1,897 @@ +use crate::traits::{ObligationCause, ObligationCauseCode}; +use crate::ty::diagnostics::suggest_constraining_type_param; +use crate::ty::{self, BoundRegion, Region, Ty, TyCtxt}; +use rustc_ast as ast; +use rustc_errors::Applicability::{MachineApplicable, MaybeIncorrect}; +use rustc_errors::{pluralize, DiagnosticBuilder}; +use rustc_hir as hir; +use rustc_hir::def_id::DefId; +use rustc_span::symbol::{sym, Symbol}; +use rustc_span::{BytePos, MultiSpan, Span}; +use rustc_target::spec::abi; + +use std::borrow::Cow; +use std::fmt; +use std::ops::Deref; + +#[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable)] +pub struct ExpectedFound<T> { + pub expected: T, + pub found: T, +} + +impl<T> ExpectedFound<T> { + pub fn new(a_is_expected: bool, a: T, b: T) -> Self { + if a_is_expected { + ExpectedFound { expected: a, found: b } + } else { + ExpectedFound { expected: b, found: a } + } + } +} + +// Data structures used in type unification +#[derive(Clone, Debug, TypeFoldable)] +pub enum TypeError<'tcx> { + Mismatch, + UnsafetyMismatch(ExpectedFound<hir::Unsafety>), + AbiMismatch(ExpectedFound<abi::Abi>), + Mutability, + TupleSize(ExpectedFound<usize>), + FixedArraySize(ExpectedFound<u64>), + ArgCount, + + RegionsDoesNotOutlive(Region<'tcx>, Region<'tcx>), + RegionsInsufficientlyPolymorphic(BoundRegion, Region<'tcx>), + RegionsOverlyPolymorphic(BoundRegion, Region<'tcx>), + RegionsPlaceholderMismatch, + + Sorts(ExpectedFound<Ty<'tcx>>), + IntMismatch(ExpectedFound<ty::IntVarValue>), + FloatMismatch(ExpectedFound<ast::FloatTy>), + Traits(ExpectedFound<DefId>), + VariadicMismatch(ExpectedFound<bool>), + + /// Instantiating a type variable with the given type would have + /// created a cycle (because it appears somewhere within that + /// type). + CyclicTy(Ty<'tcx>), + ProjectionMismatched(ExpectedFound<DefId>), + ExistentialMismatch(ExpectedFound<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>), + ObjectUnsafeCoercion(DefId), + ConstMismatch(ExpectedFound<&'tcx ty::Const<'tcx>>), + + IntrinsicCast, + /// Safe `#[target_feature]` functions are not assignable to safe function pointers. + TargetFeatureCast(DefId), +} + +pub enum UnconstrainedNumeric { + UnconstrainedFloat, + UnconstrainedInt, + Neither, +} + +/// Explains the source of a type err in a short, human readable way. This is meant to be placed +/// in parentheses after some larger message. You should also invoke `note_and_explain_type_err()` +/// afterwards to present additional details, particularly when it comes to lifetime-related +/// errors. +impl<'tcx> fmt::Display for TypeError<'tcx> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + use self::TypeError::*; + fn report_maybe_different( + f: &mut fmt::Formatter<'_>, + expected: &str, + found: &str, + ) -> fmt::Result { + // A naive approach to making sure that we're not reporting silly errors such as: + // (expected closure, found closure). + if expected == found { + write!(f, "expected {}, found a different {}", expected, found) + } else { + write!(f, "expected {}, found {}", expected, found) + } + } + + let br_string = |br: ty::BoundRegion| match br { + ty::BrNamed(_, name) => format!(" {}", name), + _ => String::new(), + }; + + match *self { + CyclicTy(_) => write!(f, "cyclic type of infinite size"), + Mismatch => write!(f, "types differ"), + UnsafetyMismatch(values) => { + write!(f, "expected {} fn, found {} fn", values.expected, values.found) + } + AbiMismatch(values) => { + write!(f, "expected {} fn, found {} fn", values.expected, values.found) + } + Mutability => write!(f, "types differ in mutability"), + TupleSize(values) => write!( + f, + "expected a tuple with {} element{}, \ + found one with {} element{}", + values.expected, + pluralize!(values.expected), + values.found, + pluralize!(values.found) + ), + FixedArraySize(values) => write!( + f, + "expected an array with a fixed size of {} element{}, \ + found one with {} element{}", + values.expected, + pluralize!(values.expected), + values.found, + pluralize!(values.found) + ), + ArgCount => write!(f, "incorrect number of function parameters"), + RegionsDoesNotOutlive(..) => write!(f, "lifetime mismatch"), + RegionsInsufficientlyPolymorphic(br, _) => write!( + f, + "expected bound lifetime parameter{}, found concrete lifetime", + br_string(br) + ), + RegionsOverlyPolymorphic(br, _) => write!( + f, + "expected concrete lifetime, found bound lifetime parameter{}", + br_string(br) + ), + RegionsPlaceholderMismatch => write!(f, "one type is more general than the other"), + Sorts(values) => ty::tls::with(|tcx| { + report_maybe_different( + f, + &values.expected.sort_string(tcx), + &values.found.sort_string(tcx), + ) + }), + Traits(values) => ty::tls::with(|tcx| { + report_maybe_different( + f, + &format!("trait `{}`", tcx.def_path_str(values.expected)), + &format!("trait `{}`", tcx.def_path_str(values.found)), + ) + }), + IntMismatch(ref values) => { + write!(f, "expected `{:?}`, found `{:?}`", values.expected, values.found) + } + FloatMismatch(ref values) => { + write!(f, "expected `{:?}`, found `{:?}`", values.expected, values.found) + } + VariadicMismatch(ref values) => write!( + f, + "expected {} fn, found {} function", + if values.expected { "variadic" } else { "non-variadic" }, + if values.found { "variadic" } else { "non-variadic" } + ), + ProjectionMismatched(ref values) => ty::tls::with(|tcx| { + write!( + f, + "expected {}, found {}", + tcx.def_path_str(values.expected), + tcx.def_path_str(values.found) + ) + }), + ExistentialMismatch(ref values) => report_maybe_different( + f, + &format!("trait `{}`", values.expected), + &format!("trait `{}`", values.found), + ), + ConstMismatch(ref values) => { + write!(f, "expected `{}`, found `{}`", values.expected, values.found) + } + IntrinsicCast => write!(f, "cannot coerce intrinsics to function pointers"), + TargetFeatureCast(_) => write!( + f, + "cannot coerce functions with `#[target_feature]` to safe function pointers" + ), + ObjectUnsafeCoercion(_) => write!(f, "coercion to object-unsafe trait object"), + } + } +} + +impl<'tcx> TypeError<'tcx> { + pub fn must_include_note(&self) -> bool { + use self::TypeError::*; + match self { + CyclicTy(_) | UnsafetyMismatch(_) | Mismatch | AbiMismatch(_) | FixedArraySize(_) + | Sorts(_) | IntMismatch(_) | FloatMismatch(_) | VariadicMismatch(_) + | TargetFeatureCast(_) => false, + + Mutability + | TupleSize(_) + | ArgCount + | RegionsDoesNotOutlive(..) + | RegionsInsufficientlyPolymorphic(..) + | RegionsOverlyPolymorphic(..) + | RegionsPlaceholderMismatch + | Traits(_) + | ProjectionMismatched(_) + | ExistentialMismatch(_) + | ConstMismatch(_) + | IntrinsicCast + | ObjectUnsafeCoercion(_) => true, + } + } +} + +impl<'tcx> ty::TyS<'tcx> { + pub fn sort_string(&self, tcx: TyCtxt<'_>) -> Cow<'static, str> { + match self.kind { + ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Str | ty::Never => { + format!("`{}`", self).into() + } + ty::Tuple(ref tys) if tys.is_empty() => format!("`{}`", self).into(), + + ty::Adt(def, _) => format!("{} `{}`", def.descr(), tcx.def_path_str(def.did)).into(), + ty::Foreign(def_id) => format!("extern type `{}`", tcx.def_path_str(def_id)).into(), + ty::Array(t, n) => { + let n = tcx.lift(&n).unwrap(); + match n.try_eval_usize(tcx, ty::ParamEnv::empty()) { + _ if t.is_simple_ty() => format!("array `{}`", self).into(), + Some(n) => format!("array of {} element{} ", n, pluralize!(n)).into(), + None => "array".into(), + } + } + ty::Slice(ty) if ty.is_simple_ty() => format!("slice `{}`", self).into(), + ty::Slice(_) => "slice".into(), + ty::RawPtr(_) => "*-ptr".into(), + ty::Ref(_, ty, mutbl) => { + let tymut = ty::TypeAndMut { ty, mutbl }; + let tymut_string = tymut.to_string(); + if tymut_string != "_" + && (ty.is_simple_text() || tymut_string.len() < "mutable reference".len()) + { + format!("`&{}`", tymut_string).into() + } else { + // Unknown type name, it's long or has type arguments + match mutbl { + hir::Mutability::Mut => "mutable reference", + _ => "reference", + } + .into() + } + } + ty::FnDef(..) => "fn item".into(), + ty::FnPtr(_) => "fn pointer".into(), + ty::Dynamic(ref inner, ..) => { + if let Some(principal) = inner.principal() { + format!("trait object `dyn {}`", tcx.def_path_str(principal.def_id())).into() + } else { + "trait object".into() + } + } + ty::Closure(..) => "closure".into(), + ty::Generator(..) => "generator".into(), + ty::GeneratorWitness(..) => "generator witness".into(), + ty::Tuple(..) => "tuple".into(), + ty::Infer(ty::TyVar(_)) => "inferred type".into(), + ty::Infer(ty::IntVar(_)) => "integer".into(), + ty::Infer(ty::FloatVar(_)) => "floating-point number".into(), + ty::Placeholder(..) => "placeholder type".into(), + ty::Bound(..) => "bound type".into(), + ty::Infer(ty::FreshTy(_)) => "fresh type".into(), + ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".into(), + ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(), + ty::Projection(_) => "associated type".into(), + ty::Param(p) => format!("type parameter `{}`", p).into(), + ty::Opaque(..) => "opaque type".into(), + ty::Error(_) => "type error".into(), + } + } + + pub fn prefix_string(&self) -> Cow<'static, str> { + match self.kind { + ty::Infer(_) + | ty::Error(_) + | ty::Bool + | ty::Char + | ty::Int(_) + | ty::Uint(_) + | ty::Float(_) + | ty::Str + | ty::Never => "type".into(), + ty::Tuple(ref tys) if tys.is_empty() => "unit type".into(), + ty::Adt(def, _) => def.descr().into(), + ty::Foreign(_) => "extern type".into(), + ty::Array(..) => "array".into(), + ty::Slice(_) => "slice".into(), + ty::RawPtr(_) => "raw pointer".into(), + ty::Ref(.., mutbl) => match mutbl { + hir::Mutability::Mut => "mutable reference", + _ => "reference", + } + .into(), + ty::FnDef(..) => "fn item".into(), + ty::FnPtr(_) => "fn pointer".into(), + ty::Dynamic(..) => "trait object".into(), + ty::Closure(..) => "closure".into(), + ty::Generator(..) => "generator".into(), + ty::GeneratorWitness(..) => "generator witness".into(), + ty::Tuple(..) => "tuple".into(), + ty::Placeholder(..) => "higher-ranked type".into(), + ty::Bound(..) => "bound type variable".into(), + ty::Projection(_) => "associated type".into(), + ty::Param(_) => "type parameter".into(), + ty::Opaque(..) => "opaque type".into(), + } + } +} + +impl<'tcx> TyCtxt<'tcx> { + pub fn note_and_explain_type_err( + self, + db: &mut DiagnosticBuilder<'_>, + err: &TypeError<'tcx>, + cause: &ObligationCause<'tcx>, + sp: Span, + body_owner_def_id: DefId, + ) { + use self::TypeError::*; + debug!("note_and_explain_type_err err={:?} cause={:?}", err, cause); + match err { + Sorts(values) => { + let expected_str = values.expected.sort_string(self); + let found_str = values.found.sort_string(self); + if expected_str == found_str && expected_str == "closure" { + db.note("no two closures, even if identical, have the same type"); + db.help("consider boxing your closure and/or using it as a trait object"); + } + if expected_str == found_str && expected_str == "opaque type" { + // Issue #63167 + db.note("distinct uses of `impl Trait` result in different opaque types"); + let e_str = values.expected.to_string(); + let f_str = values.found.to_string(); + if e_str == f_str && &e_str == "impl std::future::Future" { + // FIXME: use non-string based check. + db.help( + "if both `Future`s have the same `Output` type, consider \ + `.await`ing on both of them", + ); + } + } + match (&values.expected.kind, &values.found.kind) { + (ty::Float(_), ty::Infer(ty::IntVar(_))) => { + if let Ok( + // Issue #53280 + snippet, + ) = self.sess.source_map().span_to_snippet(sp) + { + if snippet.chars().all(|c| c.is_digit(10) || c == '-' || c == '_') { + db.span_suggestion( + sp, + "use a float literal", + format!("{}.0", snippet), + MachineApplicable, + ); + } + } + } + (ty::Param(expected), ty::Param(found)) => { + let generics = self.generics_of(body_owner_def_id); + let e_span = self.def_span(generics.type_param(expected, self).def_id); + if !sp.contains(e_span) { + db.span_label(e_span, "expected type parameter"); + } + let f_span = self.def_span(generics.type_param(found, self).def_id); + if !sp.contains(f_span) { + db.span_label(f_span, "found type parameter"); + } + db.note( + "a type parameter was expected, but a different one was found; \ + you might be missing a type parameter or trait bound", + ); + db.note( + "for more information, visit \ + https://doc.rust-lang.org/book/ch10-02-traits.html\ + #traits-as-parameters", + ); + } + (ty::Projection(_), ty::Projection(_)) => { + db.note("an associated type was expected, but a different one was found"); + } + (ty::Param(p), ty::Projection(proj)) | (ty::Projection(proj), ty::Param(p)) => { + let generics = self.generics_of(body_owner_def_id); + let p_span = self.def_span(generics.type_param(p, self).def_id); + if !sp.contains(p_span) { + db.span_label(p_span, "this type parameter"); + } + let hir = self.hir(); + let mut note = true; + if let Some(generics) = generics + .type_param(p, self) + .def_id + .as_local() + .map(|id| hir.local_def_id_to_hir_id(id)) + .and_then(|id| self.hir().find(self.hir().get_parent_node(id))) + .as_ref() + .and_then(|node| node.generics()) + { + // Synthesize the associated type restriction `Add<Output = Expected>`. + // FIXME: extract this logic for use in other diagnostics. + let trait_ref = proj.trait_ref(self); + let path = + self.def_path_str_with_substs(trait_ref.def_id, trait_ref.substs); + let item_name = self.item_name(proj.item_def_id); + let path = if path.ends_with('>') { + format!("{}, {} = {}>", &path[..path.len() - 1], item_name, p) + } else { + format!("{}<{} = {}>", path, item_name, p) + }; + note = !suggest_constraining_type_param( + self, + generics, + db, + &format!("{}", proj.self_ty()), + &path, + None, + ); + } + if note { + db.note("you might be missing a type parameter or trait bound"); + } + } + (ty::Param(p), ty::Dynamic(..) | ty::Opaque(..)) + | (ty::Dynamic(..) | ty::Opaque(..), ty::Param(p)) => { + let generics = self.generics_of(body_owner_def_id); + let p_span = self.def_span(generics.type_param(p, self).def_id); + if !sp.contains(p_span) { + db.span_label(p_span, "this type parameter"); + } + db.help("type parameters must be constrained to match other types"); + if self.sess.teach(&db.get_code().unwrap()) { + db.help( + "given a type parameter `T` and a method `foo`: +``` +trait Trait<T> { fn foo(&self) -> T; } +``` +the only ways to implement method `foo` are: +- constrain `T` with an explicit type: +``` +impl Trait<String> for X { + fn foo(&self) -> String { String::new() } +} +``` +- add a trait bound to `T` and call a method on that trait that returns `Self`: +``` +impl<T: std::default::Default> Trait<T> for X { + fn foo(&self) -> T { <T as std::default::Default>::default() } +} +``` +- change `foo` to return an argument of type `T`: +``` +impl<T> Trait<T> for X { + fn foo(&self, x: T) -> T { x } +} +```", + ); + } + db.note( + "for more information, visit \ + https://doc.rust-lang.org/book/ch10-02-traits.html\ + #traits-as-parameters", + ); + } + (ty::Param(p), _) | (_, ty::Param(p)) => { + let generics = self.generics_of(body_owner_def_id); + let p_span = self.def_span(generics.type_param(p, self).def_id); + if !sp.contains(p_span) { + db.span_label(p_span, "this type parameter"); + } + } + (ty::Projection(proj_ty), _) => { + self.expected_projection( + db, + proj_ty, + values, + body_owner_def_id, + &cause.code, + ); + } + (_, ty::Projection(proj_ty)) => { + let msg = format!( + "consider constraining the associated type `{}` to `{}`", + values.found, values.expected, + ); + if !self.suggest_constraint( + db, + &msg, + body_owner_def_id, + proj_ty, + values.expected, + ) { + db.help(&msg); + db.note( + "for more information, visit \ + https://doc.rust-lang.org/book/ch19-03-advanced-traits.html", + ); + } + } + _ => {} + } + debug!( + "note_and_explain_type_err expected={:?} ({:?}) found={:?} ({:?})", + values.expected, values.expected.kind, values.found, values.found.kind, + ); + } + CyclicTy(ty) => { + // Watch out for various cases of cyclic types and try to explain. + if ty.is_closure() || ty.is_generator() { + db.note( + "closures cannot capture themselves or take themselves as argument;\n\ + this error may be the result of a recent compiler bug-fix,\n\ + see issue #46062 <https://github.com/rust-lang/rust/issues/46062>\n\ + for more information", + ); + } + } + TargetFeatureCast(def_id) => { + let attrs = self.get_attrs(*def_id); + let target_spans = attrs + .deref() + .iter() + .filter(|attr| attr.has_name(sym::target_feature)) + .map(|attr| attr.span); + db.note( + "functions with `#[target_feature]` can only be coerced to `unsafe` function pointers" + ); + db.span_labels(target_spans, "`#[target_feature]` added here"); + } + _ => {} + } + } + + fn suggest_constraint( + &self, + db: &mut DiagnosticBuilder<'_>, + msg: &str, + body_owner_def_id: DefId, + proj_ty: &ty::ProjectionTy<'tcx>, + ty: Ty<'tcx>, + ) -> bool { + let assoc = self.associated_item(proj_ty.item_def_id); + let trait_ref = proj_ty.trait_ref(*self); + if let Some(item) = self.hir().get_if_local(body_owner_def_id) { + if let Some(hir_generics) = item.generics() { + // Get the `DefId` for the type parameter corresponding to `A` in `<A as T>::Foo`. + // This will also work for `impl Trait`. + let def_id = if let ty::Param(param_ty) = proj_ty.self_ty().kind { + let generics = self.generics_of(body_owner_def_id); + generics.type_param(¶m_ty, *self).def_id + } else { + return false; + }; + + // First look in the `where` clause, as this might be + // `fn foo<T>(x: T) where T: Trait`. + for predicate in hir_generics.where_clause.predicates { + if let hir::WherePredicate::BoundPredicate(pred) = predicate { + if let hir::TyKind::Path(hir::QPath::Resolved(None, path)) = + pred.bounded_ty.kind + { + if path.res.opt_def_id() == Some(def_id) { + // This predicate is binding type param `A` in `<A as T>::Foo` to + // something, potentially `T`. + } else { + continue; + } + } else { + continue; + } + + if self.constrain_generic_bound_associated_type_structured_suggestion( + db, + &trait_ref, + pred.bounds, + &assoc, + ty, + msg, + ) { + return true; + } + } + } + for param in hir_generics.params { + if self.hir().opt_local_def_id(param.hir_id).map(|id| id.to_def_id()) + == Some(def_id) + { + // This is type param `A` in `<A as T>::Foo`. + return self.constrain_generic_bound_associated_type_structured_suggestion( + db, + &trait_ref, + param.bounds, + &assoc, + ty, + msg, + ); + } + } + } + } + false + } + + /// An associated type was expected and a different type was found. + /// + /// We perform a few different checks to see what we can suggest: + /// + /// - In the current item, look for associated functions that return the expected type and + /// suggest calling them. (Not a structured suggestion.) + /// - If any of the item's generic bounds can be constrained, we suggest constraining the + /// associated type to the found type. + /// - If the associated type has a default type and was expected inside of a `trait`, we + /// mention that this is disallowed. + /// - If all other things fail, and the error is not because of a mismatch between the `trait` + /// and the `impl`, we provide a generic `help` to constrain the assoc type or call an assoc + /// fn that returns the type. + fn expected_projection( + &self, + db: &mut DiagnosticBuilder<'_>, + proj_ty: &ty::ProjectionTy<'tcx>, + values: &ExpectedFound<Ty<'tcx>>, + body_owner_def_id: DefId, + cause_code: &ObligationCauseCode<'_>, + ) { + let msg = format!( + "consider constraining the associated type `{}` to `{}`", + values.expected, values.found + ); + let body_owner = self.hir().get_if_local(body_owner_def_id); + let current_method_ident = body_owner.and_then(|n| n.ident()).map(|i| i.name); + + // We don't want to suggest calling an assoc fn in a scope where that isn't feasible. + let callable_scope = match body_owner { + Some( + hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(..), .. }) + | hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. }) + | hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }), + ) => true, + _ => false, + }; + let impl_comparison = matches!( + cause_code, + ObligationCauseCode::CompareImplMethodObligation { .. } + | ObligationCauseCode::CompareImplTypeObligation { .. } + | ObligationCauseCode::CompareImplConstObligation + ); + let assoc = self.associated_item(proj_ty.item_def_id); + if !callable_scope || impl_comparison { + // We do not want to suggest calling functions when the reason of the + // type error is a comparison of an `impl` with its `trait` or when the + // scope is outside of a `Body`. + } else { + // If we find a suitable associated function that returns the expected type, we don't + // want the more general suggestion later in this method about "consider constraining + // the associated type or calling a method that returns the associated type". + let point_at_assoc_fn = self.point_at_methods_that_satisfy_associated_type( + db, + assoc.container.id(), + current_method_ident, + proj_ty.item_def_id, + values.expected, + ); + // Possibly suggest constraining the associated type to conform to the + // found type. + if self.suggest_constraint(db, &msg, body_owner_def_id, proj_ty, values.found) + || point_at_assoc_fn + { + return; + } + } + + if let ty::Opaque(def_id, _) = proj_ty.self_ty().kind { + // When the expected `impl Trait` is not defined in the current item, it will come from + // a return type. This can occur when dealing with `TryStream` (#71035). + if self.constrain_associated_type_structured_suggestion( + db, + self.def_span(def_id), + &assoc, + values.found, + &msg, + ) { + return; + } + } + + if self.point_at_associated_type(db, body_owner_def_id, values.found) { + return; + } + + if !impl_comparison { + // Generic suggestion when we can't be more specific. + if callable_scope { + db.help(&format!("{} or calling a method that returns `{}`", msg, values.expected)); + } else { + db.help(&msg); + } + db.note( + "for more information, visit \ + https://doc.rust-lang.org/book/ch19-03-advanced-traits.html", + ); + } + if self.sess.teach(&db.get_code().unwrap()) { + db.help( + "given an associated type `T` and a method `foo`: +``` +trait Trait { +type T; +fn foo(&self) -> Self::T; +} +``` +the only way of implementing method `foo` is to constrain `T` with an explicit associated type: +``` +impl Trait for X { +type T = String; +fn foo(&self) -> Self::T { String::new() } +} +```", + ); + } + } + + fn point_at_methods_that_satisfy_associated_type( + &self, + db: &mut DiagnosticBuilder<'_>, + assoc_container_id: DefId, + current_method_ident: Option<Symbol>, + proj_ty_item_def_id: DefId, + expected: Ty<'tcx>, + ) -> bool { + let items = self.associated_items(assoc_container_id); + // Find all the methods in the trait that could be called to construct the + // expected associated type. + // FIXME: consider suggesting the use of associated `const`s. + let methods: Vec<(Span, String)> = items + .items + .iter() + .filter(|(name, item)| { + ty::AssocKind::Fn == item.kind && Some(**name) != current_method_ident + }) + .filter_map(|(_, item)| { + let method = self.fn_sig(item.def_id); + match method.output().skip_binder().kind { + ty::Projection(ty::ProjectionTy { item_def_id, .. }) + if item_def_id == proj_ty_item_def_id => + { + Some(( + self.sess.source_map().guess_head_span(self.def_span(item.def_id)), + format!("consider calling `{}`", self.def_path_str(item.def_id)), + )) + } + _ => None, + } + }) + .collect(); + if !methods.is_empty() { + // Use a single `help:` to show all the methods in the trait that can + // be used to construct the expected associated type. + let mut span: MultiSpan = + methods.iter().map(|(sp, _)| *sp).collect::<Vec<Span>>().into(); + let msg = format!( + "{some} method{s} {are} available that return{r} `{ty}`", + some = if methods.len() == 1 { "a" } else { "some" }, + s = pluralize!(methods.len()), + are = if methods.len() == 1 { "is" } else { "are" }, + r = if methods.len() == 1 { "s" } else { "" }, + ty = expected + ); + for (sp, label) in methods.into_iter() { + span.push_span_label(sp, label); + } + db.span_help(span, &msg); + return true; + } + false + } + + fn point_at_associated_type( + &self, + db: &mut DiagnosticBuilder<'_>, + body_owner_def_id: DefId, + found: Ty<'tcx>, + ) -> bool { + let hir_id = + match body_owner_def_id.as_local().map(|id| self.hir().local_def_id_to_hir_id(id)) { + Some(hir_id) => hir_id, + None => return false, + }; + // When `body_owner` is an `impl` or `trait` item, look in its associated types for + // `expected` and point at it. + let parent_id = self.hir().get_parent_item(hir_id); + let item = self.hir().find(parent_id); + debug!("expected_projection parent item {:?}", item); + match item { + Some(hir::Node::Item(hir::Item { kind: hir::ItemKind::Trait(.., items), .. })) => { + // FIXME: account for `#![feature(specialization)]` + for item in &items[..] { + match item.kind { + hir::AssocItemKind::Type => { + // FIXME: account for returning some type in a trait fn impl that has + // an assoc type as a return type (#72076). + if let hir::Defaultness::Default { has_value: true } = item.defaultness + { + if self.type_of(self.hir().local_def_id(item.id.hir_id)) == found { + db.span_label( + item.span, + "associated type defaults can't be assumed inside the \ + trait defining them", + ); + return true; + } + } + } + _ => {} + } + } + } + Some(hir::Node::Item(hir::Item { + kind: hir::ItemKind::Impl { items, .. }, .. + })) => { + for item in &items[..] { + match item.kind { + hir::AssocItemKind::Type => { + if self.type_of(self.hir().local_def_id(item.id.hir_id)) == found { + db.span_label(item.span, "expected this associated type"); + return true; + } + } + _ => {} + } + } + } + _ => {} + } + false + } + + /// Given a slice of `hir::GenericBound`s, if any of them corresponds to the `trait_ref` + /// requirement, provide a strucuted suggestion to constrain it to a given type `ty`. + fn constrain_generic_bound_associated_type_structured_suggestion( + &self, + db: &mut DiagnosticBuilder<'_>, + trait_ref: &ty::TraitRef<'tcx>, + bounds: hir::GenericBounds<'_>, + assoc: &ty::AssocItem, + ty: Ty<'tcx>, + msg: &str, + ) -> bool { + // FIXME: we would want to call `resolve_vars_if_possible` on `ty` before suggesting. + bounds.iter().any(|bound| match bound { + hir::GenericBound::Trait(ptr, hir::TraitBoundModifier::None) => { + // Relate the type param against `T` in `<A as T>::Foo`. + ptr.trait_ref.trait_def_id() == Some(trait_ref.def_id) + && self.constrain_associated_type_structured_suggestion( + db, ptr.span, assoc, ty, msg, + ) + } + _ => false, + }) + } + + /// Given a span corresponding to a bound, provide a structured suggestion to set an + /// associated type to a given type `ty`. + fn constrain_associated_type_structured_suggestion( + &self, + db: &mut DiagnosticBuilder<'_>, + span: Span, + assoc: &ty::AssocItem, + ty: Ty<'tcx>, + msg: &str, + ) -> bool { + if let Ok(has_params) = + self.sess.source_map().span_to_snippet(span).map(|snippet| snippet.ends_with('>')) + { + let (span, sugg) = if has_params { + let pos = span.hi() - BytePos(1); + let span = Span::new(pos, pos, span.ctxt()); + (span, format!(", {} = {}", assoc.ident, ty)) + } else { + (span.shrink_to_hi(), format!("<{} = {}>", assoc.ident, ty)) + }; + db.span_suggestion_verbose(span, msg, sugg, MaybeIncorrect); + return true; + } + false + } +} |