diff options
| -rw-r--r-- | compiler/rustc_hir_analysis/src/collect.rs | 66 | ||||
| -rw-r--r-- | compiler/rustc_span/src/symbol.rs | 1 | ||||
| -rw-r--r-- | library/core/src/iter/traits/iterator.rs | 1 | ||||
| -rw-r--r-- | src/test/ui/typeck/typeck_type_placeholder_item.rs | 8 | ||||
| -rw-r--r-- | src/test/ui/typeck/typeck_type_placeholder_item.stderr | 23 |
5 files changed, 96 insertions, 3 deletions
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs index b7d599f57fd..0a7a3038d00 100644 --- a/compiler/rustc_hir_analysis/src/collect.rs +++ b/compiler/rustc_hir_analysis/src/collect.rs @@ -24,14 +24,20 @@ use rustc_hir as hir; use rustc_hir::def_id::{DefId, LocalDefId}; use rustc_hir::intravisit::{self, Visitor}; use rustc_hir::{GenericParamKind, Node}; +use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; +use rustc_infer::infer::TyCtxtInferExt; use rustc_middle::hir::nested_filter; use rustc_middle::ty::query::Providers; use rustc_middle::ty::util::{Discr, IntTypeExt}; -use rustc_middle::ty::{self, AdtKind, Const, IsSuggestable, ToPredicate, Ty, TyCtxt}; +use rustc_middle::ty::{ + self, AdtKind, Const, IsSuggestable, ToPredicate, Ty, TyCtxt, TypeVisitable, +}; use rustc_span::symbol::{kw, sym, Ident, Symbol}; use rustc_span::Span; use rustc_target::spec::abi; +use rustc_trait_selection::infer::InferCtxtExt; use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName; +use rustc_trait_selection::traits::ObligationCtxt; use std::iter; mod generics_of; @@ -1224,7 +1230,17 @@ fn infer_return_ty_for_fn_sig<'tcx>( // to prevent the user from getting a papercut while trying to use the unique closure // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`). diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound"); - diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html"); + diag.note( + "for more information on `Fn` traits and closure types, see \ + https://doc.rust-lang.org/book/ch13-01-closures.html", + ); + } else if let Some(i_ty) = suggest_impl_iterator(tcx, ret_ty, ty.span, hir_id, def_id) { + diag.span_suggestion( + ty.span, + "replace with an appropriate return type", + format!("impl Iterator<Item = {}>", i_ty), + Applicability::MachineApplicable, + ); } diag.emit(); @@ -1242,6 +1258,52 @@ fn infer_return_ty_for_fn_sig<'tcx>( } } +fn suggest_impl_iterator<'tcx>( + tcx: TyCtxt<'tcx>, + ret_ty: Ty<'tcx>, + span: Span, + hir_id: hir::HirId, + def_id: LocalDefId, +) -> Option<Ty<'tcx>> { + let Some(iter_trait) = tcx.get_diagnostic_item(sym::Iterator) else { return None; }; + let Some(iterator_item) = tcx.get_diagnostic_item(sym::IteratorItem) else { return None; }; + if !tcx + .infer_ctxt() + .build() + .type_implements_trait(iter_trait, [ret_ty], tcx.param_env(iter_trait)) + .must_apply_modulo_regions() + { + return None; + } + let infcx = tcx.infer_ctxt().build(); + let ocx = ObligationCtxt::new_in_snapshot(&infcx); + // Find the type of `Iterator::Item`. + let origin = TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span }; + let ty_var = infcx.next_ty_var(origin); + let projection = ty::Binder::dummy(ty::PredicateKind::Clause(ty::Clause::Projection( + ty::ProjectionPredicate { + projection_ty: tcx.mk_alias_ty(iterator_item, tcx.mk_substs([ret_ty.into()].iter())), + term: ty_var.into(), + }, + ))); + // Add `<ret_ty as Iterator>::Item = _` obligation. + ocx.register_obligation(crate::traits::Obligation::misc( + tcx, + span, + hir_id, + tcx.param_env(def_id), + projection, + )); + if ocx.select_where_possible().is_empty() + && let item_ty = infcx.resolve_vars_if_possible(ty_var) + && !item_ty.references_error() + && !item_ty.has_placeholders() + { + return Some(item_ty); + } + None +} + fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> { let icx = ItemCtxt::new(tcx, def_id); let item = tcx.hir().expect_item(def_id.expect_local()); diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs index 90f654c68ec..85510fa2c66 100644 --- a/compiler/rustc_span/src/symbol.rs +++ b/compiler/rustc_span/src/symbol.rs @@ -213,6 +213,7 @@ symbols! { Is, ItemContext, Iterator, + IteratorItem, Layout, Left, LinkedList, diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs index bac836292f8..dcbed4e963f 100644 --- a/library/core/src/iter/traits/iterator.rs +++ b/library/core/src/iter/traits/iterator.rs @@ -66,6 +66,7 @@ fn _assert_is_object_safe(_: &dyn Iterator<Item = ()>) {} #[must_use = "iterators are lazy and do nothing unless consumed"] pub trait Iterator { /// The type of the elements being iterated over. + #[rustc_diagnostic_item = "IteratorItem"] #[stable(feature = "rust1", since = "1.0.0")] type Item; diff --git a/src/test/ui/typeck/typeck_type_placeholder_item.rs b/src/test/ui/typeck/typeck_type_placeholder_item.rs index 22fedb22d66..b96c5271339 100644 --- a/src/test/ui/typeck/typeck_type_placeholder_item.rs +++ b/src/test/ui/typeck/typeck_type_placeholder_item.rs @@ -220,3 +220,11 @@ fn value() -> Option<&'static _> { const _: Option<_> = map(value); //~^ ERROR the placeholder `_` is not allowed within types on item signatures for constants + +fn evens_squared(n: usize) -> _ { +//~^ ERROR the placeholder `_` is not allowed within types on item signatures for return types + (1..n).filter(|x| x % 2 == 0).map(|x| x * x) +} + +const _: _ = (1..10).filter(|x| x % 2 == 0).map(|x| x * x); +//~^ ERROR the placeholder `_` is not allowed within types on item signatures for constants diff --git a/src/test/ui/typeck/typeck_type_placeholder_item.stderr b/src/test/ui/typeck/typeck_type_placeholder_item.stderr index c57f71b8057..034bdae5f2e 100644 --- a/src/test/ui/typeck/typeck_type_placeholder_item.stderr +++ b/src/test/ui/typeck/typeck_type_placeholder_item.stderr @@ -428,6 +428,27 @@ LL | const _: Option<_> = map(value); | not allowed in type signatures | help: replace with the correct type: `Option<u8>` +error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types + --> $DIR/typeck_type_placeholder_item.rs:224:31 + | +LL | fn evens_squared(n: usize) -> _ { + | ^ + | | + | not allowed in type signatures + | help: replace with an appropriate return type: `impl Iterator<Item = usize>` + +error[E0121]: the placeholder `_` is not allowed within types on item signatures for constants + --> $DIR/typeck_type_placeholder_item.rs:229:10 + | +LL | const _: _ = (1..10).filter(|x| x % 2 == 0).map(|x| x * x); + | ^ not allowed in type signatures + | +note: however, the inferred type `Map<Filter<std::ops::Range<i32>, [closure@$DIR/typeck_type_placeholder_item.rs:229:29: 229:32]>, [closure@$DIR/typeck_type_placeholder_item.rs:229:49: 229:52]>` cannot be named + --> $DIR/typeck_type_placeholder_item.rs:229:14 + | +LL | const _: _ = (1..10).filter(|x| x % 2 == 0).map(|x| x * x); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + error[E0121]: the placeholder `_` is not allowed within types on item signatures for functions --> $DIR/typeck_type_placeholder_item.rs:140:31 | @@ -636,7 +657,7 @@ LL | const D: _ = 42; | not allowed in type signatures | help: replace with the correct type: `i32` -error: aborting due to 69 previous errors +error: aborting due to 71 previous errors Some errors have detailed explanations: E0121, E0282, E0403. For more information about an error, try `rustc --explain E0121`. |