diff options
| -rw-r--r-- | compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs | 54 | ||||
| -rw-r--r-- | tests/ui/traits/fn-trait-cast-diagnostic.rs | 26 | ||||
| -rw-r--r-- | tests/ui/traits/fn-trait-cast-diagnostic.stderr | 43 | ||||
| -rw-r--r-- | tests/ui/traits/issue-99875.stderr | 5 |
4 files changed, 111 insertions, 17 deletions
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs index 0c7ffb056cc..41a64a844ce 100644 --- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs +++ b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs @@ -374,6 +374,7 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> { }) } } + impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> { fn report_fulfillment_errors( &self, @@ -852,6 +853,29 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> { let mut suggested = self.suggest_dereferences(&obligation, &mut err, trait_predicate); suggested |= self.suggest_fn_call(&obligation, &mut err, trait_predicate); + let impl_candidates = self.find_similar_impl_candidates(trait_predicate); + suggested = if let &[cand] = &impl_candidates[..] { + let cand = cand.trait_ref; + if let (ty::FnPtr(_), ty::FnDef(..)) = + (cand.self_ty().kind(), trait_ref.self_ty().skip_binder().kind()) + { + err.span_suggestion( + span.shrink_to_hi(), + format!( + "the trait `{}` is implemented for fn pointer `{}`, try casting using `as`", + cand.print_only_trait_path(), + cand.self_ty(), + ), + format!(" as {}", cand.self_ty()), + Applicability::MaybeIncorrect, + ); + true + } else { + false + } + } else { + false + } || suggested; suggested |= self.suggest_remove_reference(&obligation, &mut err, trait_predicate); suggested |= self.suggest_semicolon_removal( @@ -1968,27 +1992,25 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> { candidates.sort(); candidates.dedup(); let len = candidates.len(); - if candidates.len() == 0 { + if candidates.is_empty() { return false; } - if candidates.len() == 1 { - let ty_desc = match candidates[0].self_ty().kind() { - ty::FnPtr(_) => Some("fn pointer"), - _ => None, - }; - let the_desc = match ty_desc { - Some(desc) => format!(" implemented for {} `", desc), - None => " implemented for `".to_string(), - }; + if let &[cand] = &candidates[..] { + let (desc, mention_castable) = + match (cand.self_ty().kind(), trait_ref.self_ty().skip_binder().kind()) { + (ty::FnPtr(_), ty::FnDef(..)) => { + (" implemented for fn pointer `", ", cast using `as`") + } + (ty::FnPtr(_), _) => (" implemented for fn pointer `", ""), + _ => (" implemented for `", ""), + }; err.highlighted_help(vec![ - ( - format!("the trait `{}` ", candidates[0].print_only_trait_path()), - Style::NoStyle, - ), + (format!("the trait `{}` ", cand.print_only_trait_path()), Style::NoStyle), ("is".to_string(), Style::Highlight), - (the_desc, Style::NoStyle), - (candidates[0].self_ty().to_string(), Style::Highlight), + (desc.to_string(), Style::NoStyle), + (cand.self_ty().to_string(), Style::Highlight), ("`".to_string(), Style::NoStyle), + (mention_castable.to_string(), Style::NoStyle), ]); return true; } diff --git a/tests/ui/traits/fn-trait-cast-diagnostic.rs b/tests/ui/traits/fn-trait-cast-diagnostic.rs new file mode 100644 index 00000000000..e20aa210e58 --- /dev/null +++ b/tests/ui/traits/fn-trait-cast-diagnostic.rs @@ -0,0 +1,26 @@ +// There are two different instances to check that even if +// the trait is implemented for the output of a function, +// it will still be displayed if the function itself implements a trait. +trait Foo {} + +impl Foo for fn() -> bool {} +impl Foo for bool {} + +fn example() -> bool { + true +} + +trait NoOtherFoo {} + +impl NoOtherFoo for fn() -> bool {} + +fn do_on_foo(v: impl Foo) {} +fn do_on_single_foo(v: impl NoOtherFoo) {} + +fn main() { + do_on_foo(example); + //~^ ERROR the trait bound + + do_on_single_foo(example); + //~^ ERROR the trait bound +} diff --git a/tests/ui/traits/fn-trait-cast-diagnostic.stderr b/tests/ui/traits/fn-trait-cast-diagnostic.stderr new file mode 100644 index 00000000000..6851dcdd504 --- /dev/null +++ b/tests/ui/traits/fn-trait-cast-diagnostic.stderr @@ -0,0 +1,43 @@ +error[E0277]: the trait bound `fn() -> bool {example}: Foo` is not satisfied + --> $DIR/fn-trait-cast-diagnostic.rs:21:15 + | +LL | do_on_foo(example); + | --------- ^^^^^^^ the trait `Foo` is not implemented for fn item `fn() -> bool {example}` + | | + | required by a bound introduced by this call + | +note: required by a bound in `do_on_foo` + --> $DIR/fn-trait-cast-diagnostic.rs:17:22 + | +LL | fn do_on_foo(v: impl Foo) {} + | ^^^ required by this bound in `do_on_foo` +help: use parentheses to call this function + | +LL | do_on_foo(example()); + | ++ +help: the trait `Foo` is implemented for fn pointer `fn() -> bool`, try casting using `as` + | +LL | do_on_foo(example as fn() -> bool); + | +++++++++++++++ + +error[E0277]: the trait bound `fn() -> bool {example}: NoOtherFoo` is not satisfied + --> $DIR/fn-trait-cast-diagnostic.rs:24:22 + | +LL | do_on_single_foo(example); + | ---------------- ^^^^^^^ the trait `NoOtherFoo` is not implemented for fn item `fn() -> bool {example}` + | | + | required by a bound introduced by this call + | +note: required by a bound in `do_on_single_foo` + --> $DIR/fn-trait-cast-diagnostic.rs:18:29 + | +LL | fn do_on_single_foo(v: impl NoOtherFoo) {} + | ^^^^^^^^^^ required by this bound in `do_on_single_foo` +help: the trait `NoOtherFoo` is implemented for fn pointer `fn() -> bool`, try casting using `as` + | +LL | do_on_single_foo(example as fn() -> bool); + | +++++++++++++++ + +error: aborting due to 2 previous errors + +For more information about this error, try `rustc --explain E0277`. diff --git a/tests/ui/traits/issue-99875.stderr b/tests/ui/traits/issue-99875.stderr index 3ff8f12f1b8..fb6eebbd254 100644 --- a/tests/ui/traits/issue-99875.stderr +++ b/tests/ui/traits/issue-99875.stderr @@ -6,12 +6,15 @@ LL | takes(function); | | | required by a bound introduced by this call | - = help: the trait `Trait` is implemented for fn pointer `fn(Argument) -> Return` note: required by a bound in `takes` --> $DIR/issue-99875.rs:9:18 | LL | fn takes(_: impl Trait) {} | ^^^^^ required by this bound in `takes` +help: the trait `Trait` is implemented for fn pointer `fn(Argument) -> Return`, try casting using `as` + | +LL | takes(function as fn(Argument) -> Return); + | +++++++++++++++++++++++++ error[E0277]: the trait bound `[closure@$DIR/issue-99875.rs:14:11: 14:34]: Trait` is not satisfied --> $DIR/issue-99875.rs:14:11 |