From 9337d4fde89ded13243d67bec0b03f7fc553cbf9 Mon Sep 17 00:00:00 2001 From: Matthew Jasper Date: Tue, 9 Feb 2021 23:00:33 +0000 Subject: [PATCH] Print closure signatures when reporting placeholder errors --- .../nice_region_error/placeholder_error.rs | 38 ++++++++++++++++--- src/test/ui/issues/issue-57843.stderr | 2 +- src/test/ui/lifetimes/issue-79187.stderr | 2 +- .../issue-57611-trait-alias.nll.stderr | 2 +- .../issue-57611-trait-alias.stderr | 6 +-- 5 files changed, 38 insertions(+), 12 deletions(-) diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs index 285666b7acb9..46986d8d58b6 100644 --- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs +++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs @@ -386,12 +386,38 @@ impl NiceRegionError<'me, 'tcx> { let mut note = if same_self_type { let mut self_ty = expected_trait_ref.map(|tr| tr.self_ty()); self_ty.highlight.maybe_highlighting_region(vid, actual_has_vid); - format!( - "{}`{}` must implement `{}`", - if leading_ellipsis { "..." } else { "" }, - self_ty, - expected_trait_ref.map(|tr| tr.print_only_trait_path()), - ) + + if self_ty.value.is_closure() + && self + .tcx() + .fn_trait_kind_from_lang_item(expected_trait_ref.value.def_id) + .is_some() + { + let closure_sig = self_ty.map(|closure| { + if let ty::Closure(_, substs) = closure.kind() { + self.tcx().signature_unclosure( + substs.as_closure().sig(), + rustc_hir::Unsafety::Normal, + ) + } else { + bug!("type is not longer closure"); + } + }); + + format!( + "{}closure with signature `{}` must implement `{}`", + if leading_ellipsis { "..." } else { "" }, + closure_sig, + expected_trait_ref.map(|tr| tr.print_only_trait_path()), + ) + } else { + format!( + "{}`{}` must implement `{}`", + if leading_ellipsis { "..." } else { "" }, + self_ty, + expected_trait_ref.map(|tr| tr.print_only_trait_path()), + ) + } } else if passive_voice { format!( "{}`{}` would have to be implemented for the type `{}`", diff --git a/src/test/ui/issues/issue-57843.stderr b/src/test/ui/issues/issue-57843.stderr index acd48b6c7e5b..2ab49ec61cf5 100644 --- a/src/test/ui/issues/issue-57843.stderr +++ b/src/test/ui/issues/issue-57843.stderr @@ -4,7 +4,7 @@ error: implementation of `FnOnce` is not general enough LL | Foo(Box::new(|_| ())); | ^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough | - = note: `[closure@$DIR/issue-57843.rs:25:18: 25:24]` must implement `FnOnce<(&'1 bool,)>`, for any lifetime `'1`... + = note: closure with signature `fn(&'2 bool)` must implement `FnOnce<(&'1 bool,)>`, for any lifetime `'1`... = note: ...but it actually implements `FnOnce<(&'2 bool,)>`, for some specific lifetime `'2` error: aborting due to previous error diff --git a/src/test/ui/lifetimes/issue-79187.stderr b/src/test/ui/lifetimes/issue-79187.stderr index 3627ab5ed1e9..3c0439fb660e 100644 --- a/src/test/ui/lifetimes/issue-79187.stderr +++ b/src/test/ui/lifetimes/issue-79187.stderr @@ -4,7 +4,7 @@ error: implementation of `FnOnce` is not general enough LL | thing(f); | ^^^^^ implementation of `FnOnce` is not general enough | - = note: `[closure@$DIR/issue-79187.rs:4:13: 4:19]` must implement `FnOnce<(&'1 u32,)>`, for any lifetime `'1`... + = note: closure with signature `fn(&'2 u32)` must implement `FnOnce<(&'1 u32,)>`, for any lifetime `'1`... = note: ...but it actually implements `FnOnce<(&'2 u32,)>`, for some specific lifetime `'2` error: aborting due to previous error diff --git a/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.nll.stderr b/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.nll.stderr index 59b14eedc24b..a5409582288f 100644 --- a/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.nll.stderr +++ b/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.nll.stderr @@ -30,7 +30,7 @@ error: implementation of `FnOnce` is not general enough LL | type Bar = impl Baz; | ^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough | - = note: `[closure@$DIR/issue-57611-trait-alias.rs:25:9: 25:14]` must implement `FnOnce<(&'1 X,)>`, for any lifetime `'1`... + = note: closure with signature `fn(&'2 X) -> &'2 X` must implement `FnOnce<(&'1 X,)>`, for any lifetime `'1`... = note: ...but it actually implements `FnOnce<(&'2 X,)>`, for some specific lifetime `'2` error: aborting due to 4 previous errors diff --git a/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.stderr b/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.stderr index 59c91d52cca9..91c9d459ad8c 100644 --- a/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.stderr +++ b/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.stderr @@ -4,7 +4,7 @@ error: implementation of `FnOnce` is not general enough LL | type Bar = impl Baz; | ^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough | - = note: `[closure@$DIR/issue-57611-trait-alias.rs:25:9: 25:14]` must implement `FnOnce<(&'1 X,)>`, for any lifetime `'1`... + = note: closure with signature `fn(&'2 X) -> &X` must implement `FnOnce<(&'1 X,)>`, for any lifetime `'1`... = note: ...but it actually implements `FnOnce<(&'2 X,)>`, for some specific lifetime `'2` error[E0308]: mismatched types @@ -27,7 +27,7 @@ error: implementation of `FnOnce` is not general enough LL | type Bar = impl Baz; | ^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough | - = note: `[closure@$DIR/issue-57611-trait-alias.rs:25:9: 25:14]` must implement `FnOnce<(&'1 X,)>`, for any lifetime `'1`... + = note: closure with signature `fn(&'2 X) -> &'2 X` must implement `FnOnce<(&'1 X,)>`, for any lifetime `'1`... = note: ...but it actually implements `FnOnce<(&'2 X,)>`, for some specific lifetime `'2` error[E0308]: mismatched types @@ -50,7 +50,7 @@ error: implementation of `FnOnce` is not general enough LL | type Bar = impl Baz; | ^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough | - = note: `[closure@$DIR/issue-57611-trait-alias.rs:25:9: 25:14]` must implement `FnOnce<(&'1 X,)>`, for any lifetime `'1`... + = note: closure with signature `fn(&'2 X) -> &'2 X` must implement `FnOnce<(&'1 X,)>`, for any lifetime `'1`... = note: ...but it actually implements `FnOnce<(&'2 X,)>`, for some specific lifetime `'2` error: aborting due to 5 previous errors