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Rollup merge of #95260 - compiler-errors:fn, r=davidtwco

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Better suggestions for `Fn`-family trait selection errors

1. Suppress suggestions to add `std::ops::Fn{,Mut,Once}` bounds when a type already implements `Fn{,Mut,Once}`
2. Add a note that points out that a type does in fact implement `Fn{,Mut,Once}`, but the arguments vary (either by number or by actual arguments)
3. Add a note that points out that a type does in fact implement `Fn{,Mut,Once}`, but not the right one (e.g. implements `FnMut`, but `Fn` is required).

Fixes #95147
This commit is contained in:
Matthias Krüger 2022-04-01 06:59:41 +02:00 • committed by GitHub
commit 94b1960535
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8 changed files with 255 additions and 9 deletions
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18
compiler/rustc_middle/src/ty/closure.rs
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@ -119,9 +119,21 @@ impl<'tcx> ClosureKind {
/// See `Ty::to_opt_closure_kind` for more details.
pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
match self {
ty::ClosureKind::Fn => tcx.types.i8,
ty::ClosureKind::FnMut => tcx.types.i16,
ty::ClosureKind::FnOnce => tcx.types.i32,
ClosureKind::Fn => tcx.types.i8,
ClosureKind::FnMut => tcx.types.i16,
ClosureKind::FnOnce => tcx.types.i32,
}
}
pub fn from_def_id(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ClosureKind> {
if Some(def_id) == tcx.lang_items().fn_once_trait() {
Some(ClosureKind::FnOnce)
} else if Some(def_id) == tcx.lang_items().fn_mut_trait() {
Some(ClosureKind::FnMut)
} else if Some(def_id) == tcx.lang_items().fn_trait() {
Some(ClosureKind::Fn)
} else {
None
}
}
}