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Rollup merge of #88963 - fee1-dead:const-iterator, r=oli-obk

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Coerce const FnDefs to implement const Fn traits

You can now pass a FnDef to a function expecting `F` where `F: ~const FnTrait`.

r? ``@oli-obk``

``@rustbot`` label T-compiler F-const_trait_impl
This commit is contained in:
Manish Goregaokar 2021-10-01 14:46:48 -07:00 • committed by GitHub
commit 743e842afb
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GPG key ID: 4AEE18F83AFDEB23
11 changed files with 79 additions and 37 deletions
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6
compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
View file

@ -476,7 +476,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
..
} = self_ty.fn_sig(self.tcx()).skip_binder()
{
candidates.vec.push(FnPointerCandidate);
candidates.vec.push(FnPointerCandidate { is_const: false });
}
}
// Provide an impl for suitable functions, rejecting `#[target_feature]` functions (RFC 2396).
@ -489,7 +489,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
} = self_ty.fn_sig(self.tcx()).skip_binder()
{
if self.tcx().codegen_fn_attrs(def_id).target_features.is_empty() {
candidates.vec.push(FnPointerCandidate);
candidates
.vec
.push(FnPointerCandidate { is_const: self.tcx().is_const_fn(def_id) });
}
}
}

2
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
View file

@ -92,7 +92,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
Ok(ImplSource::Generator(vtable_generator))
}
FnPointerCandidate => {
FnPointerCandidate { .. } => {
let data = self.confirm_fn_pointer_candidate(obligation)?;
Ok(ImplSource::FnPointer(data))
}

17
compiler/rustc_trait_selection/src/traits/select/mod.rs
View file

@ -1112,6 +1112,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// generator, this will raise error in other places
// or ignore error with const_async_blocks feature
GeneratorCandidate => {}
// FnDef where the function is const
FnPointerCandidate { is_const: true } => {}
ConstDropCandidate => {}
_ => {
// reject all other types of candidates
@ -1539,6 +1541,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
}
}
// Drop otherwise equivalent non-const fn pointer candidates
(FnPointerCandidate { .. }, FnPointerCandidate { is_const: false }) => true,
// Global bounds from the where clause should be ignored
// here (see issue #50825). Otherwise, we have a where
// clause so don't go around looking for impls.
@ -1549,7 +1554,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplCandidate(..)
| ClosureCandidate
| GeneratorCandidate
| FnPointerCandidate
| FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
| TraitUpcastingUnsizeCandidate(_)
@ -1567,7 +1572,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplCandidate(_)
| ClosureCandidate
| GeneratorCandidate
| FnPointerCandidate
| FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
| TraitUpcastingUnsizeCandidate(_)
@ -1597,7 +1602,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplCandidate(..)
| ClosureCandidate
| GeneratorCandidate
| FnPointerCandidate
| FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
| TraitUpcastingUnsizeCandidate(_)
@ -1609,7 +1614,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplCandidate(..)
| ClosureCandidate
| GeneratorCandidate
| FnPointerCandidate
| FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
| TraitUpcastingUnsizeCandidate(_)
@ -1690,7 +1695,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplCandidate(_)
| ClosureCandidate
| GeneratorCandidate
| FnPointerCandidate
| FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
| TraitUpcastingUnsizeCandidate(_)
@ -1699,7 +1704,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplCandidate(_)
| ClosureCandidate
| GeneratorCandidate
| FnPointerCandidate
| FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
| TraitUpcastingUnsizeCandidate(_)