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Use implicit (not explicit) rules for promotability by default in const fn #75502

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Merged
merged 1 commit into from
Sep 19, 2020
Merged

Use implicit (not explicit) rules for promotability by default in const fn #75502

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9 changes: 8 additions & 1 deletion compiler/rustc_mir/src/transform/promote_consts.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -734,7 +734,14 @@ impl<'tcx> Validator<'_, 'tcx> {
) -> Result<(), Unpromotable> {
let fn_ty = callee.ty(self.body, self.tcx);

if !self.explicit && self.const_kind.is_none() {
// `const` and `static` use the explicit rules for promotion regardless of the `Candidate`,
// meaning calls to `const fn` can be promoted.
let context_uses_explicit_promotion_rules = matches!(
self.const_kind,
Some(hir::ConstContext::Static(_) | hir::ConstContext::Const)
);

if !self.explicit && !context_uses_explicit_promotion_rules {
if let ty::FnDef(def_id, _) = *fn_ty.kind() {
// Never promote runtime `const fn` calls of
// functions without `#[rustc_promotable]`.
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