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Make TypeFoldable::is_global() false when fresh tys/consts are present

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This ensures that `ParamEnv::and` preserves the original `caller_bounds`
when we have a value containing fresh tys/consts. This ensures that when
we cache a `SelectionCandidate`, the cache key (a `ParamEnvAnd`)
contains all of the information that influenced the computation of our
result (e.g. we may end up choosing a `ParamCandidate`)
This commit is contained in:
Aaron Hill 2021-05-01 16:52:54 -04:00
parent 5f304a5d79
commit 91daf705b4
No known key found for this signature in database
GPG key ID: B4087E510E98B164
2 changed files with 19 additions and 2 deletions
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6
compiler/rustc_middle/src/ty/flags.rs
View file

@ -141,7 +141,9 @@ impl FlagComputation {
&ty::Infer(infer) => {
self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
match infer {
ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_) => {}
ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_) => {
self.add_flags(TypeFlags::HAS_TY_FRESH)
}
ty::TyVar(_) | ty::IntVar(_) | ty::FloatVar(_) => {
self.add_flags(TypeFlags::HAS_TY_INFER)
@ -278,7 +280,7 @@ impl FlagComputation {
ty::ConstKind::Infer(infer) => {
self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
match infer {
InferConst::Fresh(_) => {}
InferConst::Fresh(_) => self.add_flags(TypeFlags::HAS_CT_FRESH),
InferConst::Var(_) => self.add_flags(TypeFlags::HAS_CT_INFER),
}
}

15
compiler/rustc_type_ir/src/lib.rs
View file

@ -59,6 +59,15 @@ bitflags! {
| TypeFlags::HAS_CT_INFER.bits
| TypeFlags::HAS_TY_PLACEHOLDER.bits
| TypeFlags::HAS_CT_PLACEHOLDER.bits
// We consider 'freshened' types and constants
// to depend on a particular fn.
// The freshening process throws away information,
// which can make things unsuitable for use in a global
// cache. Note that there is no 'fresh lifetime' flag -
// freshening replaces all lifetimes with `ReErased`,
// which is different from how types/const are freshened.
| TypeFlags::HAS_TY_FRESH.bits
| TypeFlags::HAS_CT_FRESH.bits
| TypeFlags::HAS_FREE_LOCAL_REGIONS.bits;
/// Does this have `Projection`?
@ -90,6 +99,12 @@ bitflags! {
/// Does this value have parameters/placeholders/inference variables which could be
/// replaced later, in a way that would change the results of `impl` specialization?
const STILL_FURTHER_SPECIALIZABLE = 1 << 17;
/// Does this value have `InferTy::FreshTy/FreshIntTy/FreshFloatTy`?
const HAS_TY_FRESH = 1 << 18;
/// Does this value have `InferConst::Fresh`?
const HAS_CT_FRESH = 1 << 19;
}
}