bjoernager/rust
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Don't throw away information just to recompute it again

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This commit is contained in:
Oli Scherer 2022-09-08 15:18:43 +00:00
parent 00fcc82df2
commit 8aed75bee0
3 changed files with 22 additions and 26 deletions
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12
compiler/rustc_infer/src/infer/mod.rs
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@ -1022,7 +1022,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
cause: &ObligationCause<'tcx>,
param_env: ty::ParamEnv<'tcx>,
predicate: ty::PolyCoercePredicate<'tcx>,
) -> Option<InferResult<'tcx, ()>> {
) -> Result<InferResult<'tcx, ()>, (TyVid, TyVid)> {
let subtype_predicate = predicate.map_bound(|p| ty::SubtypePredicate {
a_is_expected: false, // when coercing from `a` to `b`, `b` is expected
a: p.a,
@ -1036,7 +1036,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
cause: &ObligationCause<'tcx>,
param_env: ty::ParamEnv<'tcx>,
predicate: ty::PolySubtypePredicate<'tcx>,
) -> Option<InferResult<'tcx, ()>> {
) -> Result<InferResult<'tcx, ()>, (TyVid, TyVid)> {
// Check for two unresolved inference variables, in which case we can
// make no progress. This is partly a micro-optimization, but it's
// also an opportunity to "sub-unify" the variables. This isn't
@ -1055,12 +1055,12 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
match (r_a.kind(), r_b.kind()) {
(&ty::Infer(ty::TyVar(a_vid)), &ty::Infer(ty::TyVar(b_vid))) => {
self.inner.borrow_mut().type_variables().sub(a_vid, b_vid);
return None;
return Err((a_vid, b_vid));
}
_ => {}
}
Some(self.commit_if_ok(|_snapshot| {
Ok(self.commit_if_ok(|_snapshot| {
let ty::SubtypePredicate { a_is_expected, a, b } =
self.replace_bound_vars_with_placeholders(predicate);
@ -1848,7 +1848,7 @@ impl<'tcx> TyOrConstInferVar<'tcx> {
/// Tries to extract an inference variable from a type, returns `None`
/// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`).
pub fn maybe_from_ty(ty: Ty<'tcx>) -> Option<Self> {
fn maybe_from_ty(ty: Ty<'tcx>) -> Option<Self> {
match *ty.kind() {
ty::Infer(ty::TyVar(v)) => Some(TyOrConstInferVar::Ty(v)),
ty::Infer(ty::IntVar(v)) => Some(TyOrConstInferVar::TyInt(v)),
@ -1859,7 +1859,7 @@ impl<'tcx> TyOrConstInferVar<'tcx> {
/// Tries to extract an inference variable from a constant, returns `None`
/// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).
pub fn maybe_from_const(ct: ty::Const<'tcx>) -> Option<Self> {
fn maybe_from_const(ct: ty::Const<'tcx>) -> Option<Self> {
match ct.kind() {
ty::ConstKind::Infer(InferConst::Var(v)) => Some(TyOrConstInferVar::Const(v)),
_ => None,