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Rollup merge of #108947 - compiler-errors:ct-infer-no-shapeshifting, r=BoxyUwU

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Don't even try to combine consts with incompatible types

~I left a more detailed explanation for why this fixes this issue in the UI test, but in general, we should not try to unify const infer vars and rigid consts if they have incompatible types. That's because we don't want something like a `ConstArgHasType` predicate to suddenly go from passing to failing, or vice versa, due to a shallow resolve.~

1. Use the `type_of` for a parameter in `try_eval_lit_or_param`, instead of the "expected" type from a `WithOptConstParam` def id.
2. Don't combine consts that have incompatible types.

Fixes #108781
This commit is contained in:
Matthias Krüger 2023-03-10 19:59:20 +01:00 • committed by GitHub
commit 145e6204bc
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11 changed files with 74 additions and 34 deletions
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9
compiler/rustc_middle/src/ty/consts.rs
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@ -135,6 +135,9 @@ impl<'tcx> Const<'tcx> {
_,
&hir::Path { res: Res::Def(DefKind::ConstParam, def_id), .. },
)) => {
// Use the type from the param's definition, since we can resolve it,
// not the expected parameter type from WithOptConstParam.
let param_ty = tcx.type_of(def_id).subst_identity();
match tcx.named_bound_var(expr.hir_id) {
Some(rbv::ResolvedArg::EarlyBound(_)) => {
// Find the name and index of the const parameter by indexing the generics of
@ -143,14 +146,14 @@ impl<'tcx> Const<'tcx> {
let generics = tcx.generics_of(item_def_id);
let index = generics.param_def_id_to_index[&def_id];
let name = tcx.item_name(def_id);
Some(tcx.mk_const(ty::ParamConst::new(index, name), ty))
Some(tcx.mk_const(ty::ParamConst::new(index, name), param_ty))
}
Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => Some(tcx.mk_const(
ty::ConstKind::Bound(debruijn, ty::BoundVar::from_u32(index)),
ty,
param_ty,
)),
Some(rbv::ResolvedArg::Error(guar)) => {
Some(tcx.const_error_with_guaranteed(ty, guar))
Some(tcx.const_error_with_guaranteed(param_ty, guar))
}
arg => bug!("unexpected bound var resolution for {:?}: {arg:?}", expr.hir_id),
}