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Rollup merge of #124027 - oli-obk:define_opaque_types9, r=compiler-errors

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Prefer identity equality over equating types during coercion.

These types are always generic only over their own generic parameters with no inference variables involved.

r? `@compiler-errors`

I love touching code that [hasn't changed meaningfully since 2016](https://github.com/rust-lang/rust/pull/41937)
This commit is contained in:
Guillaume Gomez 2024-04-17 00:00:24 +02:00 committed by GitHub
commit c7b009f38a
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1 changed files with 13 additions and 22 deletions
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21
compiler/rustc_hir_analysis/src/coherence/builtin.rs
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@ -10,8 +10,8 @@ use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_hir::lang_items::LangItem;
use rustc_hir::ItemKind;
use rustc_infer::infer::outlives::env::OutlivesEnvironment;
use rustc_infer::infer::TyCtxtInferExt;
use rustc_infer::infer::{self, RegionResolutionError};
use rustc_infer::infer::{DefineOpaqueTypes, TyCtxtInferExt};
use rustc_infer::traits::Obligation;
use rustc_middle::ty::adjustment::CoerceUnsizedInfo;
use rustc_middle::ty::{self, suggest_constraining_type_params, Ty, TyCtxt, TypeVisitableExt};
@ -189,10 +189,7 @@ fn visit_implementation_of_dispatch_from_dyn(checker: &Checker<'_>) -> Result<()
// even if they do not carry that attribute.
use rustc_type_ir::TyKind::*;
match (source.kind(), target.kind()) {
(&Ref(r_a, _, mutbl_a), Ref(r_b, _, mutbl_b))
if infcx.at(&cause, param_env).eq(DefineOpaqueTypes::No, r_a, *r_b).is_ok()
&& mutbl_a == *mutbl_b =>
{
(&Ref(r_a, _, mutbl_a), Ref(r_b, _, mutbl_b)) if r_a == *r_b && mutbl_a == *mutbl_b => {
Ok(())
}
(&RawPtr(_, a_mutbl), &RawPtr(_, b_mutbl)) if a_mutbl == b_mutbl => Ok(()),
@ -230,10 +227,7 @@ fn visit_implementation_of_dispatch_from_dyn(checker: &Checker<'_>) -> Result<()
}
}
if let Ok(ok) =
infcx.at(&cause, param_env).eq(DefineOpaqueTypes::No, ty_a, ty_b)
{
if ok.obligations.is_empty() {
if ty_a == ty_b {
res = Err(tcx.dcx().emit_err(errors::DispatchFromDynZST {
span,
name: field.name,
@ -242,7 +236,6 @@ fn visit_implementation_of_dispatch_from_dyn(checker: &Checker<'_>) -> Result<()
return false;
}
}
return true;
})
@ -433,15 +426,13 @@ pub fn coerce_unsized_info<'tcx>(
// something more accepting, but we use
// equality because we want to be able to
// perform this check without computing
// variance where possible. (This is because
// we may have to evaluate constraint
// variance or constraining opaque types' hidden types.
// (This is because we may have to evaluate constraint
// expressions in the course of execution.)
// See e.g., #41936.
if let Ok(ok) = infcx.at(&cause, param_env).eq(DefineOpaqueTypes::No, a, b) {
if ok.obligations.is_empty() {
if a == b {
return None;
}
}
// Collect up all fields that were significantly changed
// i.e., those that contain T in coerce_unsized T -> U