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Rollup merge of #99079 - compiler-errors:issue-99073, r=oli-obk

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Check that RPITs constrained by a recursive call in a closure are compatible

Fixes #99073

Adapts a similar visitor pattern to `find_opaque_ty_constraints` (that we use to check TAITs), but with some changes:
0. Only walk the "OnlyBody" children, instead of all items in the RPIT's defining scope
1. Only walk through the body's children if we found a constraining usage
2. Don't actually do any inference, just do a comparison and error if they're mismatched

----

r? `@oli-obk` -- you know all this impl-trait stuff best... is this the right approach? I can explain the underlying issue better if you'd like, in case that might reveal a better solution. Not sure if it's possible to gather up the closure's defining usages of the RPIT while borrowck'ing the outer function, that might be a better place to put this check...
This commit is contained in:
Yuki Okushi 2022-07-27 19:05:32 +09:00 • committed by GitHub
commit 3b780fc279
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7 changed files with 140 additions and 72 deletions
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2
compiler/rustc_infer/src/infer/opaque_types.rs
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@ -430,7 +430,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
}
#[instrument(skip(self), level = "trace")]
pub fn opaque_ty_origin_unchecked(&self, def_id: LocalDefId, span: Span) -> OpaqueTyOrigin {
fn opaque_ty_origin_unchecked(&self, def_id: LocalDefId, span: Span) -> OpaqueTyOrigin {
let origin = match self.tcx.hir().expect_item(def_id).kind {
hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => origin,
ref itemkind => {