[Constraint System] Fix covariant erasure for constrained existentials

angela-laar · angela-laar · commit cdd526e05848 · 2023-03-30T14:55:47.000-07:00
Use of an associated type in the member is not considered invariant
if that associated type has been made concrete by the existential type.
diff --git a/lib/Sema/ConstraintSystem.cpp b/lib/Sema/ConstraintSystem.cpp
@@ -2113,7 +2113,7 @@ typeEraseExistentialSelfReferences(
       if (t->is<GenericTypeParamType>()) {
         erasedTy = baseTy;
       } else {
-        erasedTy = existentialSig->getNonDependentUpperBounds(t);
+        erasedTy = existentialSig->getDependentUpperBounds(t);
       }
 
       if (metatypeDepth) {

Original file line number	Diff line number	Diff line change
`@@ -2113,7 +2113,7 @@ typeEraseExistentialSelfReferences(`
`2113`	`2113`	`if (t->is<GenericTypeParamType>()) {`
`2114`	`2114`	`erasedTy = baseTy;`
`2115`	`2115`	`} else {`
`2116`		`- erasedTy = existentialSig->getNonDependentUpperBounds(t);`
	`2116`	`+ erasedTy = existentialSig->getDependentUpperBounds(t);`
`2117`	`2117`	`}`
`2118`	`2118`
`2119`	`2119`	`if (metatypeDepth) {`