Start lookup *outside* of D when D is, e.g. an ExtensionDecl, since the attribute is outside of it.

David Ungar · David Ungar · commit 44cc14a05136 · 2020-03-25T11:17:13.000-07:00
diff --git a/lib/Sema/TypeCheckAttr.cpp b/lib/Sema/TypeCheckAttr.cpp
@@ -2643,7 +2643,7 @@ void AttributeChecker::visitFrozenAttr(FrozenAttr *attr) {
 }
 
 void AttributeChecker::visitCustomAttr(CustomAttr *attr) {
-  auto dc = D->getInnermostDeclContext();
+  auto dc = D->getDeclContext();
 
   // Figure out which nominal declaration this custom attribute refers to.
   auto nominal = evaluateOrDefault(

Original file line number	Diff line number	Diff line change
`@@ -2643,7 +2643,7 @@ void AttributeChecker::visitFrozenAttr(FrozenAttr *attr) {`
`2643`	`2643`	`}`
`2644`	`2644`
`2645`	`2645`	`void AttributeChecker::visitCustomAttr(CustomAttr *attr) {`
`2646`		`- auto dc = D->getInnermostDeclContext();`
	`2646`	`+ auto dc = D->getDeclContext();`
`2647`	`2647`
`2648`	`2648`	`// Figure out which nominal declaration this custom attribute refers to.`
`2649`	`2649`	`auto nominal = evaluateOrDefault(`