[ASTScope] Avoid adding accessors in macro expansions

`visitParsedAccessors` currently iterates over any non-implicit
accessor that happens to be present. This means we end up with
accessors added by macro expansions if the expansion happens before
the ASTScope expansion. Make sure we avoid adding such accessors to
the ASTScope tree, they should instead use their own tree. Ideally
we'd better formalize `visitParsedAccessors` such that it only ever
visits non-expansion accessors, but I'm leaving that for another day.

Author: hamishknight

lib/AST/ASTScopeCreation.cpp

@@ -610,6 +610,12 @@ ASTScopeImpl *ScopeCreator::addToScopeTreeAndReturnInsertionPoint(
 void ScopeCreator::addChildrenForParsedAccessors(
     AbstractStorageDecl *asd, ASTScopeImpl *parent) {
   asd->visitParsedAccessors([&](AccessorDecl *ad) {
+    // Ignore accessors added by macro expansions.
+    // TODO: This ought to be the default behavior of `visitParsedAccessors`,
+    // we ought to have a different entrypoint for clients that care about
+    // the semantic set of "explicit" accessors.
+    if (ad->isInMacroExpansionInContext())
+      return;
     assert(asd == ad->getStorage());
     this->addToScopeTree(ad, parent);
   });