[AST] Don't compute type in ClosureExpr::capturesSelfEnablingImplictSelf

This predicate can be determined without computing the full type of
the declaration.

Author: DougGregor

lib/AST/Expr.cpp

@@ -1968,8 +1968,15 @@ bool ClosureExpr::hasEmptyBody() const {
 }
 
 bool ClosureExpr::capturesSelfEnablingImplictSelf() const {
-  if (auto *VD = getCapturedSelfDecl())
-    return VD->isSelfParamCapture() && !VD->getType()->is<WeakStorageType>();
+  if (auto *VD = getCapturedSelfDecl()) {
+    if (!VD->isSelfParamCapture())
+      return false;
+
+    if (auto *attr = VD->getAttrs().getAttribute<ReferenceOwnershipAttr>())
+      return attr->get() != ReferenceOwnership::Weak;
+
+    return true;
+  }
   return false;
 }