[ConstraintSystem] Handle simplifying function result locator path

elements when the anchor is an unapplied decl reference in
simplifyLocator.

In this case, there's nothing to extract, so simply remove the path
element and continue on.

Author: hborla

lib/Sema/ConstraintSystem.cpp

@@ -4327,6 +4327,12 @@ void constraints::simplifyLocator(ASTNode &anchor,
         continue;
       }
 
+      // If the anchor is an unapplied decl ref, there's nothing to extract.
+      if (isExpr<DeclRefExpr>(anchor) || isExpr<OverloadedDeclRefExpr>(anchor)) {
+        path = path.slice(1);
+        continue;
+      }
+
       break;
 
     case ConstraintLocator::AutoclosureResult: