[cursorinfo] Avoid use of null raw value in enum element decl

SR-12283
rdar://59857568

Author: benlangmuir

lib/AST/ASTWalker.cpp

@@ -398,11 +398,12 @@ class Traversal : public ASTVisitor<Traversal, Expr*, Stmt*,
     }
 
     if (auto *rawLiteralExpr = ED->getRawValueUnchecked()) {
-      Expr *newRawExpr = doIt(rawLiteralExpr);
-      if (auto newRawLiteralExpr = dyn_cast<LiteralExpr>(newRawExpr))
-        ED->setRawValueExpr(newRawLiteralExpr);
-      else
+      if (Expr *newRawExpr = doIt(rawLiteralExpr)) {
+        auto *newLiteralRawExpr = cast<LiteralExpr>(newRawExpr);
+        ED->setRawValueExpr(newLiteralRawExpr);
+      } else {
         return true;
+      }
     }
     return false;
   }

test/SourceKit/CursorInfo/sr-12283-enum-element-value.swift

@@ -0,0 +1,10 @@
+enum StringEnum: String {
+  case foo = "foo"
+}
+
+enum IntEnum: Int {
+  case foo = 12
+}
+
+// RUN: %sourcekitd-test -req=cursor -pos=2:14 %s -- %s
+// RUN: %sourcekitd-test -req=cursor -pos=6:14 %s -- %s