Bug 1385843 - Handle nested eval-in-frame better in ThrowUninitializedThis. r=tcampbell

js/src/jit-test/tests/debug/bug1385843.js

@@ -0,0 +1,22 @@
+var g = newGlobal();
+g.parent = this;
+g.count = 0;
+g.eval("(" + function() {
+    var dbg = new Debugger(parent);
+    dbg.onEnterFrame = function(frame) {
+        if (count === 5)
+            dbg.onEnterFrame = undefined;
+        count++;
+        var ex = frame.eval("this").throw.unsafeDereference();
+        assertEq(ex.message.includes("uninitialized"), true);
+        assertEq(ex.message.includes("Foo2"), true);
+    }
+} + ")()");
+class Foo1 {};
+class Foo2 extends Foo1 {
+    constructor() {
+        super();
+    }
+};
+new Foo2();
+assertEq(g.count, 6);

js/src/vm/Interpreter.cpp

@@ -5192,6 +5192,8 @@ js::ThrowUninitializedThis(JSContext* cx, AbstractFramePtr frame)
         Scope* startingScope;
         if (frame.isDebuggerEvalFrame()) {
             AbstractFramePtr evalInFramePrev = frame.asInterpreterFrame()->evalInFramePrev();
+            while (evalInFramePrev.isDebuggerEvalFrame())
+                evalInFramePrev = evalInFramePrev.asInterpreterFrame()->evalInFramePrev();
             startingScope = evalInFramePrev.script()->bodyScope();
         } else {
             MOZ_ASSERT(frame.isEvalFrame());