--- a/js/src/jit-test/tests/debug/bug980585.js
+++ b/js/src/jit-test/tests/debug/bug980585.js
@@ -1,10 +1,10 @@
 var g = newGlobal();
 var dbg = new Debugger(g);
 
 try {
-  g.eval("function f() { var array = ['a', 'b']; [1].map(function () {}); return {array}; }");
+  g.eval("function f() { [1].map(function () {}); const x = 42; x = 43; } f();");
 } catch (e) {
   // Ignore the syntax error.
 }
 
 dbg.findScripts();

--- a/js/src/jsfun.h
+++ b/js/src/jsfun.h
@@ -337,19 +337,26 @@ class JSFunction : public js::NativeObje
 
             flags_ &= ~INTERPRETED_LAZY;
             flags_ |= INTERPRETED;
             initScript(script);
         }
         return nonLazyScript();
     }
 
-    JSScript* nonLazyScript() const {
+    // The state of a JSFunction whose script errored out during bytecode
+    // compilation. Such JSFunctions are only reachable via GC iteration and
+    // not from script.
+    bool hasUncompiledScript() const {
         MOZ_ASSERT(hasScript());
-        MOZ_ASSERT(u.i.s.script_);
+        return !u.i.s.script_;
+    }
+
+    JSScript* nonLazyScript() const {
+        MOZ_ASSERT(!hasUncompiledScript());
         return u.i.s.script_;
     }
 
     bool getLength(JSContext* cx, uint16_t* length) {
         JS::RootedFunction self(cx, this);
         if (self->isInterpretedLazy() && !self->getOrCreateScript(cx))
             return false;
 

--- a/js/src/jsscript.cpp
+++ b/js/src/jsscript.cpp
@@ -3906,17 +3906,17 @@ LazyScript::hasUncompiledEnclosingScript
     //
     // If the enclosing scope is a function with a null script or has a script
     // without code, it was not successfully compiled.
 
     if (!enclosingScope() || !enclosingScope()->is<JSFunction>())
         return false;
 
     JSFunction& fun = enclosingScope()->as<JSFunction>();
-    return fun.isInterpreted() && (!fun.hasScript() || !fun.nonLazyScript()->code());
+    return !fun.hasScript() || fun.hasUncompiledScript() || !fun.nonLazyScript()->code();
 }
 
 uint32_t
 LazyScript::staticLevel(JSContext* cx) const
 {
     for (StaticScopeIter<NoGC> ssi(enclosingScope()); !ssi.done(); ssi++) {
         if (ssi.type() == StaticScopeIter<NoGC>::Function)
             return ssi.funScript()->staticLevel() + 1;