[[FIX]] Labels shadowing within a function is a syntax error

Fixes #2419

src/scope-manager.js

@@ -694,7 +694,10 @@ var scopeManager = function(state, predefined, exported, declared) {
 
       addBreakLabel: function(labelName, opts) {
         var token = opts.token;
-        if (state.option.shadow === "outer") {
+        if (scopeManagerInst.funct.hasBreakLabel(labelName)) {
+          warning("E011", token, labelName);
+        }
+        else if (state.option.shadow === "outer") {
           if (scopeManagerInst.funct.has(labelName)) {
             warning("W004", token, labelName);
           } else {

tests/unit/fixtures/redef-es6.js

@@ -358,4 +358,10 @@ function zzg(zzh, zzi, zzj) {
     var zzn = null;
     const zzo = null;
     let zzp = null;
-}());
+}());
+
+zj: while(true) {
+    zj: while(true) {
+        break zj;
+    }
+}

tests/unit/options.js

@@ -112,10 +112,12 @@ exports.shadowEs6 = function (test) {
     [276, "'zb' has already been declared."],
     [286, "'zd' has already been declared."],
     [301, "'zf' has already been declared."],
+    [317, "'zi' has already been declared."],
     [344, "'zzi' has already been declared."],
     [345, "'zzj' has already been declared."],
     [349, "'zzl' has already been declared."],
-    [350, "'zzm' has already been declared."]
+    [350, "'zzm' has already been declared."],
+    [364, "'zj' has already been declared."]
   ];
 
   var innerErrors = [
@@ -171,9 +173,7 @@ exports.shadowEs6 = function (test) {
     [335, "'zzd' is already defined in outer scope."],
     [336, "'zze' is already defined in outer scope."],
     [337, "'zzf' is already defined in outer scope."],
-    [358, "'zzn' is already defined in outer scope."],
-    /* labels */
-    [317, "'zi' is already defined in outer scope."] // should always error
+    [358, "'zzn' is already defined in outer scope."]
   ];
 
   var testRun = TestRun(test);