handle TCO for calls that exceed the functions parameter count - fixes #1589

src/babel/transformation/transformers/es6/tail-call.js

@@ -51,7 +51,7 @@ var visitor = {
   },
 
   ReferencedIdentifier(node, parent, scope, state) {
-    if (node.name === "arguments" && !state.isShadowed) {
+    if (node.name === "arguments" && (!state.isShadowed || node._shadowedFunctionLiteral)) {
       state.needsArguments = true;
       state.argumentsPaths.push(this);
     }
@@ -211,6 +211,7 @@ class TailCallTransformer {
       var decl = t.variableDeclarator(this.argumentsId);
       if (this.argumentsId) {
         decl.init = t.identifier("arguments");
+        decl.init._shadowedFunctionLiteral = true;
       }
       topVars.push(decl);
     }
@@ -291,7 +292,8 @@ class TailCallTransformer {
   }
 
   subTransformCallExpression(node) {
-    var callee = node.callee, thisBinding, args;
+    var callee = node.callee;
+    var thisBinding, args;
 
     if (t.isMemberExpression(callee, { computed: false }) && t.isIdentifier(callee.property)) {
       switch (callee.property.name) {
@@ -301,6 +303,7 @@ class TailCallTransformer {
 
         case "apply":
           args = node.arguments[1] || t.identifier("undefined");
+          this.needsArguments = true;
           break;
 
         default:
@@ -334,6 +337,10 @@ class TailCallTransformer {
       args = t.arrayExpression(node.arguments);
     }
 
+    if (t.isArrayExpression(args) && args.elements.length > this.node.params.length) {
+      this.needsArguments = true;
+    }
+
     var argumentsId = this.getArgumentsId();
     var params      = this.getParams();
 

test/core/fixtures/transformation/es6.tail-call/max-args/actual.js

@@ -0,0 +1,9 @@
+var count = (i = 10) => {
+  if (!i) return;
+  return count(i - 1);
+};
+
+function count2(i = 10) {
+  if (!i) return;
+  return count2(i - 1);
+}

test/core/fixtures/transformation/es6.tail-call/max-args/expected.js

@@ -0,0 +1,33 @@
+"use strict";
+
+var count = function count() {
+  var _arguments = arguments;
+  var _again = true;
+
+  _function: while (_again) {
+    i = undefined;
+    _again = false;
+    var i = _arguments[0] === undefined ? 10 : _arguments[0];
+
+    if (!i) return;
+    _arguments = [i - 1];
+    _again = true;
+    continue _function;
+  }
+};
+
+function count2() {
+  var _arguments2 = arguments;
+  var _again2 = true;
+
+  _function2: while (_again2) {
+    i = undefined;
+    _again2 = false;
+    var i = _arguments2[0] === undefined ? 10 : _arguments2[0];
+
+    if (!i) return;
+    _arguments2 = [i - 1];
+    _again2 = true;
+    continue _function2;
+  }
+}