fix tail call recursion on functions with less arguments than parameters - fixes #1938

test/core/fixtures/transformation/es6.tail-call/parameter-exceeds/actual.js

@@ -0,0 +1,15 @@
+function foo(a, b) {
+  if (b) {
+    return foo(b);
+  } else {
+    return a;
+  }
+}
+
+function foo(a, b) {
+  if (b) {
+    return foo("a", "b", "c");
+  } else {
+    return a;
+  }
+}

test/core/fixtures/transformation/es6.tail-call/parameter-exceeds/exec.js

@@ -0,0 +1,9 @@
+function foo(a, b) {
+  if (b) {
+    return foo(b);
+  } else {
+    return a;
+  }
+}
+
+assert.equal(foo("Michael", "Jackson"), "Jackson");

test/core/fixtures/transformation/es6.tail-call/parameter-exceeds/expected.js

@@ -0,0 +1,28 @@
+"use strict";
+
+function foo(a, b) {
+  if (b) {
+    return foo(b);
+  } else {
+    return a;
+  }
+}
+
+function foo(_x, _x2) {
+  var _again = true;
+
+  _function: while (_again) {
+    var a = _x,
+        b = _x2;
+    _again = false;
+
+    if (b) {
+      _x = "a";
+      _x2 = "b";
+      _again = true;
+      continue _function;
+    } else {
+      return a;
+    }
+  }
+}