hoist param declaration when performing tco - fixes #1478

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

@@ -181,9 +181,11 @@ class TailCallTransformer {
       var declarations = flatten(map(this.vars, function (decl) {
         return decl.declarations;
       }));
+
       var assignment = reduceRight(declarations, function (expr, decl) {
         return t.assignmentExpression("=", decl.id, expr);
       }, t.identifier("undefined"));
+
       var statement = t.expressionStatement(assignment);
       statement._blockHoist = Infinity;
       body.unshift(statement);
@@ -191,7 +193,9 @@ class TailCallTransformer {
 
     var paramDecls = this.paramDecls;
     if (paramDecls.length > 0) {
-      body.unshift(t.variableDeclaration("var", paramDecls));
+      var paramDecl = t.variableDeclaration("var", paramDecls);
+      paramDecl._blockHoist = Infinity;
+      body.unshift(paramDecl);
     }
 
     body.unshift(t.expressionStatement(

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

@@ -7,8 +7,8 @@
   var _again = true;
 
   _function: while (_again) {
-    _again = false;
     var n = _x;
+    _again = false;
 
     if (n <= 0) {
       console.log(_this, _arguments);

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

@@ -6,8 +6,8 @@
   var _again = true;
 
   _function: while (_again) {
-    _again = false;
     var n = _x;
+    _again = false;
     if (n <= 0) {
       return "foo";
     } else {
@@ -26,4 +26,4 @@
       continue _function;
     }
   }
-})(1000000, true) === "foo";
+})(1000000, true) === "foo";

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

@@ -5,9 +5,9 @@ function fact(_x2) {
   var _again = true;
 
   _function: while (_again) {
+    var n = _x2;
     acc = undefined;
     _again = false;
-    var n = _x2;
     var acc = _arguments[1] === undefined ? 1 : _arguments[1];
     if (n > 1) {
       _arguments = [_x2 = n - 1, acc * n];
@@ -17,4 +17,4 @@ function fact(_x2) {
       return acc;
     }
   }
-}
+}

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

@@ -5,12 +5,12 @@
   var _again = true;
 
   _function: while (_again) {
+    var n = _x2;
     m = local1 = local2 = local3 = undefined;
 
     var g = function g() {};
 
     _again = false;
-    var n = _x2;
     var m = _arguments[1] === undefined ? getDefaultValue() : _arguments[1];
 
     // `m` should be `getDefaultValue()` after first pass
@@ -27,4 +27,4 @@
     _again = true;
     continue _function;
   }
-})(1000000, true) === "foo";
+})(1000000, true) === "foo";

test/core/fixtures/transformation/es6.tail-call/try-catch/expected.js

@@ -14,8 +14,8 @@
   var _again = true;
 
   _function: while (_again) {
-    _again = false;
     var n = _x;
+    _again = false;
 
     if (n <= 0) {
       return "foo";
@@ -47,8 +47,8 @@
   var _again2 = true;
 
   _function2: while (_again2) {
-    _again2 = false;
     var n = _x2;
+    _again2 = false;
 
     if (n <= 0) {
       return "foo";
@@ -60,4 +60,4 @@
       continue _function2;
     }
   }
-})(1000000) === "foo";
+})(1000000) === "foo";