Clean up transformations after #714.

Since now we have runtime helper, we don't need
expression -> statement conversions anymore.

lib/6to5/transformation/transformers/es6/tail-call.js

@@ -12,51 +12,21 @@ function transformExpression(node, scope, state) {
   return (function subTransform(node) {
     switch (node.type) {
       case "ConditionalExpression":
-        var callConsequent = subTransform(node.consequent);
-        var callAlternate = subTransform(node.alternate);
-        if (!callConsequent && !callAlternate) {
-          return;
-        }
-
-        // if ternary operator had tail recursion in value, convert to optimized if-statement
-        node.type = "IfStatement";
-        node.consequent = callConsequent ? t.toBlock(callConsequent) : returnBlock(node.consequent);
-        if (callAlternate) {
-          node.alternate = t.isIfStatement(callAlternate) ? callAlternate : t.toBlock(callAlternate);
-        } else {
-          node.alternate = returnBlock(node.alternate);
-        }
-        return [node];
+        // any value of ternary operator can be final one
+        subTransform(node.consequent);
+        subTransform(node.alternate);
+        break;
 
       case "LogicalExpression":
-        // only call in right-value of can be optimized
-        var callRight = subTransform(node.right);
-        if (!callRight) {
-          return;
-        }
-
-        var test = state.wrapSideEffect(node.left);
-        if (node.operator === "&&") {
-          test.expr = t.unaryExpression("!", test.expr);
-        }
-        return [t.ifStatement(test.expr, returnBlock(test.ref))].concat(callRight);
+        // only right expression can be final and so optimized
+        subTransform(node.right);
+        break;
 
       case "SequenceExpression":
+        // only last element of sequence can be optimized
         var seq = node.expressions;
-
-        // only last element can be optimized
-        var lastCall = subTransform(seq[seq.length - 1]);
-        if (!lastCall) {
-          return;
-        }
-
-        // remove converted expression from sequence
-        // and convert to regular expression if needed
-        if (--seq.length === 1) {
-          node = seq[0];
-        }
-
-        return [t.expressionStatement(node)].concat(lastCall);
+        subTransform(seq[seq.length - 1]);
+        break;
 
       case "CallExpression":
         var callee = node.callee, thisBinding;
@@ -77,10 +47,9 @@ function transformExpression(node, scope, state) {
           args.push(thisBinding);
         }
 
-        return [t.returnStatement(t.callExpression(
-          state.getHelperRef(),
-          args
-        ))];
+        node.callee = state.getHelperRef();
+        node.arguments = args;
+        break;
     }
   })(node);
 }
@@ -92,7 +61,8 @@ var functionChildrenVisitor = {
       this.skip();
       // transform return argument into statement if
       // it contains tail recursion
-      return transformExpression(node.argument, scope, state);
+      transformExpression(node.argument, scope, state);
+      return;
     } else if (t.isFunction(node)) {
       return this.skip();
     } else if (t.isTryStatement(parent)) {

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

@@ -5,9 +5,5 @@
     console.log(this, arguments);
     return "foo";
   }
-  if (Math.random() > 0.5) {
-    return to5Runtime.tailCall(f.call, [this, n - 1], f);
-  } else {
-    return to5Runtime.tailCall(f.apply, [this, [n - 1]], f);
-  }
+  return Math.random() > 0.5 ? to5Runtime.tailCall(f.call, [this, n - 1], f) : to5Runtime.tailCall(f.apply, [this, [n - 1]], f);
 })(1000000) === "foo";

test/fixtures/transformation/es6-tail-call/cross-function/actual.js

@@ -1,7 +1,7 @@
 function f(n) {
-    return n <= 0 ? "foo" : g(n - 1);
+  return n <= 0 ? "foo" : g(n - 1);
 }
 
 function g(n) {
-    return n <= 0 ? "goo" : f(n - 1);
+  return n <= 0 ? "goo" : f(n - 1);
 }

test/fixtures/transformation/es6-tail-call/cross-function/expected.js

@@ -1,17 +1,9 @@
 "use strict";
 
 function f(n) {
-    if (n <= 0) {
-        return "foo";
-    } else {
-        return to5Runtime.tailCall(g, [n - 1]);
-    }
+  return n <= 0 ? "foo" : to5Runtime.tailCall(g, [n - 1]);
 }
 
 function g(n) {
-    if (n <= 0) {
-        return "goo";
-    } else {
-        return to5Runtime.tailCall(f, [n - 1]);
-    }
+  return n <= 0 ? "goo" : to5Runtime.tailCall(f, [n - 1]);
 }

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

@@ -1,18 +1,5 @@
 "use strict";
 
 (function f(n) {
-  var _temp;
-  if (n <= 0) {
-    return "foo";
-  } else {
-    doSmth();
-
-    if (!(_temp = getTrueValue())) {
-      return _temp;
-    }
-    if (_temp = getFalseValue()) {
-      return _temp;
-    }
-    return to5Runtime.tailCall(f, [n - 1]);
-  }
+  return n <= 0 ? "foo" : (doSmth(), getTrueValue() && (getFalseValue() || to5Runtime.tailCall(f, [n - 1])));
 })(1000000, true) === "foo";

test/fixtures/transformation/es6-tail-call/side-effect/actual.js

@@ -1,5 +1,5 @@
 function f() {
-    return getObj().method();
+  return getObj().method();
 }
 
 function g() {

test/fixtures/transformation/es6-tail-call/side-effect/expected.js

@@ -6,9 +6,5 @@ function f() {
 }
 
 function g() {
-  var _temp;
-  if (_temp = getFalseValue()) {
-    return _temp;
-  }
-  return to5Runtime.tailCall(getValue);
+  return getFalseValue() || to5Runtime.tailCall(getValue);
 }