From 4da09b73bc4e84efdf1017481c30b8e427172f38 Mon Sep 17 00:00:00 2001
From: Ron Buckton <rbuckton@microsoft.com>
Date: Wed, 6 Apr 2016 15:49:53 -0700
Subject: [PATCH] Fixes extra parens around yield downleveled from await

---
 src/compiler/factory.ts                            | 14 +++++++++++---
 src/compiler/transformers/ts.ts                    |  2 +-
 .../reference/FunctionDeclaration10_es6.js         |  2 +-
 tests/baselines/reference/classExpressionES63.js   |  8 ++++----
 4 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/src/compiler/factory.ts b/src/compiler/factory.ts
index 6fbc4f13037..573679b4f1a 100644
--- a/src/compiler/factory.ts
+++ b/src/compiler/factory.ts
@@ -1272,10 +1272,19 @@ namespace ts {
         // If `a ** d` is on the left of operator `**`, we need to parenthesize to preserve
         // the intended order of operations: `(a ** b) ** c`
         const binaryOperatorPrecedence = getOperatorPrecedence(SyntaxKind.BinaryExpression, binaryOperator);
+        const binaryOperatorAssociativity = getOperatorAssociativity(SyntaxKind.BinaryExpression, binaryOperator);
         const emittedOperand = skipPartiallyEmittedExpressions(operand);
         const operandPrecedence = getExpressionPrecedence(emittedOperand);
         switch (compareValues(operandPrecedence, binaryOperatorPrecedence)) {
             case Comparison.LessThan:
+                // If the operand is the right side of a right-associative binary operation
+                // and is a yield expression, then we do not need parentheses.
+                if (!isLeftSideOfBinary
+                    && binaryOperatorAssociativity === Associativity.Right
+                    && operand.kind === SyntaxKind.YieldExpression) {
+                    return false;
+                }
+
                 return true;
 
             case Comparison.GreaterThan:
@@ -1287,12 +1296,11 @@ namespace ts {
                     // left associative:
                     //  (a*b)/x    ->  a*b/x
                     //  (a**b)/x   ->  a**b/x
-
+                    //
                     // Parentheses are needed for the left operand when the binary operator is
                     // right associative:
                     //  (a/b)**x   ->  (a/b)**x
                     //  (a**b)**x  ->  (a**b)**x
-                    const binaryOperatorAssociativity = getOperatorAssociativity(SyntaxKind.BinaryExpression, binaryOperator);
                     return binaryOperatorAssociativity === Associativity.Right;
                 }
                 else {
@@ -1326,7 +1334,7 @@ namespace ts {
                     // associative:
                     //  x/(a**b)    -> x/a**b
                     //  x**(a**b)   -> x**a**b
-
+                    //
                     // Parentheses are needed for the right operand when the operand is left
                     // associative:
                     //  x/(a*b)     -> x/(a*b)
diff --git a/src/compiler/transformers/ts.ts b/src/compiler/transformers/ts.ts
index 182ea518d30..1d8dd46edee 100644
--- a/src/compiler/transformers/ts.ts
+++ b/src/compiler/transformers/ts.ts
@@ -748,7 +748,7 @@ namespace ts {
         function transformConstructorParameters(constructor: ConstructorDeclaration, hasExtendsClause: boolean) {
             return constructor
                 ? visitNodes(constructor.parameters, visitor, isParameter)
-                : hasExtendsClause ? [createRestParameter(createUniqueName("args"))] : [];
+                : hasExtendsClause ? [createRestParameter("args")] : [];
         }
 
         /**
diff --git a/tests/baselines/reference/FunctionDeclaration10_es6.js b/tests/baselines/reference/FunctionDeclaration10_es6.js
index 79a1740b17e..6ac2ec8d194 100644
--- a/tests/baselines/reference/FunctionDeclaration10_es6.js
+++ b/tests/baselines/reference/FunctionDeclaration10_es6.js
@@ -4,7 +4,7 @@ function * foo(a = yield => yield) {
 
 //// [FunctionDeclaration10_es6.js]
 function* foo(a) {
-    if (a === void 0) { a = (yield); }
+    if (a === void 0) { a = yield; }
 }
 yield;
 {
diff --git a/tests/baselines/reference/classExpressionES63.js b/tests/baselines/reference/classExpressionES63.js
index 7bb41817079..254014c9458 100644
--- a/tests/baselines/reference/classExpressionES63.js
+++ b/tests/baselines/reference/classExpressionES63.js
@@ -12,13 +12,13 @@ let C = class extends class extends class {
         this.a = 1;
     }
 } {
-    constructor(...args_1) {
-        super(...args_1);
+    constructor(...args) {
+        super(...args);
         this.b = 2;
     }
 } {
-    constructor(...args_2) {
-        super(...args_2);
+    constructor(...args) {
+        super(...args);
         this.c = 3;
     }
 };