From 5b45db790729508553016572a5cddb8e806bc214 Mon Sep 17 00:00:00 2001
From: Ron Buckton <ron.buckton@microsoft.com>
Date: Wed, 17 Jan 2018 11:55:43 -0800
Subject: [PATCH] PR Feedback

---
 src/compiler/transformers/es2017.ts | 51 +++++++++++++++--------------
 src/compiler/utilities.ts           | 26 ++++++++++++---
 2 files changed, 49 insertions(+), 28 deletions(-)

diff --git a/src/compiler/transformers/es2017.ts b/src/compiler/transformers/es2017.ts
index 79668dc0b8c..905686c8861 100644
--- a/src/compiler/transformers/es2017.ts
+++ b/src/compiler/transformers/es2017.ts
@@ -86,31 +86,34 @@ namespace ts {
         }
 
         function asyncBodyVisitor(node: Node): VisitResult<Node> {
-            switch (node.kind) {
-                case SyntaxKind.VariableStatement:
-                    return visitVariableStatementInAsyncBody(<VariableStatement>node);
-                case SyntaxKind.ForStatement:
-                    return visitForStatementInAsyncBody(<ForStatement>node);
-                case SyntaxKind.ForInStatement:
-                    return visitForInStatementInAsyncBody(<ForInStatement>node);
-                case SyntaxKind.ForOfStatement:
-                    return visitForOfStatementInAsyncBody(<ForOfStatement>node);
-                case SyntaxKind.CatchClause:
-                    return visitCatchClauseInAsyncBody(<CatchClause>node);
-                case SyntaxKind.Block:
-                case SyntaxKind.SwitchStatement:
-                case SyntaxKind.CaseBlock:
-                case SyntaxKind.CaseClause:
-                case SyntaxKind.DefaultClause:
-                case SyntaxKind.TryStatement:
-                case SyntaxKind.DoStatement:
-                case SyntaxKind.WhileStatement:
-                case SyntaxKind.IfStatement:
-                case SyntaxKind.WithStatement:
-                case SyntaxKind.LabeledStatement:
-                    return visitEachChild(node, asyncBodyVisitor, context);
+            if (isNodeWithPossibleHoistedDeclaration(node)) {
+                switch (node.kind) {
+                    case SyntaxKind.VariableStatement:
+                        return visitVariableStatementInAsyncBody(node);
+                    case SyntaxKind.ForStatement:
+                        return visitForStatementInAsyncBody(node);
+                    case SyntaxKind.ForInStatement:
+                        return visitForInStatementInAsyncBody(node);
+                    case SyntaxKind.ForOfStatement:
+                        return visitForOfStatementInAsyncBody(node);
+                    case SyntaxKind.CatchClause:
+                        return visitCatchClauseInAsyncBody(node);
+                    case SyntaxKind.Block:
+                    case SyntaxKind.SwitchStatement:
+                    case SyntaxKind.CaseBlock:
+                    case SyntaxKind.CaseClause:
+                    case SyntaxKind.DefaultClause:
+                    case SyntaxKind.TryStatement:
+                    case SyntaxKind.DoStatement:
+                    case SyntaxKind.WhileStatement:
+                    case SyntaxKind.IfStatement:
+                    case SyntaxKind.WithStatement:
+                    case SyntaxKind.LabeledStatement:
+                        return visitEachChild(node, asyncBodyVisitor, context);
+                    default:
+                        return Debug.assertNever(node, "Unhandled node.");
+                }
             }
-            Debug.assert(!isNodeWithPossibleVarDeclaration(node), "Unhandled node.");
             return visitor(node);
         }
 
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 7b80da8f639..eabc9921c1a 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -1761,14 +1761,32 @@ namespace ts {
         return getAssignmentTargetKind(node) !== AssignmentKind.None;
     }
 
+    export type NodeWithPossibleHoistedDeclaration =
+        | Block
+        | VariableStatement
+        | WithStatement
+        | IfStatement
+        | SwitchStatement
+        | CaseBlock
+        | CaseClause
+        | DefaultClause
+        | LabeledStatement
+        | ForStatement
+        | ForInStatement
+        | ForOfStatement
+        | DoStatement
+        | WhileStatement
+        | TryStatement
+        | CatchClause;
+
     /**
-     * Indicates whether a node could contain embedded statements that share the same `var`
-     * declaration scope as its parent.
+     * Indicates whether a node could contain a `var` VariableDeclarationList that contributes to
+     * the same `var` declaration scope as the node's parent.
      */
-    export function isNodeWithPossibleVarDeclaration(node: Node) {
+    export function isNodeWithPossibleHoistedDeclaration(node: Node): node is NodeWithPossibleHoistedDeclaration {
         switch (node.kind) {
-            case SyntaxKind.SourceFile:
             case SyntaxKind.Block:
+            case SyntaxKind.VariableStatement:
             case SyntaxKind.WithStatement:
             case SyntaxKind.IfStatement:
             case SyntaxKind.SwitchStatement: