From 81fb3f702a9322139d433570d01f1dcde9abb729 Mon Sep 17 00:00:00 2001
From: Tingan Ho <tingan87@gmail.com>
Date: Tue, 1 Aug 2017 22:10:12 +0200
Subject: [PATCH] Addresses CR feedback

---
 src/compiler/binder.ts                                |  2 +-
 src/compiler/checker.ts                               | 11 -----------
 src/compiler/diagnosticMessages.json                  |  4 ----
 src/compiler/transformers/es2015.ts                   |  3 ++-
 src/compiler/transformers/esnext.ts                   |  2 +-
 src/compiler/types.ts                                 |  2 +-
 .../statements/tryStatements/invalidTryStatements.ts  |  5 -----
 7 files changed, 5 insertions(+), 24 deletions(-)

diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index aa42d1b251b..45880f855fd 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -2924,7 +2924,7 @@ namespace ts {
         if (!node.variableDeclaration) {
             transformFlags |= TransformFlags.AssertESNext;
         }
-        else if (/* node.variableDeclaration && */ isBindingPattern(node.variableDeclaration.name)) {
+        else if (isBindingPattern(node.variableDeclaration.name)) {
             transformFlags |= TransformFlags.AssertES2015;
         }
 
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 6d07025a41f..f3979d80441 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -20885,17 +20885,6 @@ namespace ts {
                         }
                     }
                 }
-                else if (/* !catchClause.variableDeclaration && */ languageVersion < ScriptTarget.ESNext) {
-                    const blockLocals = catchClause.block.locals;
-                    if (blockLocals) {
-                        forEachKey(blockLocals, caughtName => {
-                            if (caughtName === "_ignoredCatchParameter") {
-                                const localSymbol = blockLocals.get(caughtName);
-                                grammarErrorOnNode(localSymbol.valueDeclaration, Diagnostics.Duplicate_identifier_ignoredCatchParameter_Compiler_uses_the_parameter_declaration_ignoredCatchParameter_to_bind_ignored_catched_exceptions);
-                            }
-                        });
-                    }
-                }
 
                 checkBlock(catchClause.block);
             }
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index fbd91f33905..3b4b0ddf667 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -2196,10 +2196,6 @@
         "category": "Error",
         "code": 2713
     },
-    "Duplicate identifier '_ignoredCatchParameter'. Compiler uses the parameter declaration '_ignoredCatchParameter' to bind ignored catched exceptions.": {
-        "category": "Error",
-        "code": 2714
-    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
diff --git a/src/compiler/transformers/es2015.ts b/src/compiler/transformers/es2015.ts
index ebfd0b0069f..41e68baa523 100644
--- a/src/compiler/transformers/es2015.ts
+++ b/src/compiler/transformers/es2015.ts
@@ -3173,7 +3173,8 @@ namespace ts {
         function visitCatchClause(node: CatchClause): CatchClause {
             const ancestorFacts = enterSubtree(HierarchyFacts.BlockScopeExcludes, HierarchyFacts.BlockScopeIncludes);
             let updated: CatchClause;
-            if (node.variableDeclaration && isBindingPattern(node.variableDeclaration.name)) {
+            Debug.assert(!!node.variableDeclaration, "Catch clauses should always be present when downleveling ES2015 code.");
+            if (isBindingPattern(node.variableDeclaration.name)) {
                 const temp = createTempVariable(/*recordTempVariable*/ undefined);
                 const newVariableDeclaration = createVariableDeclaration(temp);
                 setTextRange(newVariableDeclaration, node.variableDeclaration);
diff --git a/src/compiler/transformers/esnext.ts b/src/compiler/transformers/esnext.ts
index 597b9d55b16..11e79ae9eeb 100644
--- a/src/compiler/transformers/esnext.ts
+++ b/src/compiler/transformers/esnext.ts
@@ -216,7 +216,7 @@ namespace ts {
 
         function visitCatchClause(node: CatchClause): CatchClause {
             if (!node.variableDeclaration) {
-                return updateCatchClause(node, createVariableDeclaration("_ignoredCatchParameter"), node.block);
+                return updateCatchClause(node, createVariableDeclaration(createTempVariable(/*recordTempVariable*/ undefined)), node.block);
             }
             return visitEachChild(node, visitor, context);
         }
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index c97020c1142..9cf8e6fdf00 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -1807,7 +1807,7 @@ namespace ts {
 
     export interface CatchClause extends Node {
         kind: SyntaxKind.CatchClause;
-        parent?: TryStatement; // We parse missing try statements
+        parent?: TryStatement; // We make this optional to parse missing try statements
         variableDeclaration?: VariableDeclaration;
         block: Block;
     }
diff --git a/tests/cases/conformance/statements/tryStatements/invalidTryStatements.ts b/tests/cases/conformance/statements/tryStatements/invalidTryStatements.ts
index 6ecdfe10656..c838cf45f69 100644
--- a/tests/cases/conformance/statements/tryStatements/invalidTryStatements.ts
+++ b/tests/cases/conformance/statements/tryStatements/invalidTryStatements.ts
@@ -8,10 +8,5 @@ function fn() {
     try { } catch (z: any) { }
     try { } catch (a: number) { }
     try { } catch (y: string) { }
-
-    
-    try { } catch { 
-        let _ignoredCatchParameter; // Should error since we downlevel emit this variable.
-    }
 }