Merge pull request #17517 from tinganho/IgnoredCatchParameter

Ignored catch parameter

src/compiler/binder.ts

@@ -2921,7 +2921,10 @@ namespace ts {
     function computeCatchClause(node: CatchClause, subtreeFlags: TransformFlags) {
         let transformFlags = subtreeFlags;
 
-        if (node.variableDeclaration && isBindingPattern(node.variableDeclaration.name)) {
+        if (!node.variableDeclaration) {
+            transformFlags |= TransformFlags.AssertESNext;
+        }
+        else if (isBindingPattern(node.variableDeclaration.name)) {
             transformFlags |= TransformFlags.AssertES2015;
         }
 

src/compiler/checker.ts

@@ -481,7 +481,7 @@ namespace ts {
             Type,
             ResolvedBaseConstructorType,
             DeclaredType,
-            ResolvedReturnType
+            ResolvedReturnType,
         }
 
         const enum CheckMode {

src/compiler/emitter.ts

@@ -2133,10 +2133,12 @@ namespace ts {
         function emitCatchClause(node: CatchClause) {
             const openParenPos = writeToken(SyntaxKind.CatchKeyword, node.pos);
             write(" ");
-            writeToken(SyntaxKind.OpenParenToken, openParenPos);
-            emit(node.variableDeclaration);
-            writeToken(SyntaxKind.CloseParenToken, node.variableDeclaration ? node.variableDeclaration.end : openParenPos);
-            write(" ");
+            if (node.variableDeclaration) {
+                writeToken(SyntaxKind.OpenParenToken, openParenPos);
+                emit(node.variableDeclaration);
+                writeToken(SyntaxKind.CloseParenToken, node.variableDeclaration.end);
+                write(" ");
+            }
             emit(node.block);
         }
 

src/compiler/factory.ts

@@ -2128,14 +2128,14 @@ namespace ts {
             : node;
     }
 
-    export function createCatchClause(variableDeclaration: string | VariableDeclaration, block: Block) {
+    export function createCatchClause(variableDeclaration: string | VariableDeclaration | undefined, block: Block) {
         const node = <CatchClause>createSynthesizedNode(SyntaxKind.CatchClause);
         node.variableDeclaration = typeof variableDeclaration === "string" ? createVariableDeclaration(variableDeclaration) : variableDeclaration;
         node.block = block;
         return node;
     }
 
-    export function updateCatchClause(node: CatchClause, variableDeclaration: VariableDeclaration, block: Block) {
+    export function updateCatchClause(node: CatchClause, variableDeclaration: VariableDeclaration | undefined, block: Block) {
         return node.variableDeclaration !== variableDeclaration
             || node.block !== block
             ? updateNode(createCatchClause(variableDeclaration, block), node)

src/compiler/parser.ts

@@ -4799,11 +4799,16 @@ namespace ts {
         function parseCatchClause(): CatchClause {
             const result = <CatchClause>createNode(SyntaxKind.CatchClause);
             parseExpected(SyntaxKind.CatchKeyword);
-            if (parseExpected(SyntaxKind.OpenParenToken)) {
+
+            if (parseOptional(SyntaxKind.OpenParenToken)) {
                 result.variableDeclaration = parseVariableDeclaration();
+                parseExpected(SyntaxKind.CloseParenToken);
+            }
+            else {
+                // Keep shape of node to avoid degrading performance.
+                result.variableDeclaration = undefined;
             }
 
-            parseExpected(SyntaxKind.CloseParenToken);
             result.block = parseBlock(/*ignoreMissingOpenBrace*/ false);
             return finishNode(result);
         }

src/compiler/transformers/es2015.ts

@@ -2491,7 +2491,7 @@ namespace ts {
             const catchVariable = getGeneratedNameForNode(errorRecord);
             const returnMethod = createTempVariable(/*recordTempVariable*/ undefined);
             const values = createValuesHelper(context, expression, node.expression);
-            const next = createCall(createPropertyAccess(iterator, "next" ), /*typeArguments*/ undefined, []);
+            const next = createCall(createPropertyAccess(iterator, "next"), /*typeArguments*/ undefined, []);
 
             hoistVariableDeclaration(errorRecord);
             hoistVariableDeclaration(returnMethod);
@@ -3173,6 +3173,7 @@ namespace ts {
         function visitCatchClause(node: CatchClause): CatchClause {
             const ancestorFacts = enterSubtree(HierarchyFacts.BlockScopeExcludes, HierarchyFacts.BlockScopeIncludes);
             let updated: CatchClause;
+            Debug.assert(!!node.variableDeclaration, "Catch clause variable should always be present when downleveling ES2015.");
             if (isBindingPattern(node.variableDeclaration.name)) {
                 const temp = createTempVariable(/*recordTempVariable*/ undefined);
                 const newVariableDeclaration = createVariableDeclaration(temp);

src/compiler/transformers/esnext.ts

@@ -101,6 +101,8 @@ namespace ts {
                     return visitExpressionStatement(node as ExpressionStatement);
                 case SyntaxKind.ParenthesizedExpression:
                     return visitParenthesizedExpression(node as ParenthesizedExpression, noDestructuringValue);
+                case SyntaxKind.CatchClause:
+                    return visitCatchClause(node as CatchClause);
                 default:
                     return visitEachChild(node, visitor, context);
             }
@@ -212,6 +214,17 @@ namespace ts {
             return visitEachChild(node, noDestructuringValue ? visitorNoDestructuringValue : visitor, context);
         }
 
+        function visitCatchClause(node: CatchClause): CatchClause {
+            if (!node.variableDeclaration) {
+                return updateCatchClause(
+                    node,
+                    createVariableDeclaration(createTempVariable(/*recordTempVariable*/ undefined)),
+                    visitNode(node.block, visitor, isBlock)
+                );
+            }
+            return visitEachChild(node, visitor, context);
+        }
+
         /**
          * Visits a BinaryExpression that contains a destructuring assignment.
          *

src/compiler/types.ts

@@ -1808,7 +1808,7 @@ namespace ts {
     export interface CatchClause extends Node {
         kind: SyntaxKind.CatchClause;
         parent?: TryStatement;
-        variableDeclaration: VariableDeclaration;
+        variableDeclaration?: VariableDeclaration;
         block: Block;
     }
 
@@ -4020,7 +4020,6 @@ namespace ts {
         ContainsBindingPattern = 1 << 23,
         ContainsYield = 1 << 24,
         ContainsHoistedDeclarationOrCompletion = 1 << 25,
-
         ContainsDynamicImport = 1 << 26,
 
         // Please leave this as 1 << 29.