Support optional catch binding (stage 4 / ES2019) (#2455)

* support optional catch binding (stage 4 / ES2019)

* correct test indentation: looks like this is a tabs codebase(!)

* switch default ecmaVersion to 2019; remove acorn options from option catch param test

src/Module.ts

@@ -101,7 +101,7 @@ export interface AstContext {
 
 export const defaultAcornOptions: AcornOptions = {
 	// TODO TypeScript waiting for acorn types to be updated
-	ecmaVersion: <any>2018,
+	ecmaVersion: <any>2019,
 	sourceType: 'module',
 	preserveParens: false
 };

src/ast/nodes/CatchClause.ts

@@ -8,7 +8,7 @@ import { PatternNode } from './shared/Pattern';
 
 export default class CatchClause extends NodeBase {
 	type: NodeType.tCatchClause;
-	param: PatternNode;
+	param: PatternNode | null;
 	body: BlockStatement;
 
 	scope: CatchScope;
@@ -20,14 +20,15 @@ export default class CatchClause extends NodeBase {
 
 	initialise() {
 		this.included = false;
-		this.param.declare('parameter', UNKNOWN_EXPRESSION);
+
+		if (this.param) {
+			this.param.declare('parameter', UNKNOWN_EXPRESSION);
+		}
 	}
 
 	parseNode(esTreeNode: GenericEsTreeNode) {
-		this.body = <BlockStatement>new this.context.nodeConstructors.BlockStatement(
-			esTreeNode.body,
-			this,
-			this.scope
+		this.body = <BlockStatement>(
+			new this.context.nodeConstructors.BlockStatement(esTreeNode.body, this, this.scope)
 		);
 		super.parseNode(esTreeNode);
 	}

test/function/samples/optional-catch-binding/_config.js

@@ -0,0 +1,9 @@
+const assert = require('assert');
+
+module.exports = {
+	description: 'allows optional catch binding with appropriate acorn settings',
+	minNodeVersion: 10,
+	exports(exports) {
+		assert.equal(exports.foo, true);
+	}
+};

test/function/samples/optional-catch-binding/main.js

@@ -0,0 +1,7 @@
+export let foo;
+
+try {
+	foo();
+} catch {
+	foo = true;
+}