Always reparse bracketed @param names into ? modifiers (#3660)

Author: ahejlsberg

CHANGES.md

@@ -247,18 +247,6 @@ var f = (x) => x,
   g = (x) => x;
 ```
 
-#### Optional marking on parameter names now makes the parameter both optional and undefined:
-
-```js
-/** @param {number} [x] */
-function f(x) {
-  return x;
-}
-```
-
-This behaves the same as TypeScript's `x?: number` syntax.
-Strada makes the parameter optional but does not add `undefined` to the type.
-
 #### Type assertions with `@type` tags now prevent narrowing of the type.
 
 ```js

internal/checker/grammarchecks.go

@@ -705,10 +705,9 @@ func (c *Checker) checkGrammarParameterList(parameters *ast.NodeList) bool {
 				return c.grammarErrorOnNode(parameter.Name(), diagnostics.A_rest_parameter_cannot_have_an_initializer)
 			}
 		} else if isOptionalDeclaration(parameter.AsNode()) {
-			// !!!
-			// used to be hasEffectiveQuestionToken for JSDoc
 			seenOptionalParameter = true
-			if parameter.QuestionToken != nil && parameter.Initializer != nil {
+			// A reparsed '?' token indicates a bracketed name in @param tag
+			if parameter.QuestionToken != nil && parameter.QuestionToken.Flags&ast.NodeFlagsReparsed == 0 && parameter.Initializer != nil {
 				return c.grammarErrorOnNode(parameter.Name(), diagnostics.Parameter_cannot_have_question_mark_and_initializer)
 			}
 		} else if seenOptionalParameter && parameter.Initializer == nil {

internal/parser/reparser.go

@@ -404,7 +404,7 @@ func (p *Parser) reparseHosted(tag *ast.Node, parent *ast.Node, jsDoc *ast.Node)
 				if param.Type == nil && parameterTag.TypeExpression != nil {
 					param.AsParameterDeclaration().Type = p.reparseJSDocTypeLiteral(parameterTag.TypeExpression.Type())
 				}
-				if param.QuestionToken == nil && param.Initializer == nil {
+				if param.QuestionToken == nil {
 					if question := p.makeQuestionIfOptional(parameterTag); question != nil {
 						param.QuestionToken = question
 					}

testdata/baselines/reference/submodule/compiler/argumentsReferenceInConstructor1_Js.types

@@ -10,7 +10,7 @@ class A {
 	 * @param {object} [foo={}]
 	 */
 	constructor(foo = {}) {
->foo : object
+>foo : object | undefined
 >{} : {}
 
 		/**

testdata/baselines/reference/submodule/compiler/argumentsReferenceInConstructor2_Js.types

@@ -10,7 +10,7 @@ class A {
 	 * @param {object} [foo={}]
 	 */
 	constructor(foo = {}) {
->foo : object
+>foo : object | undefined
 >{} : {}
 
 		/**

testdata/baselines/reference/submodule/compiler/argumentsReferenceInConstructor3_Js.types

@@ -24,7 +24,7 @@ class B extends A {
 	 * @param {object} [foo={}]
 	 */
 	constructor(foo = {}) {
->foo : object
+>foo : object | undefined
 >{} : {}
 
 		super();

testdata/baselines/reference/submodule/compiler/argumentsReferenceInConstructor4_Js.types

@@ -10,7 +10,7 @@ class A {
 	 * @param {object} [foo={}]
 	 */
 	constructor(foo = {}) {
->foo : object
+>foo : object | undefined
 >{} : {}
 
 		const key = "bar";

testdata/baselines/reference/submodule/compiler/argumentsReferenceInConstructor5_Js.types

@@ -19,7 +19,7 @@ class A {
 	 * @param {object} [foo={}]
 	 */
 	constructor(foo = {}) {
->foo : object
+>foo : object | undefined
 >{} : {}
 
 		/**

testdata/baselines/reference/submodule/compiler/argumentsReferenceInMethod1_Js.types

@@ -9,7 +9,7 @@ class A {
 	 */
 	m(foo = {}) {
 >m : (foo?: object) => void
->foo : object
+>foo : object | undefined
 >{} : {}
 
 		/**

testdata/baselines/reference/submodule/compiler/argumentsReferenceInMethod2_Js.types

@@ -9,7 +9,7 @@ class A {
 	 */
 	m(foo = {}) {
 >m : (foo?: object) => void
->foo : object
+>foo : object | undefined
 >{} : {}
 
 		/**