Method parseParameterEx

internal/parser/parser.go:3320–3359

(inOuterAwaitContext bool, allowAmbiguity bool)

}

func (p *Parser) parseParameterEx(inOuterAwaitContext bool, allowAmbiguity bool) *ast.Node {
	pos := p.nodePos()
	jsdoc := p.jsdocScannerInfo()
	// FormalParameter [Yield,Await]:
	//      BindingElement[?Yield,?Await]
	// Decorators are parsed in the outer [Await] context, the rest of the parameter is parsed in the function's [Await] context.
	saveContextFlags := p.contextFlags
	p.setContextFlags(ast.NodeFlagsAwaitContext, inOuterAwaitContext)
	modifiers := p.parseModifiersEx(true /*allowDecorators*/, false /*permitConstAsModifier*/, false /*stopOnStartOfClassStaticBlock*/)
	p.contextFlags = saveContextFlags
	if p.token == ast.KindThisKeyword {
		result := p.factory.NewParameterDeclaration(
			modifiers,
			nil, /*dotDotDotToken*/
			p.createIdentifier(true /*isIdentifier*/),
			nil, /*questionToken*/
			p.parseTypeAnnotation(),
			nil, /*initializer*/
		)
		if modifiers != nil {
			p.parseErrorAtRange(modifiers.Nodes[0].Loc, diagnostics.Neither_decorators_nor_modifiers_may_be_applied_to_this_parameters)
		}
		p.withJSDoc(p.finishNode(result, pos), jsdoc)
		return result
	}
	dotDotDotToken := p.parseOptionalToken(ast.KindDotDotDotToken)
	if !allowAmbiguity && !p.isParameterNameStart() {
		return nil
	}
	result := p.factory.NewParameterDeclaration(
		modifiers,
		dotDotDotToken,
		p.parseNameOfParameter(modifiers),
		p.parseOptionalToken(ast.KindQuestionToken),
		p.parseTypeAnnotation(),
		p.parseInitializer(),
	)
	p.withJSDoc(p.finishNode(result, pos), jsdoc)
	return result
}

func (p *Parser) isParameterNameStart() bool {
	// Be permissive about await and yield by calling isBindingIdentifier instead of isIdentifier; disallowing