More type checking (#184)

Author: ahejlsberg

internal/ast/ast.go

@@ -4260,6 +4260,10 @@ func (node *TupleTypeNode) ForEachChild(v Visitor) bool {
 	return visitNodeList(v, node.Elements)
 }
 
+func IsTupleTypeNode(node *Node) bool {
+	return node.Kind == KindTupleType
+}
+
 // NamedTupleTypeMember
 
 type NamedTupleMember struct {
@@ -4287,6 +4291,7 @@ func (node *NamedTupleMember) ForEachChild(v Visitor) bool {
 func (node *NamedTupleMember) Name() *DeclarationName {
 	return node.name
 }
+
 func IsNamedTupleMember(node *Node) bool {
 	return node.Kind == KindNamedTupleMember
 }
@@ -4308,6 +4313,10 @@ func (node *OptionalTypeNode) ForEachChild(v Visitor) bool {
 	return visit(v, node.Type)
 }
 
+func IsOptionalTypeNode(node *Node) bool {
+	return node.Kind == KindOptionalType
+}
+
 // RestTypeNode
 
 type RestTypeNode struct {
@@ -4325,6 +4334,10 @@ func (node *RestTypeNode) ForEachChild(v Visitor) bool {
 	return visit(v, node.Type)
 }
 
+func IsRestTypeNode(node *Node) bool {
+	return node.Kind == KindRestType
+}
+
 // ParenthesizedTypeNode
 
 type ParenthesizedTypeNode struct {

internal/ast/utilities.go

@@ -553,6 +553,13 @@ func SkipParentheses(node *Expression) *Expression {
 	return SkipOuterExpressions(node, OEKParentheses)
 }
 
+func SkipTypeParentheses(node *Node) *Node {
+	for IsParenthesizedTypeNode(node) {
+		node = node.AsParenthesizedTypeNode().Type
+	}
+	return node
+}
+
 func SkipPartiallyEmittedExpressions(node *Expression) *Expression {
 	return SkipOuterExpressions(node, OEKPartiallyEmittedExpressions)
 }
@@ -843,6 +850,14 @@ func IsImportMeta(node *Node) bool {
 	return false
 }
 
+func WalkUpBindingElementsAndPatterns(binding *Node) *Node {
+	node := binding.Parent
+	for IsBindingElement(node.Parent) {
+		node = node.Parent.Parent
+	}
+	return node.Parent
+}
+
 func IsInJSFile(node *Node) bool {
 	return node != nil && node.Flags&NodeFlagsJavaScriptFile != 0
 }