Use accessors on Node instead of casts and field accesses (#2052)

Author: ahejlsberg

internal/ast/ast.go

@@ -617,6 +617,8 @@ func (n *Node) StatementList() *NodeList {
 		return n.AsBlock().Statements
 	case KindModuleBlock:
 		return n.AsModuleBlock().Statements
+	case KindCaseClause, KindDefaultClause:
+		return n.AsCaseOrDefaultClause().Statements
 	}
 	panic("Unhandled case in Node.StatementList: " + n.Kind.String())
 }
@@ -1038,6 +1040,10 @@ func (n *Node) Statement() *Statement {
 		return n.AsForStatement().Statement
 	case KindForInStatement, KindForOfStatement:
 		return n.AsForInOrOfStatement().Statement
+	case KindWithStatement:
+		return n.AsWithStatement().Statement
+	case KindLabeledStatement:
+		return n.AsLabeledStatement().Statement
 	}
 	panic("Unhandled case in Node.Statement: " + n.Kind.String())
 }
@@ -1068,8 +1074,11 @@ func (n *Node) ElementList() *NodeList {
 		return n.AsNamedExports().Elements
 	case KindObjectBindingPattern, KindArrayBindingPattern:
 		return n.AsBindingPattern().Elements
+	case KindArrayLiteralExpression:
+		return n.AsArrayLiteralExpression().Elements
+	case KindTupleType:
+		return n.AsTupleTypeNode().Elements
 	}
-
 	panic("Unhandled case in Node.ElementList: " + n.Kind.String())
 }
 
@@ -1081,22 +1090,22 @@ func (n *Node) Elements() []*Node {
 	return nil
 }
 
-func (n *Node) postfixToken() *Node {
+func (n *Node) PostfixToken() *Node {
 	switch n.Kind {
-	case KindEnumMember:
-		return n.AsEnumMember().PostfixToken
-	case KindPropertyAssignment:
-		return n.AsPropertyAssignment().PostfixToken
+	case KindMethodDeclaration:
+		return n.AsMethodDeclaration().PostfixToken
 	case KindShorthandPropertyAssignment:
 		return n.AsShorthandPropertyAssignment().PostfixToken
+	case KindMethodSignature:
+		return n.AsMethodSignatureDeclaration().PostfixToken
 	case KindPropertySignature:
 		return n.AsPropertySignatureDeclaration().PostfixToken
+	case KindPropertyAssignment:
+		return n.AsPropertyAssignment().PostfixToken
 	case KindPropertyDeclaration:
 		return n.AsPropertyDeclaration().PostfixToken
-	case KindMethodSignature:
-		return n.AsMethodSignatureDeclaration().PostfixToken
-	case KindMethodDeclaration:
-		return n.AsMethodDeclaration().PostfixToken
+	case KindEnumMember:
+		return n.AsEnumMember().PostfixToken
 	case KindGetAccessor:
 		return n.AsGetAccessorDeclaration().PostfixToken
 	case KindSetAccessor:
@@ -1116,7 +1125,7 @@ func (n *Node) QuestionToken() *TokenNode {
 	case KindNamedTupleMember:
 		return n.AsNamedTupleMember().QuestionToken
 	}
-	postfix := n.postfixToken()
+	postfix := n.PostfixToken()
 	if postfix != nil && postfix.Kind == KindQuestionToken {
 		return postfix
 	}
@@ -1163,26 +1172,6 @@ func (n *Node) ClassName() *Node {
 	panic("Unhandled case in Node.ClassName: " + n.Kind.String())
 }
 
-func (n *Node) PostfixToken() *Node {
-	switch n.Kind {
-	case KindParameter:
-		return n.AsParameterDeclaration().QuestionToken
-	case KindMethodDeclaration:
-		return n.AsMethodDeclaration().PostfixToken
-	case KindShorthandPropertyAssignment:
-		return n.AsShorthandPropertyAssignment().PostfixToken
-	case KindMethodSignature:
-		return n.AsMethodSignatureDeclaration().PostfixToken
-	case KindPropertySignature:
-		return n.AsPropertySignatureDeclaration().PostfixToken
-	case KindPropertyAssignment:
-		return n.AsPropertyAssignment().PostfixToken
-	case KindPropertyDeclaration:
-		return n.AsPropertyDeclaration().PostfixToken
-	}
-	return nil
-}
-
 // Determines if `n` contains `descendant` by walking up the `Parent` pointers from `descendant`. This method panics if
 // `descendant` or one of its ancestors is not parented except when that node is a `SourceFile`.
 func (n *Node) Contains(descendant *Node) bool {
@@ -11045,7 +11034,7 @@ func (node *SourceFile) computeDeclarationMap() map[string][]*Node {
 			exportClause := node.AsExportDeclaration().ExportClause
 			if exportClause != nil {
 				if IsNamedExports(exportClause) {
-					for _, element := range exportClause.AsNamedExports().Elements.Nodes {
+					for _, element := range exportClause.Elements() {
 						visit(element)
 					}
 				} else {
@@ -11068,7 +11057,7 @@ func (node *SourceFile) computeDeclarationMap() map[string][]*Node {
 					if namedBindings.Kind == KindNamespaceImport {
 						addDeclaration(namedBindings)
 					} else {
-						for _, element := range namedBindings.AsNamedImports().Elements.Nodes {
+						for _, element := range namedBindings.Elements() {
 							visit(element)
 						}
 					}

internal/ast/precedence.go

@@ -203,7 +203,7 @@ func getOperator(expression *Expression) Kind {
 func GetExpressionPrecedence(expression *Expression) OperatorPrecedence {
 	operator := getOperator(expression)
 	var flags OperatorPrecedenceFlags
-	if expression.Kind == KindNewExpression && expression.AsNewExpression().Arguments == nil {
+	if expression.Kind == KindNewExpression && expression.ArgumentList() == nil {
 		flags = OperatorPrecedenceFlagsNewWithoutArguments
 	} else if IsOptionalChain(expression) {
 		flags = OperatorPrecedenceFlagsOptionalChain