AST nodes as handles, offsets into areanas

tools/customlint/checkchildren.go

@@ -26,7 +26,7 @@ import (
 // conditionally, e.g.
 //
 //	var exprType *Type
-//	if node.Expression() != nil {
+//	if !node.Expression().IsNil() {
 //		exprType = c.checkExpressionCached(node.Expression())
 //	}
 //	if c.grammarError(node) {
@@ -238,9 +238,18 @@ func guardedNil(ret inspector.Cursor, childExpr ast.Expr) bool {
 }
 
 // condImpliesNil reports whether `cond` evaluating to `condIsTrue` implies that
-// `childExpr` is nil, i.e. `childExpr == nil` (when true) or `childExpr != nil`
-// (when false).
+// `childExpr` is nil, i.e. `childExpr == nil` or `childExpr.IsNil()` (when
+// true) or `childExpr != nil` or `!childExpr.IsNil()` (when false).
 func condImpliesNil(cond ast.Expr, childExpr ast.Expr, condIsTrue bool) bool {
+	if un, ok := cond.(*ast.UnaryExpr); ok && un.Op == token.NOT {
+		return condImpliesNil(un.X, childExpr, !condIsTrue)
+	}
+	if call, ok := cond.(*ast.CallExpr); ok && condIsTrue && len(call.Args) == 0 {
+		if sel, ok := call.Fun.(*ast.SelectorExpr); ok && sel.Sel.Name == "IsNil" {
+			return equalExpr(sel.X, childExpr)
+		}
+		return false
+	}
 	bin, ok := cond.(*ast.BinaryExpr)
 	if !ok {
 		return false

tools/customlint/testdata/checkchildren/checkchildren.go

@@ -4,6 +4,8 @@ type Node struct{}
 
 func (n *Node) Expression() *Node { return nil }
 
+func (n *Node) IsNil() bool { return n == nil }
+
 type Type struct{}
 
 type CheckMode int
@@ -40,6 +42,8 @@ func (c *Checker) checkExpressionWorker(node *Node, checkMode CheckMode) *Type {
 		return c.checkCallLike(node)
 	case node != nil:
 		return c.checkNilGuardedReturn(node)
+	case node.IsNil():
+		return c.checkIsNilGuardedReturn(node)
 	default:
 		return c.checkReturnsInReturn(node)
 	}
@@ -112,6 +116,16 @@ func (c *Checker) checkNilGuardedReturn(node *Node) *Type {
 	return c.checkExpression(node.Expression(), 0)
 }
 
+// checkIsNilGuardedReturn is like checkNilGuardedReturn, but guards with an
+// IsNil method call.
+func (c *Checker) checkIsNilGuardedReturn(node *Node) *Type {
+	c.grammarError(node)
+	if node.Expression().IsNil() {
+		return c.errorType
+	}
+	return c.checkExpression(node.Expression(), 0)
+}
+
 // checkNeverDispatched is not reachable from a worker, so it is never analyzed.
 func (c *Checker) checkNeverDispatched(node *Node) *Type {
 	if c.grammarError(node) {

tools/customlint/testdata/checkchildren/checkchildren.go.golden

@@ -4,6 +4,8 @@
 
 	func (n *Node) Expression() *Node { return nil }
 
+	func (n *Node) IsNil() bool { return n == nil }
+
 	type Type struct{}
 
 	type CheckMode int
@@ -40,6 +42,8 @@
 			return c.checkCallLike(node)
 		case node != nil:
 			return c.checkNilGuardedReturn(node)
+		case node.IsNil():
+			return c.checkIsNilGuardedReturn(node)
 		default:
 			return c.checkReturnsInReturn(node)
 		}
@@ -116,6 +120,16 @@
 		return c.checkExpression(node.Expression(), 0)
 	}
 
+	// checkIsNilGuardedReturn is like checkNilGuardedReturn, but guards with an
+	// IsNil method call.
+	func (c *Checker) checkIsNilGuardedReturn(node *Node) *Type {
+		c.grammarError(node)
+		if node.Expression().IsNil() {
+			return c.errorType
+		}
+		return c.checkExpression(node.Expression(), 0)
+	}
+
 	// checkNeverDispatched is not reachable from a worker, so it is never analyzed.
 	func (c *Checker) checkNeverDispatched(node *Node) *Type {
 		if c.grammarError(node) {

tools/scripts/tsc/ast.json

@@ -929,7 +929,7 @@
                     "goOnly": true
                 },
                 "NextContainer": {
-                    "type": "*Node",
+                    "type": "Node",
                     "goOnly": true
                 }
             },

tools/scripts/tsc/generate-encoder.ts

@@ -228,15 +228,14 @@ function goParamName(m: MemberInfo): string {
     return m.goParamName();
 }
 
-/** Get the Go accessor for a member on a cast struct (e.g., "n.IsTypeOnly", "n.Name()"). */
+/** Get the Go accessor for a member on a cast struct (e.g., "n.IsTypeOnly()", "n.Name()"). */
 function goFieldAccess(m: MemberInfo): string {
-    if (m.private) return `n.${api.capitalize(m.name)}()`;
-    return `n.${m.name}`;
+    return `n.${api.capitalize(m.name)}()`;
 }
 
 /** Get the default Go value for a non-encoded factory parameter. */
 function goDefaultValue(m: MemberInfo): string {
-    if (m.isChild()) return "nil";
+    if (m.isChild()) return childType(m) === "node" ? "ast.Node{}" : "nil";
     const dt = m.declaredType;
     if (dt.kind === "primitive") {
         switch (dt.name) {
@@ -366,9 +365,9 @@ function generateGoEncoder(): string {
 }
 
 function generateGoGetNodeDataType(w: CodeWriter) {
-    w.write("func getNodeDataType(node *ast.Node) uint32 {");
+    w.write("func getNodeDataType(node ast.Node) uint32 {");
     w.push();
-    w.write("switch node.Kind {");
+    w.write("switch node.Kind() {");
 
     const stringKinds: string[] = [];
     const extendedKinds: string[] = [];
@@ -409,9 +408,9 @@ function generateGoGetNodeDataType(w: CodeWriter) {
 }
 
 function generateGoGetChildrenPropertyMask(w: CodeWriter) {
-    w.write("func getChildrenPropertyMask(node *ast.Node) uint8 {");
+    w.write("func getChildrenPropertyMask(node ast.Node) uint8 {");
     w.push();
-    w.write("switch node.Kind {");
+    w.write("switch node.Kind() {");
 
     for (const node of api.nodes()) {
         const info = analyzeNode(node);
@@ -440,7 +439,7 @@ function generateGoGetChildrenPropertyMask(w: CodeWriter) {
                 check = `len(${goFieldAccess(m)}) > 0`;
             }
             else {
-                check = `${goFieldAccess(m)} != nil`;
+                check = `!${goFieldAccess(m)}.IsNil()`;
             }
             parts.push(`(boolToByte(${check}) << ${i})`);
         }
@@ -459,9 +458,9 @@ function generateGoGetChildrenPropertyMask(w: CodeWriter) {
 }
 
 function generateGoGetNodeCommonData(w: CodeWriter) {
-    w.write("func getNodeCommonData(node *ast.Node) uint32 {");
+    w.write("func getNodeCommonData(node ast.Node) uint32 {");
     w.push();
-    w.write("switch node.Kind {");
+    w.write("switch node.Kind() {");
 
     for (const node of api.nodes()) {
         const info = analyzeNode(node);
@@ -525,29 +524,27 @@ function generateGoGetNodeCommonData(w: CodeWriter) {
 }
 
 function generateGoRecordNodeStrings(w: CodeWriter) {
-    w.write("func recordNodeStrings(node *ast.Node, strs *stringTable) uint32 {");
+    w.write("func recordNodeStrings(node ast.Node, strs *stringTable) uint32 {");
     w.push();
-    w.write("switch node.Kind {");
+    w.write("switch node.Kind() {");
 
     for (const node of api.nodes()) {
         const info = analyzeNode(node);
         if (info.dataType !== "string" || !info.textMember) continue;
 
         const kinds = getGoKinds(node);
         const castName = goCastName(node);
-        const textAccess = info.textMember.private
-            ? `node.${castName}().${api.capitalize(info.textMember.name)}()`
-            : `node.${castName}().${info.textMember.name}`;
+        const textAccess = `node.${castName}().${api.capitalize(info.textMember.name)}()`;
 
         w.write(`case ${kinds.join(", ")}:`);
         w.push();
-        w.write(`return strs.add(${textAccess}, node.Kind, node.Pos(), node.End())`);
+        w.write(`return strs.add(${textAccess}, node.Kind(), node.Pos(), node.End())`);
         w.pop();
     }
 
     w.write("default:");
     w.push();
-    w.write(`panic(fmt.Sprintf("Unexpected node kind %v", node.Kind))`);
+    w.write(`panic(fmt.Sprintf("Unexpected node kind %v", node.Kind()))`);
     w.pop();
     w.write("}");
     w.pop();
@@ -556,10 +553,10 @@ function generateGoRecordNodeStrings(w: CodeWriter) {
 }
 
 function generateGoRecordExtendedData(w: CodeWriter) {
-    w.write("func recordExtendedData(node *ast.Node, strs *stringTable, positionMap *ast.PositionMap, extendedData *[]byte, structuredData *[]byte) uint32 {");
+    w.write("func recordExtendedData(node ast.Node, strs *stringTable, positionMap *ast.PositionMap, extendedData *[]byte, structuredData *[]byte) uint32 {");
     w.push();
     w.write("offset := uint32(len(*extendedData))");
-    w.write("switch node.Kind {");
+    w.write("switch node.Kind() {");
 
     for (const node of api.nodes()) {
         const info = analyzeNode(node);
@@ -575,7 +572,7 @@ function generateGoRecordExtendedData(w: CodeWriter) {
 
     w.write("default:");
     w.push();
-    w.write(`panic(fmt.Sprintf("unknown extended data node kind %v", node.Kind))`);
+    w.write(`panic(fmt.Sprintf("unknown extended data node kind %v", node.Kind()))`);
     w.pop();
     w.write("}");
     w.write("return offset");
@@ -611,7 +608,7 @@ function generateGoDecoder(): string {
 }
 
 function generateGoCreateStringNode(w: CodeWriter) {
-    w.write("func (d *astDecoder) createStringNode(kind ast.Kind, data uint32, commonData uint8) (*ast.Node, error) {");
+    w.write("func (d *astDecoder) createStringNode(kind ast.Kind, data uint32, commonData uint8) (ast.Node, error) {");
     w.push();
     w.write("strIdx := data & NodeDataStringIndexMask");
     w.write("text := d.getString(strIdx)");
@@ -646,7 +643,7 @@ function generateGoCreateStringNode(w: CodeWriter) {
                 }
             }
             else if (isEncodedChild(m)) {
-                args.push("nil");
+                args.push(goDefaultValue(m));
             }
             else {
                 const v = commonVars.get(m);
@@ -665,7 +662,7 @@ function generateGoCreateStringNode(w: CodeWriter) {
 
     w.write("default:");
     w.push();
-    w.write(`return nil, fmt.Errorf("unknown string node kind %v", kind)`);
+    w.write(`return ast.Node{}, fmt.Errorf("unknown string node kind %v", kind)`);
     w.pop();
     w.write("}");
     w.pop();
@@ -674,7 +671,7 @@ function generateGoCreateStringNode(w: CodeWriter) {
 }
 
 function generateGoCreateExtendedNode(w: CodeWriter) {
-    w.write("func (d *astDecoder) createExtendedNode(kind ast.Kind, data uint32, childIndices []int, commonData uint8) (*ast.Node, error) {");
+    w.write("func (d *astDecoder) createExtendedNode(kind ast.Kind, data uint32, childIndices []int, commonData uint8) (ast.Node, error) {");
     w.push();
     w.write("switch kind {");
 
@@ -693,7 +690,7 @@ function generateGoCreateExtendedNode(w: CodeWriter) {
 
     w.write("default:");
     w.push();
-    w.write(`return nil, fmt.Errorf("unknown extended data node kind %v", kind)`);
+    w.write(`return ast.Node{}, fmt.Errorf("unknown extended data node kind %v", kind)`);
     w.pop();
     w.write("}");
     w.pop();
@@ -702,7 +699,7 @@ function generateGoCreateExtendedNode(w: CodeWriter) {
 }
 
 function generateGoCreateChildrenNode(w: CodeWriter) {
-    w.write("func (d *astDecoder) createChildrenNode(kind ast.Kind, data uint32, childIndices []int, commonData uint8) (*ast.Node, error) {");
+    w.write("func (d *astDecoder) createChildrenNode(kind ast.Kind, data uint32, childIndices []int, commonData uint8) (ast.Node, error) {");
     w.push();
     w.write("mask := uint8(data & NodeDataChildMask)");
     w.write("");
@@ -752,7 +749,7 @@ function generateGoCreateChildrenNode(w: CodeWriter) {
     // Default: error for unhandled kinds
     w.write("default:");
     w.push();
-    w.write(`return nil, fmt.Errorf("unhandled node kind %v with %d children", kind, len(childIndices))`);
+    w.write(`return ast.Node{}, fmt.Errorf("unhandled node kind %v with %d children", kind, len(childIndices))`);
     w.pop();
 
     w.write("}");
@@ -960,10 +957,10 @@ function emitMultiChildDecoder(w: CodeWriter, node: NodeType, info: EncoderNodeI
         else if (ct === "rawNodeList") {
             const nlVar = `${varName}NL`;
             w.write(`${nlVar} := d.nodeListAt(it.nextIf(mask, ${i}))`);
-            w.write(`var ${varName} []*ast.Node`);
+            w.write(`var ${varName} []ast.Node`);
             w.write(`if ${nlVar} != nil {`);
             w.push();
-            w.write(`${varName} = ${nlVar}.Nodes`);
+            w.write(`${varName} = ${nlVar}.Nodes()`);
             w.pop();
             w.write("}");
             childVars.set(m, varName);