- gofmt-ify walk.go

- fixed several bugs

R=rsc
http://go/go-review/1015015

src/pkg/go/ast/walk.go

@@ -69,17 +69,27 @@ func walkBlockStmt(v Visitor, b *BlockStmt) {
 // Walk visits each of the children of n.
 //
 func Walk(v Visitor, node interface{}) {
-	if node != nil && !v.Visit(node) {
+	if node == nil || !v.Visit(node) {
 		return;
 	}
 
 	// walk children
+	// (the order of the cases matches the order
+	// of the corresponding declaration in ast.go)
 	switch n := node.(type) {
 	// Comments and fields
+	case *Comment:
+		// nothing to do
+
 	case *CommentGroup:
 		for _, c := range n.List {
 			Walk(v, c);
 		}
+		// TODO(gri): Keep comments in a list/vector instead
+		// of linking them via Next. Following next will lead
+		// to multiple visits and potentially n^2 behavior
+		// since Doc and Comments fields point into the global
+		// comments list.
 
 	case *Field:
 		walkCommentGroup(v, n.Doc);
@@ -91,13 +101,18 @@ func Walk(v Visitor, node interface{}) {
 		walkCommentGroup(v, n.Comment);
 
 	// Expressions
+	case *BadExpr, *Ident, *Ellipsis, *BasicLit:
+		// nothing to do
+
 	case *StringList:
 		for _, x := range n.Strings {
 			Walk(v, x);
 		}
 
 	case *FuncLit:
+		if n != nil {
 			Walk(v, n.Type);
+		}
 		walkBlockStmt(v, n.Body);
 
 	case *CompositeLit:
@@ -109,9 +124,7 @@ func Walk(v Visitor, node interface{}) {
 
 	case *SelectorExpr:
 		Walk(v, n.X);
-		if n.Sel != nil {
-			Walk(v, n.Sel);
-		}
+		walkIdent(v, n.Sel);
 
 	case *IndexExpr:
 		Walk(v, n.X);
@@ -163,9 +176,15 @@ func Walk(v Visitor, node interface{}) {
 		Walk(v, n.Value);
 
 	// Statements
+	case *BadStmt:
+		// nothing to do
+
 	case *DeclStmt:
 		Walk(v, n.Decl);
 
+	case *EmptyStmt:
+		// nothing to do
+
 	case *LabeledStmt:
 		walkIdent(v, n.Label);
 		Walk(v, n.Stmt);
@@ -252,7 +271,6 @@ func Walk(v Visitor, node interface{}) {
 		}
 		walkCommentGroup(v, n.Comment);
 
-		
 	case *ValueSpec:
 		walkCommentGroup(v, n.Doc);
 		walkIdentList(v, n.Names);
@@ -266,6 +284,9 @@ func Walk(v Visitor, node interface{}) {
 		Walk(v, n.Type);
 		walkCommentGroup(v, n.Comment);
 
+	case *BadDecl:
+		// nothing to do
+
 	case *GenDecl:
 		walkCommentGroup(v, n.Doc);
 		for _, s := range n.Specs {
@@ -278,7 +299,9 @@ func Walk(v Visitor, node interface{}) {
 			Walk(v, n.Recv);
 		}
 		walkIdent(v, n.Name);
+		if n.Type != nil {
 			Walk(v, n.Type);
+		}
 		walkBlockStmt(v, n.Body);
 
 	// Files and packages