2 files changed, 19 insertions, 6 deletions
diff --git a/vendor/golang.org/x/tools/go/ast/astutil/enclosing.go b/vendor/golang.org/x/tools/go/ast/astutil/enclosing.go
index 6e34df461..89f5097be 100644
--- a/vendor/golang.org/x/tools/go/ast/astutil/enclosing.go
+++ b/vendor/golang.org/x/tools/go/ast/astutil/enclosing.go
@@ -207,6 +207,9 @@ func childrenOf(n ast.Node) []ast.Node {
 		return false // no recursion
 	})
 
+	// TODO(adonovan): be more careful about missing (!Pos.Valid)
+	// tokens in trees produced from invalid input.
+
 	// Then add fake Nodes for bare tokens.
 	switch n := n.(type) {
 	case *ast.ArrayType:
@@ -226,9 +229,12 @@ func childrenOf(n ast.Node) []ast.Node {
 		children = append(children, tok(n.OpPos, len(n.Op.String())))
 
 	case *ast.BlockStmt:
-		children = append(children,
-			tok(n.Lbrace, len("{")),
-			tok(n.Rbrace, len("}")))
+		if n.Lbrace.IsValid() {
+			children = append(children, tok(n.Lbrace, len("{")))
+		}
+		if n.Rbrace.IsValid() {
+			children = append(children, tok(n.Rbrace, len("}")))
+		}
 
 	case *ast.BranchStmt:
 		children = append(children,
@@ -304,9 +310,12 @@ func childrenOf(n ast.Node) []ast.Node {
 		// TODO(adonovan): Field.{Doc,Comment,Tag}?
 
 	case *ast.FieldList:
-		children = append(children,
-			tok(n.Opening, len("(")), // or len("[")
-			tok(n.Closing, len(")"))) // or len("]")
+		if n.Opening.IsValid() {
+			children = append(children, tok(n.Opening, len("(")))
+		}
+		if n.Closing.IsValid() {
+			children = append(children, tok(n.Closing, len(")")))
+		}
 
 	case *ast.File:
 		// TODO test: Doc
diff --git a/vendor/golang.org/x/tools/go/ast/astutil/rewrite.go b/vendor/golang.org/x/tools/go/ast/astutil/rewrite.go
index 5c8dbbb7a..4ad054930 100644
--- a/vendor/golang.org/x/tools/go/ast/astutil/rewrite.go
+++ b/vendor/golang.org/x/tools/go/ast/astutil/rewrite.go
@@ -67,6 +67,10 @@ var abort = new(int) // singleton, to signal termination of Apply
 //
 // The methods Replace, Delete, InsertBefore, and InsertAfter
 // can be used to change the AST without disrupting Apply.
+//
+// This type is not to be confused with [inspector.Cursor] from
+// package [golang.org/x/tools/go/ast/inspector], which provides
+// stateless navigation of immutable syntax trees.
 type Cursor struct {
 	parent ast.Node
 	name   string