diff --git a/src/go/ast/ast.go b/src/go/ast/ast.go
index d73c323178..fd109507b8 100644
--- a/src/go/ast/ast.go
+++ b/src/go/ast/ast.go
@@ -153,10 +153,12 @@ func (g *CommentGroup) Text() string {
 // A Field represents a Field declaration list in a struct type,
 // a method list in an interface type, or a parameter/result declaration
 // in a signature.
+// Field.Names is nil for unnamed parameters (parameter lists which only contain types)
+// and embedded struct fields. In the latter case, the field name is the type name.
 //
 type Field struct {
 	Doc     *CommentGroup // associated documentation; or nil
-	Names   []*Ident      // field/method/parameter names; or nil if anonymous field
+	Names   []*Ident      // field/method/parameter names; or nil
 	Type    Expr          // field/method/parameter type
 	Tag     *BasicLit     // field tag; or nil
 	Comment *CommentGroup // line comments; or nil
@@ -207,14 +209,14 @@ func (f *FieldList) End() token.Pos {
 	return token.NoPos
 }
 
-// NumFields returns the number of (named and anonymous fields) in a FieldList.
+// NumFields returns the number of parameters or struct fields represented by a FieldList.
 func (f *FieldList) NumFields() int {
 	n := 0
 	if f != nil {
 		for _, g := range f.List {
 			m := len(g.Names)
 			if m == 0 {
-				m = 1 // anonymous field
+				m = 1
 			}
 			n += m
 		}