2 files changed, 21 insertions, 0 deletions
diff --git a/src/encoding/json/v2/fields.go b/src/encoding/json/v2/fields.go
index 9413189c08..4a02be7327 100644
--- a/src/encoding/json/v2/fields.go
+++ b/src/encoding/json/v2/fields.go
@@ -404,6 +404,7 @@ type fieldOptions struct {
 // the JSON member name and other features.
 func parseFieldOptions(sf reflect.StructField) (out fieldOptions, ignored bool, err error) {
 	tag, hasTag := sf.Tag.Lookup("json")
+	tagOrig := tag
 
 	// Check whether this field is explicitly ignored.
 	if tag == "-" {
@@ -453,6 +454,13 @@ func parseFieldOptions(sf reflect.StructField) (out fieldOptions, ignored bool,
 			err = cmp.Or(err, fmt.Errorf("Go struct field %s has JSON object name %q with invalid UTF-8", sf.Name, name))
 			name = string([]rune(name)) // replace invalid UTF-8 with utf8.RuneError
 		}
+		if name == "-" && tag[0] == '-' {
+			defer func() { // defer to let other errors take precedence
+				err = cmp.Or(err, fmt.Errorf("Go struct field %s has JSON object name %q; either "+
+					"use `json:\"-\"` to ignore the field or "+
+					"use `json:\"'-'%s` to specify %q as the name", sf.Name, out.name, strings.TrimPrefix(strconv.Quote(tagOrig), `"-`), name))
+			}()
+		}
 		if err2 == nil {
 			out.hasName = true
 			out.name = name
diff --git a/src/encoding/json/v2/fields_test.go b/src/encoding/json/v2/fields_test.go
index 1c36f80905..ae58182f29 100644
--- a/src/encoding/json/v2/fields_test.go
+++ b/src/encoding/json/v2/fields_test.go
@@ -503,6 +503,19 @@ func TestParseTagOptions(t *testing.T) {
 		wantOpts: fieldOptions{hasName: true, name: "-", quotedName: `"-"`},
 		wantErr:  errors.New("Go struct field V has malformed `json` tag: invalid trailing ',' character"),
 	}, {
+		name: jsontest.Name("DashCommaOmitEmpty"),
+		in: struct {
+			V int `json:"-,omitempty"`
+		}{},
+		wantOpts: fieldOptions{hasName: true, name: "-", quotedName: `"-"`, omitempty: true},
+		wantErr:  errors.New("Go struct field V has JSON object name \"-\"; either use `json:\"-\"` to ignore the field or use `json:\"'-',omitempty\"` to specify \"-\" as the name"),
+	}, {
+		name: jsontest.Name("QuotedDashCommaOmitEmpty"),
+		in: struct {
+			V int `json:"'-',omitempty"`
+		}{},
+		wantOpts: fieldOptions{hasName: true, name: "-", quotedName: `"-"`, omitempty: true},
+	}, {
 		name: jsontest.Name("QuotedDashName"),
 		in: struct {
 			V int `json:"'-'"`