Revert "encoding/json: implement Is on all errors"

This reverts CL 254537.

Reason for revert: Reason for revert: The recommended way to check for a type of error is errors.As. API changes should also start with a proposal.

Change-Id: I07c37428575e99c80b17525833a61831d10963bb
Reviewed-on: https://go-review.googlesource.com/c/go/+/254857
Trust: Damien Neil <dneil@google.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

1 files changed, 1 insertions, 23 deletions

diff --git a/src/encoding/json/encode_test.go b/src/encoding/json/encode_test.go
index 90826a7f47..7290eca06f 100644
--- a/src/encoding/json/encode_test.go
+++ b/src/encoding/json/encode_test.go
@@ -7,7 +7,6 @@ package json
 import (
 	"bytes"
 	"encoding"
-	"errors"
 	"fmt"
 	"log"
 	"math"
@@ -212,7 +211,7 @@ var unsupportedValues = []interface{}{
 func TestUnsupportedValues(t *testing.T) {
 	for _, v := range unsupportedValues {
 		if _, err := Marshal(v); err != nil {
-			if !errors.Is(err, &UnsupportedValueError{}) {
+			if _, ok := err.(*UnsupportedValueError); !ok {
 				t.Errorf("for %v, got %T want UnsupportedValueError", v, err)
 			}
 		} else {
@@ -1156,24 +1155,3 @@ func TestMarshalerError(t *testing.T) {
 		}
 	}
 }
-
-func TestMarshalerErrorIs(t *testing.T) {
-	err := fmt.Errorf("apackage: %w: failed to parse struct", &MarshalerError{
-		reflect.TypeOf("a"),
-		fmt.Errorf("something"),
-		"TestMarshalerErrorIs",
-	})
-	if !errors.Is(err, &MarshalerError{}) {
-		t.Fatalf("%v should be unwrapped to a MarshalerError", err)
-	}
-}
-
-func TestUnsupportedValueErrorIs(t *testing.T) {
-	err := fmt.Errorf("apackage: %w: failed to parse struct", &UnsupportedValueError{
-		Value: reflect.Value{},
-		Str:   "Foo",
-	})
-	if !errors.Is(err, &UnsupportedValueError{}) {
-		t.Fatalf("%v should be unwrapped to a UnsupportedValueError", err)
-	}
-}