fmt: make type of fmt.Errorf the same as that of errors.New

This applies only for cases where %w is not used.

The purpose of this change is to reduce test failures where tests
depend on these two being the same type, as they previously were.

Change-Id: I2dd28b93fe1d59f3cfbb4eb0875d1fb8ee699746
Reviewed-on: https://go-review.googlesource.com/c/go/+/167402
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>

2 files changed, 18 insertions, 2 deletions

diff --git a/src/fmt/errors.go b/src/fmt/errors.go
index 7506b6a20b..06416425c3 100644
--- a/src/fmt/errors.go
+++ b/src/fmt/errors.go
@@ -6,6 +6,7 @@ package fmt
 
 import (
 	"errors"
+	"internal/errinternal"
 	"strings"
 )
 
@@ -21,7 +22,7 @@ import (
 func Errorf(format string, a ...interface{}) error {
 	err, wrap := lastError(format, a)
 	if err == nil {
-		return &noWrapError{Sprintf(format, a...), nil, errors.Caller(1)}
+		return errinternal.NewError(Sprintf(format, a...), nil)
 	}
 
 	// TODO: this is not entirely correct. The error value could be
@@ -33,7 +34,7 @@ func Errorf(format string, a ...interface{}) error {
 	if wrap {
 		return &wrapError{msg, err, errors.Caller(1)}
 	}
-	return &noWrapError{msg, err, errors.Caller(1)}
+	return errinternal.NewError(msg, err)
 }
 
 func lastError(format string, a []interface{}) (err error, wrap bool) {
diff --git a/src/fmt/errors_test.go b/src/fmt/errors_test.go
index a3cd26ef3e..ed77709ea0 100644
--- a/src/fmt/errors_test.go
+++ b/src/fmt/errors_test.go
@@ -378,6 +378,21 @@ func TestErrorFormatter(t *testing.T) {
 	}
 }
 
+func TestSameType(t *testing.T) {
+	err0 := errors.New("inner")
+	want := fmt.Sprintf("%T", err0)
+
+	err := fmt.Errorf("foo: %v", err0)
+	if got := fmt.Sprintf("%T", err); got != want {
+		t.Errorf("got %v; want %v", got, want)
+	}
+
+	err = fmt.Errorf("foo %s", "bar")
+	if got := fmt.Sprintf("%T", err); got != want {
+		t.Errorf("got %v; want %v", got, want)
+	}
+}
+
 var _ errors.Formatter = wrapped{}
 
 type wrapped struct {