errors, fmt: revert rejected changes for Go 1.13

Reverts the following changes:

  https://go.googlesource.com/go/+/1f90d081391d4f5911960fd28d81d7ea5e554a8f
  https://go.googlesource.com/go/+/8bf18b56a47a98b9dd2fa03beb358312237a8c76
  https://go.googlesource.com/go/+/5402854c3557f87fa2741a52ffc15dfb1ef333cc
  https://go.googlesource.com/go/+/37f84817247d3b8e687a701ccb0d6bc7ffe3cb78
  https://go.googlesource.com/go/+/6be6f114e0d483a233101a67c9644cd72bd3ae7a

Partially reverts the followinng change, removing the errors.Opaque
function and the errors.Wrapper type definition:

  https://go.googlesource.com/go/+/62f5e8156ef56fa61e6af56f4ccc633bde1a9120

Updates documentation referencing the Wrapper type.

Change-Id: Ia622883e39cafb06809853e3fd90b21441124534
Reviewed-on: https://go-review.googlesource.com/c/go/+/176997
Run-TryBot: Damien Neil <dneil@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>

1 files changed, 2 insertions, 32 deletions

diff --git a/src/errors/errors.go b/src/errors/errors.go
index 51175b13c8..b8a46921be 100644
--- a/src/errors/errors.go
+++ b/src/errors/errors.go
@@ -5,46 +5,16 @@
 // Package errors implements functions to manipulate errors.
 package errors
 
-import (
-	"internal/errinternal"
-	"runtime"
-)
-
 // New returns an error that formats as the given text.
-//
-// The returned error contains a Frame set to the caller's location and
-// implements Formatter to show this information when printed with details.
 func New(text string) error {
-	// Inline call to errors.Callers to improve performance.
-	var s Frame
-	runtime.Callers(2, s.frames[:])
-	return &errorString{text, nil, s}
-}
-
-func init() {
-	errinternal.NewError = func(text string, err error) error {
-		var s Frame
-		runtime.Callers(3, s.frames[:])
-		return &errorString{text, err, s}
-	}
+	return &errorString{text}
 }
 
 // errorString is a trivial implementation of error.
 type errorString struct {
-	s     string
-	err   error
-	frame Frame
+	s string
 }
 
 func (e *errorString) Error() string {
-	if e.err != nil {
-		return e.s + ": " + e.err.Error()
-	}
 	return e.s
 }
-
-func (e *errorString) FormatError(p Printer) (next error) {
-	p.Print(e.s)
-	e.frame.Format(p)
-	return e.err
-}