3 files changed, 107 insertions, 0 deletions
diff --git a/src/errors/errors.go b/src/errors/errors.go
new file mode 100644
index 000000000..3085a7962
--- /dev/null
+++ b/src/errors/errors.go
@@ -0,0 +1,20 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package errors implements functions to manipulate errors.
+package errors
+
+// New returns an error that formats as the given text.
+func New(text string) error {
+	return &errorString{text}
+}
+
+// errorString is a trivial implementation of error.
+type errorString struct {
+	s string
+}
+
+func (e *errorString) Error() string {
+	return e.s
+}
diff --git a/src/errors/errors_test.go b/src/errors/errors_test.go
new file mode 100644
index 000000000..63c05d718
--- /dev/null
+++ b/src/errors/errors_test.go
@@ -0,0 +1,53 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package errors_test
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+)
+
+func TestNewEqual(t *testing.T) {
+	// Different allocations should not be equal.
+	if errors.New("abc") == errors.New("abc") {
+		t.Errorf(`New("abc") == New("abc")`)
+	}
+	if errors.New("abc") == errors.New("xyz") {
+		t.Errorf(`New("abc") == New("xyz")`)
+	}
+
+	// Same allocation should be equal to itself (not crash).
+	err := errors.New("jkl")
+	if err != err {
+		t.Errorf(`err != err`)
+	}
+}
+
+func TestErrorMethod(t *testing.T) {
+	err := errors.New("abc")
+	if err.Error() != "abc" {
+		t.Errorf(`New("abc").Error() = %q, want %q`, err.Error(), "abc")
+	}
+}
+
+func ExampleNew() {
+	err := errors.New("emit macho dwarf: elf header corrupted")
+	if err != nil {
+		fmt.Print(err)
+	}
+	// Output: emit macho dwarf: elf header corrupted
+}
+
+// The fmt package's Errorf function lets us use the package's formatting
+// features to create descriptive error messages.
+func ExampleNew_errorf() {
+	const name, id = "bimmler", 17
+	err := fmt.Errorf("user %q (id %d) not found", name, id)
+	if err != nil {
+		fmt.Print(err)
+	}
+	// Output: user "bimmler" (id 17) not found
+}
diff --git a/src/errors/example_test.go b/src/errors/example_test.go
new file mode 100644
index 000000000..0e86828f4
--- /dev/null
+++ b/src/errors/example_test.go
@@ -0,0 +1,34 @@
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package errors_test
+
+import (
+	"fmt"
+	"time"
+)
+
+// MyError is an error implementation that includes a time and message.
+type MyError struct {
+	When time.Time
+	What string
+}
+
+func (e MyError) Error() string {
+	return fmt.Sprintf("%v: %v", e.When, e.What)
+}
+
+func oops() error {
+	return MyError{
+		time.Date(1989, 3, 15, 22, 30, 0, 0, time.UTC),
+		"the file system has gone away",
+	}
+}
+
+func Example() {
+	if err := oops(); err != nil {
+		fmt.Println(err)
+	}
+	// Output: 1989-03-15 22:30:00 +0000 UTC: the file system has gone away
+}