From 571a56ba783fe6ec6c9f3aa12166e8e33652e4c5 Mon Sep 17 00:00:00 2001
From: Caleb Spare <cespare@gmail.com>
Date: Wed, 22 Feb 2023 14:28:49 -0800
Subject: [PATCH] Remove purego fallbacks (#325)

Having go-cmp panic when using the purego build tag makes it hard to use
go-cmp for testing packages that themselves have purego fallbacks.

Since go-cmp can't implement its functionality without unsafe (the
"fallback" panics) and since environments that prohibit unsafe are much
less common these days anyway, simply remove purego code entirely.

Fixes #283.
---
 cmp/{export_unsafe.go => export.go}           |  5 ---
 cmp/export_panic.go                           | 16 ---------
 .../value/{pointer_unsafe.go => pointer.go}   |  3 --
 cmp/internal/value/pointer_purego.go          | 34 -------------------
 cmp/options.go                                |  3 --
 cmp/report_reflect.go                         |  2 +-
 6 files changed, 1 insertion(+), 62 deletions(-)
 rename cmp/{export_unsafe.go => export.go} (94%)
 delete mode 100644 cmp/export_panic.go
 rename cmp/internal/value/{pointer_unsafe.go => pointer.go} (95%)
 delete mode 100644 cmp/internal/value/pointer_purego.go

diff --git a/cmp/export_unsafe.go b/cmp/export.go
similarity index 94%
rename from cmp/export_unsafe.go
rename to cmp/export.go
index e2c0f74..29f82fe 100644
--- a/cmp/export_unsafe.go
+++ b/cmp/export.go
@@ -2,9 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !purego
-// +build !purego
-
 package cmp
 
 import (
@@ -12,8 +9,6 @@ import (
 	"unsafe"
 )
 
-const supportExporters = true
-
 // retrieveUnexportedField uses unsafe to forcibly retrieve any field from
 // a struct such that the value has read-write permissions.
 //
diff --git a/cmp/export_panic.go b/cmp/export_panic.go
deleted file mode 100644
index ae851fe..0000000
--- a/cmp/export_panic.go
+++ /dev/null
@@ -1,16 +0,0 @@
-// Copyright 2017, 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.
-
-//go:build purego
-// +build purego
-
-package cmp
-
-import "reflect"
-
-const supportExporters = false
-
-func retrieveUnexportedField(reflect.Value, reflect.StructField, bool) reflect.Value {
-	panic("no support for forcibly accessing unexported fields")
-}
diff --git a/cmp/internal/value/pointer_unsafe.go b/cmp/internal/value/pointer.go
similarity index 95%
rename from cmp/internal/value/pointer_unsafe.go
rename to cmp/internal/value/pointer.go
index 16e6860..e5dfff6 100644
--- a/cmp/internal/value/pointer_unsafe.go
+++ b/cmp/internal/value/pointer.go
@@ -2,9 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !purego
-// +build !purego
-
 package value
 
 import (
diff --git a/cmp/internal/value/pointer_purego.go b/cmp/internal/value/pointer_purego.go
deleted file mode 100644
index 1a71bfc..0000000
--- a/cmp/internal/value/pointer_purego.go
+++ /dev/null
@@ -1,34 +0,0 @@
-// Copyright 2018, 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.
-
-//go:build purego
-// +build purego
-
-package value
-
-import "reflect"
-
-// Pointer is an opaque typed pointer and is guaranteed to be comparable.
-type Pointer struct {
-	p uintptr
-	t reflect.Type
-}
-
-// PointerOf returns a Pointer from v, which must be a
-// reflect.Ptr, reflect.Slice, or reflect.Map.
-func PointerOf(v reflect.Value) Pointer {
-	// NOTE: Storing a pointer as an uintptr is technically incorrect as it
-	// assumes that the GC implementation does not use a moving collector.
-	return Pointer{v.Pointer(), v.Type()}
-}
-
-// IsNil reports whether the pointer is nil.
-func (p Pointer) IsNil() bool {
-	return p.p == 0
-}
-
-// Uintptr returns the pointer as a uintptr.
-func (p Pointer) Uintptr() uintptr {
-	return p.p
-}
diff --git a/cmp/options.go b/cmp/options.go
index 1f9ca9c..62d8bdb 100644
--- a/cmp/options.go
+++ b/cmp/options.go
@@ -403,9 +403,6 @@ func (cm comparer) String() string {
 // In other cases, the cmpopts.IgnoreUnexported option can be used to ignore
 // all unexported fields on specified struct types.
 func Exporter(f func(reflect.Type) bool) Option {
-	if !supportExporters {
-		panic("Exporter is not supported on purego builds")
-	}
 	return exporter(f)
 }
 
diff --git a/cmp/report_reflect.go b/cmp/report_reflect.go
index 2ab41fa..e39f422 100644
--- a/cmp/report_reflect.go
+++ b/cmp/report_reflect.go
@@ -199,7 +199,7 @@ func (opts formatOptions) FormatValue(v reflect.Value, parentKind reflect.Kind,
 				break
 			}
 			sf := t.Field(i)
-			if supportExporters && !isExported(sf.Name) {
+			if !isExported(sf.Name) {
 				vv = retrieveUnexportedField(v, sf, true)
 			}
 			s := opts.WithTypeMode(autoType).FormatValue(vv, t.Kind(), ptrs)