From 26e605b3684adf77b420cdfc1838f94fb00712bf Mon Sep 17 00:00:00 2001
From: Joe Tsai <joetsai@digital-static.net>
Date: Tue, 7 Dec 2021 12:05:48 -0800
Subject: [PATCH] Drop hacks to work around Go reflection bugs in Go1.9

Now that Go 1.11 is the minimally supported version,
we can drop some local hacks to work around bugs in
reflect that were present in Go1.9.
---
 cmp/compare.go                         | 17 -----------------
 cmp/compare_test.go                    | 14 ++------------
 cmp/internal/flags/toolchain_legacy.go | 10 ----------
 cmp/internal/flags/toolchain_recent.go | 10 ----------
 4 files changed, 2 insertions(+), 49 deletions(-)
 delete mode 100644 cmp/internal/flags/toolchain_legacy.go
 delete mode 100644 cmp/internal/flags/toolchain_recent.go

diff --git a/cmp/compare.go b/cmp/compare.go
index 86d0903..2a54467 100644
--- a/cmp/compare.go
+++ b/cmp/compare.go
@@ -36,7 +36,6 @@ import (
 	"strings"
 
 	"github.com/google/go-cmp/cmp/internal/diff"
-	"github.com/google/go-cmp/cmp/internal/flags"
 	"github.com/google/go-cmp/cmp/internal/function"
 	"github.com/google/go-cmp/cmp/internal/value"
 )
@@ -319,7 +318,6 @@ func (s *state) tryMethod(t reflect.Type, vx, vy reflect.Value) bool {
 }
 
 func (s *state) callTRFunc(f, v reflect.Value, step Transform) reflect.Value {
-	v = sanitizeValue(v, f.Type().In(0))
 	if !s.dynChecker.Next() {
 		return f.Call([]reflect.Value{v})[0]
 	}
@@ -343,8 +341,6 @@ func (s *state) callTRFunc(f, v reflect.Value, step Transform) reflect.Value {
 }
 
 func (s *state) callTTBFunc(f, x, y reflect.Value) bool {
-	x = sanitizeValue(x, f.Type().In(0))
-	y = sanitizeValue(y, f.Type().In(1))
 	if !s.dynChecker.Next() {
 		return f.Call([]reflect.Value{x, y})[0].Bool()
 	}
@@ -372,19 +368,6 @@ func detectRaces(c chan<- reflect.Value, f reflect.Value, vs ...reflect.Value) {
 	ret = f.Call(vs)[0]
 }
 
-// sanitizeValue converts nil interfaces of type T to those of type R,
-// assuming that T is assignable to R.
-// Otherwise, it returns the input value as is.
-func sanitizeValue(v reflect.Value, t reflect.Type) reflect.Value {
-	// TODO(≥go1.10): Workaround for reflect bug (https://golang.org/issue/22143).
-	if !flags.AtLeastGo110 {
-		if v.Kind() == reflect.Interface && v.IsNil() && v.Type() != t {
-			return reflect.New(t).Elem()
-		}
-	}
-	return v
-}
-
 func (s *state) compareStruct(t reflect.Type, vx, vy reflect.Value) {
 	var addr bool
 	var vax, vay reflect.Value // Addressable versions of vx and vy
diff --git a/cmp/compare_test.go b/cmp/compare_test.go
index c7a409d..9ad9456 100644
--- a/cmp/compare_test.go
+++ b/cmp/compare_test.go
@@ -1447,14 +1447,6 @@ func embeddedTests() []test {
 		return s
 	}
 
-	// TODO(≥go1.10): Workaround for reflect bug (https://golang.org/issue/21122).
-	wantPanicNotGo110 := func(s string) string {
-		if !flags.AtLeastGo110 {
-			return ""
-		}
-		return s
-	}
-
 	return []test{{
 		label:     label + "/ParentStructA/PanicUnexported1",
 		x:         ts.ParentStructA{},
@@ -1745,8 +1737,7 @@ func embeddedTests() []test {
 		label:     label + "/ParentStructG/PanicUnexported1",
 		x:         ts.ParentStructG{},
 		y:         ts.ParentStructG{},
-		wantPanic: wantPanicNotGo110("cannot handle unexported field"),
-		wantEqual: !flags.AtLeastGo110,
+		wantPanic: "cannot handle unexported field",
 		reason:    "ParentStructG has unexported fields",
 	}, {
 		label: label + "/ParentStructG/Ignored",
@@ -1836,8 +1827,7 @@ func embeddedTests() []test {
 		label:     label + "/ParentStructI/PanicUnexported1",
 		x:         ts.ParentStructI{},
 		y:         ts.ParentStructI{},
-		wantPanic: wantPanicNotGo110("cannot handle unexported field"),
-		wantEqual: !flags.AtLeastGo110,
+		wantPanic: "cannot handle unexported field",
 		reason:    "ParentStructI has unexported fields",
 	}, {
 		label: label + "/ParentStructI/Ignored1",
diff --git a/cmp/internal/flags/toolchain_legacy.go b/cmp/internal/flags/toolchain_legacy.go
deleted file mode 100644
index 82d1d7f..0000000
--- a/cmp/internal/flags/toolchain_legacy.go
+++ /dev/null
@@ -1,10 +0,0 @@
-// Copyright 2019, 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.
-
-// +build !go1.10
-
-package flags
-
-// AtLeastGo110 reports whether the Go toolchain is at least Go 1.10.
-const AtLeastGo110 = false
diff --git a/cmp/internal/flags/toolchain_recent.go b/cmp/internal/flags/toolchain_recent.go
deleted file mode 100644
index 8646f05..0000000
--- a/cmp/internal/flags/toolchain_recent.go
+++ /dev/null
@@ -1,10 +0,0 @@
-// Copyright 2019, 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.
-
-// +build go1.10
-
-package flags
-
-// AtLeastGo110 reports whether the Go toolchain is at least Go 1.10.
-const AtLeastGo110 = true