From 44d3f89e99b954d88ab802212182a7c123ac774a Mon Sep 17 00:00:00 2001
From: David Crawshaw <crawshaw@golang.org>
Date: Tue, 22 Mar 2016 21:25:40 -0400
Subject: [PATCH] cmd/link, reflect: remove some method type data

Remove reflect type information for unexported methods that do not
satisfy any interface in the program.

Ideally the unexported method would not appear in the method list at
all, but that is tricky because the slice is built by the compiler.

Reduces binary size:

	cmd/go: 81KB (0.8%)
	jujud: 258KB (0.4%)

For #6853.

Change-Id: I25ef8df6907e9ac03b18689d584ea46e7d773043
Reviewed-on: https://go-review.googlesource.com/21033
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
---
 src/cmd/link/internal/ld/deadcode.go | 11 ----------
 src/reflect/all_test.go              | 26 ++++++++++++++++++++++++
 src/reflect/type.go                  | 30 +++++++++++++++-------------
 3 files changed, 42 insertions(+), 25 deletions(-)

diff --git a/src/cmd/link/internal/ld/deadcode.go b/src/cmd/link/internal/ld/deadcode.go
index 900364cdfb..f99f5e8984 100644
--- a/src/cmd/link/internal/ld/deadcode.go
+++ b/src/cmd/link/internal/ld/deadcode.go
@@ -86,17 +86,6 @@ func deadcode(ctxt *Link) {
 		for _, m := range d.markableMethods {
 			if (reflectSeen && m.isExported()) || d.ifaceMethod[m.m] {
 				d.markMethod(m)
-			} else if reflectSeen {
-				// This ensures the Type and Func fields of
-				// reflect.Method are filled as they were in
-				// Go 1.
-				//
-				// An argument could be made for changing this
-				// and setting those fields to nil. Doing so
-				// would reduce the binary size of typical
-				// programs like cmd/go by ~2%.
-				d.mark(m.mtyp(), m.src)
-				rem = append(rem, m)
 			} else {
 				rem = append(rem, m)
 			}
diff --git a/src/reflect/all_test.go b/src/reflect/all_test.go
index e5326a673a..bb4592b332 100644
--- a/src/reflect/all_test.go
+++ b/src/reflect/all_test.go
@@ -2367,6 +2367,32 @@ func TestNestedMethods(t *testing.T) {
 	}
 }
 
+type unexp struct{}
+
+func (*unexp) f() (int32, int8) { return 7, 7 }
+func (*unexp) g() (int64, int8) { return 8, 8 }
+
+func TestUnexportedMethods(t *testing.T) {
+	_ = (interface {
+		f() (int32, int8)
+	})(new(unexp))
+
+	typ := TypeOf(new(unexp))
+
+	if typ.Method(0).Type == nil {
+		t.Error("missing type for satisfied method 'f'")
+	}
+	if !typ.Method(0).Func.IsValid() {
+		t.Error("missing func for satisfied method 'f'")
+	}
+	if typ.Method(1).Type != nil {
+		t.Error("found type for unsatisfied method 'g'")
+	}
+	if typ.Method(1).Func.IsValid() {
+		t.Error("found func for unsatisfied method 'g'")
+	}
+}
+
 type InnerInt struct {
 	X int
 }
diff --git a/src/reflect/type.go b/src/reflect/type.go
index 736c0824cb..41e378911d 100644
--- a/src/reflect/type.go
+++ b/src/reflect/type.go
@@ -591,20 +591,22 @@ func (t *rtype) Method(i int) (m Method) {
 		m.PkgPath = *p.pkgPath
 		fl |= flagStickyRO
 	}
-	ft := (*funcType)(unsafe.Pointer(p.mtyp))
-	in := make([]Type, 0, 1+len(ft.in()))
-	in = append(in, t)
-	for _, arg := range ft.in() {
-		in = append(in, arg)
-	}
-	out := make([]Type, 0, len(ft.out()))
-	for _, ret := range ft.out() {
-		out = append(out, ret)
-	}
-	mt := FuncOf(in, out, p.mtyp.IsVariadic())
-	m.Type = mt
-	fn := unsafe.Pointer(&p.tfn)
-	m.Func = Value{mt.(*rtype), fn, fl}
+	if p.mtyp != nil {
+		ft := (*funcType)(unsafe.Pointer(p.mtyp))
+		in := make([]Type, 0, 1+len(ft.in()))
+		in = append(in, t)
+		for _, arg := range ft.in() {
+			in = append(in, arg)
+		}
+		out := make([]Type, 0, len(ft.out()))
+		for _, ret := range ft.out() {
+			out = append(out, ret)
+		}
+		mt := FuncOf(in, out, p.mtyp.IsVariadic())
+		m.Type = mt
+		fn := unsafe.Pointer(&p.tfn)
+		m.Func = Value{mt.(*rtype), fn, fl}
+	}
 	m.Index = i
 	return m
 }
-- 
2.48.1