cmd/compile: use t.AllMethods when sorting typesByString

For interface types, t.Methods contains only unexpanded method set, i.e
exclusive of interface embedding. Thus, we can't use it to detect an
interface contains embedding empty interface, like in:

	type EI interface{}

	func f() interface{ EI } {
		return nil
	}

At the time we generate runtime types, we want to check against the full
method set of interface instead.

Fixes #46386

Change-Id: Idff53ad39276be6632eb5932b76e855c15cbdd2e
Reviewed-on: https://go-review.googlesource.com/c/go/+/323649
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

2 files changed, 34 insertions, 2 deletions

diff --git a/src/cmd/compile/internal/reflectdata/reflect.go b/src/cmd/compile/internal/reflectdata/reflect.go
index b3688fca67..e07294be0f 100644
--- a/src/cmd/compile/internal/reflectdata/reflect.go
+++ b/src/cmd/compile/internal/reflectdata/reflect.go
@@ -1475,8 +1475,8 @@ func (a typesByString) Less(i, j int) bool {
 	// will be equal for the above checks, but different in DWARF output.
 	// Sort by source position to ensure deterministic order.
 	// See issues 27013 and 30202.
-	if a[i].t.Kind() == types.TINTER && a[i].t.Methods().Len() > 0 {
-		return a[i].t.Methods().Index(0).Pos.Before(a[j].t.Methods().Index(0).Pos)
+	if a[i].t.Kind() == types.TINTER && a[i].t.AllMethods().Len() > 0 {
+		return a[i].t.AllMethods().Index(0).Pos.Before(a[j].t.AllMethods().Index(0).Pos)
 	}
 	return false
 }
diff --git a/test/fixedbugs/issue46386.go b/test/fixedbugs/issue46386.go
new file mode 100644
index 0000000000..89dea8abf3
--- /dev/null
+++ b/test/fixedbugs/issue46386.go
@@ -0,0 +1,32 @@
+// compile -p=main
+
+// Copyright 2021 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 main
+
+type I interface {
+	M() interface{}
+}
+
+type S1 struct{}
+
+func (S1) M() interface{} {
+	return nil
+}
+
+type EI interface{}
+
+type S struct{}
+
+func (S) M(as interface{ I }) {}
+
+func f() interface{ EI } {
+	return &S1{}
+}
+
+func main() {
+	var i interface{ I }
+	(&S{}).M(i)
+}