From bf418db782d82fa48d04ffe9ce03c860089c7014 Mon Sep 17 00:00:00 2001
From: tdakkota <tanc13@yandex.ru>
Date: Sun, 28 Jun 2020 23:28:08 +0300
Subject: [PATCH] =?UTF-8?q?[dev.go2go]=20go/types:=20fix=20type=20check=20?=
 =?UTF-8?q?skipping=20for=20constraints=20when=20there=E2=80=99s=20more=20?=
 =?UTF-8?q?than=20one=20generic=20constraint.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Fixes #39754.
---
 src/go/types/check_test.go            |  1 +
 src/go/types/fixedbugs/issue39754.go2 | 25 +++++++++++++++++++++++++
 src/go/types/subst.go                 |  2 +-
 3 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 src/go/types/fixedbugs/issue39754.go2

diff --git a/src/go/types/check_test.go b/src/go/types/check_test.go
index 4065fb124e..cf5798d6d1 100644
--- a/src/go/types/check_test.go
+++ b/src/go/types/check_test.go
@@ -130,6 +130,7 @@ var tests = [][]string{
 	{"fixedbugs/issue39680.go2"},
 	{"fixedbugs/issue39711.go2"},
 	{"fixedbugs/issue39723.go2"},
+	{"fixedbugs/issue39754.go2"},
 	{"fixedbugs/issue39755.go2"},
 	{"fixedbugs/issue39768.go2"},
 }
diff --git a/src/go/types/fixedbugs/issue39754.go2 b/src/go/types/fixedbugs/issue39754.go2
new file mode 100644
index 0000000000..64ce3049ff
--- /dev/null
+++ b/src/go/types/fixedbugs/issue39754.go2
@@ -0,0 +1,25 @@
+// Copyright 2020 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 Optional(type T) struct {
+	p   T
+	set bool
+}
+
+func (o Optional(T)) Val() (T, bool) {
+	return o.p, true
+}
+
+type Box(type T) interface {
+	Val() (T, bool)
+}
+
+func F1(type V interface{}, A, B Box(V))() {}
+
+func main() {
+    F1(int, Optional(int), Optional(int))()
+	F1(int, Optional(int), Optional(string) /* ERROR "does not satisfy Box(V) (missing method Val)" */)()
+}
\ No newline at end of file
diff --git a/src/go/types/subst.go b/src/go/types/subst.go
index 64418bfed6..47622b7c39 100644
--- a/src/go/types/subst.go
+++ b/src/go/types/subst.go
@@ -177,7 +177,7 @@ func (check *Checker) instantiate(pos token.Pos, typ Type, targs []Type, poslist
 
 		// targ's underlying type must also be one of the interface types listed, if any
 		if iface.allTypes == nil {
-			break // nothing to do
+			continue // nothing to do
 		}
 		// iface.allTypes != nil