misc/cgo/testplugin: add test for issue 18584

Fixes #18584

Change-Id: I5f9428758999cacee49f3449e596e0a88bc06f91
Reviewed-on: https://go-review.googlesource.com/67150
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

misc/cgo/testplugin/src/issue18584/main.go

+// 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.
+
+package main
+
+import "plugin"
+
+func main() {
+	p, err := plugin.Open("plugin.so")
+	if err != nil {
+		panic(err)
+	}
+
+	sym, err := p.Lookup("G")
+	if err != nil {
+		panic(err)
+	}
+	g := sym.(func() bool)
+	if !g() {
+		panic("expected types to match, Issue #18584")
+	}
+}

misc/cgo/testplugin/src/issue18584/plugin.go

+// 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.
+
+package main
+
+import "reflect"
+
+type C struct {
+}
+
+func F(c *C) *C {
+	return nil
+}
+
+func G() bool {
+	var c *C
+	return reflect.TypeOf(F).Out(0) == reflect.TypeOf(c)
+}

misc/cgo/testplugin/test.bash

@@ -15,8 +15,8 @@ goos=$(go env GOOS)
 goarch=$(go env GOARCH)
 
 function cleanup() {
-	rm -f plugin*.so unnamed*.so iface*.so
-	rm -rf host pkg sub iface issue18676 issue19534
+	rm -f plugin*.so unnamed*.so iface*.so issue*
+	rm -rf host pkg sub iface
 }
 trap cleanup EXIT
 
@@ -61,3 +61,8 @@ _timeout 10s ./issue18676
 GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -buildmode=plugin -ldflags='-pluginpath=issue.19534' -o plugin.so src/issue19534/plugin.go
 GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -o issue19534 src/issue19534/main.go
 ./issue19534
+
+# Test for issue 18584
+GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -buildmode=plugin -o plugin.so src/issue18584/plugin.go
+GOPATH=$(pwd) go build -gcflags "$GO_GCFLAGS" -o issue18584 src/issue18584/main.go
+./issue18584