test: new test for issue 30862

New test case, inspired by gccgo issue 30862.

Updates #30862.

Change-Id: I5e494b877e4fd142b8facb527471fe1fdef39c61
Reviewed-on: https://go-review.googlesource.com/c/go/+/167744
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

test/fixedbugs/issue30862.dir/a.go

+// 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.
+
+package a
+
+var pl int
+
+type NoitfStruct struct {
+	F int
+	G int
+}
+
+//go:nointerface
+func (t *NoitfStruct) NoInterfaceMethod() {}

test/fixedbugs/issue30862.dir/b.go

+// 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.
+
+package b
+
+import "./a"
+
+type EmbedImported struct {
+	a.NoitfStruct
+}
+
+func Test() []string {
+	bad := []string{}
+	x := interface{}(new(a.NoitfStruct))
+	if _, ok := x.(interface {
+		NoInterfaceMethod()
+	}); ok {
+		bad = append(bad, "fail 1")
+	}
+
+	x = interface{}(new(EmbedImported))
+	if _, ok := x.(interface {
+		NoInterfaceMethod()
+	}); ok {
+		bad = append(bad, "fail 2")
+	}
+	return bad
+}

test/fixedbugs/issue30862.dir/main.go

+// 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.
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"./b"
+)
+
+// Test case for issue 30862.
+
+// Be aware that unless GOEXPERIMENT=fieldtrack is set when building
+// the compiler, this test will fail if executed with a regular GC
+// compiler.
+
+func main() {
+	bad := b.Test()
+	if len(bad) > 0 {
+		for _, s := range bad {
+			fmt.Fprintf(os.Stderr, "test failed: %s\n", s)
+		}
+		os.Exit(1)
+	}
+}

test/fixedbugs/issue30862.go

+// rundir
+
+// 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.
+
+// Test case for issue 30862.  This test as written will
+// fail for the main 'gc' compiler unless GOEXPERIMENT=fieldtrack
+// is set when building it, whereas gccgo has field tracking
+// enabled by default (hence the build tag below).
+
+// +build gccgo
+
+package ignored