[dev.typeparams] test: add regression test for go/defer wrapper

CL 330330 moved logic for wrapping go/defer from order to esacpe
analysis. It introduced a bug involves go/defer statement with ABI0
functions.

Consider this following code:

	package p

	//go:cgo_unsafe_args
	func g(*int) (r1 struct{}) {
		return
	}

	func f() {
		defer g(new(int))
	}

g is a cgo-like generated function with ABI0. While compiling g, we set
the offset per ABI0.

The function f is rewritten into:

	func f() {
		_0, _1 := g, new(int)
		defer func() { _0(_1) }()
	}

The temporary _0 hold function value with the same type as g, but with
class PAUTO. Thus ssagen/ssa.go:state.call cannot handle it and use
ABIDefault to set the offset, causes the offset of r1 changed

CL 330332 intended to optimize code generated for wrapping function, by
rewriting the wrapper function into:

	func f() {
		_0 := new(int)
		defer func() { g(_0) }()
	}

So it fixed the bug unintentionally.

This CL add regression test for this bug, and also add a comment to
explain while not wrapping declared function is important.

Updates #47227

Change-Id: I75c83d1d9cc7fd4699e6b218a295d0c0a10ef471
Reviewed-on: https://go-review.googlesource.com/c/go/+/334882
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>

1 files changed, 23 insertions, 0 deletions

diff --git a/test/fixedbugs/issue47227.go b/test/fixedbugs/issue47227.go
new file mode 100644
index 0000000000..a14efc9a68
--- /dev/null
+++ b/test/fixedbugs/issue47227.go
@@ -0,0 +1,23 @@
+// run fake-arg-to-force-use-of-go-run
+
+// 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.
+
+//go:build cgo
+// +build cgo
+
+package main
+
+// void f(int *p) { *p = 0x12345678; }
+import "C"
+
+func main() {
+	var x C.int
+	func() {
+		defer C.f(&x)
+	}()
+	if x != 0x12345678 {
+		panic("FAIL")
+	}
+}