test: add regress test for issue 28369

Also gofmt test/escape5.go.

Fixes #28369.

Change-Id: I0a11748fd2b5cf01cb5437ae15827d9db91c0c0d
Reviewed-on: https://go-review.googlesource.com/c/go/+/172358Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

test/escape5.go

@@ -9,7 +9,10 @@
 
 package foo
 
-import "runtime"
+import (
+	"runtime"
+	"unsafe"
+)
 
 func noleak(p *int) int { // ERROR "p does not escape"
 	return *p
@@ -245,3 +248,17 @@ func g29000() {
 	x := 1
 	f29000(2, x) // ERROR "x escapes to heap"
 }
+
+// Issue 28369: taking an address of a parameter and converting it into a uintptr causes an
+// unnecessary escape.
+
+var sink28369 uintptr
+
+func f28369(n int) int {
+	if n == 0 {
+		sink28369 = uintptr(unsafe.Pointer(&n))
+		return n
+	}
+
+	return 1 + f28369(n-1)
+}