[dev.unified] test: break escape_iface.go into unified/nounified variants

The assignment `sink, *(&ok) = y.(int)` should (and does) escape a
value to the heap, but this detail is missed because the implicit
conversion of the multi-value expression `y.(int)` isn't visible to
escape analysis (because it's not inserted until desugaring during
walk).

For Unified IR, I plan to apply this desugaring earlier (because it's
necessary for correct dictionary handling), which means we'll
now (correctly) report the heap escape.

Due to limitations of the $GOROOT/test harness, the easiest way to
handle that GOEXPERIMENT=unified gets this right while
GOEXPERIMENT=nounified does not is to split the test case into
separate files. Hence this CL.

Change-Id: I91f3a6c015cbc646ab018747e152cac2874cf24c
Reviewed-on: https://go-review.googlesource.com/c/go/+/415241
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/test/escape_iface_unified.go b/test/escape_iface_unified.go
new file mode 100644
index 0000000000..7ac8e00151
--- /dev/null
+++ b/test/escape_iface_unified.go
@@ -0,0 +1,25 @@
+// errorcheck -0 -m -l
+//go:build goexperiment.unified
+// +build goexperiment.unified
+
+// Copyright 2015 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 escape
+
+var sink interface{}
+
+func dotTypeEscape2() { // #13805, #15796
+	{
+		i := 0
+		j := 0
+		var ok bool
+		var x interface{} = i // ERROR "i does not escape"
+		var y interface{} = j // ERROR "j does not escape"
+
+		sink = x.(int) // ERROR "x.\(int\) escapes to heap"
+		// BAD: should be "y.\(int\) escapes to heap" too
+		sink, *(&ok) = y.(int)
+	}
+}