cmd/compile: recognize reassignments involving receives

Previously, reassigned was failing to detect reassignments due to
channel receives in select statements (OSELRECV, OSELRECV2), or due to
standalone 2-value receive assignments (OAS2RECV). This was reported
as a devirtualization panic, but could have caused mis-inlining as
well.

Fixes #43292.

Change-Id: Ic8079c20c0587aeacff9596697fdeba80a697b12
Reviewed-on: https://go-review.googlesource.com/c/go/+/279352
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>

1 files changed, 59 insertions, 0 deletions

diff --git a/test/fixedbugs/issue43292.go b/test/fixedbugs/issue43292.go
new file mode 100644
index 0000000000..02f1c69bd1
--- /dev/null
+++ b/test/fixedbugs/issue43292.go
@@ -0,0 +1,59 @@
+// run
+
+// Copyright 2020 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
+
+func main() {
+	{
+		i := I(A{})
+
+		b := make(chan I, 1)
+		b <- B{}
+
+		var ok bool
+		i, ok = <-b
+		_ = ok
+
+		i.M()
+	}
+
+	{
+		i := I(A{})
+
+		b := make(chan I, 1)
+		b <- B{}
+
+		select {
+		case i = <-b:
+		}
+
+		i.M()
+	}
+
+	{
+		i := I(A{})
+
+		b := make(chan I, 1)
+		b <- B{}
+
+		var ok bool
+		select {
+		case i, ok = <-b:
+		}
+		_ = ok
+
+		i.M()
+	}
+}
+
+type I interface{ M() int }
+
+type T int
+
+func (T) M() int { return 0 }
+
+type A struct{ T }
+type B struct{ T }