From 394a1ad2956f0397e83b5f0234ea7e972a307848 Mon Sep 17 00:00:00 2001
From: Keith Randall <khr@golang.org>
Date: Mon, 18 Oct 2021 10:26:18 -0700
Subject: [PATCH] cmd/compile: allow importing and exporting of
 ODYANMICDOTTYPE[2]

Fixes #49027

Change-Id: I4520b5c754027bfffbc5cd92c9c27002b248c99a
Reviewed-on: https://go-review.googlesource.com/c/go/+/356569
Trust: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
---
 src/cmd/compile/internal/typecheck/iexport.go |  8 ++++++
 src/cmd/compile/internal/typecheck/iimport.go |  5 ++++
 test/typeparam/issue49027.dir/a.go            | 21 ++++++++++++++++
 test/typeparam/issue49027.dir/main.go         | 25 +++++++++++++++++++
 test/typeparam/issue49027.go                  |  7 ++++++
 5 files changed, 66 insertions(+)
 create mode 100644 test/typeparam/issue49027.dir/a.go
 create mode 100644 test/typeparam/issue49027.dir/main.go
 create mode 100644 test/typeparam/issue49027.go

diff --git a/src/cmd/compile/internal/typecheck/iexport.go b/src/cmd/compile/internal/typecheck/iexport.go
index 3c0b8bc3198..e3dd10a56b1 100644
--- a/src/cmd/compile/internal/typecheck/iexport.go
+++ b/src/cmd/compile/internal/typecheck/iexport.go
@@ -1888,6 +1888,14 @@ func (w *exportWriter) expr(n ir.Node) {
 		w.expr(n.X)
 		w.typ(n.Type())
 
+	case ir.ODYNAMICDOTTYPE, ir.ODYNAMICDOTTYPE2:
+		n := n.(*ir.DynamicTypeAssertExpr)
+		w.op(n.Op())
+		w.pos(n.Pos())
+		w.expr(n.X)
+		w.expr(n.T)
+		w.typ(n.Type())
+
 	case ir.OINDEX, ir.OINDEXMAP:
 		n := n.(*ir.IndexExpr)
 		if go117ExportTypes {
diff --git a/src/cmd/compile/internal/typecheck/iimport.go b/src/cmd/compile/internal/typecheck/iimport.go
index df49d74a401..52236ce837b 100644
--- a/src/cmd/compile/internal/typecheck/iimport.go
+++ b/src/cmd/compile/internal/typecheck/iimport.go
@@ -1457,6 +1457,11 @@ func (r *importReader) node() ir.Node {
 		}
 		return n
 
+	case ir.ODYNAMICDOTTYPE, ir.ODYNAMICDOTTYPE2:
+		n := ir.NewDynamicTypeAssertExpr(r.pos(), op, r.expr(), r.expr())
+		n.SetType(r.typ())
+		return n
+
 	case ir.OINDEX, ir.OINDEXMAP:
 		n := ir.NewIndexExpr(r.pos(), r.expr(), r.expr())
 		if go117ExportTypes {
diff --git a/test/typeparam/issue49027.dir/a.go b/test/typeparam/issue49027.dir/a.go
new file mode 100644
index 00000000000..d3ec27deab5
--- /dev/null
+++ b/test/typeparam/issue49027.dir/a.go
@@ -0,0 +1,21 @@
+// 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.
+
+package a
+
+func Conv(v interface{}) string {
+	return conv[string](v)
+}
+
+func conv[T any](v interface{}) T {
+	return v.(T)
+}
+
+func Conv2(v interface{}) (string, bool) {
+	return conv2[string](v)
+}
+func conv2[T any](v interface{}) (T, bool) {
+	x, ok := v.(T)
+	return x, ok
+}
diff --git a/test/typeparam/issue49027.dir/main.go b/test/typeparam/issue49027.dir/main.go
new file mode 100644
index 00000000000..d0dc33d7343
--- /dev/null
+++ b/test/typeparam/issue49027.dir/main.go
@@ -0,0 +1,25 @@
+// 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.
+
+package main
+
+import (
+	"a"
+	"fmt"
+)
+
+func main() {
+	s := "foo"
+	x := a.Conv(s)
+	if x != s {
+		panic(fmt.Sprintf("got %s wanted %s", x, s))
+	}
+	y, ok := a.Conv2(s)
+	if !ok {
+		panic("conversion failed")
+	}
+	if y != s {
+		panic(fmt.Sprintf("got %s wanted %s", y, s))
+	}
+}
diff --git a/test/typeparam/issue49027.go b/test/typeparam/issue49027.go
new file mode 100644
index 00000000000..76930e5e4f6
--- /dev/null
+++ b/test/typeparam/issue49027.go
@@ -0,0 +1,7 @@
+// rundir -G=3
+
+// 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.
+
+package ignored