cmd/compile: set IsShape based on type being in the Shapes pkg

Move ShapePkg to types, and change types.NewNamed to automatically set
IsShape/HasShape if a type is in the shapes pkg. This means that
imported shape types will automatically have the correct
IsShape/HasShape flags, even though we are not explicitly
exporting/importing those flags.

Updates #48337

Change-Id: I8b6131a663205f73f395943c9d0c8bdb2a213401
Reviewed-on: https://go-review.googlesource.com/c/go/+/349869
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>

3 files changed, 43 insertions, 0 deletions

diff --git a/test/typeparam/issue48337b.dir/a.go b/test/typeparam/issue48337b.dir/a.go
new file mode 100644
index 0000000000..a3c2e88a2f
--- /dev/null
+++ b/test/typeparam/issue48337b.dir/a.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 a
+
+type Container[T any] struct {
+	X T
+}
+
+func NewContainer[T any](x T) *Container[T] {
+	return &Container[T]{x}
+}
+
+type MetaContainer struct {
+	C *Container[Value]
+}
+
+type Value struct{}
+
+func NewMetaContainer() *MetaContainer {
+	c := NewContainer(Value{})
+	// c := &Container[Value]{Value{}} // <-- this works
+	return &MetaContainer{c}
+}
diff --git a/test/typeparam/issue48337b.dir/main.go b/test/typeparam/issue48337b.dir/main.go
new file mode 100644
index 0000000000..0b2814cbc0
--- /dev/null
+++ b/test/typeparam/issue48337b.dir/main.go
@@ -0,0 +1,11 @@
+// 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"
+
+func main() {
+	a.NewMetaContainer()
+}
diff --git a/test/typeparam/issue48337b.go b/test/typeparam/issue48337b.go
new file mode 100644
index 0000000000..76930e5e4f
--- /dev/null
+++ b/test/typeparam/issue48337b.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