[dev.typeparams] cmd/compile: adding union support in types1

Add union support in types1, and allow exporting of unions, and
importing unions back into types1 and types2.

Added new test mincheck.go/mincheck.dir that tests that type lists (type
sets) are correctly exported/imported, so that types2 gives correct
errors that an instantiation doesn't fit the type list in the type param
constraint.

Change-Id: I8041c6c79289c870a95ed5a1b10e4c1c16985b12
Reviewed-on: https://go-review.googlesource.com/c/go/+/322609
Trust: Dan Scales <danscales@google.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

2 files changed, 54 insertions, 0 deletions

diff --git a/test/typeparam/mincheck.dir/a.go b/test/typeparam/mincheck.dir/a.go
new file mode 100644
index 0000000000..f1844bba9d
--- /dev/null
+++ b/test/typeparam/mincheck.dir/a.go
@@ -0,0 +1,16 @@
+// 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 Ordered interface {
+        type int, int64, float64
+}
+
+func Min[T Ordered](x, y T) T {
+        if x < y {
+                return x
+        }
+        return y
+}
diff --git a/test/typeparam/mincheck.dir/main.go b/test/typeparam/mincheck.dir/main.go
new file mode 100644
index 0000000000..72d8effcc5
--- /dev/null
+++ b/test/typeparam/mincheck.dir/main.go
@@ -0,0 +1,38 @@
+// 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() {
+	const want = 2
+	if got := a.Min[int](2, 3); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	if got := a.Min(2, 3); got != want {
+		panic(fmt.Sprintf("want %d, got %d", want, got))
+	}
+
+	if got := a.Min[float64](3.5, 2.0); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	if got := a.Min(3.5, 2.0); got != want {
+		panic(fmt.Sprintf("got %d, want %d", got, want))
+	}
+
+	const want2 = "ay"
+	if got := a.Min[string]("bb", "ay"); got != want2 { // ERROR "string does not satisfy interface{int|int64|float64}"
+		panic(fmt.Sprintf("got %d, want %d", got, want2))
+	}
+
+	if got := a.Min("bb", "ay"); got != want2 { // ERROR "string does not satisfy interface{int|int64|float64}"
+		panic(fmt.Sprintf("got %d, want %d", got, want2))
+	}
+}