[dev.typeparams] cmd/compile: enable parsing of generic code with new -G flag

Providing the -G flag instructs the compiler to accept type parameters.
For now, the compiler only parses such files and then exits.

Added a new test directory (test/typeparam) and initial test case.

Port from dev.go2go branch.

Change-Id: Ic11e33a9d5f012f8def0bdae205043659562ac73
Reviewed-on: https://go-review.googlesource.com/c/go/+/261660
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/test/typeparam/smoketest.go b/test/typeparam/smoketest.go
new file mode 100644
index 0000000000..d17809eb63
--- /dev/null
+++ b/test/typeparam/smoketest.go
@@ -0,0 +1,57 @@
+// compile -G
+
+// 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.
+
+// This file checks simple code using type parameters.
+
+package smoketest
+
+// type parameters for functions
+func f1[P any]()
+func f2[P1, P2 any, P3 any]()
+func f3[P interface{}](x P, y T1[int])
+
+// function instantiations
+var _ = f1[int]
+var _ = f2[int, string, struct{}]
+var _ = f3[bool]
+
+// type parameters for types
+type T1[P any] struct{}
+type T2[P1, P2 any, P3 any] struct{}
+type T3[P interface{}] interface{}
+
+// type instantiations
+type _ T1[int]
+type _ T2[int, string, struct{}]
+type _ T3[bool]
+
+// methods
+func (T1[P]) m1() {}
+func (x T2[P1, P2, P3]) m1() {}
+func (_ T3[_]) m1() {}
+
+// type lists
+type _ interface {
+	m1()
+	m2()
+	type int, float32, string
+	m3()
+	type bool
+}
+
+// embedded instantiated types
+type _ struct {
+	f1, f2 int
+	T1[int]
+	T2[int, string, struct{}]
+	T3[bool]
+}
+
+type _ interface {
+	m1()
+	m2()
+	T3[bool]
+}