[dev.typeparams] cmd/compile: enable type-checking of generic code

This change makes a first connection between the compiler and types2.
When the -G flag is provided, the compiler accepts code using type
parameters; with this change generic code is also type-checked (but
then compilation ends).

Change-Id: I0fa6f6213267a458a6b33afe8ff26869fd838a63
Reviewed-on: https://go-review.googlesource.com/c/go/+/264303
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, 42 insertions, 0 deletions

diff --git a/test/typeparam/tparam1.go b/test/typeparam/tparam1.go
new file mode 100644
index 0000000000..5d6dcb6a62
--- /dev/null
+++ b/test/typeparam/tparam1.go
@@ -0,0 +1,42 @@
+// errorcheck -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.
+
+// Basic type parameter list type-checking (not syntax) errors.
+
+package tparam1
+
+// The predeclared identifier "any" is only visible as a constraint
+// in a type parameter list.
+var _ any // ERROR "undeclared"
+func _(_ any) // ERROR "undeclared"
+type _[_ any /* ok here */ ] struct{}
+
+const N = 10
+
+type (
+        _[] struct{} // slice
+        _[N] struct{} // array
+        _[T any] struct{}
+        _[T, T any] struct{} // ERROR "T redeclared"
+        _[T1, T2 any, T3 any] struct{}
+)
+
+func _[T any]()
+func _[T, T any]() // ERROR "T redeclared"
+func _[T1, T2 any](x T1) T2
+
+// Type parameters are visible from opening [ to end of function.
+type C interface{}
+
+func _[T interface{}]()
+func _[T C]()
+func _[T struct{}]() // ERROR "not an interface"
+func _[T interface{ m() T }]()
+func _[T1 interface{ m() T2 }, T2 interface{ m() T1 }]() {
+        var _ T1
+}
+
+// TODO(gri) expand this