[dev.typeparams] cmd/compile: implement generic type switches

Add a new dynamicType node, which is used as a case entry when
the type being switched to is generic.

Change-Id: Ice77c6f224b8fdd3ff574fdf4a8ea5f6c7ddbe75
Reviewed-on: https://go-review.googlesource.com/c/go/+/339429
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>

10 files changed, 176 insertions, 0 deletions

diff --git a/test/typeparam/typeswitch1.go b/test/typeparam/typeswitch1.go
new file mode 100644
index 0000000000..27161b3db8
--- /dev/null
+++ b/test/typeparam/typeswitch1.go
@@ -0,0 +1,29 @@
+// run -gcflags=-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 main
+
+func f[T any](i interface{}) {
+	switch i.(type) {
+	case T:
+		println("T")
+	case int:
+		println("int")
+	case int32, int16:
+		println("int32/int16")
+	case struct { a, b T }:
+		println("struct{T,T}")
+	default:
+		println("other")
+	}
+}
+func main() {
+	f[float64](float64(6))
+	f[float64](int(7))
+	f[float64](int32(8))
+	f[float64](struct{a, b float64}{a:1, b:2})
+	f[float64](int8(9))
+}
diff --git a/test/typeparam/typeswitch1.out b/test/typeparam/typeswitch1.out
new file mode 100644
index 0000000000..4bdbccfddb
--- /dev/null
+++ b/test/typeparam/typeswitch1.out
@@ -0,0 +1,5 @@
+T
+int
+int32/int16
+struct{T,T}
+other
diff --git a/test/typeparam/typeswitch2.go b/test/typeparam/typeswitch2.go
new file mode 100644
index 0000000000..913c56321c
--- /dev/null
+++ b/test/typeparam/typeswitch2.go
@@ -0,0 +1,31 @@
+// run -gcflags=-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 main
+
+import "reflect"
+
+func f[T any](i interface{}) {
+	switch x := i.(type) {
+	case T:
+		println("T", x)
+	case int:
+		println("int", x)
+	case int32, int16:
+		println("int32/int16", reflect.ValueOf(x).Int())
+	case struct { a, b T }:
+		println("struct{T,T}", x.a, x.b)
+	default:
+		println("other", reflect.ValueOf(x).Int())
+	}
+}
+func main() {
+	f[float64](float64(6))
+	f[float64](int(7))
+	f[float64](int32(8))
+	f[float64](struct{a, b float64}{a:1, b:2})
+	f[float64](int8(9))
+}
diff --git a/test/typeparam/typeswitch2.out b/test/typeparam/typeswitch2.out
new file mode 100644
index 0000000000..944cc04cc6
--- /dev/null
+++ b/test/typeparam/typeswitch2.out
@@ -0,0 +1,5 @@
+T +6.000000e+000
+int 7
+int32/int16 8
+struct{T,T} +1.000000e+000 +2.000000e+000
+other 9
diff --git a/test/typeparam/typeswitch3.go b/test/typeparam/typeswitch3.go
new file mode 100644
index 0000000000..6ab0301140
--- /dev/null
+++ b/test/typeparam/typeswitch3.go
@@ -0,0 +1,35 @@
+// run -gcflags=-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 main
+
+type I interface { foo() int }
+
+type myint int
+
+func (x myint) foo() int { return int(x) }
+
+type myfloat float64
+func (x myfloat) foo() int { return int(x) }
+
+type myint32 int32
+func (x myint32) foo() int { return int(x) }
+
+func f[T I](i I) {
+	switch x := i.(type) {
+	case T:
+		println("T", x.foo())
+	case myint:
+		println("myint", x.foo())
+	default:
+		println("other", x.foo())
+	}
+}
+func main() {
+	f[myfloat](myint(6))
+	f[myfloat](myfloat(7))
+	f[myfloat](myint32(8))
+}
diff --git a/test/typeparam/typeswitch3.out b/test/typeparam/typeswitch3.out
new file mode 100644
index 0000000000..2c69c72c30
--- /dev/null
+++ b/test/typeparam/typeswitch3.out
@@ -0,0 +1,3 @@
+myint 6
+T 7
+other 8
diff --git a/test/typeparam/typeswitch4.go b/test/typeparam/typeswitch4.go
new file mode 100644
index 0000000000..6113026b65
--- /dev/null
+++ b/test/typeparam/typeswitch4.go
@@ -0,0 +1,33 @@
+// run -gcflags=-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 main
+
+type I interface { foo() int }
+
+type myint int
+
+func (x myint) foo() int {return int(x)}
+
+type myfloat float64
+func (x myfloat) foo() int {return int(x)}
+
+type myint32 int32
+func (x myint32) foo() int { return int(x) }
+
+func f[T I](i I) {
+	switch x := i.(type) {
+	case T, myint32:
+		println("T/myint32", x.foo())
+	default:
+		println("other", x.foo())
+	}
+}
+func main() {
+	f[myfloat](myint(6))
+	f[myfloat](myfloat(7))
+	f[myfloat](myint32(8))
+}
diff --git a/test/typeparam/typeswitch4.out b/test/typeparam/typeswitch4.out
new file mode 100644
index 0000000000..b0d54077c9
--- /dev/null
+++ b/test/typeparam/typeswitch4.out
@@ -0,0 +1,3 @@
+other 6
+T/myint32 7
+T/myint32 8
diff --git a/test/typeparam/typeswitch5.go b/test/typeparam/typeswitch5.go
new file mode 100644
index 0000000000..1fc6e0a14e
--- /dev/null
+++ b/test/typeparam/typeswitch5.go
@@ -0,0 +1,28 @@
+// run -gcflags=-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 main
+
+type myint int
+func (x myint) foo() int {return int(x)}
+
+type myfloat float64
+func (x myfloat) foo() float64 {return float64(x) }
+
+func f[T any](i interface{}) {
+	switch x := i.(type) {
+	case interface { foo() T }:
+		println("fooer", x.foo())
+	default:
+		println("other")
+	}
+}
+func main() {
+	f[int](myint(6))
+	f[int](myfloat(7))
+	f[float64](myint(8))
+	f[float64](myfloat(9))
+}
diff --git a/test/typeparam/typeswitch5.out b/test/typeparam/typeswitch5.out
new file mode 100644
index 0000000000..6b4cb4416f
--- /dev/null
+++ b/test/typeparam/typeswitch5.out
@@ -0,0 +1,4 @@
+fooer 6
+other
+other
+fooer +9.000000e+000