[dev.typeparams] go/types: implement close(ch) where ch is of type parameter type

This is a port of CL 333713 to go/types.

Change-Id: I517f52592f65cc76e11a12d9148b20c12d9e3e81
Reviewed-on: https://go-review.googlesource.com/c/go/+/335077
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/go/types/builtins.go

@@ -217,19 +217,23 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 
 	case _Close:
 		// close(c)
-		c := asChan(x.typ)
-		if c == nil {
-			check.invalidArg(x, _InvalidClose, "%s is not a channel", x)
+		if !underIs(x.typ, func(u Type) bool {
+			uch, _ := u.(*Chan)
+			if uch == nil {
+				check.invalidOp(x, _InvalidClose, "cannot close non-channel %s", x)
+				return false
+			}
+			if uch.dir == RecvOnly {
+				check.invalidOp(x, _InvalidClose, "cannot close receive-only channel %s", x)
+				return false
+			}
+			return true
+		}) {
 			return
 		}
-		if c.dir == RecvOnly {
-			check.invalidArg(x, _InvalidClose, "%s must not be a receive-only channel", x)
-			return
-		}
-
 		x.mode = novalue
 		if check.Types != nil {
-			check.recordBuiltinType(call.Fun, makeSig(nil, c))
+			check.recordBuiltinType(call.Fun, makeSig(nil, x.typ))
 		}
 
 	case _Complex:

src/go/types/testdata/check/builtins.go2

@@ -6,6 +6,45 @@
 
 package builtins
 
+// close
+
+type C0 interface{ int }
+type C1 interface{ chan int }
+type C2 interface{ chan int | <-chan int }
+type C3 interface{ chan int | chan float32 }
+type C4 interface{ chan int | chan<- int }
+type C5[T any] interface{ ~chan T | chan<- T }
+
+func _[T any](ch T) {
+	close(ch /* ERROR cannot close non-channel */)
+}
+
+func _[T C0](ch T) {
+	close(ch /* ERROR cannot close non-channel */)
+}
+
+func _[T C1](ch T) {
+	close(ch)
+}
+
+func _[T C2](ch T) {
+	close(ch /* ERROR cannot close receive-only channel */)
+}
+
+func _[T C3](ch T) {
+	close(ch)
+}
+
+func _[T C4](ch T) {
+	close(ch)
+}
+
+func _[T C5[X], X any](ch T) {
+	close(ch)
+}
+
+// make
+
 type Bmc interface {
 	~map[rune]string | ~chan int
 }
@@ -22,31 +61,31 @@ type Bss interface {
 	~[]int | ~[]string
 }
 
-func _[T any] () {
-	_ = make(T /* ERROR invalid argument */ )
-	_ = make(T /* ERROR invalid argument */ , 10)
-	_ = make(T /* ERROR invalid argument */ , 10, 20)
+func _[T any]() {
+	_ = make(T /* ERROR invalid argument */)
+	_ = make(T /* ERROR invalid argument */, 10)
+	_ = make(T /* ERROR invalid argument */, 10, 20)
 }
 
-func _[T Bmc] () {
+func _[T Bmc]() {
 	_ = make(T)
 	_ = make(T, 10)
 	_ = make /* ERROR expects 1 or 2 arguments */ (T, 10, 20)
 }
 
-func _[T Bms] () {
+func _[T Bms]() {
 	_ = make /* ERROR expects 2 arguments */ (T)
 	_ = make(T, 10)
 	_ = make /* ERROR expects 2 arguments */ (T, 10, 20)
 }
 
-func _[T Bcs] () {
+func _[T Bcs]() {
 	_ = make /* ERROR expects 2 arguments */ (T)
 	_ = make(T, 10)
 	_ = make /* ERROR expects 2 arguments */ (T, 10, 20)
 }
 
-func _[T Bss] () {
+func _[T Bss]() {
 	_ = make /* ERROR expects 2 or 3 arguments */ (T)
 	_ = make(T, 10)
 	_ = make(T, 10, 20)

src/go/types/testdata/check/builtins.src

@@ -144,7 +144,7 @@ func close1() {
 	var r <-chan int
 	close() // ERROR not enough arguments
 	close(1, 2) // ERROR too many arguments
-	close(42 /* ERROR not a channel */)
+	close(42 /* ERROR cannot close non-channel */)
 	close(r /* ERROR receive-only channel */)
 	close(c)
 	_ = close /* ERROR used as value */ (c)

src/go/types/type.go

@@ -105,11 +105,6 @@ func asPointer(t Type) *Pointer {
 	return op
 }
 
-func asTuple(t Type) *Tuple {
-	op, _ := optype(t).(*Tuple)
-	return op
-}
-
 func asSignature(t Type) *Signature {
 	op, _ := optype(t).(*Signature)
 	return op
@@ -120,11 +115,6 @@ func asMap(t Type) *Map {
 	return op
 }
 
-func asChan(t Type) *Chan {
-	op, _ := optype(t).(*Chan)
-	return op
-}
-
 // If the argument to asInterface, asNamed, or asTypeParam is of the respective type
 // (possibly after expanding an instance type), these methods return that type.
 // Otherwise the result is nil.