go/test/chan/perm.go

// errorcheck

// Copyright 2009 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.

// Test various correct and incorrect permutations of send-only,
// receive-only, and bidirectional channels.
// Does not compile.

package main

var (
	cr <-chan int
	cs chan<- int
	c  chan int
)

func main() {
	cr = c  // ok
	cs = c  // ok
	c = cr  // ERROR "illegal types|incompatible|cannot"
	c = cs  // ERROR "illegal types|incompatible|cannot"
	cr = cs // ERROR "illegal types|incompatible|cannot"
	cs = cr // ERROR "illegal types|incompatible|cannot"

	var n int
	<-n    // ERROR "receive from non-chan|expected channel"
	n <- 2 // ERROR "send to non-chan|must be channel"

	c <- 0       // ok
	<-c          // ok
	x, ok := <-c // ok
	_, _ = x, ok

	cr <- 0      // ERROR "send"
	<-cr         // ok
	x, ok = <-cr // ok
	_, _ = x, ok

	cs <- 0      // ok
	<-cs         // ERROR "receive"
	x, ok = <-cs // ERROR "receive"
	_, _ = x, ok

	select {
	case c <- 0: // ok
	case x := <-c: // ok
		_ = x

	case cr <- 0: // ERROR "send"
	case x := <-cr: // ok
		_ = x

	case cs <- 0: // ok
	case x := <-cs: // ERROR "receive"
		_ = x
	}

	for _ = range cs { // ERROR "receive"
	}

	for range cs { // ERROR "receive"
	}

	close(c)
	close(cs)
	close(cr) // ERROR "receive"
	close(n)  // ERROR "invalid operation.*non-chan type|must be channel"
}