cmd/compile: imperfect compile error message

[zigo101]

What version of Go are you using (go version)?

$ go version
go version go1.16 linux/amd64

Does this issue reproduce with the latest release?

Yes

What did you do?

  package main

  func main() {
    var a, b = 1, -2
    println(a<-b)
  }

What did you expect to see?

syntax error: a is not channel, unexpected <-

What did you see instead?

syntax error: unexpected <-, expecting comma or )

BTW, go fmt doesn't work for much code which fails to compile.
But I think it should work here.

[griesemer]

a <- b is a send statement, not an expression. The error message seems quite reasonable. The parser usually doesn't comment on what type a variable is, either.

[zigo101]

I understand. But the message doesn't make people realize the real cause at the first time.
And, the second half "expecting comma or )" is not very accurate. Comma and ) are not the only possibilities.