by emage@spamcop.net:

What steps will reproduce the problem?
1. Put the following code in test.go:

  package main

  func main() {
        bar := make(chan bool);
        select {
        case _ = <-bar:
                return
        }
  }

2. Run 8g test.go

What is the expected output?

Some error related to the line with the case clause, which probably ought
to be just "<-bar" instead of "_ = <-bar".

What do you see instead?

  <epoch>: fatal error: dowidth: unknown type: blank

What is your $GOOS?  $GOARCH?

GOOS=linux GOARCH=386

Which revision are you sync'ed to?  (hg log -l 1)

4076:9a2607678b31