Before filing a bug, please check whether it has been fixed since
the latest release: run "hg pull -u" and retry what you did to
reproduce the problem.  Thanks.

What steps will reproduce the problem?
1. gofmt -r='8->9'
2.
3.

What is the expected output?
None, hangs waiting for stdin

What do you see instead?
parsing pattern 8: input:1:1: expected 'EOF', found newline

Which compiler are you using (5g, 6g, 8g, gccgo)?
(happens on amd64 and 386 machines)

Which operating system are you using?
linux

Which revision are you using?  (hg identify)
9b116c4a5f91 tip

Please provide any additional information below.
Note that there's no test for rewrite rules in src/cmd/gofmt/test.sh.  Perhaps there
should be one.