Formatter: fails when assign to local var within parenthesis

[maiha]

code: test.cr

(
  a = 1
  a
)

run

% crystal tool format test.cr
Using compiled compiler at `.build/crystal'
Error: couldn't format 'test.cr', please report a bug including the contents of it: https://github.com/crystal-lang/crystal/issues

expecting =, not `IDENT, a`, at :2:3 (Exception)
  from /mnt/src/compiler/crystal/tools/formatter.cr:4564:7 in 'check'
  from /mnt/src/compiler/crystal/tools/formatter.cr:4539:7 in 'write_token'
  from /mnt/src/compiler/crystal/tools/formatter.cr:4545:7 in 'write_token'

version

% crystal --version
Using compiled compiler at `.build/crystal'
Crystal 0.24.0 [ea4187c] (2017-11-08)

LLVM: 3.8.0
Default target: x86_64-pc-linux-gnu

Thank you,