Formatter: fails when %{...} strings are used inside macros

[bcardiff]

File: foo.cr

macro oh(name)
  {% begin %}
    raise %{Oh {{name.id}} }
  {% end %}
end

oh no

The program builds and run as expected

$ crystal src/foo.cr 
Oh no  (Exception)
0x10e749892: *CallStack::unwind:Array(Pointer(Void)) at ??
0x10e749831: *CallStack#initialize:Array(Pointer(Void)) at ??
0x10e749808: *CallStack::new:CallStack at ??
0x10e743b01: *raise<Exception>:NoReturn at ??
0x10e743ae1: *raise<String>:NoReturn at ??
0x10e743638: __crystal_main at ??
0x10e748ac8: main at ??

But it fails to format

$ crystal tool format src/foo.cr
Error:, couldn't format 'src/foo.cr', please report a bug ...

---

$ crystal --version
Crystal 0.21.1 (2017-03-07) LLVM 3.9.1

[asterite]

This actually fails to compile:

macro x
  %{}
end

Syntax error in foo.cr:1: unterminated macro

macro x
      ^