invalid dart codegen

[jmesserly]

this file has invalid code, snippet below.
pub run dart_style:format test/dart_codegen/expect/dart.async/stream.dart

I added some newlines after curlies and semicolons to make it readable

 factory Stream.periodic(Duration period, [T computation(int computationCount)]) {
if (computation == null) computation = ((__x48) => DDC$RT.wrap((<bottom> f(dynamic __u43)) {
<bottom> c(dynamic x0) => ((__x42) => DDC$RT.cast(__x42, Null, T, "CastResult", """line 126, column 44 of dart:async/stream.dart: """, __x42 is T, false))(f(x0));
 return f == null ? null : c;

}

there's rolling parse failure starting from <bottom> f(

[jmesserly]

fyi to @munificent ... it's not a formatter bug :)
fyi to @vsmenon I think this was introduced in https://chromereviews.googleplex.com/157727013

[leafpetersen]

I believe that this was fixed in https://chromereviews.googleplex.com/151297013 .