package:dart_style v2.3.7

• Allow passing a language version to DartFomatter(). Formatted code will be
  parsed at that version. If omitted, defaults to the latest version. In a
  future release, this parameter will become required.
• Allow opting out of formatting for a region of code using // dart format off
  and // dart format on comments. Note: This only works using the new tall
  style and requires passing the --enable-experiment=tall-style experiment
  flag (#361).
• Preserve type parameters on old-style function-typed formals that also use
  this. or super. (#1321).
• Correctly format imports with both as and if clauses (#1544).
• Remove temporary work around for analyzer 6.2.0 from dart_style 2.3.6.
• Require package:analyzer >=6.5.0 <7.0.0.