Template Haskell doesn't support Haskell 2010 default declarations
Briefly describe the problem your proposal solves and why this problem should be solved.
The only Haskell 2010 declaration type not supported by Template Haskell is the
default declaration, described in section 4.3.4 of the report.
There may be good reasons for not including it in the Template Haskell implementation, but I don't see that it was ever considered and rejected. So, here's the opportunity to consider it and, if need be, reject it.
The primary reason for adding it would be consistency. If you need another, I'm relying on Template Haskell as a quick&dirty pretty-printer for parsed Haskell 2010 code in a little hobby project. It's a part of my test suite, which is currently failing due to the impossibility to represent all of Haskell 2010 declarations in Template Haskell.