Debugging specialization

Alexis King lexi.lambda at
Thu Oct 24 17:13:14 UTC 2019

Hi all,

I am trying to understand why GHC is not specializing an imported INLINABLE instance method, and the information provided by -ddump-spec -Wall-missed-specialisations has not been enough to help me figure it out. Is there some easy/well-trodden way that I could build GHC with some additional instrumentation in place to help me better understand the decisions being made by the specializer, or is -ddump-spec the most granularity available?

I’ve noticed that Specialise.hs has handful of pprTrace calls sprinkled about, but they are all commented out. Is the recommended method to just uncomment these calls and rebuild GHC?


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