Enabling TypeHoles by default

Krzysztof Gogolewski krz.gogolewski at gmail.com
Mon Jan 13 18:42:35 UTC 2014


As discussed on ghc-devs, I propose to enable -XTypeHoles in GHC by
default. Rationale:

(1) This way holes are far easier to use; just entering "_" allows to check
type of a subexpression, no need of adding "-XTypeHoles".

(2) This affects error messages only; i.e. the set of programs that compile
stays the same - Haskell 2010. The only exception is that if you use
-fdefer-type-errors, then a program with a hole compiles, but this seems
fine with philosophy of -fdefer-type-errors.

If so: would you like it to be in 7.8 or wait a cycle? My preference is
7.8, two people (John and Richard) suggested 7.10.

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