RFC re #10196 & GHC 7.10.2: Allow Unicode Lm category for 2nd+ character on in identifiers
Herbert Valerio Riedel
hvriedel at gmail.com
Wed May 6 08:22:32 UTC 2015
As you may be aware, GHC 7.10.1 updated its Unicode catalog to version
7.0, thereby causing some subscript symbols to change character
properties, thereby causing GHC 7.10.1 to reject some Unicode-subscript
characters that GHC 7.8.4 accepted.
See https://ghc.haskell.org/trac/ghc/ticket/10196 for specific examples.
In order to address this regression, one suggestion is to allow
characters in the 'Letter, Modifier' category from the 2nd position
on in an identifier. This however may do more than just fix the
regression, as it looks from  that it would allow many more new
identifiers than were previously possible.
So, is allowing 'Lm'-chars the the 2nd+ characters in an identifier a
sensible change for addressing #10196 or not. If it's a bad idea, are
there other suggestions worth considering?
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