[GHC] #10196: Regression regarding Unicode subscript characters in identifiers

[GHC]

#10196: Regression regarding Unicode subscript characters in identifiers
-------------------------------------+-------------------------------------
        Reporter:  thomie            |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:  7.10.2
       Component:  Compiler          |                 Version:  7.10.1
  (Parser)                           |                Keywords:
      Resolution:                    |            Architecture:
Operating System:  Unknown/Multiple  |  Unknown/Multiple
 Type of failure:  GHC rejects       |               Test Case:
  valid program                      |                Blocking:
      Blocked By:                    |  Differential Revisions:
 Related Tickets:  #5108             |
-------------------------------------+-------------------------------------

Old description:

> As reported by both hvr as user Yongqian Li:
>
> The Unicode7 update in GHC 7.10 had the side effect of breaking code
> making use of subscript symbols that did compile with GHC 7.8.4, but
> won't anymore with GHC 7.10.1:
>
> For instance, GHCi 7.8.4 accepts
>
>    let xᵦ = 1
>    let xᵤ = 1
>    let xᵩ = 1
>    let xᵢ = 1
>    let xᵪ = 1
>    let xᵣ = 1
>    let xₙ = 1
>
> whereas GHC 7.10.1RC fails parsing those with a lexical error. (NB: GHC
> 7.8 does not accept *all* latin subscript letters either).

New description:

 As reported by both hvr as user Yongqian Li:

 The [changeset:d4fd16801bc59034abdc6214e60fcce2b21af9c8 Unicode 7.0
 update] in GHC 7.10 had the side effect of breaking code making use of
 subscript symbols that did compile with GHC 7.8.4, but won't anymore with
 GHC 7.10.1:

 For instance, GHCi 7.8.4 accepts

 {{{#!hs
    let xᵦ = 1
    let xᵤ = 1
    let xᵩ = 1
    let xᵢ = 1
    let xᵪ = 1
    let xᵣ = 1
    let xₙ = 1
 }}}

 whereas GHC 7.10.1RC fails parsing those with a lexical error. (NB: GHC
 7.8 does not accept ''all'' latin subscript letters either).

--

Comment (by hvr):

 Minor markup improvement in ticket-description

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10196#comment:2>
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