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  • #8258

Closed
Open
Opened Sep 09, 2013 by Herbert Valerio Riedel@hvr🕺Maintainer

GHC accepts `data Foo where` in H2010 mode

According to the Haskell2010 report,

The grammar productions relevant for data declarations are the following:

topdecl	→ data [context =>] simpletype [= constrs] [deriving]

(from 4.2.1 Algebraic Datatype Declarations)

However, GHC 7.0.4/7.4.2/7.6.3/HEAD all happily compile the following Haskell module without any warning when using -XHaskell2010 -Wall, even though this is not valid Haskell2010 afaik:

module Foo where

data Foo where

The trailing where in the data declaration is not valid Haskell2010 (without language extensions such as GADT).

At the very least, this divergence from the Haskell Report should be mentioned in 14.1.1. Divergence from Haskell 98 and Haskell 2010.

Trac metadata
Trac field Value
Version 7.0.4
Type Bug
TypeOfFailure OtherFailure
Priority low
Resolution Unresolved
Component Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture
Assignee
Assign to
8.6.1
Milestone
8.6.1 (Past due)
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None
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Reference: ghc/ghc#8258