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 | |
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Blocking | |
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Operating system | |
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