implicit parameters and type synonyms
I wouldn't call this a bug. But we have various pieces of code at Galois that rely on this undocumented (AFAIK) feature of GHC:
Allow implicit parameter constraints in type synonyms and float the constraints out when the synonym is used.
So, given the following program:
{-# OPTIONS -fglasgow-exts -fimplicit-params #-}
module TestIP where
type PPEnv = Int
type Doc = Char
type PPDoc = (?env :: PPEnv) => Doc
f :: Char -> PPDoc
f = succ
In ghc 6.4.1 and 6.2.1 it compiles fine. In ghc 6.5.20060526 I get this:
src $ ghci ~/TestIP.hs
___ ___ _
/ _ \ /\ /\/ __(_)
/ /_\// /_/ / / | | GHC Interactive, version 6.5.20060526, for Haskell 98.
/ /_\\/ __ / /___| | http://www.haskell.org/ghc/
\____/\/ /_/\____/|_| Type :? for help.
Loading package base-1.0 ... linking ... done.
[1 of 1] Compiling TestIP ( /Users/tullsen/TestIP.hs, interpreted )
/Users/tullsen/TestIP.hs:10:4:
Couldn't match expected type `PPDoc' against inferred type `Char'
Probable cause: `succ' is applied to too many arguments
In the expression: succ
In the definition of `f': f = succ
Failed, modules loaded: none.
Prelude>
So, my question is Is this a bug or the removing of an undocumented 'feature'?
Thanks,
Mark
Trac metadata
Trac field | Value |
---|---|
Version | 6.5 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | Unknown |
Architecture | Unknown |