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  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
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  • #11098
Closed
Open
Issue created Nov 16, 2015 by Richard Eisenberg@raeDeveloper

PartialTypeSignatures mishandles type variables that begin with an underscore

The following GHCi exchange was reported here (you need not follow the link to understand this ticket, though).

Prelude Language.Haskell.TH> runQ [d|foo :: forall _a . _a -> _a;foo x = x|]
[SigD foo_6 (ForallT [PlainTV _a_5] [] (AppT (AppT ArrowT (WildCardT (Just _a_5))) (WildCardT (Just _a_5)))),FunD foo_6 [Clause [VarP x_7] (NormalB (VarE x_7)) []]]

The problem is that the quoted expression uses no wildcards, yet the TH output does. That quoted expression just uses a type variable that begins with an underscore. Such an expression was allowed in Haskell long before wildcards.

Trac metadata
Trac field Value
Version 7.10.2
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Template Haskell
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Architecture
Edited Mar 10, 2019 by Richard Eisenberg
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