#4525: Type synonyms not expanded consistently in errors
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Reporter: igloo | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 7.2.1
Component: Compiler (Type checker) | Version: 7.1
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Comment(by simonpj):
Actually this is deliberate. The "couldn't match" part describes the
actual incompatibility encountered. The "actual/expected" part describes
the original types being unified. A more typical case might be
{{{
Couldn't match expected type `Char' with actual type `Int'
Expected type: Char -> a
Actual type: Int -> a
}}}
It would be possible to make the first, "couldn't match", bit speak in
terms of any immediate type synonym. That would make your original error
look ok, and also:
{{{
Couldn't match expected type `Char' with actual type `Foo'
Expected type: Char -> a
Actual type: Foo -> a
}}}
Would that be better? Anyone?
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4525#comment:1>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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