#4309: Painfully large errors with silly GADT instances
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Reporter: pumpkin | Owner:
Type: bug | Status: closed
Priority: normal | Milestone:
Component: Compiler | Version: 6.12.3
Resolution: fixed | Keywords:
Testcase: deriving/should_fail/drvfail011 | Blockedby:
Difficulty: | Os:
Unknown/Multiple
Blocking: | Architecture:
Unknown/Multiple
Failure: None/Unknown |
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Changes (by simonpj):
* status: new => closed
* testcase: => deriving/should_fail/drvfail011
* resolution: => fixed
Comment:
OK, done
{{{
Wed Sep 15 00:23:01 PDT 2010 [email protected]
* Less voluminous error when derived code doesn't typecheck
M ./compiler/typecheck/TcInstDcls.lhs -8 +12
}}}
The error message now looks like:
{{{
drvfail011.hs:8:1:
No instance for (Eq a)
arising from a use of `=='
In the expression: ((a1 == b1))
In an equation for `==': == (T1 a1) (T1 b1) = ((a1 == b1))
When typechecking the code for `=='
in a standalone derived instance for `Eq (T a)':
To see the code I am typechecking, use -ddump-deriv
In the instance declaration for `Eq (T a)'
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4309#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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