Opened 13 years ago

Closed 13 years ago

Last modified 48 years ago

#294 closed bug (Fixed)

GHCi does not find instances

Reported by: nobody Owned by: nobody
Priority: normal Milestone:
Component: Compiler Version: 6.4
Keywords: Cc:
Operating System: Architecture:
Type of failure: None/Unknown Test Case:
Blocked By: Blocking:
Related Tickets: Differential Rev(s):
Wiki Page:


This report concerns GHC HEAD (6.3) as downloaded from
CVS around 2PM on 20 Jan 2005.

It seems GHCi does not find some instance declarations.

Consider the following trivial example:

module Foo where
data Foo = Foo
instance Show Foo where
    show Foo = "Foo"

When loaded into GHCi, regardless of whether it is
first compiled or not, GHCi claims that Foo is not an
of Show. E.g.

Prelude> :load Foo
Compiling Foo              ( Foo.hs, interpreted )
Ok, modules loaded: Foo.
*Foo> show Foo
    No instance for (Show Foo)
      arising from use of `show' at <interactive>:1:0-3
    Probable fix: add an instance declaration for (Show
    In the definition of `it': it = show Foo
*Foo> :i Foo
data Foo = Foo
-- Defined at Foo.hs:3:5

But Foo is plainly an instance of Show.

GHC itself has no problems with this
(of course).




Change History (1)

comment:1 Changed 13 years ago by simonpj

Status: assignedclosed
Logged In: YES 

Fixed, thank you
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