Standalone deriving Show at GHCi prompt causes divergence when printing
Deriving a show instance for a data type (defined either with the standard Haskell 98 syntax or with GADT syntax) within GHCi using the command:
instance Show <typename>
causes divergence/stack overflow when printing values of that type. The issue does not manifest itself when you use the standard deriving mechanism within a Haskell source file.
Minimum example necessary to replicate:
module Main (
main
)
where
-- At GHCi prompt type
-- instance Show Bool'
-- then
-- True'
-- to get a stack overflow
data Bool'
= True'
| False'
main = return ()
Trac metadata
Trac field | Value |
---|---|
Version | 7.4.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | GHCi |
Test case | |
Differential revisions | |
BlockedBy | |
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Blocking | |
CC | |
Operating system | |
Architecture |