GHC panic on type wildcard in left-hand side of data family
While playing around with data families I received the following output by ghc/ghci:
ghc: panic! (the 'impossible' happened)
(GHC version 7.10.3 for x86_64-unknown-linux):
rnHsTyKi HsWildcardTy
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
I had accidentally left a wildcard _
on the left-hand side of a data instance definition.
To reproduce enter the following code into a file and try to load that file into ghci, or try to compile it with ghc:
data family Bug x
data instance Bug _ = Bug
The expected behavior would be a (non-panic) error message of some sort.
Trac metadata
Trac field | Value |
---|---|
Version | 7.10.3 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
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Blocking | |
CC | |
Operating system | |
Architecture |