Decomposition rule for equalities is too weak in case of higher-kinded type families
foo :: (F Int a ~ F Int [a]) => a -> [a]
foo = undefined
gives us
Occurs check: cannot construct the infinite type: a = [a]
but
foo :: (F Int a ~ F Bool [a]) => a -> [a]
foo = undefined
doesn't - although both should lead to the same error.
Trac metadata
Trac field | Value |
---|---|
Version | 6.9 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | Multiple |
Architecture | Multiple |