Operator (!) causes weird pretty printing and parsing
class Key key where
data TotalMap key :: Type -> Type
(!) :: TotalMap key val -> (key -> val)
instance Key Bool where
data TotalMap Bool val = BoolMap val val
(!) :: TotalMap Bool val -> (Bool -> val)
(BoolMap f _) ! False = f
puts unnecessary parentheses around the wildcard pattern:
tf6t.hs:14:3-23: error: …
Parse error in pattern: (BoolMap f (_))
Compilation failed.
and with no parentheses
BoolMap f _ ! False = f
it talks about missing method, pattern bindings and doesn't list a space between !
and False
:
tf6t.hs:13:3-5: error: …
The class method signature for ‘!’ lacks an accompanying binding
(The class method signature must be given where ‘!’ is declared)
tf6t.hs:14:3-25: error: …
Pattern bindings (except simple variables) not allowed in instance declaration:
BoolMap f _ !False = f
Compilation failed.
All of these issues go away if the operator is called something other than !
, it works if written prefix
(!) (BoolMap f _) False = f
Trac metadata
Trac field | Value |
---|---|
Version | 8.0.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Parser) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |