Warn about possible missing -XScopedTypeVariables on errors.
Suggest that the user they may wish to add -XScopedTypeVariables, if an error results from a free type variable which would be bound in its scope with the flag enabled. (i.e. if its name exists as a variable in the type declaration).
I ran into this problem on code similar to this:
instance (Sized a n, Nat n) => Rep a where
emptyRep = replicate (toInt (undefined :: n)) 0
and it took me some time to solve, and only by having vague knowledge that such a flag existed.
Trac metadata
Trac field | Value |
---|---|
Version | 7.6.1 |
Type | FeatureRequest |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |