Languages should express our intent, and giving type and instance
declarations the ability to be localised will enable them to serve as
better vehicles of expression.
That said,
Imants Cekusins
local types and instances
is this not an attempt to move module functionality inside function?
Same counter-argument can be applied to local functions.
would this not encourage larger functions? are larger functions a good thing?
Same as above.
could this not be better addressed by allowing explicit export / hiding of instances in a module?
If I interpret the intent correctly, this is specifically about finer granularity than module level.
does not type declaration inside function come at a performance cost?
Generally speaking, and whether this suggested cost is real, Haskell programmers are more or less used to pay the cost of abstraction. -- с уважениeм / respectfully, Косырев Сергей