0004993: A program using recursive modules doesn't compile since 3.10

Notes
(0005419) garrigue (manager) 2010-04-30 05:13	I should have mentioned that this program is particularly important, as it demonstrated the power of ocaml recursive modules by encoding the expression problem without using polymorphic variants. This was presented at IFIP WG2.8 in 2005. So this is is kind of unfortunate that this doesn't work anymore. On the other hand, I understand that recursive modules were not a finished feature at that time, so maybe I was just lucky.

(0005445) xleroy (administrator) 2010-05-04 15:24	Jacques, I know this code is dear to your heart :-) The typechecking of recursive modules was unsound in 3.09, and what I think are the correct typing rules could not be implemented because they give rise to cycles of type abbreviations that cause the typechecker to loop. So, what's implemented today is a conservative approximation, and I'm not surprised it rejects some useful codes. At any rate, I learnt one thing the hard way: recursive modules will never be 100% right until the type-checker is resistant to cyclic abbreviations (treating them as abstract types instead of stupidly looping).

Relationships