[Haskell-cafe] Status of TypeDirectedNameResolution proposal?

Simon Peyton-Jones simonpj at microsoft.com
Fri Nov 20 04:23:25 EST 2009

| >   * General Type Directed Name Resolution (GTDNR):
| >       For every function application "f x" in the program where "f" is a
| >       name, "f" is resolved based on the type of the argument "x".
| >
| You suggest that GTDNR might not be a good idea, well why not? One
| reason is that it can potentially lead to a whole lot of guessing,
| slowing the compiler down dramatically and maybe even so much guessing
| that there are multiple whole-program resolutions (oh noes!). So how can
| we control that combinatorial exploration of alternatives? One way would
| be to restrict the places where we allow guessing. There's still
| potential room for combinatorial explosions but they're greatly reduced,
| both because we reduce the number of variables in the problem (so the
| combinatorics are smaller), and because we (generally) will have a good
| deal of non-variable context to anchor the disambiguation process and
| hopefully resolve the variables easily.

Yes.  I'm confident that GTDNR is not viable.  The TDNR proposal is carefully constrained to give a uni-directional "information flow" from the "record field" to select the function.  I don't think that the vastly more general idea you propose is going to work when combined with ordinary HM type inference, type classes, type functions, etc etc.

Of course, I could be wrong.


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