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clarify(?) the documentation of ['a on_sol]

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Gabriel Scherer 2024-01-07 22:37:37 +01:00
parent 3cf46e36c2
commit 97e3c01eaa
1 changed files with 10 additions and 9 deletions
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19
src/Constraint.ml
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@ -57,11 +57,16 @@ module Make (T : Utils.Functor) = struct
| Do : ('a, 'e) t T.t -> ('a, 'e) t
and 'a on_sol = (variable -> STLC.ty) -> 'a
(** A value of type [('a, 'e) t] represents a part of an
inference constraint, but the value of type ['a] that
it produces on success may depend on the solution to
the whole constraint, not just for this part of the
constraint.
(** ['a on_sol] represents an elaborated witness of type ['a] that
depends on the solution to the whole constraint -- represented
by a mapping from inference variables to elaborated types,
[variable -> STLC.ty].
This is used in the success constraint above
[Ret : 'a on_sol -> ('a, 'e) t];
using just [Ret : 'a -> ('a, 'e) t] would not work, as the
witness we want to produce may depend on the solution to the
whole constraint.
For example, consider the untyped term
[(lambda y. 42) 0]
@ -75,10 +80,6 @@ module Make (T : Utils.Functor) = struct
handle the application of [0]. We have to solve the
whole constraint, and then come back to elaborate an
explictly-typed term [lambda (y : int). 42].
The solution to the whole constraint is represented by
a mapping from inference variables to elaborated
types.
*)
let (let+) c f = Map(c, f)