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Introduce a "scope" mechanism to judgments and use for binder instantiation - #463
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My thoughts:I really like the scope mechanism. Quite nice. I'd like to see it factored out into its own PR that we can land first, that should be relatively easy to merge, and then to look more closely at the follow-up changes. |
nikomatsakis
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nikomatsakis
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A rule can prove some of its conditions inside a scope:
(
(scope(enter_forall(env, binder) => (env, body)) with(c)
(prove(env, body) => c))
--------------------
(prove(env, Goal::ForAll(binder)) => c)
)
* The expression enters the scope. It evaluates to a pair: the scope, and
what is inside it, which the pattern binds for the nested conditions.
Like any other condition's expression, it may fail; the rule then does
not apply.
* Those bindings, and any the nested conditions make, end with the
`scope` condition.
* Only the `with` variables come out. Each proof of the nested conditions
leaves the scope with its values for them (`Scope::leave`), and the
rest of the rule sees what that yields.
So a rule cannot forget to leave a scope, nor use what was inside it
afterwards.
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This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed. Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers. |
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What does this PR do?
This introduces a new
scope(...)primitive to judgement functions, which effectively function like a closure. This can allow us to run some code when we exit that scope.AI disclosure