Kill the LazyResolver #28092
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Kill the LazyResolver #28092
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Witness matching is a source of a lot of ad-hoc cycles, and mixes the logic that performs resolution, caching, validation, and cycle detection into one place. To make matters worse, some checkers kick off other checks in order to cache work for further declarations, and access an internal cache on their subject conformance for many requirements at once, or sometimes just one requirement. None of this fits into the request evaluator's central view of the caching. This is further evidenced by the fact that if you attempt to move the caching step into the evaluator, it overcaches the same witness and trips asserts. As a start, define requests for the resolution steps, and flush some hacks around forcing witness resolution. The caching logic is mostly untouched (the requests don't actually cache anything), but some cycle breaking is now handled in the evaluator itself. Once witness matching has been refactored to cache with the evaluator, all of these hacks can go away. My urge to destroy the LazyResolver outweighs the compromises here.
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@swift-ci please test |
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@swift-ci please test source compatibility |
slavapestov
approved these changes
Nov 5, 2019
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⛵️ |
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Put the final nail in the LazyResolver's coffin. Devirtualize all remaining uses of the LazyResolver, and replace it with the concept of a "legacy global type checker" instance. Finally, to support that notion, make TypeChecker behave more like a singleton than it does today.
This is built on top of a rebased copy of #28009.