Refactor variance into a query #41510
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There are now two queries: crate and item. The crate one computes the variance of all items in the crate; it is sort of an implementation detail, and not meant to be used. The item one reads from the crate one, synthesizing correct deps in lieu of the red-green algorithm. At the same time, remove the `variance_computed` flag, which was a horrible hack used to force invariance early on (e.g. when type-checking constants). This is only needed because of trait applications, and traits are always invariant anyway. Therefore, we now change to take advantage of the query system: - When asked to compute variances for a trait, just return a vector saying 'all invariant'. - Remove the corresponding "inferreds" from traits, and tweak the constraint generation code to understand that traits are always inferred.
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looks like we still got some bugs |
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This removes the last use of methods to mutate
DepTrackingMap, at least outside thety::mapsmodule. (cc #40614) This will also get nicer (and more efficient) with the red-green algorithm, but for now it's ok.Fixes #40614
r? @michaelwoerister