propagate outlives between types and regions #22
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Before, we would always have a `Some` ClosureRegionRequirements if we were inferring values for a closure. Now we only do is it has a non-empty set of outlives requirements.
This allows us to re-use the `normalize` method on `TypeCheck`, which is important since normalization may create fresh region variables. This is not an ideal solution, though, since the current representation of "liveness constraints" (a vector of (region, point) pairs) is rather inefficient. Could do somewhat better by converting to indices, but it'd still be less good than the older code. Unclear how important this is.
In the future, `check_type_tests` will also potentially propagate constriants to its caller.
The existing flags did not consider `'static` to be "free". This then fed into what was "erasable" -- but `'static` is most certainly erasable.
Currently, we only propagate type tests that exclude all regions from the type.
This is needed to allow the `ClosureRegionRequirements` to capture types that include regions.
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The input/output types found in `UniversalRegions` are not normalized. The old code used to assign them directly into the MIR, which would lead to errors when there was a projection in a argument or return type. This also led to some special cases in the `renumber` code. We now renumber uniformly but then pass the input/output types into the MIR type-checker, which equates them with the types found in MIR. This allows us to normalize at the same time.
Turns out this works but we had no test targeting it.
We don't need to know the vector of region bounds; we only care if there were any region bounds at all.
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merging this branch (all tests passed locally) |
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Sep 16, 2019
declare EnvKey before use to fix build error
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This branch is targeting rust-lang#45826. I am running tests now but it seems to be at a consistent point and ready for merging.