- `ParamEnv::empty()` -- does not reveal all, good for typeck
- `ParamEnv::reveal_all()` -- does, good for trans
- `param_env.with_reveal_all()` -- converts an existing parameter environment
This adds an `UnpackedKind` type as a typesafe counterpart to `Kind`. This should make future changes to kinds (such as const generics!) more resilient, as the type-checker should catch more potential issues.
It's inefficient, and the substitution there doesn't account for the
extra regions used by NLL inference, so it's a bad thing to encourage.
As it happens all callers already know if they have a closure or not,
from what I can tell.
move closure kind, signature into `ClosureSubsts`
Instead of using side-tables, store the closure-kind and signature in the substitutions themselves. This has two key effects:
- It means that the closure's type changes as inference finds out more things, which is very nice.
- As a result, it avoids the need for the `freshen_closure_like` code (though we still use it for generators).
- It avoids cyclic closures calls.
- These were never meant to be supported, precisely because they make a lot of the fancy inference that we do much more complicated. However, due to an oversight, it was previously possible -- if challenging -- to create a setup where a closure *directly* called itself (see e.g. #21410).
We have to see what the effect of this change is, though. Needs a crater run. Marking as [WIP] until that has been assessed.
r? @arielb1
This commit refactors the `collect_crate_translation_items` function to only
require the `TyCtxt` instead of a `SharedCrateContext` in preparation for
query-ifying this portion of trans.
This commit moves the calculation of the `LanguageItems` structure into a
query rather than being calculated before the `TyCtxt` exists, with the eventual
end goal of removing some `CrateStore` methods.
Optimize initialization of arrays using repeat expressions
This PR was inspired by [this thread](https://www.reddit.com/r/rust/comments/6o8ok9/understanding_rust_performances_a_newbie_question/) on Reddit.
It tries to bring array initialization in the same ballpark as `Vec::from_elem()` for unoptimized builds.
For optimized builds this should relieve LLVM of having to figure out the construct we generate is in fact a `memset()`.
To that end this emits `llvm.memset()` when:
* the array is of integer type and all elements are zero (`Vec::from_elem()` also explicitly optimizes for this case)
* the array elements are byte sized
If the array is zero-sized initialization is omitted entirely.
This elides initialization for zero-sized arrays:
* for zero-sized elements we previously emitted an empty loop
* for arrays with a length of zero we previously emitted a loop with zero
iterations
This emits llvm.memset() instead of a loop over each element when:
* all elements are zero integers
* elements are byte sized
