Support FRU pattern with `[feature(capture_disjoint_fields)]`
In case of a functional record update syntax for creating a structure, `ExprUseVisitor` to only detect the precise use of some of the field in the `..x` part of the syntax. However, when we start building MIR, we
1. First, build the place for `x`
2. and then, add precise field projections so that only some parts of `x` end up getting read.
When `capture_disjoint_fields` is enabled, and FRU is used within a closure `x` won't be completely captured, and therefore the first step will fail. This PR updates `mir_build` to create a place builder in the first step and then create place from the builder only after applying the field projection.
Closes https://github.com/rust-lang/project-rfc-2229/issues/32
r? ``````@nikomatsakis``````
- Closures now use closure_min_captures to figure out captured paths
- Build upvar_mutbls using closure_min_captures
- Change logic in limit_capture_mutability to differentiate b/w
capturing parent's local variable or capturing a variable that is
captured by the parent (in case of nested closure) using PlaceBase.
Co-authored-by: Roxane Fruytier <roxane.fruytier@hotmail.com>
- Use closure_min_capture maps to capture precise paths
- PlaceBuilder now searches for ancestors in min_capture list
- Add API to `Ty` to allow access to the n-th element in a
tuple in O(1) time.
Co-authored-by: Roxane Fruytier <roxane.fruytier@hotmail.com>
- This allows us to delay figuring out the index of a capture
in the closure structure when all projections to atleast form
a capture have been applied to the builder
Co-authored-by: Roxane Fruytier <roxane.fruytier@hotmail.com>
ExprKind::SelfRef was used to express accessing `self` in
the desugared Closure/Generator struct when lowering captures in THIR.
Since we handle captures in MIR now, we don't need `ExprKind::Self`.
This allows us to:
- Handle precise Places captured by a closure directly in MIR. Handling
captures in MIR is easier since we can rely on/ tweak PlaceBuilder to
generate `mir::Place`s that resemble how we store captures (`hir::Place`).
- Allows us to handle `let _ = x` case when feature `capture_disjoint_fields`
is enabled directly in MIR. This is required to be done in MIR since
patterns are desugared in MIR.
