[10/n] Split constants and functions' arguments into disjoint bodies.
_This is part of a series ([prev](https://github.com/rust-lang/rust/pull/38053) | [next]()) of patches designed to rework rustc into an out-of-order on-demand pipeline model for both better feature support (e.g. [MIR-based](https://github.com/solson/miri) early constant evaluation) and incremental execution of compiler passes (e.g. type-checking), with beneficial consequences to IDE support as well.
If any motivation is unclear, please ask for additional PR description clarifications or code comments._
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Finishes the signature-body split started in #37918, namely:
* `trait` items are separated just like `impl` items were, for uniformity, closing #37712
* `static`s, `const`s (including associated ones), `enum` discriminants and array lengths get bodies
* even the count in "repeat expressions", i.e. `n` in `[x; n]`, which fixes#24414
* arguments' patterns are moved to the bodies, with the types staying in `FnDecl`
* `&self` now desugars to `self: &Self` instead of `self: &_` (similarly for other `self` forms)
* `astconv`'s and metadata's (for rustdoc) informative uses are explicitly ignored for the purposes of the dep graph. this could be fixed in the future by hashing the exact information being extracted about the arguments as opposed to generating a dependency on *the whole body*
I no longer remember why I needed this (or thought I did). The way
that the `BitDenotation` is passed around in all existing use cases
(and planned future ones), the thing that were in the `Ctxt` can just
be part of `Self` instead.
(I think ariel had been pushing me to do this back when I first put in
this infrastructure; it took me a while to see how much of pain the
`Ctxt` was causing.)
MIR cleanups and predecessor cache
This PR cleans up a few things in MIR and adds a predecessor cache to allow graph algorithms to be run easily.
r? @nikomatsakis
(Includes a regression test, which needed to go into `compile-fail/`
due to weaknesses when combining `#[deny(warnings)]` with
`tcx.sess.span_warn(..)`)
(updated with review feedback from arielb1.)
this introduces a DropAndReplace terminator as a fix to #30380. That terminator
is suppsoed to be translated by desugaring during drop elaboration, which is
not implemented in this commit, so this breaks `-Z orbit` temporarily.
Also got rid of the `trait HasMoveData`, since I am now just imposing
the constraint that `BitDenotation<Ctxt=MoveData<'tcx>>` where
necessary instead.
(The static semantics of `rustc_peek` is derived from attributes
attached to the function being compiled; in this case,
`rustc_peek(&expr)` observes the dataflow state for the l-value
`expr`.)
Incorporates many fixes contributed by arielb1.
----
revise borrowck::mir::dataflow code to allow varying domain for bitvectors.
This particular code implements the `BitDenotation` trait for three
analyses:
* `MovingOutStatements`, which, like `borrowck::move_data`, maps each
bit-index to a move instruction, and a 1 means "the effect of this
move reaches this point" (and the assigned l-value, if a scoped
declaration, is still in scope).
* `MaybeInitializedLvals`, which maps each bit-index to an l-value.
A 1 means "there exists a control flow path to this point that
initializes the associated l-value."
* `MaybeUninitializedLvals`, which maps each bit-index to an l-value
A 1 means "there exists a control flow path to this point that
de-initializes the associated l-value."
----
Revised `graphviz` dataflow-rendering support in `borrowck::mir`.
One big difference is that this code is now parameterized over the
`BitDenotation`, so that it can be used to render dataflow results
independent of how the dataflow bitvectors are interpreted; see where
reference to `MoveOut` is replaced by the type parameter `D`.
----
Factor out routine to query subattributes in `#[rustc_mir(..)]`.
(Later commits build upon this for some unit testing and instrumentation.)
----
thread through a tcx so that I can query types of lvalues as part of analysis.
----
Revised `BitDenotation::Ctxt`, allowing variation beyond `MoveData`.
The main motivation is to ease threading through a `TyCtxt`.
(In hindsight it might have been better to instead attach the `TyCtxt`
to each of the different dataflow implementations, but that would
require e.g. switching away from having a `Default` impl, so I am
leaving that experiment for another time.)
