(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.)
emit (via debug!) scary message from `fn borrowck_mir` until basic
prototype is in place.
Gather children of move paths and set their kill bits in
dataflow. (Each node has a link to the child that is first among its
siblings.)
Hooked in libgraphviz based rendering, including of borrowck dataflow
state.
doing this well required some refactoring of the code, so I cleaned it
up more generally (adding comments to explain what its trying to do
and how it is doing it).
Update: this newer version addresses most review comments (at least
the ones that were largely mechanical changes), but I left the more
interesting revisions to separate followup commits (in this same PR).
