There are now two queries: crate and item. The crate one computes the
variance of all items in the crate; it is sort of an implementation
detail, and not meant to be used. The item one reads from the crate one,
synthesizing correct deps in lieu of the red-green algorithm.
At the same time, remove the `variance_computed` flag, which was a
horrible hack used to force invariance early on (e.g. when type-checking
constants). This is only needed because of trait applications, and
traits are always invariant anyway. Therefore, we now change to take
advantage of the query system:
- When asked to compute variances for a trait, just return a vector
saying 'all invariant'.
- Remove the corresponding "inferreds" from traits, and tweak the
constraint generation code to understand that traits are always
inferred.
This is a more principled version of the `RefCell` we were using
before. We now allocate a `Steal<Mir<'tcx>>` for each intermediate MIR
pass; when the next pass steals the entry, any later attempts to use it
will panic (there is no way to *test* if MIR is stolen, you're just
supposed to *know*).
The new setup is as follows. There is a pipeline of MIR passes that each
run **per def-id** to optimize a particular function. You are intended
to request MIR at whatever stage you need it. At the moment, there is
only one stage you can request:
- `optimized_mir(def_id)`
This yields the final product. Internally, it pulls the MIR for the
given def-id through a series of steps. Right now, these are still using
an "interned ref-cell" but they are intended to "steal" from one
another:
- `mir_build` -- performs the initial construction for local MIR
- `mir_pass_set` -- performs a suite of optimizations and transformations
- `mir_pass` -- an individual optimization within a suite
So, to construct the optimized MIR, we invoke:
mir_pass_set((MIR_OPTIMIZED, def_id))
which will build up the final MIR.
Overall goal: reduce the amount of context a mir pass needs so that it
resembles a query.
- The hooks are no longer "threaded down" to the pass, but rather run
automatically from the top-level (we also thread down the current pass
number, so that the files are sorted better).
- The hook now receives a *single* callback, rather than a callback per-MIR.
- The traits are no longer lifetime parameters, which moved to the
methods -- given that we required
`for<'tcx>` objecs, there wasn't much point to that.
- Several passes now store a `String` instead of a `&'l str` (again, no
point).
Removal pass for anonymous parameters
Removes occurences of anonymous parameters from the
rustc codebase, as they are to be deprecated.
See issue #41686 and RFC 1685.
r? @frewsxcv
Add a lint to disallow anonymous parameters
Adds a (allow by default) lint to disallow anonymous parameters, like it was decided in RFC 1685 (rust-lang/rfcs#1685).
cc tracking issue #41686
