NLL: Limit two-phase borrows to autoref-introduced borrows
This imposes a restriction on two-phase borrows so that it only applies to autoref-introduced borrows.
The goal is to ensure that our initial deployment of two-phase borrows is very conservative. We want it to still cover the `v.push(v.len());` example, but we do not want it to cover cases like `let imm = &v; let mu = &mut v; mu.push(imm.len());`
(Why do we want it to be conservative? Because when you are not conservative, then the results you get, at least with the current analysis, are tightly coupled to details of the MIR construction that we would rather remain invisible to the end user.)
Fix#46747
I decided, for this PR, to add a debug-flag `-Z two-phase-beyond-autoref`, to re-enable the more general approach. But my intention here is *not* that we would eventually turn on that debugflag by default; the main reason I added it was that I thought it was useful for writing tests to be able to write source that looks like desugared MIR.
Namely, the mutable borrows also carries a flag indicating whether
they should support two-phase borrows.
This allows us to thread down, from the point of the borrow's
introduction, whether the particular adjustment that created it is one
that yields two-phase mutable borrows.
Previously, unused variables would get a note that the warning could be
silenced by prefixing the variable with an underscore, but that doesn't
work for field shorthand patterns, which the liveness analysis didn't
know about.
The "to avoid this warning" verbiage seemed unnecessary.
Resolves#47390.
No longer parse it.
Remove AutoTrait variant from AST and HIR.
Remove backwards compatibility lint.
Remove coherence checks, they make no sense for the new syntax.
Remove from rustdoc.
Fix ICE when calling non-functions within closures
The visitor for walking function bodies did not previously properly
handle error-cases for function calls. These are now ignored,
preventing the panic. This fixes#46771.
The Generics now contain one Vec of an enum for the generic parameters,
rather than two separate Vec's for lifetime and type parameters.
Additionally, places that previously used Vec<LifetimeDef> now use
Vec<GenericParam> instead.
The visitor for walking function bodies did not previously properly
handle error-cases for function calls. These are now ignored,
preventing the panic.
Lifetime Resolution for Generic Associated Types
Tracking Issue: https://github.com/rust-lang/rust/issues/44265
r? @nikomatsakis
This PR implements lifetime resolution for generic associated types. 🎉
## Remaining Work Before Merge
I'm going to go do these things in the next day or so. Please let me know if you spot anything in my changes until then.
- [x] If I'm not mistaken, at least some tests should pass now. I need to go through the tests and re-enable the ones that should work by removing the appropriate `~ ERROR` comments
