Fixes rust-lang#132203

This is a compatibility hack, because I think the new behavior is better.
When an A `include_str!` B, and B `include_str!` C, the path to C should
be resolved relative to B, not A. That's how `include!` itself works,
so that's how `include_str!` with should work.

This makes download-rustc="if-unchanged" more functional and useful
for library developers.

Signed-off-by: onur-ozkan <work@onurozkan.dev>

Signed-off-by: onur-ozkan <work@onurozkan.dev>

The initial naming of "Abi" was an awful mistake, conveying wrong ideas
about how psABIs worked and even more about what the enum meant.
It was only meant to represent the way the value would be described to
a codegen backend as it was lowered to that intermediate representation.
It was never meant to mean anything about the actual psABI handling!
The conflation is because LLVM typically will associate a certain form
with a certain ABI, but even that does not hold when the special cases
that actually exist arise, plus the IR annotations that modify the ABI.

Reframe `rustc_abi::Abi` as the `BackendRepr` of the type, and rename
`BackendRepr::Aggregate` as `BackendRepr::Memory`. Unfortunately, due to
the persistent misunderstandings, this too is now incorrect:
- Scattered ABI-relevant code is entangled with BackendRepr
- We do not always pre-compute a correct BackendRepr that reflects how
  we "actually" want this value to be handled, so we leave the backend
  interface to also inject various special-cases here
- In some cases `BackendRepr::Memory` is a "real" aggregate, but in
  others it is in fact using memory, and in some cases it is a scalar!

Our rustc-to-backend lowering code handles this sort of thing right now.
That will eventually be addressed by lifting duplicated lowering code
to either rustc_codegen_ssa or rustc_target as appropriate.

This allows them to be blessed, regardless of platform.

…r-errors,petrochenkov

Remap impl-trait lifetimes on HIR instead of AST lowering

Current AST->HIR lowering goes out of its way to remap lifetimes for opaque types. This is complicated and leaks into upstream and downstream code.

This PR stops trying to be clever during lowering, and prefers to do this remapping during the HIR->ty lowering. The remapping computation easily fits into the bound var resolution code. Its result can be used in by `generics_of` and `hir_ty_lowering::new_opaque` to add the proper parameters and arguments.

See an example on the doc for query `opaque_captured_lifetimes`.

Based on rust-lang#129244

Fixes rust-lang#125249
Fixes rust-lang#126850

cc `@compiler-errors` `@spastorino`
r? `@petrochenkov`

…ack, r=GuillaumeGomez

rustdoc: make doctest span tweak a 2024 edition change

Fixes rust-lang#132203

This is a compatibility hack, because I think the new behavior is better. When an A `include_str!` B, and B `include_str!` C, the path to C should be resolved relative to B, not A. That's how `include!` itself works, so that's how `include_str!` with should work.

… r=compiler-errors

Rename `rustc_abi::Abi` to `BackendRepr`

Remove the confabulation of `rustc_abi::Abi` with what "ABI" actually means by renaming it to `BackendRepr`, and rename `Abi::Aggregate` to `BackendRepr::Memory`. The type never actually represented how things are passed, as that has to have `PassMode` considered, at minimum, but rather it just is how we represented some things to the backend. This conflation arose because LLVM, the primary backend at the time, would lower certain IR forms using certain ABIs. Even that only somewhat was true, as it broke down when one ventured significantly afield of what is described by the System V AMD64 ABI either by using different architectures, ABI-modifying IR annotations, the same architecture **with different ISA extensions enabled**, or other... unexpected delights.

Unfortunately both names are still somewhat of a misnomer right now, as people have written code for years based on this misunderstanding. Still, their original names are even moreso, and for better or worse, this backend code hasn't received as much maintenance as the rest of the compiler, lately. Actually arriving at a correct end-state will simply require us to disentangle a lot of code in order to fix, much of it pointlessly repeated in several places. Thus this is not an "actual fix", just a way to deflect further misunderstandings.

…e-library, r=Kobzol

force-recompile library changes on download-rustc="if-unchanged"

This makes the download-rustc="if-unchanged" option more functional and useful for library developers.

Implements the second item from [this tracking issue](rust-lang#131744).

Merge `HostPolarity` and `BoundConstness`

They're basically the same thing, and I think `BoundConstness` is easier to use.

r? fee1-dead or reassign