Extract `rustc_ast_lowering` crate from `rustc`
Working towards https://github.com/rust-lang/rust/issues/65031.
This PR moves `src/librustc/hir/lowering{/, .rs}` to its own crate (`librustc_ast_lowering`) which is very self-contained (only `fn lower_crate` and `trait Resolver` are exposed).
r? @Mark-Simulacrum
The callbacks have precisely two states: the default, and the one
present throughout almost all of the rustc run (the filled in value
which has access to TyCtxt).
We used to store this as a thread local, and reset it on each thread to
the non-default value. But this is somewhat wasteful, since there is no
reason to set it globally -- while the callbacks themselves access TLS,
they do not do so in a manner that fails in when we do not have TLS to
work with.
Merge `TraitItem` & `ImplItem into `AssocItem`
In this PR we:
- Merge `{Trait,Impl}Item{Kind?}` into `AssocItem{Kind?}` as discussed in https://github.com/rust-lang/rust/issues/65041#issuecomment-538105286.
- This is done by using the cover grammar of both forms.
- In particular, it requires that we syntactically allow (under `#[cfg(FALSE)]`):
- `default`ness on `trait` items,
- `impl` items without a body / definition (`const`, `type`, and `fn`),
- and associated `type`s in `impl`s with bounds, e.g., `type Foo: Ord;`.
- The syntactic restrictions are replaced by semantic ones in `ast_validation`.
- Move syntactic restrictions around C-variadic parameters from the parser into `ast_validation`:
- `fn`s in all contexts now syntactically allow `...`,
- `...` can occur anywhere in the list syntactically (`fn foo(..., x: usize) {}`),
- and `...` can be the sole parameter (`fn foo(...) {}`.
r? @petrochenkov
This commit builds on #65501 continue to simplify the build system and
compiler now that we no longer have multiple LLVM backends to ship by
default. Here this switches the compiler back to what it once was long
long ago, which is linking LLVM directly to the compiler rather than
dynamically loading it at runtime. The `codegen-backends` directory of
the sysroot no longer exists and all relevant support in the build
system is removed. Note that `rustc` still supports a dynamically loaded
codegen backend as it did previously, it just no longer supports
dynamically loaded codegen backends in its own sysroot.
Additionally as part of this the `librustc_codegen_llvm` crate now once
again explicitly depends on all of its crates instead of implicitly
loading them through the sysroot. This involved filling out its
`Cargo.toml` and deleting all the now-unnecessary `extern crate`
annotations in the header of the crate. (this in turn required adding a
number of imports for names of macros too).
The end results of this change are:
* Rustbuild's build process for the compiler as all the "oh don't forget
the codegen backend" checks can be easily removed.
* Building `rustc_codegen_llvm` is much simpler since it's simply
another compiler crate.
* Managing the dependencies of `rustc_codegen_llvm` is much simpler since
it's "just another `Cargo.toml` to edit"
* The build process should be a smidge faster because there's more
parallelism in the main rustc build step rather than splitting
`librustc_codegen_llvm` out to its own step.
* The compiler is expected to be slightly faster by default because the
codegen backend does not need to be dynamically loaded.
* Disabling LLVM as part of rustbuild is still supported, supporting
multiple codegen backends is still supported, and dynamic loading of a
codegen backend is still supported.
Add options to --extern flag.
This changes the `--extern` flag so that it can take a series of options that changes its behavior. The general syntax is `[opts ':'] name ['=' path]` where `opts` is a comma separated list of options. Two options are supported, `priv` which replaces `--extern-private` and `noprelude` which avoids adding the crate to the extern prelude.
```text
--extern priv:mylib=/path/to/libmylib.rlib
--extern noprelude:alloc=/path/to/liballoc.rlib
```
`noprelude` is to be used by Cargo's build-std feature in order to use `--extern` to reference standard library crates.
This also includes a second commit which adds the `aux-crate` directive to compiletest. I can split this off into a separate PR if desired, but it helps with defining these kinds of tests. It is based on #54020, and can be used in the future to replace and simplify some of the Makefile tests.
Rename `bool::then_*` to `bool::to_option_*` and use where appropriate
Name change following https://github.com/rust-lang/rfcs/pull/2757. Also try it out throughout the compiler in places I think makes the code more readable.
Handle GlobalCtxt directly from librustc_interface query system
This PR constructs the `GlobalCtxt` as a member of the `Queries` in librustc_interface.
This simplifies the code to construct it, at the expense of added complexity in the query control flow.
This allows to handle the arenas directly from librustc_interface.
Based on #66707
r? @Zoxc
