This saves the storage space used by about 32 bits per `Fingerprint`.
On average, this reduces the size of the `/target/{mode}/incremental`
folder by roughly 5%.

Fixes #45875

It is also intended for use with unions.

Rename ReprExtern to ReprC, and similarily rename a few other fields and locals that mentioned "extern repr"

Upgrade `log` to `0.4` in multiple crates.

The same effect can be achieved using -Cllvm-args=-debug

Refs #46437 as it removes LLVMRustSetDebug()

This showed up on the Windows bot for testing this PR, and this pr allows
`mark_incr_comp_session_as_invalid` ok if it's already invalid, hopefully
avoiding scary ICEs and instead leaving the nicely printed errors

This is only applicable when neither of --emit=llvm-ir or --emit=llvm-bc are not
requested.

In case either of these outputs are wanted, but the benefits of such context are
desired as well, -Zfewer_names option provides the same functionality regardless
of the outputs requested.

These no longer work now that Cargo changes the cwd of rustc while it's running.
Instead use an absolute path that's set by rustbuild.

Fixes #47094

Besides fixing that bug, this change has a user-visible effect on the spans in the "incompatible repr hints" warning and another error: they now point at `foo` and/or `bar` in `repr(foo, bar)` instead of the whole attribute. This is sometimes more precise (e.g., `#[repr(C, packed)]` on an enum points at the `packed`) but sometimes not. I moved a compile-fail test to a ui test to illustrate how it now looks in the common case of only one attribute.

Update `rand` crate to `0.3.19`.
Update `log` crate to `0.3.9` and `0.4.1`.
Update `parking_lot_core` crate to `0.2.9`.
Upgrade all flate2 dependencies to `1.0.1`.
- Update `rust-installer` submodule.

So it's not mistaken for dead code.

Solves incorrect diagnostics for unused or deprecated imports. Closes #46576.

Deprecated imports had an existing test which asserted the incorrect span.
That test has been corrected as part of this commit.

This is the first part of the RFC 1937 that supports new
`Termination` trait in the rust `main` function.

Use span label instead of span note for single line spans in
"incompatible arm" diagnostic.

These can happen if prior errors disable defaulting.

Fixes #43825.

This commit is the next attempt to enable multiple codegen units by default in
release mode, getting some of those sweet, sweet parallelism wins by running
codegen in parallel. Performance should not be lost due to ThinLTO being on by
default as well.

Closes #45320

When a parse error occurs on a block, the parser will recover and create
a block with the statements collected until that point. Now a flag
stating that a recovery has been performed in this block is propagated
so that the type checker knows that the type of the block (which will be
identified as `()`) shouldn't be checked against the expectation to
reduce the amount of irrelevant diagnostic errors shown to the user.

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.