Fix sized check ICE in asm check
Fixes (beta nominated, so doesn't close) #99122
1. Moves a check for unresolved inference variables to _before_ other checks that could possibly ICE. We're not changing behavior here, just doing the same thing earlier in the function.
2. Erases region variables in sized check (which are not resolved at this point) because rustc will also ICE when region vars are passed to a query which does not canonicalize them.
Fix duplicated type annotation suggestion
Before, there was more or less duplicated suggestions to add type hints.
Fix by clearing more generic suggestions when a more specific suggestion
is possible.
This fixes#93506 .
Fix rustdoc help options
Fixes#98976.
Since you're the one who found out about the problem and also provided the solution (thanks for both!):
r? ```@jyn514```
Support `-A`, `-W`, `-D` and `-F` when running `./x.py clippy`
Resolves#97059
This PR adds support for `-A`, `-W`, `-D` and `-F` when running `./x.py clippy`.
Create fresh lifetime parameters for bare fn trait too
The current code fails to account for the equivalence between `dyn FnMut(&mut u8)` and bare `FnMut(&mut u8)`, and treated them differently.
This PR introduces a special case for `Fn` traits, which are always fully resolved.
Fixes#98616Fixes#98726
This will require a beta-backport, as beta contains that bug.
r? `@petrochenkov`
This extracts the linux-isms into variables, so that the script can be
extended to do PGO on windows. These variables will be overriden in a
few spots, in windows-specific blocks.
When building LLVM/LLD as part of a build that asks LLVM to generate profiles, e.g. when
doing PGO, cmake or clang-cl don't automatically link clang's profiler runtime in,
causing undefined reference errors at link-time.
We do that manually, by adding clang's resource library folder to the library search path:
- for LLVM itself, by extending the linker args that `rustc_llvm`'s build script
uses, to avoid the linker errors when linking `rustc_driver`.
- for LLD, by extending cmake's linker flags during the LLD build step.
Mention similarly named associated type even if it's not clearly in supertrait
Due to query cycle avoidance, we sometimes restrict the candidates in `complain_about_assoc_type_not_found` too much so that we can't detect typo replacements from just supertraits.
This creates a more general note of the existence of a similarly named associated type from _all_ visible traits when possible.
Fixes#55673
explain doc comments in macros a bit
Open to suggestions on improving this... macro parsing is very foreign to me.
Should we have a structured suggestion to turn them into their regular non-doc comments?
Fixes#92846Fixes#97850
Currently, for the enums and comparison traits we always check the tag
for equality before doing anything else. This is a bit clumsy. This
commit changes things so that the tags are handled very much like a
zeroth field in the enum.
For `eq`/ne` this makes the code slightly cleaner.
For `partial_cmp` and `cmp` it's a more notable change: in the case
where the tags aren't equal, instead of having a tag equality check
followed by a tag comparison, it just does a single tag comparison.
The commit also improves how `Hash` works for enums: instead of having
duplicated code to hash the tag for every arm within the match, we do
it just once before the match.
All this required replacing the `EnumNonMatchingCollapsed` value with a
new `EnumTag` value.
For fieldless enums the new code is particularly improved. All the code
now produced is close to optimal, being very similar to what you'd write
by hand.
Remove unsupported options in configure.py
I've seen people using `optimize = false` and `full-bootstrap = true` in the past, without knowing
that they're not recommended. Remove `optimize` and a few other options that are always a bad idea,
and document that full-bootstrap is only for testing reproducible builds.
Use `tag` in names of things referring to tags, instead of the
mysterious `vi`.
Also change `arg_N` in output to `argN`, which has the same length as
`self` and so results in nicer vertical alignments.
By producing `&T` expressions for fields instead of `T`. This matches
what the existing comments (e.g. on `FieldInfo`) claim is happening, and
it's also what most of the trait-specific code needs.
The exception is `PartialEq`, which needs `T` expressions for lots of
special case error messaging to work. So we now convert the `&T` back to
a `T` for `PartialEq`.
E.g. improving code like this:
```
match &*self {
&Enum1::Single { x: ref __self_0 } => {
::core:#️⃣:Hash::hash(&*__self_0, state)
}
}
```
to this:
```
match self {
Enum1::Single { x: __self_0 } => {
::core:#️⃣:Hash::hash(&*__self_0, state)
}
}
```
by removing the `&*`, the `&`, and the `ref`.
I suspect the current generated code predates deref-coercion.
The commit also gets rid of `use_temporaries`, instead passing around
`always_copy`, which makes things a little clearer. And it fixes up some
comments.
Fix `x build library/std compiler/rustc`
Previously, this was broken because of improper caching:
1. `StepDescription::maybe_run` builds `Compile::Std`, which only built `std` and not `proc_macro`
1. `Std` calls `builder.ensure(StdLink)`
1. `Rustc` calls `ensure(Std)`, which builds all crates, including `proc_macro`
1. `Rustc` calls `ensure(StdLink)`. `ensure` would see that it had already been run and do nothing. <-- bug is here
1. Cargo gives an error that `proc_macro` doesn't exist.
This fixes the caching by adding `crates` to `StdLink`, so it will get rerun if the crates that are built change.
Fixes https://github.com/rust-lang/rust/issues/99129.
Before:
```
thread 'main' panicked at 'Unable to build RLS', dist.rs:42:9
```
After:
```
thread 'main' panicked at 'Unable to build submodule tool RLS (use `missing-tools = true` to ignore this failure)
note: not all tools are available on all nightlies
help: see https://forge.rust-lang.org/infra/toolstate.html for more information', dist.rs:43:9
```
Allow using `download-ci-llvm = true` outside the git checkout
`@bjorn3` noticed that this is already allowed today when download-llvm is disabled, but breaks with it enabled:
```
$ ./rust2/x.py build
fatal: not a git repository (or any of the parent directories): .git
thread 'main' panicked at 'command did not execute successfully: "git" "rev-list" "--author=bors@rust-lang.org" "-n1" "--first-parent" "HEAD" "--" "/home/jnelson/rust-lang/rust2/src/llvm-project" "/home/jnelson/rust-lang/rust2/src/bootstrap/download-ci-llvm-stamp" "/home/jnelson/rust-lang/rust2/src/version"
expected success, got: exit status: 128', src/bootstrap/native.rs:134:20
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```
Support it too for consistency. It's unclear to me when anyone would need to use this, but `@bjorn3`
feels we should support it, and it's not much additional effort to get it working.
Previously, this was broken because of improper caching:
1. `StepDescription::maybe_run` builds `Compile::Std`, which only built `std` and not `proc_macro`
1. `Std` calls `builder.ensure(StdLink)`
1. `Rustc` calls `ensure(Std)`, which builds all crates, including `proc_macro`
1. `Rustc` calls `ensure(StdLink)`. `ensure` would see that it had already been run and do nothing. <-- bug is here
1. Cargo gives an error that `proc_macro` doesn't exist.
This fixes the caching by adding `crates` to `StdLink`, so it will get rerun if the crates that are
built change. This also does the same for `RustcLink`; it doesn't matter in practice currently
because nothing uses it except `impl Step for Rustc`, but it will avoid bugs if we start using it in
the future (e.g. to build individual crates for rustfmt).
Fix `download-ci-llvm` NixOS patching for binaries
LLVM tools should also be patched, since they are used in some tests, specially,
- src/test/run-make-fulldeps/cross-lang-lto (llvm-ar)
- src/test/run-make-fulldeps/cross-lang-lto-upstream-rlibs (llvm-ar)
- src/test/run-make-fulldeps/issue-64153 (llvm-objdump)
To be more future proof, we should patch all binaries in `bin`, which is done in this PR.
Group .test-arrow CSS rules and fix rgb/rgba property
Surprisingly, the web browsers were handling the `rgb`/`rgba` typo correctly. At least it now is as expected.
For the rest, it's simply grouping `.test-arrow` rules.
r? ``@Dylan-DPC``
promote placeholder bounds to 'static obligations
In NLL, when we are promoting a bound out from a closure, if we have a requirement that `T: 'a` where `'a` is in a higher universe, we were previously ignoring that, which is totally wrong. We should be promoting those constraints to `'static`, since universes are not expressible across closure boundaries.
Fixes#98693
~~(Marking as WIP because I'm still running tests, haven't add the new test, etc)~~
r? ``@jackh726``
LLVM tools should also be patched, since they are used in some tests,
specially,
- src/test/run-make-fulldeps/cross-lang-lto (llvm-ar)
- src/test/run-make-fulldeps/cross-lang-lto-upstream-rlibs (llvm-ar)
- src/test/run-make-fulldeps/issue-64153 (llvm-objdump)
To be more future proof, we should patch all binaries in `bin`.
@bjorn3 noticed that this is already allowed today when download-llvm is disabled, but breaks with it enabled:
```
$ ./rust2/x.py build
fatal: not a git repository (or any of the parent directories): .git
thread 'main' panicked at 'command did not execute successfully: "git" "rev-list" "--author=bors@rust-lang.org" "-n1" "--first-parent" "HEAD" "--" "/home/jnelson/rust-lang/rust2/src/llvm-project" "/home/jnelson/rust-lang/rust2/src/bootstrap/download-ci-llvm-stamp" "/home/jnelson/rust-lang/rust2/src/version"
expected success, got: exit status: 128', src/bootstrap/native.rs:134:20
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```
Support it too for consistency. It's unclear to me when anyone would need to use this, but @bjorn3
feels we should support it, and it's not much additional effort to get it working.
This also updates a bunch of other git commands that were similarly depending on the current directory.
I've seen people using `optimize = false` and `full-bootstrap = true` in the past, without knowing
that they're not recommended. Remove `optimize` and a few other options that are always a bad idea,
and document that full-bootstrap is only for testing reproducible builds.
Previously, drop-tracking would incorrectly assume the struct would be dropped immediately, which
was not true: when the field had a type with a manual `Drop` impl, the drop becomes observable and
has to be dropped after the await instead.
For reasons I don't understand, this also fixes another error crater popped up related to type parameters.
#98476
proc_macro: Fix expand_expr expansion of bool literals
Previously, the expand_expr method would expand bool literals as a
`Literal` token containing a `LitKind::Bool`, rather than as an `Ident`.
This is not a valid token, and the `LitKind::Bool` case needs to be
handled seperately.
Tests were added to more deeply compare the streams in the expand-expr
test suite to catch mistakes like this in the future.
improve print styles
this change removes some interactive elements in ``@media` print` form.
more specifically, it removes the sidebar, source links, the expand/collapse toggle buttons, and the `#copy-path` button.
it also adjusts some spacing and removes the `.top-doc` description completely if it's currently collapsed.
Partially stabilize const_slice_from_raw_parts
This doesn't stabilize methods working on mutable pointers.
This pull request continues from #94946.
Pinging `@rust-lang/wg-const-eval` this because I use `rustc_allow_const_fn_unstable`. I believe this is justifiable as it's already possible to use `slice::from_raw_parts` in stable by abusing `transmute`. The stable alternative to this would be to provide a stable const implementation of `std::ptr::from_raw_parts` (as it can already be implemented in stable).
```rust
use std::mem;
#[repr(C)]
struct Slice<T> {
data: *const T,
len: usize,
}
fn main() {
let data: *const i32 = [1, 2, 3, 4].as_ptr();
let len = 4;
println!("{:?}", unsafe {
mem::transmute::<Slice<i32>, &[i32]>(Slice { data, len })
});
}
```
`@rustbot` modify labels: +T-libs-api
don't allow ZST in ScalarInt
There are several indications that we should not ZST as a ScalarInt:
- We had two ways to have ZST valtrees, either an empty `Branch` or a `Leaf` with a ZST in it.
`ValTree::zst()` used the former, but the latter could possibly arise as well.
- Likewise, the interpreter had `Immediate::Uninit` and `Immediate::Scalar(Scalar::ZST)`.
- LLVM codegen already had to special-case ZST ScalarInt.
So I propose we stop using ScalarInt to represent ZST (which are clearly not integers). Instead, we can add new ZST variants to those types that did not have other variants which could be used for this purpose.
Based on https://github.com/rust-lang/rust/pull/98831. Only the commits starting from "don't allow ZST in ScalarInt" are new.
r? `@oli-obk`
Fix several issues during cross compiling
- When cross compiling LLVM on an arm64 macOS machine to x86_64, CMake will produce universal binaries by default, causing link errors. Explicitly set `CMAKE_OSX_ARCHITECTURES` to the one single target architecture so that the executables and libraries will be single architecture.
- When cross compiling rustc with `llvm.clang = true`, `CLANG_TABLEGEN` has to be set to the host `clang-tblgen` executable to build clang.
Implement support for DWARF version 5.
DWARF version 5 brings a number of improvements over version 4. Quoting from
the announcement [1]:
> Version 5 incorporates improvements in many areas: better data compression,
> separation of debugging data from executable files, improved description of
> macros and source files, faster searching for symbols, improved debugging
> optimized code, as well as numerous improvements in functionality and
> performance.
On platforms where DWARF version 5 is supported (Linux, primarily), this commit
adds support for it behind a new `-Z dwarf-version=5` flag.
[1]: https://dwarfstd.org/Public_Review.php
r? ``@michaelwoerister``
Before, there was more or less duplicated suggestions to add type hints.
Fix by clearing more generic suggestions when a more specific suggestion
is possible.
This fixes#93506 .
Track implicit `Sized` obligations in type params
When we evaluate `ty::GenericPredicates` we introduce the implicit
`Sized` predicate of type params, but we do so with only the `Predicate`
its `Span` as context, we don't have an `Obligation` or
`ObligationCauseCode` we could influence. To try and carry this
information through, we add a new field to `ty::GenericPredicates` that
tracks both which predicates come from a type param and whether that
param has any bounds already (to use in suggestions).
We also suggest adding a `?Sized` bound if appropriate on E0599.
Address part of #98539.
DWARF version 5 brings a number of improvements over version 4. Quoting from
the announcement [1]:
> Version 5 incorporates improvements in many areas: better data compression,
> separation of debugging data from executable files, improved description of
> macros and source files, faster searching for symbols, improved debugging
> optimized code, as well as numerous improvements in functionality and
> performance.
On platforms where DWARF version 5 is supported (Linux, primarily), this commit
adds support for it behind a new `-Z dwarf-version=5` flag.
[1]: https://dwarfstd.org/Public_Review.php
don't succeed `evaluate_obligation` query if new opaque types were registered
fixes#98608fixes#98604
The root cause of all this is that in type flag computation we entirely ignore nongeneric things like struct fields and the signature of function items. So if a flag had to be set for a struct if it is set for a field, that will only happen if the field is generic, as only the generic parameters are checked.
I now believe we cannot use type flags to handle opaque types. They seem like the wrong tool for this.
Instead, this PR replaces the previous logic by adding a new variant of `EvaluatedToOk`: `EvaluatedToOkModuloOpaqueTypes`, which says that there were some opaque types that got hidden types bound, but that binding may not have been legal (because we don't know if the opaque type was in its defining scope or not).
Highlight conflicting param-env candidates
This could probably be further improved by noting _why_ equivalent param-env candidates (modulo regions) leads to ambiguity.
Fixes#98786
More derive output improvements
This PR includes:
- Some test improvements.
- Some cosmetic changes to derive output that make the code look more like what a human would write.
- Some more fundamental improvements to `cmp` and `partial_cmp` generation.
r? `@Mark-Simulacrum`
Add test for and fix rust-lang/rust-clippy#9131
This lint seems to have been broken by #98446 -- but of course, there was no clippy test for this case at the time.
`expr.span.ctxt().outer_expn_data()` now has `MacroKind::Derive` instead of `MacroKind::Attr` for something like:
```
#[derive(Clone, Debug)]
pub struct UnderscoreInStruct {
_foo: u32,
}
```
---
changelog: none
closes: https://github.com/rust-lang/rust-clippy/issues/9131
Fix caching bug in `download-rustc = true`
When moving this to rustbuild, I introduced a bug: if you had the file already downloaded, but
deleted the sysroot for whatever reason, rustbuil would fail to unpack the cached tarball.
This only affects people if they have a cached tarball, which is probably why we haven't seen an issue yet -
wiping `build/cache` would work around the issue, or just not deleting `build/$TARGET/stage2`.
Fixes the following error:
```
thread 'main' panicked at 'fs::read_dir(&lib_dir) failed with No such file or directory (os error 2) ("/home/jnelson/rust-lang/rust2/build/x86_64-unknown-linux-gnu/ci-rustc/lib")', config.rs:1563:20
```
r? ``@Mark-Simulacrum``
sess: stabilize `--terminal-width` as `--diagnostic-width`
Formerly `-Zterminal-width`, `--terminal-width` allows the user or build
tool to inform rustc of the width of the terminal so that diagnostics
can be truncated.
Pending agreement to stabilize, see tracking issue at #84673.
r? ```@oli-obk```
this change removes some interactive elements in `@media print` form.
more specifically, it removes the source links, the expand/collapse toggle buttons, and the `#copy-path` button.
it also adjusts some spacing and removes the `.top-doc` description completely if it's currently collapsed.
On partial uninit error point at where we need init
When a binding is declared without a value, borrowck verifies that all
codepaths have *one* assignment to them to initialize them fully. If
there are any cases where a condition can be met that leaves the binding
uninitialized or we attempt to initialize a field of an uninitialized
binding, we emit E0381.
We now look at all the statements that initialize the binding, and use
them to explore branching code paths that *don't* and point at them. If
we find *no* potential places where an assignment to the binding might
be missing, we display the spans of all the existing initializers to
provide some context.
Fix https://github.com/rust-lang/rust/issues/97956.
Rollup of 9 pull requests
Successful merges:
- #97917 (Implement ExitCodeExt for Windows)
- #98844 (Reword comments and rename HIR visiting methods.)
- #98979 (interpret: use AllocRange in UninitByteAccess)
- #98986 (Fix missing word in comment)
- #98994 (replace process exit with more detailed exit in src/bootstrap/*.rs)
- #98995 (Add a test for #80471)
- #99002 (suggest adding a derive for #[default] applied to variants)
- #99004 (Add a test for #70408)
- #99017 (Replace boolean argument for print_where_clause with an enum to make code more clear)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
When a binding is declared without a value, borrowck verifies that all
codepaths have *one* assignment to them to initialize them fully. If
there are any cases where a condition can be met that leaves the binding
uninitialized or we attempt to initialize a field of an unitialized
binding, we emit E0381.
We now look at all the statements that initialize the binding, and use
them to explore branching code paths that *don't* and point at them. If
we find *no* potential places where an assignment to the binding might
be missing, we display the spans of all the existing initializers to
provide some context.
Replace boolean argument for print_where_clause with an enum to make code more clear
As you suggested ``@notriddle.`` Just not sure if the naming seems good to you?
r? ``@notriddle``
interpret: use AllocRange in UninitByteAccess
also use nice new format string syntax in `interpret/error.rs`, and use the `#` flag to add `0x` prefixes where applicable.
r? ``@oli-obk``
Make lowering a query
Split from https://github.com/rust-lang/rust/pull/88186.
This PR refactors the relationship between lowering and the resolver outputs in order to make lowering itself a query.
In a first part, lowering is changed to avoid modifying resolver outputs, by maintaining its own data structures for creating new `NodeId`s and so.
Then, the `TyCtxt` is modified to allow creating new `LocalDefId`s from inside it. This is done by:
- enclosing `Definitions` in a lock, so as to allow modification;
- creating a query `register_def` whose purpose is to declare a `LocalDefId` to the query system.
See `TyCtxt::create_def` and `TyCtxt::iter_local_def_id` for more detailed explanations of the design.
Make MIR basic blocks field public
This makes it possible to mutably borrow different fields of the MIR
body without resorting to methods like `basic_blocks_local_decls_mut_and_var_debug_info`.
To preserve validity of control flow graph caches in the presence of
modifications, a new struct `BasicBlocks` wraps together basic blocks
and control flow graph caches.
The `BasicBlocks` dereferences to `IndexVec<BasicBlock, BasicBlockData>`.
On the other hand a mutable access requires explicit `as_mut()` call.
incr: cache dwarf objects in work products
Cache DWARF objects alongside object files in work products when those exist so that DWARF object files are available for thorin in packed mode in incremental scenarios.
r? `@michaelwoerister`
Finishing touches for `#[expect]` (RFC 2383)
This PR adds documentation and some functionality to rustc's lint passes, to manually fulfill expectations. This is needed for some lints in Clippy. Hopefully, it should be one of the last things before we can move forward with stabilizing this feature.
As part of this PR, I've also updated `clippy::duplicate_mod` to showcase how this new functionality can be used and to ensure that it works correctly.
---
changelog: [`duplicate_mod`]: Fixed lint attribute interaction
r? `@wesleywiser`
cc: https://github.com/rust-lang/rust/issues/97660, https://github.com/rust-lang/rust/issues/85549
And I guess that's it. Here have a magical unicorn 🦄
implement detail_exit but I'm not sure it is right.
not create new file and write detail exit in lib.rs
replace std::process::exit to detail_exit
that is not related to code runnning.
remove pub
interpret: remove support for unsized_locals
I added support for unsized_locals in https://github.com/rust-lang/rust/pull/59780 but the current implementation is a crude hack and IMO definitely not the right way to have unsized locals in MIR. It also [causes problems](https://rust-lang.zulipchat.com/#narrow/stream/146212-t-compiler.2Fconst-eval/topic/Missing.20Layout.20Check.20in.20.60interpret.2Foperand.2Ers.60.3F). and what codegen does is unsound and has been for years since clearly nobody cares (so I hope nobody actually relies on that implementation and I'll be happy if Miri ensures they do not). I think if we want to have unsized locals in Miri/MIR we should add them properly, either by having a `StorageLive` that takes metadata or by having an `alloca` that returns a pointer (making the ptr indirection explicit) or something like that.
So, this PR removes the `LocalValue::Unallocated` hack. It adds `Immediate::Uninit`, for several reasons:
- This lets us still do fairly little work in `push_stack_frame`, in particular we do not actually have to create any allocations.
- If/when I remove `ScalarMaybeUninit`, we will need something like this to have an "optimized" representation of uninitialized locals. Without this we'd have to put uninitialized integers into the heap!
- const-prop needs some way to indicate "I don't know the value of this local'; it used to use `LocalValue::Unallocated` for that, now it can use `Immediate::Uninit`.
There is still a fundamental difference between `LocalValue::Unallocated` and `Immediate::Uninit`: the latter is considered a regular local that you can read from and write to, it just has a more optimized representation when compared with an actual `Allocation` that is fully uninit. In contrast, `LocalValue::Unallocated` had this really odd behavior where you would write to it but not read from it. (This is in fact what caused the problems mentioned above.)
While at it I also did two drive-by cleanups/improvements:
- In `pop_stack_frame`, do the return value copying and local deallocation while the frame is still on the stack. This leads to better error locations being reported. The old errors were [sometimes rather confusing](https://rust-lang.zulipchat.com/#narrow/stream/269128-miri/topic/Cron.20Job.20Failure.202022-06-24/near/287445522).
- Deduplicate `copy_op` and `copy_op_transmute`.
r? `@oli-obk`
rustdoc: Add more semantic information to impl IDs
Take over of #92745.
I fixed the last remaining issue for the links in the sidebar (mentioned by `@jsha)` and fixed the few links broken in the std/core docs.
cc `@camelid`
r? `@notriddle`
Rename the `--output-width` flag to `--diagnostic-width` as this appears
to be the preferred name within the compiler team.
Signed-off-by: David Wood <david.wood@huawei.com>
Rename the `--terminal-width` flag to `--output-width` as the behaviour
doesn't just apply to terminals (and so is slightly less accurate).
Signed-off-by: David Wood <david.wood@huawei.com>
Formerly `-Zterminal-width`, `--terminal-width` allows the user or build
tool to inform rustc of the width of the terminal so that diagnostics
can be truncated.
Signed-off-by: David Wood <david.wood@huawei.com>
Cache DWARF objects alongside object files in work products when those
exist so that DWARF object files are available for thorin in packed mode
in incremental scenarios.
Signed-off-by: David Wood <david.wood@huawei.com>
fix typo in note about multiple inaccessible type aliases
Mainly intended as a small typo fix ("aliass" -> "aliases") for the case where a type cannot be found in scope but there are multiple inaccessible type aliases that match the missing type.
In general this change would use the correct plural form in this scenario for base words that end with 's'.
macros: `LintDiagnostic` derive
- Move `LintDiagnosticBuilder` into `rustc_errors` so that a diagnostic derive can refer to it.
- Introduce a `DecorateLint` trait, which is equivalent to `SessionDiagnostic` or `AddToDiagnostic` but for lints. Necessary without making more changes to the lint infrastructure as `DecorateLint` takes a `LintDiagnosticBuilder` and re-uses all of the existing logic for determining what type of diagnostic a lint should be emitted as (e.g. error/warning).
- Various refactorings of the diagnostic derive machinery (extracting `build_field_mapping` helper and moving `sess` field out of the `DiagnosticDeriveBuilder`).
- Introduce a `LintDiagnostic` derive macro that works almost exactly like the `SessionDiagnostic` derive macro except that it derives a `DecorateLint` implementation instead. A new derive is necessary for this because `SessionDiagnostic` is intended for when the generated code creates the diagnostic. `AddToDiagnostic` could have been used but it would have required more changes to the lint machinery.
~~At time of opening this pull request, ignore all of the commits from #98624, it's just the last few commits that are new.~~
r? `@oli-obk`
