Cycles in normalization can cause evaluations to change from Unknown to
Err. This means that some selection that were applicable no longer are.
To avoid this:
* Selection candidates that are known to be applicable are prefered
over candidates that are not.
* We don't ICE if a candidate is no longer applicable.
Rewrite `collect_tokens` implementations to use a flattened buffer
Instead of trying to collect tokens at each depth, we 'flatten' the
stream as we go allong, pushing open/close delimiters to our buffer
just like regular tokens. One capturing is complete, we reconstruct a
nested `TokenTree::Delimited` structure, producing a normal
`TokenStream`.
The reconstructed `TokenStream` is not created immediately - instead, it is
produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This
closure stores a clone of the original `TokenCursor`, plus a record of the
number of calls to `next()/next_desugared()`. This is sufficient to reconstruct
the tokenstream seen by the callback without storing any additional state. If
the tokenstream is never used (e.g. when a captured `macro_rules!` argument is
never passed to a proc macro), we never actually create a `TokenStream`.
This implementation has a number of advantages over the previous one:
* It is significantly simpler, with no edge cases around capturing the
start/end of a delimited group.
* It can be easily extended to allow replacing tokens an an arbitrary
'depth' by just using `Vec::splice` at the proper position. This is
important for PR #76130, which requires us to track information about
attributes along with tokens.
* The lazy approach to `TokenStream` construction allows us to easily
parse an AST struct, and then decide after the fact whether we need a
`TokenStream`. This will be useful when we start collecting tokens for
`Attribute` - we can discard the `LazyTokenStream` if the parsed
attribute doesn't need tokens (e.g. is a builtin attribute).
The performance impact seems to be neglibile (see
https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a
small slowdown on a few benchmarks, but it only rises above 1% for incremental
builds, where it represents a larger fraction of the much smaller instruction
count. There a ~1% speedup on a few other incremental benchmarks - my guess is
that the speedups and slowdowns will usually cancel out in practice.
rustdoc: Show the correct source filename in page titles, without `.html`
Previously the title would be
lib.rs.html -- source
if `lib.rs` was the actual source filename. Now the title is
lib.rs - source
Improve wording of "cannot multiply" type error
For example, if you had this code:
fn foo(x: i32, y: f32) -> f32 {
x * y
}
You would get this error:
error[E0277]: cannot multiply `f32` to `i32`
--> src/lib.rs:2:7
|
2 | x * y
| ^ no implementation for `i32 * f32`
|
= help: the trait `Mul<f32>` is not implemented for `i32`
However, that's not usually how people describe multiplication. People
usually describe multiplication like how the division error words it:
error[E0277]: cannot divide `i32` by `f32`
--> src/lib.rs:2:7
|
2 | x / y
| ^ no implementation for `i32 / f32`
|
= help: the trait `Div<f32>` is not implemented for `i32`
So that's what this change does. It changes this:
error[E0277]: cannot multiply `f32` to `i32`
--> src/lib.rs:2:7
|
2 | x * y
| ^ no implementation for `i32 * f32`
|
= help: the trait `Mul<f32>` is not implemented for `i32`
To this:
error[E0277]: cannot multiply `i32` by `f32`
--> src/lib.rs:2:7
|
2 | x * y
| ^ no implementation for `i32 * f32`
|
= help: the trait `Mul<f32>` is not implemented for `i32`
Add Pin::static_ref, static_mut.
This adds `Pin::static_ref` and `Pin::static_mut`, which convert a static reference to a pinned static reference.
Static references are effectively already pinned, as what they refer to has to live forever and can never be moved.
---
Context: I want to update the `sys` and `sys_common` mutexes/rwlocks/condvars to use `Pin<&self>` in their functions, instead of only warning in the unsafety comments that they may not be moved. That should make them a little bit less dangerous to use. Putting such an object in a `static` (e.g. through `sys_common::StaticMutex`) fulfills the requirements about never moving it, but right now there's no safe way to get a `Pin<&T>` to a `static`. This solves that.
The optimization introduces additional uses of the discriminant operand, but
does not ensure that it is still valid to evaluate it or that it still
evaluates to the same value.
Evaluate it once at original position, and store the result in a new temporary.
Rollup of 9 pull requests
Successful merges:
- #78046 (Add codegen test for issue #73827)
- #78061 (Optimize const value interning for ZST types)
- #78070 (we can test std and core panic macros together)
- #78076 (Move orphan module-name/mod.rs files into module-name.rs files)
- #78129 (Wrapping intrinsics doc links update.)
- #78133 (Add some MIR-related regression tests)
- #78144 (Don't update `entries` in `TypedArena` if T does not need drop)
- #78145 (Drop unneeded `mut`)
- #78157 (Remove unused type from librustdoc)
Failed merges:
r? `@ghost`
Drop unneeded `mut`
These parameters don't get modified.
Note that `trailing_comment` is pub and gets exported from `rustc_ast_pretty`. Is that considered to be a stable API? If yes, and you want to reserve the right to modify `self` in `trailing_comment` in the future, that hunk would need to be dropped.
Don't update `entries` in `TypedArena` if T does not need drop
As far as I can tell, `entries` is only used when dropping `TypedArenaChunk`s and their contents. It is already ignored there, if T is not `mem::needs_drop`, this PR just skips updating it's value.
You can see `TypedArenaChunk` ignoring the entry count in L71. The reasoning is similar to what you can find in `DroplessArena`.
r? @oli-obk
Wrapping intrinsics doc links update.
The links in the wrapping intrinsics docs now refer to the `wrapping_*` functions, not the `checked_*` functions.
Since having enabled the download-ci-llvm option,
and having rebased on top of f05b47ccdf,
I've noticed that I had to update the llvm-project
submodule manually if it was checked out.
Orignally, the submodule update logic was
introduced to reduce the friction for contributors
to manage the submodules, or in other words, to prevent
getting PRs that have unwanted submodule rollbacks
because the contributors didn't run git submodule update.
This commit adds logic to ensure there is no inadvertent
LLVM submodule rollback in a PR if download-ci-llvm
(or llvm-config) is enabled. It will detect whether the
llvm-project submodule is initialized, and if so, update
it in any case. If it is not initialized, behaviour is
kept to not do any update/initialization.
An alternative to the chosen implementation would
be to not pass the --init command line arg to
`git submodule update` for the src/llvm-project
submodule. This would show a confusing error message
however on all builds with an uninitialized repo.
We could pass the --silent param, but we still want
it to print something if it is initialized and has
to update something.
So we just do a manual check for whether the
submodule is initialized.
Disable MatchBranchSimplification
This optimization can result in unsoundness, because it introduces
additional uses of a place holding the discriminant value without
ensuring that it is valid to do so.
Found by validation from #77369 / #78147.
