Two lexer tweaks
19 days later, I haven't received a review of my commits in #36470. In an attempt to make some progress, I'm going to split up the changes. Here are the ones that don't relate to renaming things.
Speed up `plug_leaks`
Profiling shows that `plug_leaks` and the functions it calls are hot on some benchmarks. It's very common that `skol_map` is empty in this function, and we can specialize `plug_leaks` in that case for some big speed-ups.
The PR has two commits. I'm fairly confident that the first one is correct -- I traced through the code to confirm that the `fold_regions` and `pop_skolemized` calls are no-ops when `skol_map` is empty, and I also temporarily added an assertion to check that `result` ends up having the same value as `value` in that case. This commit is responsible for most of the improvement.
I'm less confident about the second commit. The call to `resolve_type_vars_is_possible` can change `value` when `skol_map` is empty... but testing suggests that it doesn't matter if the call is
omitted.
So, please check both patches carefully, especially the second one!
Here are the speed-ups for the first commit alone.
stage1 compiler (built with old rustc, using glibc malloc), doing debug builds:
```
futures-rs-test 4.710s vs 4.538s --> 1.038x faster (variance: 1.009x, 1.005x)
issue-32062-equ 0.415s vs 0.368s --> 1.129x faster (variance: 1.009x, 1.010x)
issue-32278-big 1.884s vs 1.808s --> 1.042x faster (variance: 1.020x, 1.017x)
jld-day15-parse 1.907s vs 1.668s --> 1.143x faster (variance: 1.011x, 1.007x)
piston-image-0. 13.024s vs 12.421s --> 1.049x faster (variance: 1.004x, 1.012x)
rust-encoding-0 3.335s vs 3.276s --> 1.018x faster (variance: 1.021x, 1.028x)
```
stage2 compiler (built with new rustc, using jemalloc), doing debug builds:
```
futures-rs-test 4.167s vs 4.065s --> 1.025x faster (variance: 1.006x, 1.018x)
issue-32062-equ 0.383s vs 0.343s --> 1.118x faster (variance: 1.012x, 1.016x)
issue-32278-big 1.680s vs 1.621s --> 1.036x faster (variance: 1.007x, 1.007x)
jld-day15-parse 1.671s vs 1.478s --> 1.131x faster (variance: 1.016x, 1.004x)
piston-image-0. 11.336s vs 10.852s --> 1.045x faster (variance: 1.003x, 1.006x)
rust-encoding-0 3.036s vs 2.971s --> 1.022x faster (variance: 1.030x, 1.032x)
```
I've omitted the benchmarks for which the change was negligible.
And here are the speed-ups for the first and second commit in combination.
stage1 compiler (built with old rustc, using glibc malloc), doing debug
builds:
```
futures-rs-test 4.684s vs 4.498s --> 1.041x faster (variance: 1.012x, 1.012x)
issue-32062-equ 0.413s vs 0.355s --> 1.162x faster (variance: 1.019x, 1.006x)
issue-32278-big 1.869s vs 1.763s --> 1.060x faster (variance: 1.013x, 1.018x)
jld-day15-parse 1.900s vs 1.602s --> 1.186x faster (variance: 1.010x, 1.003x)
piston-image-0. 12.907s vs 12.352s --> 1.045x faster (variance: 1.005x, 1.006x)
rust-encoding-0 3.254s vs 3.248s --> 1.002x faster (variance: 1.063x, 1.045x)
```
stage2 compiler (built with new rustc, using jemalloc), doing debug builds:
```
futures-rs-test 4.183s vs 4.046s --> 1.034x faster (variance: 1.007x, 1.004x)
issue-32062-equ 0.380s vs 0.340s --> 1.117x faster (variance: 1.020x, 1.003x)
issue-32278-big 1.671s vs 1.616s --> 1.034x faster (variance: 1.031x, 1.012x)
jld-day15-parse 1.661s vs 1.417s --> 1.172x faster (variance: 1.013x, 1.005x)
piston-image-0. 11.347s vs 10.841s --> 1.047x faster (variance: 1.007x, 1.010x)
rust-encoding-0 3.050s vs 3.000s --> 1.017x faster (variance: 1.016x, 1.012x)
```
@eddyb: `git blame` suggests that you should review this. Thanks!
Avoid introducing `run` twice in the Rust book
As it stands, getting-started.md and guessing-game.md both introduce `run` as a new command. I switched it so that the 2nd refers back to the first introduction, rather than re-introducing the command.
(First ever FOSS PR, sorry if I screwed up anything obvious :) )
r? @steveklabnik
Improve error message and snippet for "did you mean `x`"
- Fixes#36164
- Part of #35233
Based on the standalone example https://is.gd/8STXMd posted by @nikomatsakis and using the third formatting option mentioned in #36164 and agreed by @jonathandturner.
Note however this does not address the question of [how to handle an empty or unknown suggestion](https://github.com/rust-lang/rust/issues/36164#issuecomment-244460024). @nikomatsakis any suggestions on how best to address that part?
std: Stabilize and deprecate APIs for 1.13
This commit is intended to be backported to the 1.13 branch, and works with the
following APIs:
Stabilized
* `i32::checked_abs`
* `i32::wrapping_abs`
* `i32::overflowing_abs`
* `RefCell::try_borrow`
* `RefCell::try_borrow_mut`
Deprecated
* `BinaryHeap::push_pop`
* `BinaryHeap::replace`
* `SipHash13`
* `SipHash24`
* `SipHasher` - use `DefaultHasher` instead in the `std::collections::hash_map`
module
Closes#28147Closes#34767Closes#35057Closes#35070
This commit is intended to be backported to the 1.13 branch, and works with the
following APIs:
Stabilized
* `i32::checked_abs`
* `i32::wrapping_abs`
* `i32::overflowing_abs`
* `RefCell::try_borrow`
* `RefCell::try_borrow_mut`
* `DefaultHasher`
* `DefaultHasher::new`
* `DefaultHasher::default`
Deprecated
* `BinaryHeap::push_pop`
* `BinaryHeap::replace`
* `SipHash13`
* `SipHash24`
* `SipHasher` - use `DefaultHasher` instead in the `std::collections::hash_map`
module
Closes#28147Closes#34767Closes#35057Closes#35070
rustdoc: Fix documenting rustc-macro crates
This commit adds a "hack" to the session to track whether we're a rustdoc
session or not. If we're rustdoc then we skip the expansion to add the
rustc-macro infrastructure.
Closes#36820
Clarify HashMap's capacity handling.
HashMap has two notions of "capacity":
- "Usable capacity": the number of elements a hash map can hold without
resizing. This is the meaning of "capacity" used in HashMap's API,
e.g. the `with_capacity()` function.
- "Internal capacity": the number of allocated slots. Except for the
zero case, it is always larger than the usable capacity (because some
slots must be left empty) and is always a power of two.
HashMap's code is confusing because it does a poor job of
distinguishing these two meanings. I propose using two different terms
for these two concepts. Because "capacity" is already used in HashMap's
API to mean "usable capacity", I will use a different word for "internal
capacity". I propose "span", though I'm happy to consider other names.
Enforce the shadowing restrictions from RFC 1560 for today's macros
This PR enforces a weakened version of the shadowing restrictions from RFC 1560. More specifically,
- If a macro expansion contains a `macro_rules!` macro definition that is used outside of the expansion, the defined macro may not shadow an existing macro.
- If a macro expansion contains a `#[macro_use] extern crate` macro import that is used outside of the expansion, the imported macro may not shadow an existing macro.
This is a [breaking-change]. For example,
```rust
macro_rules! m { () => {} }
macro_rules! n { () => {
macro_rules! m { () => {} } //< This shadows an existing macro.
m!(); //< This is inside the expansion that generated `m`'s definition, so it is OK.
} }
n!();
m!(); //< This use of `m` is outside the expansion, so it causes the shadowing to be an error.
```
r? @nrc
The two branches of this `if` compute the same value. This commit gets
rid of the first branch, which makes this calculation identical to the
one in scan_block_comment().
First, assert! is redundant w.r.t. the unwrap() immediately afterwards.
Second, `byte_offset_diff` is effectively computed as
`current_byte_offset + ch.len_utf8() - current_byte_offset` (with `next`
as an intermediate) which is silly and can be simplified.
This commit avoids the `resolve_type_vars_if_possible` call in
`plug_leaks` when `skol_map` is empty, which is the common case. It also
changes the signature of `plug_leaks` slightly to avoid the need for a
`clone` of `value`. These changes give speed-ups of up a few percent on
some of the rustc-benchmarks.
This commit avoids the `fold_regions` call in `plug_leaks` when
`skol_map` is empty, which is the common case. This gives speed-ups of
up to 1.14x on some of the rustc-benchmarks.
Restrict where in the tree platform-specific cfgs may be mentioned
With the ports of Rust never ending, it's important that we keep things tidy. The main thing this PR does is introduce a new "pal" (platform abstraction layer) tidy check that limits where platform-specific CFGs may appear.
This is intended to maintain existing standards of code organization
in hopes that the standard library will continue to be refactored to
isolate platform-specific bits, making porting easier; where "standard
library" roughly means "all the dependencies of the std and test
crates".
This generally means placing restrictions on where `cfg(unix)`,
`cfg(windows)`, `cfg(target_os)` and `cfg(target_env)` may appear,
the basic objective being to isolate platform-specific code to the
platform-specific `std::sys` modules, and to the allocation,
unwinding, and libc crates.
Following are the basic rules, though there are currently
exceptions:
- core may not have platform-specific code
- liballoc_system may have platform-specific code
- liballoc_jemalloc may have platform-specific code
- libpanic_abort may have platform-specific code
- libpanic_unwind may have platform-specific code
- other crates in the std facade may not
- std may have platform-specific code in the following places
- sys/unix/
- sys/windows/
- os/
There are plenty of exceptions today though, noted in the whitelist.
The end-state, IMO, is for the standard library to be portable by porting only `std::sys` (possibly extracted to its own crate), an allocator crate, an unwinder crate, and possibly a libc crate (if std depends on it); but that outcome is far off and independent of the utility of enforcing where such code lives today.
cc @rust-lang/libs
As it stands, getting-started and guessing-game both introduce `run` as
a new command. The second should probably make it clear that the reader
has seen it before :)
This is intended to maintain existing standards of code organization
in hopes that the standard library will continue to be refactored to
isolate platform-specific bits, making porting easier; where "standard
library" roughly means "all the dependencies of the std and test
crates".
This generally means placing restrictions on where `cfg(unix)`,
`cfg(windows)`, `cfg(target_os)` and `cfg(target_env)` may appear,
the basic objective being to isolate platform-specific code to the
platform-specific `std::sys` modules, and to the allocation,
unwinding, and libc crates.
Following are the basic rules, though there are currently
exceptions:
- core may not have platform-specific code
- liballoc_system may have platform-specific code
- liballoc_jemalloc may have platform-specific code
- libpanic_abort may have platform-specific code
- libpanic_unwind may have platform-specific code
- other crates in the std facade may not
- std may have platform-specific code in the following places
- sys/unix/
- sys/windows/
- os/
There are plenty of exceptions today though, noted in the whitelist.
Refactor layout to store offsets of fields, not offsets after fields
This is the next PR moving us towards being able to reorder struct fields.
The old code implicitly stored the offset of the first field. This is inadequate because the first field may no longer be offset 0 in future. This PR refactors `layout` to use a `offsets` vector instead of a `offset_after_field` vector.
Documentation change to macros.rs for `includes!`
I'm not sure if this documentation is clear or extensive enough, but this is just to get started on the problem, fixes issue #36387.
