It's not clear what this means, because a macro in item position can expand to
zero or more items. For now we disallow it, which is technically a
[breaking-change]
but is landing without an RFC. The `pub` keyword previously had no effect,
which seems quite unintended.
Fixes#18317.
Fixes#14660.
This PR is an optimization of the `FromIterator` implementation of `Vec`
Benchmark: https://gist.github.com/alexcrichton/03d666159a28a80e7c70
Before:
test macro_repeat1 ... bench: 57 ns/iter (+/- 1)
test macro_repeat2 ... bench: 56 ns/iter (+/- 1)
test map_clone1 ... bench: 828 ns/iter (+/- 13)
test map_clone2 ... bench: 828 ns/iter (+/- 8)
test repeat1 ... bench: 1104 ns/iter (+/- 10)
test repeat2 ... bench: 1106 ns/iter (+/- 11)
After:
test macro_repeat1 ... bench: 75 ns/iter (+/- 21)
test macro_repeat2 ... bench: 59 ns/iter (+/- 31)
test map_clone1 ... bench: 34 ns/iter (+/- 22)
test map_clone2 ... bench: 52 ns/iter (+/- 21)
test repeat1 ... bench: 34 ns/iter (+/- 11)
test repeat2 ... bench: 33 ns/iter (+/- 12)
The idea behind this optimization is to avoid all bounds checks for space
already allocated into the vector. This may involve running the iterator twice,
but the first run of the iterator should be optimizable to a memcpy or memset if
possible.
The same treatment can in theory be applied to `Vec::extend` but the benchmarks
for that currently get *worse* if the change is applied. This appears to be some
LLVM optimizations going awry but it's seems prudent to land at least the
`collect` portion beforehand.
Fixes#22047
Range<u64> and Range<i64> may be longer than usize::MAX on 32-bit
platforms, and thus they cannot fulfill the protocol for
ExactSizeIterator. We don't want a nonobvious platform dependency in
basic iterator traits, so the trait impl is removed.
The logic of this change assumes that usize is at least 32-bit.
This is technically a breaking change; note that Range<usize> and
Range<isize> are always ExactSizeIterators.
[breaking-change]
if found on the `main()` function. This lets you write tests that live
in `compile-fail` but are expected to compile successfully. This is
handy when you have many small variations on a theme that you want to
keep together, and you are just testing the type checker, not the
runtime semantics.
Added a second note about keeping the reference.md list up-to-date to
the bottom of the list, since not everyone (including me) reads the
big comment at the top of it. :)
Ensured that the feature gate list in reference.md is kept in
alphabetical order.
Names of structs, enums, traits, type aliases and type parameters (i.e. all identifiers that can be used as full paths in type position) are not allowed to match the names of primitive types.
See #20427 for more information.
This is a minor [breaking-change]
It is not totally clear if we should just use whitespace, or if the full
unicode word-breaking algorithm is more correct. If there is demand we
can reconsider this decision (and consider the precise algorithm to use
in detail).
cc #15628.
borrowck: Prevent partial reinitialization of uninitialized structures
This is a pnkfelix-swiped squash of #22079, which was a rebase and revision of #18963Fixes#18571.
It is only allowed in paths now, where it will either work inside a `trait`
or `impl` item, or not resolve outside of it.
[breaking-change]
Closes#22137
