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
This resolves a number of bugs that trigger stack overflows or other cyclic errors.
r? @nick29581 (it is based on work that you started)
f? @jroesch (also based on your branch)
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.
Replaced outdated use of the `range(start, end)` function where
approriate with `start..end`, and tweaked the examples to compile and run with the latest rust. I also fixed two periphery compile issues in reference.md which were occluding whether there were any new errors created by these changes, so I fixed them.
PR #22012 followup: clean up vtable::check_object_cast by reusing `fresh_ty`
(hat tip to nikomatsakis, who was the one who pointed out this simplification to the logic.)
