As part of the ongoing effort to document all methods with examples,
this commit adds the missing examples for the `BTreeMap` collection
type.
This is part of issue #29348.
The first time I read the docs for `insert()`, I thought it was saying
it didn't update existing *values*, and I was confused. Reword the docs
to make it clear that `insert()` does update values.
This is a standard "clean out libstd" commit which removes all 1.5-and-before
deprecated functionality as it's now all been deprecated for at least one entire
cycle.
{BTree,Hash}{Map,Set} will not update their key if it already exists, which
can matter with more complex keys. This behavior is now documented.
Fixes#26888
I needed it in `RawVec`, `Vec`, and `TypedArena` for `rustc` to
bootstrap; but of course that alone was not sufficient for `make
check`.
Later I added `unsafe_destructor_blind_to_params` to collections, in
particular `LinkedList` and `RawTable` (the backing representation for
`HashMap` and `HashSet`), to get the regression tests exercising
cyclic structure from PR #27185 building.
----
Note that the feature is `dropck_parametricity` (which is not the same
as the attribute's name). We will almost certainly vary our strategy
here in the future, so it makes some sense to have a not-as-ugly name
for the feature gate. (The attribute name was deliberately selected to
be ugly looking.)
When both the key and value types were zero-sized, `BTreeMap` previously
called `heap::allocate` with `size == 0` for leaf nodes, which is
undefined behavior, and jemalloc would attempt to read invalid memory,
crashing the process.
This avoids undefined behavior by allocating enough space to store one
edge in leaf nodes that would otherwise have `size == 0`. Although this
uses extra memory, maps with zero-sized key types that have sensible
implementations of the ordering traits can only contain a single
key-value pair (and therefore only a single leaf node), and maps with
key and value types that are both zero-sized have few uses, if any.
Furthermore, this is a temporary fix that will likely be unnecessary
once the `BTreeMap` implementation is rewritten to use parent pointers.
Closes#28493.
This does cause some breakage due to deficiencies in resolve -
`path::Components` is both an `Iterator` and implements `Eq`, `Ord`,
etc. If one calls e.g. `partial_cmp` on a `Components` and passes a
`&Components` intending to target the `PartialOrd` impl, the compiler
will select the `partial_cmp` from `Iterator` and then error out. I
doubt anyone will run into breakage from `Components` specifically, but
we should see if there are third party types that will run into issues.
`iter::order::equals` wasn't moved to `Iterator` since it's exactly the
same as `iter::order::eq` but with an `Eq` instead of `PartialEq` bound,
which doensn't seem very useful.
I also updated `le`, `gt`, etc to use `partial_cmp` which lets us drop
the extra `PartialEq` bound.
cc #27737
This commit removes all unstable and deprecated functions in the standard
library. A release was recently cut (1.3) which makes this a good time for some
spring cleaning of the deprecated functions.
The replacements are functions that usually use a single `mem::transmute` in
their body and restrict input and output via more concrete types than `T` and
`U`. Worth noting are the `transmute` functions for slices and the `from_utf8*`
family for mutable slices. Additionally, `mem::transmute` was often used for
casting raw pointers, when you can already cast raw pointers just fine with
`as`.
This permits collections with `String` keys to be ranged over with
`&str` bounds. The `K` defaults for `Min` and `Max` permit the default
type parameter fallback to work with things like
```rust
use std::collections::{BTreeSet, Bound};
let set = BTreeSet::<String>::new();
set.range(Bound::Included("a"), Bound::Unbounded);
```
Without the defaults, the type of the maximum bound would be
unconstrained.
This commit is an implementation of [RFC 1184][rfc] which tweaks the behavior of
the `#![no_std]` attribute and adds a new `#![no_core]` attribute. The
`#![no_std]` attribute now injects `extern crate core` at the top of the crate
as well as the libcore prelude into all modules (in the same manner as the
standard library's prelude). The `#![no_core]` attribute disables both std and
core injection.
[rfc]: https://github.com/rust-lang/rfcs/pull/1184
