There are two interesting kinds of breakage illustrated here:
1. `Box<Trait>` in many contexts is treated as `Box<Trait + 'static>`,
due to [RFC 599]. However, in a type like `&'a Box<Trait>`, the
`Box<Trait>` type will be expanded to `Box<Trait + 'a>`, again due
to [RFC 599]. This, combined with the fix to Issue 25199, leads to
a borrowck problem due the combination of this function signature
(in src/libstd/net/parser.rs):
```rust
fn read_or<T>(&mut self, parsers: &mut [Box<FnMut(&mut Parser) -> Option<T>>]) -> Option<T>;
```
with this call site (again in src/libstd/net/parser.rs):
```rust
fn read_ip_addr(&mut self) -> Option<IpAddr> {
let ipv4_addr = |p: &mut Parser| p.read_ipv4_addr().map(|v4| IpAddr::V4(v4));
let ipv6_addr = |p: &mut Parser| p.read_ipv6_addr().map(|v6| IpAddr::V6(v6));
self.read_or(&mut [Box::new(ipv4_addr), Box::new(ipv6_addr)])
}
```
yielding borrowck errors like:
```
parser.rs:265:27: 265:69 error: borrowed value does not live long enough
parser.rs:265 self.read_or(&mut [Box::new(ipv4_addr), Box::new(ipv6_addr)])
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```
(full log at: https://gist.github.com/pnkfelix/e2e80f1a71580f5d3103 )
The issue here is perhaps subtle: the `parsers` argument is
inferred to be taking a slice of boxed objects with the implicit
lifetime bound attached to the `self` parameter to `read_or`.
Meanwhile, the fix to Issue 25199 (added in a forth-coming commit)
is forcing us to assume that each boxed object may have a
destructor that could refer to state of that lifetime, and
*therefore* that inferred lifetime is required to outlive the boxed
object itself.
In this case, the relevant boxed object here is not going to make
any such references; I believe it is just an artifact of how the
expression was built that it is not assigned type:
`Box<FnMut(&mut Parser) -> Option<T> + 'static>`.
(i.e., mucking with the expression is probably one way to fix this
problem).
But the other way to fix it, adopted here, is to change the
`read_or` method type to force make the (presumably-intended)
`'static` bound explicit on the boxed `FnMut` object.
(Note: this is still just the *first* example of breakage.)
2. In `macro_rules.rs`, the `TTMacroExpander` trait defines a method
with signature:
```rust
fn expand<'cx>(&self, cx: &'cx mut ExtCtxt, ...) -> Box<MacResult+'cx>;
```
taking a `&'cx mut ExtCtxt` as an argument and returning a
`Box<MacResult'cx>`.
The fix to Issue 25199 (added in aforementioned forth-coming
commit) assumes that a value of type `Box<MacResult+'cx>` may, in
its destructor, refer to a reference of lifetime `'cx`; thus the
`'cx` lifetime is forced to outlive the returned value.
Meanwhile, within `expand.rs`, the old code was doing:
```rust
match expander.expand(fld.cx, ...).make_pat() { ... => immutable borrow of fld.cx ... }
```
The problem is that the `'cx` lifetime, inferred for the
`expander.expand` call, has now been extended so that it has to
outlive the temporary R-value returned by `expanded.expand`. But
call is also reborrowing `fld.cx` *mutably*, which means that this
reborrow must end before any immutable borrow of `fld.cx`; but
there is one of those within the match body. (Note that the
temporary R-values for the input expression to `match` all live as
long as the whole `match` expression itself (see Issue #3511 and PR
#11585).
To address this, I moved the construction of the pat value into its
own `let`-statement, so that the `Box<MacResult>` will only live
for as long as the initializing expression for the `let`-statement,
and thus allow the subsequent immutable borrow within the `match`.
[RFC 599]: https://github.com/rust-lang/rfcs/blob/master/text/0599-default-object-bound.md
These implementations were intended to be unstable, but currently the stability
attributes cannot handle a stable trait with an unstable `impl` block. This
commit also audits the rest of the standard library for explicitly-`#[unstable]`
impl blocks. No others were removed but some annotations were changed to
`#[stable]` as they're defacto stable anyway.
One particularly interesting `impl` marked `#[stable]` as part of this commit
is the `Add<&[T]>` impl for `Vec<T>`, which uses `push_all` and implicitly
clones all elements of the vector provided.
Closes#24791
The IP and socket address types all had `FromStr` implemented but the
implementations were not marked stable, nor was the error type returned ready to
be properly stabilized.
This commit marks the implementations of `FromStr` as stable and also renamed
the `ParseError` structure to `AddrParseError`. The error is now also an opaque
structure that cannot be constructed outside the standard library.
cc #22949
[breaking-change]
This commit performs a stabilization pass over the std::net module,
incorporating the changes from RFC 923. Specifically, the following actions were
taken:
Stable functionality:
* `net` (the name)
* `Shutdown`
* `Shutdown::{Read, Write, Both}`
* `lookup_host`
* `LookupHost`
* `SocketAddr`
* `SocketAddr::{V4, V6}`
* `SocketAddr::port`
* `SocketAddrV4`
* `SocketAddrV4::{new, ip, port}`
* `SocketAddrV6`
* `SocketAddrV4::{new, ip, port, flowinfo, scope_id}`
* Common trait impls for socket addr structures
* `ToSocketAddrs`
* `ToSocketAddrs::Iter`
* `ToSocketAddrs::to_socket_addrs`
* `ToSocketAddrs for {SocketAddr*, (Ipv*Addr, u16), str, (str, u16)}`
* `Ipv4Addr`
* `Ipv4Addr::{new, octets, to_ipv6_compatible, to_ipv6_mapped}`
* `Ipv6Addr`
* `Ipv6Addr::{new, segments, to_ipv4}`
* `TcpStream`
* `TcpStream::connect`
* `TcpStream::{peer_addr, local_addr, shutdown, try_clone}`
* `{Read,Write} for {TcpStream, &TcpStream}`
* `TcpListener`
* `TcpListener::bind`
* `TcpListener::{local_addr, try_clone, accept, incoming}`
* `Incoming`
* `UdpSocket`
* `UdpSocket::bind`
* `UdpSocket::{recv_from, send_to, local_addr, try_clone}`
Unstable functionality:
* Extra methods on `Ipv{4,6}Addr` for various methods of inspecting the address
and determining qualities of it.
* Extra methods on `TcpStream` to configure various protocol options.
* Extra methods on `UdpSocket` to configure various protocol options.
Deprecated functionality:
* The `socket_addr` method has been renamed to `local_addr`
This commit is a breaking change due to the restructuring of the `SocketAddr`
type as well as the renaming of the `socket_addr` method. Migration should be
fairly straightforward, however, after accounting for the new level of
abstraction in `SocketAddr` (protocol distinction at the socket address level,
not the IP address).
[breaking-change]
This commit is an implementation of [RFC 807][rfc] which adds a `std::net`
module for basic neworking based on top of `std::io`. This module serves as a
replacement for the `std::old_io::net` module and networking primitives in
`old_io`.
[rfc]: fillmein
The major focus of this redesign is to cut back on the level of abstraction to
the point that each of the networking types is just a bare socket. To this end
functionality such as timeouts and cloning has been removed (although cloning
can be done through `duplicate`, it may just yield an error).
With this `net` module comes a new implementation of `SocketAddr` and `IpAddr`.
This work is entirely based on #20785 and the only changes were to alter the
in-memory representation to match the `libc`-expected variants and to move from
public fields to accessors.
