Rust 1.7: what's new, what was stabilized

Short answerRust 1.7 was released on Mar 3, 2016: 5 compatibility notes that can affect existing code.

Mar 3, 2016release date

0language stabilizations

0APIs stabilized

-new edition

← Rust 1.6 All versions Rust 1.8 →

Can it break my build?

The release lists these compatibility notes. Most only affect rare code, but read them before you raise your toolchain in CI:

Soundness fixes to the interactions between associated types and
[Several bugs in the compiler's visibility calculations were
Defaulted type parameters were accidentally accepted in positions
[Parsing "." as a float results in an error instead of 0][1.7p].
[Borrows of closure parameters may not outlive the closure][1.7bc].

Use it

rustup update stable        # get the newest release
rustup install 1.7          # or exactly this one
rustup override set 1.7     # pin a project to it

To require at least this version from users of your crate, set rust-version = "1.7" under [package] in Cargo.toml. Cargo then refuses to build it on older compilers with a clear message, and with resolver 3 (the default on the 2024 edition, Rust 1.85+) it also prefers dependency versions that support it.

Full release notes

Libraries

Stabilized APIs
Path
[Path::strip_prefix] (renamed from relative_from)
[path::StripPrefixError] (new error type returned from strip_prefix)
Ipv4Addr
[Ipv4Addr::is_loopback]
[Ipv4Addr::is_private]
[Ipv4Addr::is_link_local]
[Ipv4Addr::is_multicast]
[Ipv4Addr::is_broadcast]
[Ipv4Addr::is_documentation]
Ipv6Addr
[Ipv6Addr::is_unspecified]
[Ipv6Addr::is_loopback]
[Ipv6Addr::is_multicast]
Vec
[Vec::as_slice]
[Vec::as_mut_slice]
String
[String::as_str]
[String::as_mut_str]
Slices
<[T]>::[clone_from_slice], which now requires the two slices to be the same length
<[T]>::[sort_by_key]
checked, saturated, and overflowing operations
[i32::checked_rem], [i32::checked_neg], [i32::checked_shl], [i32::checked_shr]
[i32::saturating_mul]
[i32::overflowing_add], [i32::overflowing_sub], [i32::overflowing_mul], [i32::overflowing_div]
[i32::overflowing_rem], [i32::overflowing_neg], [i32::overflowing_shl], [i32::overflowing_shr]
[u32::checked_rem], [u32::checked_neg], [u32::checked_shl], [u32::checked_shl]
[u32::saturating_mul]
[u32::overflowing_add], [u32::overflowing_sub], [u32::overflowing_mul], [u32::overflowing_div]
[u32::overflowing_rem], [u32::overflowing_neg], [u32::overflowing_shl], [u32::overflowing_shr]
and checked, saturated, and overflowing operations for other primitive types
FFI
[ffi::IntoStringError]
[CString::into_string]
[CString::into_bytes]
[CString::into_bytes_with_nul]
From<CString> for Vec<u8>
IntoStringError
[IntoStringError::into_cstring]
[IntoStringError::utf8_error]
Error for IntoStringError
Hashing
[std::hash::BuildHasher]
[BuildHasher::Hasher]
[BuildHasher::build_hasher]
[std::hash::BuildHasherDefault]
[HashMap::with_hasher]
[HashMap::with_capacity_and_hasher]
[HashSet::with_hasher]
[HashSet::with_capacity_and_hasher]
[std::collections::hash_map::RandomState]
[RandomState::new]
[Validating UTF-8 is faster by a factor of between 7 and 14x for ASCII input][1.7utf8]. This means that creating Strings and strs from bytes is faster.
[The performance of LineWriter (and thus io::stdout) was improved by using memchr to search for newlines][1.7m].
[f32::to_degrees and f32::to_radians are stable][1.7f]. The f64 variants were stabilized previously.
[BTreeMap was rewritten to use less memory and improve the performance of insertion and iteration, the latter by as much as 5x][1.7bm].
[BTreeSet and its iterators, Iter, IntoIter, and Range are covariant over their contained type][1.7bt].
[LinkedList and its iterators, Iter and IntoIter are covariant over their contained type][1.7ll].
[str::replace now accepts a Pattern][1.7rp], like other string searching methods.
[Any is implemented for unsized types][1.7a].
[Hash is implemented for Duration][1.7h].

Misc

[When running tests with --test, rustdoc will pass --cfg arguments to the compiler][1.7dt].
[The compiler is built with RPATH information by default][1.7rpa]. This means that it will be possible to run rustc when installed in unusual configurations without configuring the dynamic linker search path explicitly.
[rustc passes --enable-new-dtags to GNU ld][1.7dta]. This makes any RPATH entries (emitted with -C rpath) *not* take precedence over LD_LIBRARY_PATH.

Cargo

[cargo rustc accepts a --profile flag that runs rustc under any of the compilation profiles, 'dev', 'bench', or 'test'][1.7cp].
[The rerun-if-changed build script directive no longer causes the build script to incorrectly run twice in certain scenarios][1.7rr].

Compatibility Notes

Soundness fixes to the interactions between associated types and lifetimes, specified in RFC 1214, now generate errors for code that violates the new rules. This is a significant change that is known to break existing code, so it has emitted warnings for the new error cases since 1.4 to give crate authors time to adapt. The details of what is changing are subtle; read the RFC for more.
Several bugs in the compiler's visibility calculations were fixed. Since this was found to break significant amounts of code, the new errors will be emitted as warnings for several release cycles, under the private_in_public lint.
Defaulted type parameters were accidentally accepted in positions that were not intended. In this release, defaulted type parameters appearing outside of type definitions will generate a warning, which will become an error in future releases.
Parsing "." as a float results in an error instead of 0. That is, ".".parse::<f32>() returns Err, not Ok(0.0).
Borrows of closure parameters may not outlive the closure.

Release notes from the Rust project's RELEASES.md (MIT or Apache-2.0); summaries above are ours.

← Rust 1.6 All versions Rust 1.8 →

Up next

Next releaseRust 1.8Released Apr 14, 2016.Read it next →

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