Implement RFC 2056 trivial constraints in where clauses
This is an implementation of the new behaviour for #48214. Tests are mostly updated to show the effects of this. Feature gate hasn't been added yet.
Some things that are worth noting and are maybe not want we want
* `&mut T: Copy` doesn't allow as much as someone might expect because there is often an implicit reborrow.
* ~There isn't a check that a where clause is well-formed any more, so `where Vec<str>: Debug` is now allowed (without a `str: Sized` bound).~
r? @nikomatsakis
Ensure derive(PartialOrd) is no longer accidentally exponential
Previously, two comparison operations would be generated for each field, each of which could delegate to another derived PartialOrd. Now we use ordering and optional chaining to ensure each pair of fields is only compared once, addressing https://github.com/rust-lang/rust/issues/49650#issuecomment-379467572.
Closes#49505.
r? @Manishearth (sorry for changing it again so soon!)
Close#50755
This commit updates one of the edition lints to only suggest deleting `extern
crate` if it actually works. Otherwise this can yield some confusing behavior
with rustfix specifically where if you accidentally deny the `rust_2018_idioms`
lint in the 2015 edition it's suggesting features that don't work!
This commit fixes a hard error where the `#![feature(rust_2018_preview)]`
feature was forbidden to be mentioned when the `--edition 2018` flag was passed.
This instead silently accepts that feature gate despite it not being necessary.
It's intended that this will help ease the transition into the 2018 edition as
users will, for the time being, start off with the `rust_2018_preview` feature
and no longer immediately need to remove it.
Closes#50662
lint: deny incoherent_fundamental_impls by default
Warn the ecosystem of the pending intent-to-disallow in #49799.
There are 4 ICEs on my machine, look unrelated (having happened before in https://github.com/rust-lang/rust/issues/49146#issuecomment-384473523)
```rust
thread 'main' panicked at 'assertion failed: position <= slice.len()', libserialize/leb128.rs:97:1
```
```
[run-pass] run-pass/allocator/xcrate-use2.rs
[run-pass] run-pass/issue-12133-3.rs
[run-pass] run-pass/issue-32518.rs
[run-pass] run-pass/trait-default-method-xc-2.rs
```
r? @nikomatsakis
Immutably and implicitly borrow all pattern ids for their guards (NLL only)
This is an important piece of rust-lang/rust#27282.
It applies only to NLL mode. It is a change to MIR codegen that is currently toggled on only when NLL is turned on. It thus affect MIR-borrowck but not the earlier static analyses (such as the type checker).
This change makes it so that any pattern bindings of type T for a match arm will map to a `&T` within the context of the guard expression for that arm, but will continue to map to a `T` in the context of the arm body.
To avoid surfacing this type distinction in the user source code (which would be a severe change to the language and would also require far more revision to the compiler internals), any occurrence of such an identifier in the guard expression will automatically get a deref op applied to it.
So an input like:
```rust
let place = (1, Foo::new());
match place {
(1, foo) if inspect(foo) => feed(foo),
...
}
```
will be treated as if it were really something like:
```rust
let place = (1, Foo::new());
match place {
(1, Foo { .. }) if { let tmp1 = &place.1; inspect(*tmp1) }
=> { let tmp2 = place.1; feed(tmp2) },
...
}
```
And an input like:
```rust
let place = (2, Foo::new());
match place {
(2, ref mut foo) if inspect(foo) => feed(foo),
...
}
```
will be treated as if it were really something like:
```rust
let place = (2, Foo::new());
match place {
(2, Foo { .. }) if { let tmp1 = & &mut place.1; inspect(*tmp1) }
=> { let tmp2 = &mut place.1; feed(tmp2) },
...
}
```
In short, any pattern binding will always look like *some* kind of `&T` within the guard at least in terms of how the MIR-borrowck views it, and this will ensure that guard expressions cannot mutate their the match inputs via such bindings. (It also ensures that guard expressions can at most *copy* values from such bindings; non-Copy things cannot be moved via these pattern bindings in guard expressions, since one cannot move out of a `&T`.)
Rollup of 12 pull requests
Successful merges:
- #50302 (Add query search order check)
- #50320 (Fix invalid path generation in rustdoc search)
- #50349 (Rename "show type declaration" to "show declaration")
- #50360 (Clarify wordings of the `unstable_name_collision` lint.)
- #50365 (Use two vectors in nearest_common_ancestor.)
- #50393 (Allow unaligned reads in constants)
- #50401 (Revert "Implement FromStr for PathBuf")
- #50406 (Forbid constructing empty identifiers from concat_idents)
- #50407 (Always inline simple BytePos and CharPos methods.)
- #50416 (check if the token is a lifetime before parsing)
- #50417 (Update Cargo)
- #50421 (Fix ICE when using a..=b in a closure.)
Failed merges:
guard expressions of matches (activated only when using
new NLL mode).
Review feedback: removed 27282 from filename. (The test still
references it in a relevant comment in the file itself so that seemed
like a reasonable compromise.)
Implement tool_attributes feature (RFC 2103)
cc #44690
This is currently just a rebased and compiling (hopefully) version of #47773.
Let's see if travis likes this. I will add the implementation for `tool_lints` this week.
Reduce maximum repr(align(N)) to 2^29
The current maximum `repr(align(N))` alignment is larger than the maximum alignment accepted by LLVM, which can cause issues for huge values of `N`, as seen in #49492. Fixes#49492.
r? @rkruppe
check that #[used] is used only on statics
this attribute has no effect on other items. This makes the implementation match what's described in the RFC.
cc #40289
r? @nagisa
Rollup of 7 pull requests
Successful merges:
- #49707 (Add "the Rustc book")
- #50222 (Bump bootstrap compiler to 2018-04-24)
- #50227 (Fix ICE with erroneous `impl Trait` in a trait impl)
- #50229 (Add setting to go to item if there is only one result)
- #50231 (Add more doc aliases)
- #50246 (Make dump_{alloc,allocs,local}() no-ops when tracing is disabled.)
- #49894 (Rename InternedString to LocalInternedString and introduce a new thread-safe InternedString)
Failed merges:
Previously, two comparison operations would be generated for each field, each of which could delegate to another derived PartialOrd. Now we use ordering and optional chaining to ensure each pair of fields is only compared once.
A comment already stated that this test should be disabled, but its
`should_fail` is not enough to excuse it from a compiler panic. Remove
it from the `revisions` list to disable it harder.
