The wording of RFC #495 enables moves out of slices. Unfortuantely, non-zeroing
moves out of slices introduce a very annoying complication: as slices can
vary in their length, indexes from the start and end may or may not overlap
depending on the slice's exact length, which prevents assigning a particular
drop flag for each individual element.
For example, in the code
```Rust
fn foo<T>(a: Box<[Box<[T]>]>, c: bool) -> T {
match (a, c) {
(box [box [t, ..], ..], true) => t,
(box [.., box [.., t]], false) => t,
_ => panic!()
}
}
```
If the condition is false, we have to drop the first element
of `a`, unless `a` has size 1 in which case we drop all the elements
of it but the last.
If someone comes with a nice way of handling it, we can always re-allow
moves out of slices.
This is a [breaking-change], but it is behind the `slice_patterns` feature
gate and was not allowed until recently.
Be more specific when type parameter shadows primitive type
When a type parameter shadows a primitive type, the error message
was non obvious. For example, given the file `file.rs`:
```rust
trait Parser<T> {
fn parse(text: &str) -> Option<T>;
}
impl<bool> Parser<bool> for bool {
fn parse(text: &str) -> Option<bool> {
Some(true)
}
}
fn main() {
println!("{}", bool::parse("ok").unwrap_or(false));
}
```
The output was:
```bash
% rustc file.rs
error[E0308]: mismatched types
--> file.rs:7:14
|
7 | Some(true)
| ^^^^ expected type parameter, found bool a
|
= note: expected type `bool`
= note: found type `bool`
error: aborting due to previous error
```
We now show extra information about the type:
```bash
% rustc file.rs
error[E0308]: mismatched types
--> file.rs:7:14
|
7 | Some(true)
| ^^^^ expected type parameter, found bool a
|
= note: expected type `bool` (type parameter)
= note: found type `bool` (bool)
error: aborting due to previous error
```
Fixes#35030
When a type parameter shadows a primitive type, the error message
was non obvious. For example, given the file `file.rs`:
```rust
trait Parser<T> {
fn parse(text: &str) -> Option<T>;
}
impl<bool> Parser<bool> for bool {
fn parse(text: &str) -> Option<bool> {
Some(true)
}
}
fn main() {
println!("{}", bool::parse("ok").unwrap_or(false));
}
```
The output was:
```bash
% rustc file.rs
error[E0308]: mismatched types
--> file.rs:7:14
|
7 | Some(true)
| ^^^^ expected type parameter, found bool
|
= note: expected type `bool`
= note: found type `bool`
error: aborting due to previous error
```
We now show extra information about the type:
```bash
% rustc file.rs
error[E0308]: mismatched types
--> file.rs:7:14
|
7 | Some(true)
| ^^^^ expected type parameter, found bool
|
= note: expected type `bool` (type parameter)
= note: found type `bool` (bool)
error: aborting due to previous error
```
Fixes#35030
rustbuild: Fix dependency tracking with new Cargo
The recent Cargo update changed filenames, which broke a lot of incremental
rustbuild builds. What it thought were the output files were indeed no longer
the output files! (wreaking havoc).
This commit updates this to stop guessing filenames of Cargo and just manage
stamp files instead.
clear obligations-added flag with nested fulfillcx
This flag is a debugging measure designed to detect cases where we start
a snapshot, create type variables, register obligations involving those
type variables in the fulfillment cx, and then have to unroll the
snapshot, leaving "dangling type variables" behind. HOWEVER, in some
cases the flag is wrong. In particular, we sometimes create a
"mini-fulfilment-cx" in which we enroll obligations. As long as this
fulfillment cx is fully drained before we return, this is not a problem,
as there won't be any escaping obligations in the main cx. So we add a
fn to save/restore the flag.
Fixes#36053.
r? @arielb1
invoke drop glue with a ptr to (data, meta)
This is done by creating a little space on the stack. Hokey, but it's the simplest fix I can see, and I am in "kill regressions" mode right now.
Fixes#35546
r? @eddyb
Use primitive indexing in slice's Index/IndexMut
[T]'s Index implementation is normally not used for indexing, instead
the compiler supplied indexing is used.
Use the compiler supplied version in Index/IndexMut.
This removes an inconsistency:
Compiler supplied bound check failures look like this:
thread 'main' panicked at 'index out of bounds: the len is 3 but the index is 4'
If you convince Rust to use the Index impl for slices, bounds check
failure looks like this instead:
thread 'main' panicked at 'assertion failed: index < self.len()'
The latter is used if you for example use Index generically:
```rust
use std::ops::Index;
fn foo<T: ?Sized>(x: &T) where T: Index<usize> { &x[4]; }
foo(&[1, 2, 3][..])
```
Assign node ids during macro expansion
After this PR,
- The `ExtCtxt` can access `resolve`'s `Resolver` through the trait object `ext::base::Resolver`.
- The `Resolver` trait object can load macros and replaces today's `MacroLoader` trait object.
- The macro expander uses the `Resolver` trait object to resolve macro invocations.
- The macro expander assigns node ids and builds the `Resolver`'s `macros_at_scope` map.
- This is groundwork for merging import resolution and expansion.
- Performance of expansion together with node id assignment improves by ~5%.
**EDIT:** Since Github is reordering the commits, here is `git log`:
- b54e1e3997: Differentiate between monotonic and non-monotonic expansion and only assign node ids during monotonic expansion.
- 78c0039878: Expand generated test harnesses and macro registries.
- f3c2dca353: Remove scope placeholders from the crate root.
- c86c8d41a2: Perform node id assignment and `macros_at_scope` construction during the `InvocationCollector` and `PlaceholderExpander` folds.
- 72a636975f: Move macro resolution into `librustc_resolve`.
- 20b43b2323: Rewrite the unit tests in `ext/expand.rs` as a `compile-fail` test.
- a9821e1658: Refactor `ExtCtxt` to use a `Resolver` instead of a `MacroLoader`.
- 60440b226d: Refactor `noop_fold_stmt_kind` out of `noop_fold_stmt`.
- 50f94f6c95: Avoid needless reexpansions.
r? @nrc
Fix indeterminism in ty::TraitObject representation.
Make sure that projection bounds in `ty::TraitObject` are sorted in a way that is stable across compilation sessions and crate boundaries.
This PR
+ moves `DefPathHashes` up into `librustc` so it can be used there to create a stable sort key for `DefId`s,
+ changes `PolyExistentialProjection::sort_key()` to take advantage of the above,
+ and removes the unused `PolyProjectionPredicate::sort_key()` and `ProjectionTy::sort_key()` methods.
Fixes#36155
Improve shallow `Clone` deriving
`Copy` unions now support `#[derive(Clone)]`.
Less code is generated for `#[derive(Clone, Copy)]`.
+
Unions now support `#[derive(Eq)]`.
Less code is generated for `#[derive(Eq)]`.
---
Example of code reduction:
```
enum E {
A { a: u8, b: u16 },
B { c: [u8; 100] },
}
```
Before:
```
fn clone(&self) -> E {
match (&*self,) {
(&E::A { a: ref __self_0, b: ref __self_1 },) => {
::std::clone::assert_receiver_is_clone(&(*__self_0));
::std::clone::assert_receiver_is_clone(&(*__self_1));
*self
}
(&E::B { c: ref __self_0 },) => {
::std::clone::assert_receiver_is_clone(&(*__self_0));
*self
}
}
}
```
After:
```
fn clone(&self) -> E {
{
let _: ::std::clone::AssertParamIsClone<u8>;
let _: ::std::clone::AssertParamIsClone<u16>;
let _: ::std::clone::AssertParamIsClone<[u8; 100]>;
*self
}
}
```
All the matches are removed, bound assertions are more lightweight.
`let _: Checker<CheckMe>;`, unlike `checker(&check_me);`, doesn't have to be translated by rustc_trans and then inlined by LLVM, it doesn't even exist in MIR, this means faster compilation.
---
Union impls are generated like this:
```
union U {
a: u8,
b: u16,
c: [u8; 100],
}
```
```
fn clone(&self) -> U {
{
let _: ::std::clone::AssertParamIsCopy<Self>;
*self
}
}
```
Fixes https://github.com/rust-lang/rust/issues/36043
cc @durka
r? @alexcrichton
Inherit overflow checks for sum and product
We have previously documented the fact that these will panic on overflow, but I think this behavior is what people actually want/expect. `#[rustc_inherit_overflow_checks]` didn't exist when we discussed these for stabilization.
r? @alexcrichton
Closes#35807
[T]'s Index implementation is normally not used for indexing, instead
the compiler supplied indexing is used.
Use the compiler supplied version in Index/IndexMut.
This removes an inconsistency:
Compiler supplied bound check failures look like this:
thread 'main' panicked at 'index out of bounds: the len is 3 but the index is 4'
If you convince Rust to use the Index impl for slices, bounds check
failure looks like this instead:
thread 'main' panicked at 'assertion failed: index < self.len()'
The latter is used if you for example use Index generically::
use std::ops::Index;
fn foo<T: ?Sized>(x: &T) where T: Index<usize> { &x[4]; }
foo(&[1, 2, 3][..])
Documentation of what Default does for each type
Addresses #36265
I haven't changed the following types due to doubts:
1)src/libstd/ffi/c_str.rs
2)src/libcore/iter/sources.rs
3)src/libcore/hash/mod.rs
4)src/libcore/hash/mod.rs
5)src/librustc/middle/privacy.rs
r? @steveklabnik
This flag is a debugging measure designed to detect cases where we start
a snapshot, create type variables, register obligations involving those
type variables in the fulfillment cx, and then have to unroll the
snapshot, leaving "dangling type variables" behind. HOWEVER, in some
cases the flag is wrong. In particular, we sometimes create a
"mini-fulfilment-cx" in which we enroll obligations. As long as this
fulfillment cx is fully drained before we return, this is not a problem,
as there won't be any escaping obligations in the main cx. So we add a
fn to save/restore the flag.
rustdoc: Don't add extra newlines for fully opaque structs
Changes the definition for braced structs with only private or hidden fields to save space on the page.
Before:
```
pub struct Vec<T> {
// some fields omitted
}
```
After:
```
pub struct Vec<T> { /* fields omitted */ }
```
This also cleans up empty braced structs.
Before:
```
pub struct Foo {
}
```
After:
```
pub struct Foo {}
```
[before](https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html) [after](https://ollie27.github.io/rust_doc_test/std/vec/struct.Vec.html)
cc #34713
