Implement Unsized Rvalues
This PR is the first step to implement RFC1909: unsized rvalues (#48055).
## Implemented
- `Sized` is removed for arguments and local bindings. (under `#![feature(unsized_locals)]`)
- Unsized locations are allowed in MIR
- Unsized places and operands are correctly translated at codegen
## Not implemented in this PR
- Additional `Sized` checks:
- tuple struct constructor (accidentally compiles now)
- closure arguments at closure generation (accidentally compiles now)
- upvars (ICEs now)
- Generating vtable for `fn method(self)` (ICEs now)
- VLAs: `[e; n]` where `n` isn't const
- Reduce unnecessary allocations
## Current status
- [x] Fix `__rust_probestack` (rust-lang-nursery/compiler-builtins#244)
- [x] Get the fix merged
- [x] `#![feature(unsized_locals)]`
- [x] Give it a tracking issue number
- [x] Lift sized checks in typeck and MIR-borrowck
- [ ] <del>Forbid `A(unsized-expr)`</del> will be another PR
- [x] Minimum working codegen
- [x] Add more examples and fill in unimplemented codegen paths
- [ ] <del>Loosen object-safety rules (will be another PR)</del>
- [ ] <del>Implement `Box<FnOnce>` (will be another PR)</del>
- [ ] <del>Reduce temporaries (will be another PR)</del>
Rollup of 10 pull requests
Successful merges:
- #52946 (Documented impl From on line 367 of libserialize/json.rs)
- #53234 (Remove Travis shutdown debug scripts, and remove CI-specific DNS settings)
- #53313 (Two small improvements)
- #53360 (Addressed #51602)
- #53364 (Warn if the user tries to use GATs)
- #53373 (Tweak unclosed delimiter parser error)
- #53377 (std: Use target_pointer_width for BACKTRACE_ELF_SIZE)
- #53395 (Use #[non_exhaustive] on internal enums)
- #53399 (Tidy: ignore non-Markdown files when linting for the Unstable Book)
- #53412 (syntax_ext: remove leftover span_err_if_not_stage0 macro.)
Addressed #51602Fixed#51602
r? @estebank
here I have addressed the case where `in` was not expected right after `if` block. Speaking of `type ascription` I am not sure if this the best approach which I have implemented. Plus I think one more test case can be added to test `type-ascription` case, though I don't have any at this point of time. I will ping you again if all existing testcases pass.
TokenStream::extend
Two new insta-stable impls in libproc_macro:
```rust
impl Extend<TokenTree> for TokenStream
impl Extend<TokenStream> for TokenStream
```
`proc_macro::TokenStream` already implements `FromIterator<TokenTree>` and `FromIterator<TokenStream>` so I elected to support the same input types for `Extend`.
**This commit reduces compile time of Serde derives by 60% (takes less than half as long to compile)** as measured by building our test suite:
```console
$ git clone https://github.com/serde-rs/serde
$ cd serde/test_suite
$ cargo check --tests --features proc-macro2/nightly
$ rm -f ../target/debug/deps/libtest_*.rmeta
$ time cargo check --tests --features proc-macro2/nightly
Before: 20.8 seconds
After: 8.6 seconds
```
r? @alexcrichton
A few cleanups and minor improvements for the lexer
- improve readability by adjusting the formatting of some function signatures and adding some newlines
- reorder some functions for easier reading
- remove redundant `'static` in `const`s
- remove some explicit `return`s
- read directly to a `String` in `gather_comments_and_literals`
- change `unwrap_or!` (macro) to `unwrap_or` (function)
- move an `assert!`ion from `try_next_token` (called in a loop) to `try_real_token` after all calls to `try_next_token`
- `#[inline]` some one-liner functions
- assign directly from an `if-else` expression
- refactor a `match` to `map_or`
- add a `token::is_irrelevant` function to detect tokens that are not "`real`"
Move SmallVector and ThinVec out of libsyntax
- move `libsyntax::util::SmallVector` tests to `librustc_data_structures::small_vec`
- remove `libsyntax::util::SmallVector`
- move `libsyntax::util::thin_vec` to `librustc_data_structures::thin_vec`
Other than moving these data structures where they belong it allows modules using `SmallVector<T>` (`SmallVec<[T; 1]>`) to specify their own length (e.g. 8 or 32) independently from `libsyntax`.
Fix a few regressions from enabling macro modularization
The first commit restores the old behavior for some minor unstable stuff (`rustc_*` and `derive_*` attributes) and adds a new feature gate for arbitrary tokens in non-macro attributes.
The second commit fixes https://github.com/rust-lang/rust/issues/53205
The third commit fixes https://github.com/rust-lang/rust/issues/53144.
Same technique is used as for other things blocking expansion progress - if something causes indeterminacy too often, then prohibit it.
In this case referring to crate-local macro-expanded `#[macro_export]` macros via module-relative paths is prohibited, see comments in code for more details.
cc https://github.com/rust-lang/rust/pull/50911
Emit error for pattern arguments in trait methods
The error and check for this already existed, but the parser didn't try to parse trait method arguments as patterns, so the error was never emitted. This surfaces the error, so we get better errors than simple parse errors.
This improves the error message described in https://github.com/rust-lang/rust/issues/53046.
r? @petrochenkov
Don't collect() when size_hint is useless
This adjusts PRs #52738 and #52697 by falling back to calculating capacity and extending or pushing in a loop where `collect()` can't be trusted to calculate the right capacity.
It is a performance win.
The error and check for this already existed, but the parser didn't try to parse trait method arguments as patterns, so the error was never emitted. This surfaces the error, so we get better errors than simple parse errors.
Suggest comma when missing in macro call
When missing a comma in a macro call, suggest it, regardless of
position. When a macro call doesn't match any of the patterns, check
if the call's token stream could be missing a comma between two idents,
and if so, create a new token stream containing the comma and try to
match against the macro patterns. If successful, emit the suggestion.
This works on arbitrary macros, with no need of special support from
the macro writers.
```
error: no rules expected the token `d`
--> $DIR/missing-comma.rs:26:18
|
LL | foo!(a, b, c d, e);
| -^
| |
| help: missing comma here
```
Follow up to #52397.
resolve: Support custom attributes when macro modularization is enabled
Basically, if resolution of a single-segment attribute is a determined error, then we interpret it as a custom attribute.
Since custom attributes are integrated into general macro resolution, `feature(custom_attribute)` now requires and implicitly enables macro modularization (`feature(use_extern_macros)`).
Actually, a few other "advanced" macro features now implicitly enable macro modularization too (and one bug was found and fixed in process of enabling it).
The first two commits are preliminary cleanups/refactorings.
