"Missing" patterns are possible in bare fn types (`fn f(u32)`) and
similar places. Currently these are represented in the AST with
`ast::PatKind::Ident` with no `by_ref`, no `mut`, an empty ident, and no
sub-pattern. This flows through to `{hir,thir}::PatKind::Binding` for
HIR and THIR.
This is a bit nasty. It's very non-obvious, and easy to forget to check
for the exceptional empty identifier case.
This commit adds a new variant, `PatKind::Missing`, to do it properly.
The process I followed:
- Add a `Missing` variant to `{ast,hir,thir}::PatKind`.
- Chang `parse_param_general` to produce `ast::PatKind::Missing`
instead of `ast::PatKind::Missing`.
- Look through `kw::Empty` occurrences to find functions where an
existing empty ident check needs replacing with a `PatKind::Missing`
check: `print_param`, `check_trait_item`, `is_named_param`.
- Add a `PatKind::Missing => unreachable!(),` arm to every exhaustive
match identified by the compiler.
- Find which arms are actually reachable by running the test suite,
changing them to something appropriate, usually by looking at what
would happen to a `PatKind::Ident`/`PatKind::Binding` with no ref, no
`mut`, an empty ident, and no subpattern.
Quite a few of the `unreachable!()` arms were never reached. This makes
sense because `PatKind::Missing` can't happen in every pattern, only
in places like bare fn tys and trait fn decls.
I also tried an alternative approach: modifying `ast::Param::pat` to
hold an `Option<P<Pat>>` instead of a `P<Pat>`, but that quickly turned
into a very large and painful change. Adding `PatKind::Missing` is much
easier.
Mostly parser: Eliminate code that's been dead / semi-dead since the removal of type ascription syntax
**Disclaimer**: This PR is intended to mostly clean up code as opposed to bringing about behavioral changes. Therefore it doesn't aim to address any of the 'FIXME: remove after a month [dated: 2023-05-02]: "type ascription syntax has been removed, see issue [#]101728"'.
---
By commit:
1. Removes truly dead code:
* Since 1.71 (#109128) `let _ = { f: x };` is a syntax error as opposed to a semantic error which allows the parse-time diagnostic (suggestion) "*struct literal body without path // you might have forgotten […]*" to kick in.
* The analysis-time diagnostic (suggestion) from <=1.70 "*cannot find value \`f\` in this scope // you might have forgotten […]*" is therefore no longer reachable.
2. Updates `is_certainly_not_a_block` to be in line with the current grammar:
* The seq. `{ ident:` is definitely not the start of a block. Before the removal of ty ascr, `{ ident: ty_start` would begin a block expr.
* This shouldn't make more code compile IINM, it should *ultimately* only affect diagnostics.
* For example, `if T { f: () } {}` will now be interpreted as an `if` with struct lit `T { f: () }` as its *condition* (which is banned in the parser anyway) as opposed to just `T` (with the *consequent* being `f : ()` which is also invalid (since 1.71)). The diagnostics are almost the same because we have two separate parse recovery procedures + diagnostics: `StructLiteralNeedingParens` (*invalid struct lit*) before and `StructLiteralNotAllowedHere` (*struct lits aren't allowed here*) now, as you can see from the diff.
* (As an aside, even before this PR, fn `maybe_suggest_struct_literal` should've just used the much older & clearer `StructLiteralNotAllowedHere`)
* NB: This does sadly regress the compiler output for `tests/ui/parser/type-ascription-in-pattern.rs` but that can be fixed in follow-up PRs. It's not super important IMO and a natural consequence.
3. Removes code that's become dead due to the prior commit.
* Basically reverts #106620 + #112475 (without regressing rustc's output!).
* Now the older & more robust parse recovery procedure (cc `StructLiteralNotAllowedHere`) takes care of the cases the removed code used to handle.
* This automatically fixes the suggestions for \[[playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=7e2030163b11ee96d17adc3325b01780)\]:
* `if Ty::<i32> { f: K }.m() {}`: `if Ty::<i32> { SomeStruct { f: K } }.m() {}` (broken) → ` if (Ty::<i32> { f: K }).m() {}`
* `if <T as Trait>::Out { f: K::<> }.m() {}`: `if <T as Trait>(::Out { f: K::<> }).m() {}` (broken) → `if (<T as Trait>::Out { f: K::<> }).m() {}`
4. Merge and simplify UI tests pertaining to this issue, so it's easier to add more regression tests like for the two cases mentioned above.
5. Merge UI tests and add the two regression tests.
Best reviewed commit by commit (on request I'll partially squash after approval).
StructLiteralNeedingParens is no longer reachable always giving
precedence to StructLiteralNotAllowedHere.
As an aside: The former error struct shouldn't've existed in the
first place. We should've just used the latter in this branch.
Add support for postfix yield expressions
We've been having a discussion about whether we want postfix yield, or want to stick with prefix yield, or have both. I figured it's easy enough to support both for now and let us play around with them while the feature is still experimental.
This PR treats `yield x` and `x.yield` as semantically equivalent. There was a suggestion to make `yield x` have a `()` type (so it only works in coroutines with `Resume = ()`. I think that'd be worth trying, either in a later PR, or before this one merges, depending on people's opinions.
#43122
Make `Parser::parse_expr_cond` public
This allows usage in rustfmt and rustfmt forks.
I'm using this for custom macro formatting, see 30c83df9e1/src/parse/macros/html.rs (L57)
It would be great if this could be upstreamed so I don't need to rely on a fork.
Add `#[define_opaques]` attribute and require it for all type-alias-impl-trait sites that register a hidden type
Instead of relying on the signature of items to decide whether they are constraining an opaque type, the opaque types that the item constrains must be explicitly listed.
A previous version of this PR used an actual attribute, but had to keep the resolved `DefId`s in a side table.
Now we just lower to fields in the AST that have no surface syntax, instead a builtin attribute macro fills in those fields where applicable.
Note that for convenience referencing opaque types in associated types from associated methods on the same impl will not require an attribute. If that causes problems `#[defines()]` can be used to overwrite the default of searching for opaques in the signature.
One wart of this design is that closures and static items do not have generics. So since I stored the opaques in the generics of functions, consts and methods, I would need to add a custom field to closures and statics to track this information. During a T-types discussion we decided to just not do this for now.
fixes#131298
compiler: Use `size_of` from the prelude instead of imported
Use `std::mem::{size_of, size_of_val, align_of, align_of_val}` from the prelude instead of importing or qualifying them. Apply this change across the compiler.
These functions were added to all preludes in Rust 1.80.
r? ``@compiler-errors``
Use `std::mem::{size_of, size_of_val, align_of, align_of_val}` from the
prelude instead of importing or qualifying them.
These functions were added to all preludes in Rust 1.80.
This involves replacing `nt_pretty_printing_compatibility_hack` with
`stream_pretty_printing_compatibility_hack`.
The handling of statements in `transcribe` is slightly different to
other nonterminal kinds, due to the lack of `from_ast` implementation
for empty statements.
Notable test changes:
- `tests/ui/proc-macro/expand-to-derive.rs`: the diff looks large but
the only difference is the insertion of a single invisible-delimited
group around a metavar.
Rollup of 12 pull requests
Successful merges:
- #135767 (Future incompatibility warning `unsupported_fn_ptr_calling_conventions`: Also warn in dependencies)
- #137852 (Remove layouting dead code for non-array SIMD types.)
- #137863 (Fix pretty printing of unsafe binders)
- #137882 (do not build additional stage on compiler paths)
- #137894 (Revert "store ScalarPair via memset when one side is undef and the other side can be memset")
- #137902 (Make `ast::TokenKind` more like `lexer::TokenKind`)
- #137921 (Subtree update of `rust-analyzer`)
- #137922 (A few cleanups after the removal of `cfg(not(parallel))`)
- #137939 (fix order on shl impl)
- #137946 (Fix docker run-local docs)
- #137955 (Always allow rustdoc-json tests to contain long lines)
- #137958 (triagebot.toml: Don't label `test/rustdoc-json` as A-rustdoc-search)
r? `@ghost`
`@rustbot` modify labels: rollup
Implement `#[cfg]` in `where` clauses
This PR implements #115590, which supports `#[cfg]` attributes in `where` clauses.
The biggest change is, that it adds `AttrsVec` and `NodeId` to the `ast::WherePredicate` and `HirId` to the `hir::WherePredicate`.
For consistency with `rustc_lexer::TokenKind::Bang`, and because other
`ast::TokenKind` variants generally have syntactic names instead of
semantic names (e.g. `Star` and `DotDot` instead of `Mul` and `Range`).
`BinOpToken` is badly named, because it only covers the assignable
binary ops and excludes comparisons and `&&`/`||`. Its use in
`ast::TokenKind` does allow a small amount of code sharing, but it's a
clumsy factoring.
This commit removes `ast::TokenKind::BinOp{,Eq}`, replacing each one
with 10 individual variants. This makes `ast::TokenKind` more similar to
`rustc_lexer::TokenKind`, which has individual variants for all
operators.
Although the number of lines of code increases, the number of chars
decreases due to the frequent use of shorter names like `token::Plus`
instead of `token::BinOp(BinOpToken::Plus)`.
Note: there was an existing code path involving `Interpolated` in
`MetaItem::from_tokens` that was dead. This commit transfers that to the
new form, but puts an `unreachable!` call inside it.
The one notable test change is `tests/ui/macros/trace_faulty_macros.rs`.
This commit removes the complicated `Interpolated` handling in
`expected_expression_found` that results in a longer error message. But
I think the new, shorter message is actually an improvement.
The original complaint was in #71039, when the error message started
with "error: expected expression, found `1 + 1`". That was confusing
because `1 + 1` is an expression. Other than that, the reporter said
"the whole error message is not too bad if you ignore the first line".
Subsequently, extra complexity and wording was added to the error
message. But I don't think the extra wording actually helps all that
much. In particular, it still says of the `1+1` that "this is expected
to be expression". This repeats the problem from the original complaint!
This commit removes the extra complexity, reverting to a simpler error
message. This is primarily because the traversal is a pain without
`Interpolated` tokens. Nonetheless, I think the error message is
*improved*. It now starts with "expected expression, found `pat`
metavariable", which is much clearer and the real problem. It also
doesn't say anything specific about `1+1`, which is good, because the
`1+1` isn't really relevant to the error -- it's the `$e:pat` that's
important.
