Improve expression & attribute parsing
This PR includes misc improvements to expression and attribute parsing.
1. Some code simplifications
2. Better recovery for various block forms, e.g. `loop statements }` (missing `{` after `loop`). (See e.g., `block-no-opening-brace.rs` among others for examples.)
3. Added recovery for e.g., `unsafe $b` where `$b` refers to a `block` macro fragment. (See `bad-interpolated-block.rs` for examples.)
4. ^--- These are done so that code sharing in block parsing is increased.
5. Added recovery for e.g., `'label: loop { ... }` (See `labeled-no-colon-expr.rs`.)
6. Added recovery for e.g., `&'lifetime expr` (See `regions-out-of-scope-slice.rs`.)
7. Added recovery for e.g., `fn foo() = expr;` (See `fn-body-eq-expr-semi.rs`.)
8. Simplified attribute parsing code & slightly improved diagnostics.
9. Added recovery for e.g., `Box<('a) + Trait>`.
10. Added recovery for e.g, `if true #[attr] {} else #[attr] {} else #[attr] if true {}`.
r? @estebank
Permit attributes on 'if' expressions
Previously, attributes on 'if' expressions (e.g. `#[attr] if true {}`)
were disallowed during parsing. This made it impossible for macros to
perform any custom handling of such attributes (e.g. stripping them
away), since a compilation error would be emitted before they ever had a
chance to run.
This PR permits attributes on 'if' expressions ('if-attrs' from here on).
Both built-in attributes (e.g. `#[allow]`, `#[cfg]`) and proc-macro attributes are supported.
We still do *not* accept attributes on 'other parts' of an if-else
chain. That is, the following code snippet still fails to parse:
```rust
if true {} #[attr] else if false {} else #[attr] if false {} #[attr]
else {}
```
Closes https://github.com/rust-lang/rust/issues/68618
On mismatched delimiters, only point at empty blocks that are in the same line
We point at empty blocks when we have mismatched braces to detect cases where editors auto insert `}` after writing `{`. Gate this to only the case where the entire span is in the same line so we never point at explicitly empty blocks.
Parse & reject postfix operators after casts
This adds an explicit error messages for when parsing `x as Type[0]` or similar expressions. Our add an extra parse case for parsing any postfix operator (dot, indexing, method calls, await) that triggers directly after parsing `as` expressions.
My friend and I worked on this together, but they're still deciding on a github username and thus I'm submitting this for both of us.
It will immediately error out, but will also provide the rest of the parser with a useful parse tree to deal with.
There's one decision we made in how this produces the parse tree. In the situation `&x as T[0]`, one could imagine this parsing as either `&((x as T)[0])` or `((&x) as T)[0]`. We chose the latter for ease of implementation, and as it seemed the most intuitive.
Feedback welcome! This is our first change to the parser section, and it might be completely horrible.
Fixes#35813.
even more clippy cleanups
* Don't pass &mut where immutable reference (&) is sufficient (clippy::unnecessary_mut_passed)
* Use more efficient &&str to String conversion (clippy::inefficient_to_string)
* Don't always eval arguments inside .expect(), use unwrap_or_else and closure. (clippy::expect_fun_call)
* Use righthand '&' instead of lefthand "ref". (clippy::toplevel_ref_arg)
* Use simple 'for i in x' loops instead of 'while let Some(i) = x.next()' loops on iterators. (clippy::while_let_on_iterator)
* Const items have by default a static lifetime, there's no need to annotate it. (clippy::redundant_static_lifetimes)
* Remove redundant patterns when matching ( x @ _ to x) (clippy::redundant_pattern)
Previously, attributes on 'if' expressions (e.g. #[attr] if true {})
were disallowed during parsing. This made it impossible for macros to
perform any custom handling of such attributes (e.g. stripping them
away), since a compilation error would be emitted before they ever had a
chance to run.
This PR permits attributes on 'if' expressions ('if-attrs' from here on).
Both built-in attributes (e.g. `#[allow]`, `#[cfg]`) are supported.
We still do *not* accept attributes on 'other parts' of an if-else
chain. That is, the following code snippet still fails to parse:
```rust
if true {} #[attr] else if false {} else #[attr] if false {} #[attr]
else {}
```
Rename `libsyntax` to `librustc_ast`
This was the last rustc crate that wasn't following the `rustc_*` naming convention.
Follow-up to https://github.com/rust-lang/rust/pull/67763.
Implementes suggeseted changes by Centril.
This checks whether the memory location of the cast remains the same
after atttempting to parse a postfix operator after a cast has been
parsed. If the address is not the same, an illegal postfix operator
was parsed.
Previously the code generated a hash of the pointer, which was overly
complex and inefficent. Casting the pointers and comparing them
is simpler and more effcient.
rustc_parse: Tweak the function parameter name check
The function doesn't need a full token, only its edition.
Noticed while implementing https://github.com/rust-lang/rust/pull/69384.
I'm still not sure whether normalized or unnormalized token is a better fit for the edition check here, so https://github.com/rust-lang/rust/pull/69384 and this PR just keep the status quo behavior.
r? @Centril
