resolve/hygiene: `macro_rules` are not "legacy"
The "modern" vs "legacy" naming was introduced by jseyfried during initial implementation of macros 2.0.
At this point it's clear that `macro_rules` are not going anywhere and won't be deprecated in the near future.
So this PR changes the naming "legacy" (when it implies "macro_rules") to "macro_rules".
This should also help people reading this code because it's wasn't obvious that "legacy" actually meant "macro_rules" in these contexts.
The most contentious renaming here is probably
```
fn modern -> fn normalize_to_macros_2_0
fn modern_and_legacy -> fn normalize_to_macro_rules
```
Other alternatives that I could think of are `normalize_to_opaque`/`normalize_to_semitransparent`, or `strip_non_opaque`/`strip_transparent`, but they seemed less intuitive.
The documentation to these functions can be found in `symbol.rs`.
r? @matthewjasper
ast: `Mac`/`Macro` -> `MacCall`
It's now obvious that these refer to macro calls rather than to macro definitions.
It's also a single name instead of two different names in different places.
`rustc_expand` usually calls macro calls in a wide sense (including attributes and derives) "macro invocations", but structures and variants renamed in this PR are only relevant to fn-like macros, so it's simpler and clearer to just call them calls.
cc https://github.com/rust-lang/rust/pull/63586#discussion_r314232513
r? @eddyb
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
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)
