Right now the HIR contains raw `syntax::ast::Attribute` structure but nowadays
these can contain arbitrary tokens. One variant of the `Token` enum is an
"interpolated" token which basically means to shove all the tokens for a
nonterminal in this position. A "nonterminal" in this case is roughly analagous
to a macro argument:
macro_rules! foo {
($a:expr) => {
// $a is a nonterminal as an expression
}
}
Currently nonterminals contain namely items and expressions, and this poses a
problem for incremental compilation! With incremental we want a stable hash of
all HIR items, but this means we may transitively need a stable hash *of the
entire AST*, which is certainly not stable w/ node ids and whatnot. Hence today
there's a "bug" where the "stable hash" of an AST is just the raw hash value of
the AST, and this only arises with interpolated nonterminals. The downside of
this approach, however, is that a bunch of errors get spewed out during
compilation about how this isn't a great idea.
This PR is focused at fixing these warnings, basically deleting them from the
compiler. The implementation here is to alter attributes as they're lowered from
the AST to HIR, expanding all nonterminals in-place as we see them. This code
for expanding a nonterminal to a token stream already exists for the
`proc_macro` crate, so we basically just reuse the same implementation there.
After this PR it's considered a bug to have an `Interpolated` token and hence
the stable hash implementation simply uses `bug!` in this location.
Closes#40946
Parse nested closure with two consecutive parameter lists properly
This is a followup of #44332.
---
Currently, in nightly, this does not compile:
```rust
fn main() {
let f = |_||x, y| x+y;
println!("{}", f(())(1, 2)); // should print 3
}
```
`|_||x, y| x+y` should be parsed as `|_| (|x, y| x+y)`, but the parser didn't accept `||` between `_` and `x`. This patch fixes the problem.
r? @petrochenkov
Point out missing if conditional
On a case where an else conditional is missing, point this out
instead of the token immediately after the (incorrect) else block:
```
error: missing condition for `if` statemementt push fork -f
--> $DIR/issue-13483.rs:16:5
|
13 | } else if {
| ^ expected if condition here
```
instead of
```
error: expected `{`, found `else`
--> ../../src/test/ui/issue-13483.rs:14:7
|
14 | } else {
| ^^^^
```
Fix#13483.
syntax: Relax path grammar
TLDR: Accept the disambiguator `::` in "type" paths (`Type::<Args>`), accept the disambiguator `::` before parenthesized generic arguments (`Fn::(Args)`).
The "turbofish" disambiguator `::<>` in expression paths is a necessary evil required for path parsing to be both simple and to give reasonable results.
Since paths in expressions usually refer to values (but not necessarily, e.g. `Struct::<u8> { field: 0 }` is disambiguated, but refers to a type), people often consider `::<>` to be inherent to *values*, and not *expressions* and want to write disambiguated paths for values even in contexts where disambiguation is not strictly necessary, for example when a path is passed to a macro `m!(Vec::<i32>::new)`.
The problem is that currently, if the disambiguator is not *required*, then it's *prohibited*. This results in confusion - see https://github.com/rust-lang/rust/issues/41740, https://internals.rust-lang.org/t/macro-path-uses-novel-syntax/5561.
This PR makes the disambiguator *optional* instead of prohibited in contexts where it's not strictly required, so people can pass paths to macros in whatever form they consider natural (e.g. disambiguated form for value paths).
This PR also accepts the disambiguator in paths with parenthesized arguments (`Fn::(Args)`) for consistency and to simplify testing of stuff like https://github.com/rust-lang/rust/pull/41856#issuecomment-301219194.
Closes https://github.com/rust-lang/rust/issues/41740
cc @rust-lang/lang
r? @nikomatsakis
Eat open paren when parsing list in libsyntax/parse/attr.rs
This PR adds a small refactoring:
```diff
pub fn parse_meta_item_kind(&mut self) -> PResult<'a, ast::MetaItemKind> {
Ok(if self.eat(&token::Eq) {
ast::MetaItemKind::NameValue(self.parse_unsuffixed_lit()?)
- } else if self.token == token::OpenDelim(token::Paren) {
+ } else if self.eat(&token::OpenDelim(token::Paren)) {
ast::MetaItemKind::List(self.parse_meta_seq()?)
} else {
- self.eat(&token::OpenDelim(token::Paren));
ast::MetaItemKind::Word
})
}
```
in `parse_meta_item_kind()`, the parser calls `self.eat(&token::OpenDelim(token::Paren));` before returning `ast::MetaItemKind::Word` just to add `(` to expected token. It seems more natural to eat the paren when parsing `ast::MetaItemKind::List`.
On a case where an else conditional is missing, point this out
instead of the token immediately after the (incorrect) else block:
```
error: missing condition for `if` statemementt push fork -f
--> $DIR/issue-13483.rs:16:5
|
13 | } else if {
| ^ expected if condition here
```
instead of
```
error: expected `{`, found `else`
--> ../../src/test/ui/issue-13483.rs:14:7
|
14 | } else {
| ^^^^
```
Hint correct extern constant syntax
Error message for `extern "C" { const …}` is terse, and the right syntax is hard to guess given unfortunate difference between meaning of `static` in C and Rust.
I've added a hint for the right syntax.
Also reorder and space the list to make it clearer for futures updates
and to come closer to the original list.
Thanks @est31 for the instructions.
Fixes#43629.
r? @est31
This PR kicks off the implementation of the [default binding modes RFC][1] by
introducing the `pat_binding_modes` typeck table mentioned in the [mentoring
instructions][2].
`pat_binding_modes` is populated in `librustc_typeck/check/_match.rs` and
used wherever the HIR would be scraped prior to this PR. Unfortunately, one
blemish, namely a two callers to `contains_explicit_ref_binding`, remains.
This will likely have to be removed when the second part of [1], the
`pat_adjustments` table, is tackled. Appropriate comments have been added.
See #42640.
[1]: https://github.com/rust-lang/rfcs/pull/2005
[2]: https://github.com/rust-lang/rust/issues/42640#issuecomment-313535089
Add Span to ast::WhereClause
This PR adds `Span` field to `ast::WhereClause`. The motivation here is to make rustfmt's life easier when recovering comments before and after where clause.
r? @nrc
This is then later used by `proc_macro` to generate a new
`proc_macro::TokenTree` which preserves span information. Unfortunately this
isn't a bullet-proof approach as it doesn't handle the case when there's still
other attributes on the item, especially inner attributes.
Despite this the intention here is to solve the primary use case for procedural
attributes, attached to functions as outer attributes, likely bare. In this
situation we should be able to now yield a lossless stream of tokens to preserve
span information.
