The general problem we are dealing with here is this:
```
macro_rules! thrice {
($e:expr) => { $e * 3}
}
fn main() {
let x = thrice!(1 + 2);
}
```
we really want this to print 9 rather than 7.
The way rustc solves this is rather ad-hoc. In rustc, token trees are
allowed to include whole AST fragments, so 1+2 is passed through macro
expansion as a single unit. This is a significant violation of token
tree model.
In rust-analyzer, we intended to handle this in a more elegant way,
using token trees with "invisible" delimiters. The idea was is that we
introduce a new kind of parenthesis, "left $"/"right $", and let the
parser intelligently handle this.
The idea was inspired by the relevant comment in the proc_macro crate:
https://doc.rust-lang.org/stable/proc_macro/enum.Delimiter.html#variant.None
> An implicit delimiter, that may, for example, appear around tokens
> coming from a “macro variable” $var. It is important to preserve
> operator priorities in cases like $var * 3 where $var is 1 + 2.
> Implicit delimiters might not survive roundtrip of a token stream
> through a string.
Now that we are older and wiser, we conclude that the idea doesn't work.
_First_, the comment in the proc-macro crate is wishful thinking. Rustc
currently completely ignores none delimiters. It solves the (1 + 2) * 3
problem by having magical token trees which can't be duplicated:
* https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Frust-analyzer/topic/TIL.20that.20token.20streams.20are.20magic
* https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Handling.20of.20Delimiter.3A.3ANone.20by.20the.20parser
_Second_, it's not like our implementation in rust-analyzer works. We
special-case expressions (as opposed to treating all kinds of $var
captures the same) and we don't know how parser error recovery should
work with these dollar-parenthesis.
So, in this PR we simplify the whole thing away by not pretending that
we are doing something proper and instead just explicitly special-casing
expressions by wrapping them into real `()`.
In the future, to maintain bug-parity with `rustc` what we are going to
do is probably adding an explicit `CAPTURED_EXPR` *token* which we can
explicitly account for in the parser.
If/when rustc starts handling delimiter=none properly, we'll port that
logic as well, in addition to special handling.
10603: fix: Don't resolve attributes to non attribute macros r=Veykril a=Veykril
Also changes `const`s to `static`s for `Limit`s as we have interior mutability in those(though only used with a certain feature flag enabled).
Co-authored-by: Lukas Wirth <lukastw97@gmail.com>
10387: Move `IdxRange` into la-arena r=Veykril a=arzg
Currently, `IdxRange` (named `IdRange`) is located in `hir_def::item_tree`, when really it isn’t specific to `hir_def` and could become part of la-arena. The rename from `IdRange` to `IdxRange` is to maintain consistency with the naming convention used throughout la-arena (`Idx` instead of `Id`, `RawIdx` instead of `RawId`). This PR also adds a few new APIs to la-arena on top of `IdxRange` for convenience, namely:
- indexing into an `Arena` by an `IdxRange` and getting a slice of values back
- creating an `IdxRange` from an inclusive range
Currently this PR also exposes a new `Arena::next_idx` method to make constructing inclusive`IdxRange`s using `IdxRange::new` easier; however, it would in my opinion be better to remove this as it allows for easy creation of out-of-bounds `Idx`s, when `IdxRange::new_inclusive` mostly covers the same use-case while being less error-prone.
I decided to bump the la-arena version to 0.3.0 from 0.2.0 because adding a new `Index` impl for `Arena` turned out to be a breaking change: I had to add a type hint in `crates/hir_def/src/body/scope.rs` when one wasn’t necessary before, since rustc couldn’t work out the type of a closure parameter now that there are multiple `Index` impls. I’m not sure whether this is the right decision, though.
Co-authored-by: Aramis Razzaghipour <aramisnoah@gmail.com>
I don't like our macro tests -- they are brittle and don't inspire
confidence. I think the reason for that is that we try to unit-test
them, but that is at odds with reality, where macro expansion
fundamentally depends on name resolution.
Consider these expples
{ 92 }
async { 92 }
'a: { 92 }
#[a] { 92 }
Previously the tree for them were
BLOCK_EXPR
{ ... }
EFFECT_EXPR
async
BLOCK_EXPR
{ ... }
EFFECT_EXPR
'a:
BLOCK_EXPR
{ ... }
BLOCK_EXPR
#[a]
{ ... }
As you see, it gets progressively worse :) The last two items are
especially odd. The last one even violates the balanced curleys
invariant we have (#10357) The new approach is to say that the stuff in
`{}` is stmt_list, and the block is stmt_list + optional modifiers
BLOCK_EXPR
STMT_LIST
{ ... }
BLOCK_EXPR
async
STMT_LIST
{ ... }
BLOCK_EXPR
'a:
STMT_LIST
{ ... }
BLOCK_EXPR
#[a]
STMT_LIST
{ ... }
FragmentKind played two roles:
* entry point to the parser
* syntactic category of a macro call
These are different use-cases, and warrant different types. For example,
macro can't expand to visibility, but we have such fragment today.
This PR introduces `ExpandsTo` enum to separate this two use-cases.
I suspect we might further split `FragmentKind` into `$x:specifier` enum
specific to MBE, and a general parser entry point, but that's for
another PR!
9970: feat: Implement attribute input token mapping, fix attribute item token mapping r=Veykril a=Veykril
The token mapping for items with attributes got overwritten partially by the attributes non-item input, since attributes have two different inputs, the item and the direct input both.
This PR gives attributes a second TokenMap for its direct input. We now shift all normal input IDs by the item input maximum(we maybe wanna swap this see below) similar to what we do for macro-rules/def. For mapping down we then have to figure out whether we are inside the direct attribute input or its item input to pick the appropriate mapping which can be done with some token range comparisons.
Fixes https://github.com/rust-analyzer/rust-analyzer/issues/9867
Co-authored-by: Lukas Wirth <lukastw97@gmail.com>
9989: Fix two more “a”/“an” typos (this time the other way) r=lnicola a=steffahn
Follow-up to #9987
you guys are still merging these fast 😅
_this time I thought – for sure – that I’d get this commit into #9987 before it’s merged…_
Co-authored-by: Frank Steffahn <frank.steffahn@stu.uni-kiel.de>
Today, rust-analyzer (and rustc, and bat, and IntelliJ) fail badly on
some kinds of maliciously constructed code, like a deep sequence of
nested parenthesis.
"Who writes 100k nested parenthesis" you'd ask?
Well, in a language with macros, a run-away macro expansion might do
that (see the added tests)! Such expansion can be broad, rather than
deep, so it bypasses recursion check at the macro-expansion layer, but
triggers deep recursion in parser.
In the ideal world, the parser would just handle deeply nested structs
gracefully. We'll get there some day, but at the moment, let's try to be
simple, and just avoid expanding macros with unbalanced parenthesis in
the first place.
closes#9358
We generally avoid "syntax only" helper wrappers, which don't do much:
they make code easier to write, but harder to read. They also make
investigations harder, as "find_usages" needs to be invoked both for the
wrapped and unwrapped APIs
