Merge #6965

6965: Properly attach attributes to Param instead of parent ParamList r=matklad a=Veykril

Fixes #2783, fixes #2781

The problem with `let _a = [0,#[cfg(feature = "L")]0];` has already been fixed some time ago it seems:
<details>
  <summary>Syntax Tree for the const item</summary>

```
  [email protected]
    [email protected] "let"
    [email protected] " "
    [email protected]
      [email protected]
        [email protected] "_a"
    [email protected] " "
    [email protected] "="
    [email protected] " "
    [email protected]
      [email protected] "["
      [email protected]
        [email protected] "0"
      [email protected] ","
      [email protected]
        [email protected]
          [email protected] "#"
          [email protected] "["
          [email protected]
            [email protected]
              [email protected]
                [email protected] "cfg"
          [email protected]
            [email protected] "("
            [email protected] "feature"
            [email protected] " "
            [email protected] "="
            [email protected] " "
            [email protected] "\"L\""
            [email protected] ")"
          [email protected] "]"
        [email protected] "0"
      [email protected] "]"
    [email protected] ";"
```
</details>

Co-authored-by: Lukas Wirth <[email protected]>

1 files changed, 5 insertions, 3 deletions

diff --git a/crates/parser/src/grammar/expressions/atom.rs b/crates/parser/src/grammar/expressions/atom.rs
index 18b63feb7..e897d5a52 100644
--- a/crates/parser/src/grammar/expressions/atom.rs
+++ b/crates/parser/src/grammar/expressions/atom.rs
@@ -156,11 +156,13 @@ fn tuple_expr(p: &mut Parser) -> CompletedMarker {
     let mut saw_expr = false;
     while !p.at(EOF) && !p.at(T![')']) {
         saw_expr = true;
-        if !p.at_ts(EXPR_FIRST) {
-            p.error("expected expression");
+
+        // test tuple_attrs
+        // const A: (i64, i64) = (1, #[cfg(test)] 2);
+        if !expr_with_attrs(p) {
             break;
         }
-        expr(p);
+
         if !p.at(T![')']) {
             saw_comma = true;
             p.expect(T![,]);