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]>

2 files changed, 13 insertions, 12 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![,]);
diff --git a/crates/parser/src/grammar/params.rs b/crates/parser/src/grammar/params.rs
index 3ee4e4fca..2d006a1d5 100644
--- a/crates/parser/src/grammar/params.rs
+++ b/crates/parser/src/grammar/params.rs
@@ -47,20 +47,23 @@ fn list_(p: &mut Parser, flavor: Flavor) {
     if let FnDef = flavor {
         // test self_param_outer_attr
         // fn f(#[must_use] self) {}
+        let m = p.start();
         attributes::outer_attrs(p);
-        opt_self_param(p);
+        opt_self_param(p, m);
     }
 
     while !p.at(EOF) && !p.at(ket) {
         // test param_outer_arg
         // fn f(#[attr1] pat: Type) {}
+        let m = p.start();
         attributes::outer_attrs(p);
 
         if !p.at_ts(PARAM_FIRST) {
             p.error("expected value parameter");
+            m.abandon(p);
             break;
         }
-        let param = param(p, flavor);
+        let param = param(p, m, flavor);
         if !p.at(ket) {
             p.expect(T![,]);
         }
@@ -77,9 +80,8 @@ const PARAM_FIRST: TokenSet = patterns::PATTERN_FIRST.union(types::TYPE_FIRST);
 
 struct Variadic(bool);
 
-fn param(p: &mut Parser, flavor: Flavor) -> Variadic {
+fn param(p: &mut Parser, m: Marker, flavor: Flavor) -> Variadic {
     let mut res = Variadic(false);
-    let m = p.start();
     match flavor {
         // test param_list_vararg
         // extern "C" { fn printf(format: *const i8, ...) -> i32; }
@@ -151,10 +153,8 @@ fn variadic_param(p: &mut Parser) -> bool {
 //     fn d(&'a mut self, x: i32) {}
 //     fn e(mut self) {}
 // }
-fn opt_self_param(p: &mut Parser) {
-    let m;
+fn opt_self_param(p: &mut Parser, m: Marker) {
     if p.at(T![self]) || p.at(T![mut]) && p.nth(1) == T![self] {
-        m = p.start();
         p.eat(T![mut]);
         p.eat(T![self]);
         // test arb_self_types
@@ -174,9 +174,8 @@ fn opt_self_param(p: &mut Parser) {
             (T![&], T![mut], T![self], _) => 3,
             (T![&], LIFETIME_IDENT, T![self], _) => 3,
             (T![&], LIFETIME_IDENT, T![mut], T![self]) => 4,
-            _ => return,
+            _ => return m.abandon(p),
         };
-        m = p.start();
         p.bump_any();
         if p.at(LIFETIME_IDENT) {
             lifetime(p);