Rollup merge of #150590 - ident-kw-ice, r=petrochenkov

Don't try to recover keyword as non-keyword identifier

Fixes rust-lang/rust#149692.

On beta after rust-lang/rust#146978, we ICE on

```rs
macro_rules! m {
    ($id:item()) => {}
}

m!(Self());
```

where `Self` in the macro invocation is a keyword not a "normal" identifier, while attempting to recover an missing keyword before an identifier. Except, `Self` *is* a keyword, so trying to parse that as a non-reserved identifier expectedly fails.

I suspect rust-lang/rust#146978 merely unmasked a possible code path to hit this case; this logic has been so for a good while. Previously, on stable, the error message looks something like

```rs
error: expected identifier, found keyword `Self`
 --> src/lib.rs:5:4
  |
5 | m!(Self());
  |    ^^^^ expected identifier, found keyword

error: missing `fn` or `struct` for function or struct definition
 --> src/lib.rs:5:4
  |
2 |     ($id:item()) => {}
  |      -------- while parsing argument for this `item` macro fragment
...
5 | m!(Self());
  |    ^^^^
  |
help: if you meant to call a macro, try
  |
5 | m!(Self!());
  |        +
```

I considered restoring this diagnostic, but I'm not super convinced it's worth the complexity (and to me, it's not super clear what the user actually intended here).

compiler/rustc_parse/src/parser/item.rs

@@ -408,6 +408,7 @@ impl<'a> Parser<'a> {
         let insert_span = ident_span.shrink_to_lo();
 
         let ident = if self.token.is_ident()
+            && self.token.is_non_reserved_ident()
             && (!is_const || self.look_ahead(1, |t| *t == token::OpenParen))
             && self.look_ahead(1, |t| {
                 matches!(t.kind, token::Lt | token::OpenBrace | token::OpenParen)

tests/ui/parser/macro/kw-in-const-item-pos-recovery-149692.rs

@@ -0,0 +1,11 @@
+//! More test coverage for <https://github.com/rust-lang/rust/issues/149692>; this test is
+//! specifically for `const` items.
+
+macro_rules! m {
+    (const $id:item()) => {}
+}
+
+m!(const Self());
+//~^ ERROR expected one of `!` or `::`, found `(`
+
+fn main() {}

tests/ui/parser/macro/kw-in-const-item-pos-recovery-149692.stderr

@@ -0,0 +1,11 @@
+error: expected one of `!` or `::`, found `(`
+  --> $DIR/kw-in-const-item-pos-recovery-149692.rs:8:14
+   |
+LL |     (const $id:item()) => {}
+   |            -------- while parsing argument for this `item` macro fragment
+...
+LL | m!(const Self());
+   |              ^ expected one of `!` or `::`
+
+error: aborting due to 1 previous error
+

tests/ui/parser/macro/kw-in-item-pos-recovery-149692.rs

@@ -0,0 +1,19 @@
+//! Regression test for a diagnostic ICE where we tried to recover a keyword as the identifier when
+//! we are already trying to recover a missing keyword before item.
+//!
+//! See <https://github.com/rust-lang/rust/issues/149692>.
+
+macro_rules! m {
+    ($id:item()) => {}
+}
+
+m!(Self());
+//~^ ERROR expected one of `!` or `::`, found `(`
+
+m!(Self{});
+//~^ ERROR expected one of `!` or `::`, found `{`
+
+m!(crate());
+//~^ ERROR expected one of `!` or `::`, found `(`
+
+fn main() {}

tests/ui/parser/macro/kw-in-item-pos-recovery-149692.stderr

@@ -0,0 +1,29 @@
+error: expected one of `!` or `::`, found `(`
+  --> $DIR/kw-in-item-pos-recovery-149692.rs:10:8
+   |
+LL |     ($id:item()) => {}
+   |      -------- while parsing argument for this `item` macro fragment
+...
+LL | m!(Self());
+   |        ^ expected one of `!` or `::`
+
+error: expected one of `!` or `::`, found `{`
+  --> $DIR/kw-in-item-pos-recovery-149692.rs:13:8
+   |
+LL |     ($id:item()) => {}
+   |      -------- while parsing argument for this `item` macro fragment
+...
+LL | m!(Self{});
+   |        ^ expected one of `!` or `::`
+
+error: expected one of `!` or `::`, found `(`
+  --> $DIR/kw-in-item-pos-recovery-149692.rs:16:9
+   |
+LL |     ($id:item()) => {}
+   |      -------- while parsing argument for this `item` macro fragment
+...
+LL | m!(crate());
+   |         ^ expected one of `!` or `::`
+
+error: aborting due to 3 previous errors
+