Rollup merge of #159208 - nnethercote:fix-attr_on_non_tail_expr-typo, r=chenyukang

Fix `attr_on_non_tail_expr` typo

This PR fixes a minor diagnostics bug from rust-lang/rust#117988. Details in individual commits.

r? @estebank

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -873,7 +873,7 @@ impl<'a> Parser<'a> {
                 && let ast::AttrKind::Normal(next_attr_kind) = next_attr.kind
                 && let Some(next_attr_args_span) = next_attr_kind.item.args.span()
                 && let [next_segment] = &next_attr_kind.item.path.segments[..]
-                && segment.ident.name == sym::cfg
+                && next_segment.ident.name == sym::cfg
             {
                 let next_expr = match snapshot.parse_expr() {
                     Ok(next_expr) => next_expr,

tests/ui/parser/attribute/multiple-tail-expr-behind-cfg.rs

@@ -14,6 +14,13 @@ fn bar() -> String {
     String::new()
 }
 
+fn baz() -> String {
+    #[cfg(false)]
+    [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>() //~ ERROR expected `;`, found `#`
+    #[allow(unused)]
+    String::new()
+}
+
 fn main() {
     println!("{}", foo());
 }

tests/ui/parser/attribute/multiple-tail-expr-behind-cfg.stderr

@@ -44,11 +44,30 @@ help: alternatively, consider surrounding the expression with a block
 LL |     { [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>() }
    |     +                                                             +
 
+error: expected `;`, found `#`
+  --> $DIR/multiple-tail-expr-behind-cfg.rs:19:64
+   |
+LL |     #[cfg(false)]
+   |     ------------- only `;` terminated statements or tail expressions are allowed after this attribute
+LL |     [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
+   |                                                                ^ expected `;` here
+LL |     #[allow(unused)]
+   |     - unexpected token
+   |
+help: add `;` here
+   |
+LL |     [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>();
+   |                                                                +
+help: alternatively, consider surrounding the expression with a block
+   |
+LL |     { [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>() }
+   |     +                                                             +
+
 error: cannot find attribute `attr` in this scope
   --> $DIR/multiple-tail-expr-behind-cfg.rs:13:7
    |
 LL |     #[attr]
    |       ^^^^
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors