Auto merge of #120586 - ShE3py:exprkind-err, r=fmease

Add `ErrorGuaranteed` to `ast::ExprKind::Err`

See #119967 for context
```
      \
       \
          _~^~^~_
      \) /  o o  \ (/
        '_   -   _'
        / '-----' \
```

r? fmease

src/tools/clippy/clippy_utils/src/ast_utils.rs

@@ -143,7 +143,8 @@ pub fn eq_expr(l: &Expr, r: &Expr) -> bool {
     match (&l.kind, &r.kind) {
         (Paren(l), _) => eq_expr(l, r),
         (_, Paren(r)) => eq_expr(l, r),
-        (Err, Err) => true,
+        (Err(_), Err(_)) => true,
+        (Dummy, _) | (_, Dummy) => unreachable!("comparing `ExprKind::Dummy`"),
         (Try(l), Try(r)) | (Await(l, _), Await(r, _)) => eq_expr(l, r),
         (Array(l), Array(r)) => over(l, r, |l, r| eq_expr(l, r)),
         (Tup(l), Tup(r)) => over(l, r, |l, r| eq_expr(l, r)),

src/tools/clippy/clippy_utils/src/sugg.rs

@@ -222,7 +222,8 @@ pub fn ast(
             | ast::ExprKind::Array(..)
             | ast::ExprKind::While(..)
             | ast::ExprKind::Await(..)
-            | ast::ExprKind::Err => Sugg::NonParen(snippet_with_context(cx, expr.span, ctxt, default, app).0),
+            | ast::ExprKind::Err(_)
+            | ast::ExprKind::Dummy => Sugg::NonParen(snippet_with_context(cx, expr.span, ctxt, default, app).0),
             ast::ExprKind::Range(ref lhs, ref rhs, RangeLimits::HalfOpen) => Sugg::BinOp(
                 AssocOp::DotDot,
                 lhs.as_ref().map_or("".into(), |lhs| {

src/tools/rustfmt/src/expr.rs

@@ -404,7 +404,7 @@ fn needs_space_after_range(rhs: &ast::Expr) -> bool {
             // These do not occur in the AST because macros aren't expanded.
             unreachable!()
         }
-        ast::ExprKind::Err => None,
+        ast::ExprKind::Err(_) | ast::ExprKind::Dummy => None,
     };
 
     expr_rw

src/tools/rustfmt/src/utils.rs

@@ -497,7 +497,8 @@ pub(crate) fn is_block_expr(context: &RewriteContext<'_>, expr: &ast::Expr, repr
         | ast::ExprKind::Break(..)
         | ast::ExprKind::Cast(..)
         | ast::ExprKind::Continue(..)
-        | ast::ExprKind::Err
+        | ast::ExprKind::Dummy
+        | ast::ExprKind::Err(_)
         | ast::ExprKind::Field(..)
         | ast::ExprKind::IncludedBytes(..)
         | ast::ExprKind::InlineAsm(..)