fixup! Preserve comments in empty statements

rustfmt-core/rustfmt-lib/src/formatting/stmt.rs

@@ -53,6 +53,10 @@ impl<'a> Stmt<'a> {
         result
     }
 
+    pub(crate) fn is_empty(&self) -> bool {
+        matches!(self.inner.kind, ast::StmtKind::Empty)
+    }
+
     fn is_last_expr(&self) -> bool {
         if !self.is_last {
             return false;

rustfmt-core/rustfmt-lib/src/formatting/visitor.rs

@@ -120,12 +120,9 @@ impl<'b, 'a: 'b> FmtVisitor<'a> {
             self.parse_sess.span_to_debug_info(stmt.span())
         );
 
-        // https://github.com/rust-lang/rust/issues/63679.
-        let is_all_semicolons =
-            |snippet: &str| snippet.chars().all(|c| c.is_whitespace() || c == ';');
-        if is_all_semicolons(&self.snippet(stmt.span())) {
-            // If the statement is all semicolons, just skip over it. Before that, make sure any
-            // comment snippet preceding the semicolon is picked up.
+        if stmt.is_empty() {
+            // If the statement is empty, just skip over it. Before that, make sure any comment
+            // snippet preceding the semicolon is picked up.
             let snippet = self.snippet(mk_sp(self.last_pos, stmt.span().lo()));
             let original_starts_with_newline = snippet
                 .find(|c| c != ' ')

rustfmt-core/rustfmt-lib/tests/source/issue-4018.rs

@@ -0,0 +1,13 @@
+fn main() {
+    ;
+           /* extra comment */            ;
+}
+
+fn main() {
+    println!("");
+    // comment 1
+    // comment 2
+    // comment 3
+    // comment 4
+    ;
+}

rustfmt-core/rustfmt-lib/tests/target/issue-4018.rs

@@ -0,0 +1,11 @@
+fn main() {
+    /* extra comment */
+}
+
+fn main() {
+    println!("");
+    // comment 1
+    // comment 2
+    // comment 3
+    // comment 4
+}