Fix comment rendering for sclasses (#420)

* Fixtures

* Use the same constant body renderer as classes/modules for sclasses

fixtures/small/sclass_actual.rb

@@ -3,4 +3,17 @@ class << self
   end
 end
 
+# The moon beams white on the peach blossoms,
+# the Milky Way moored silvering at midnight.
+class MoonBeam
+  # I wonder if the nightingale has noticed
+  # the spring spirit already alive in the branch?
+  class << self
+    # I can hardly get to sleep
+    # as if tenderness were a sickness.
+    def show
+    end
+  end
+end
+
 Foo.machine

fixtures/small/sclass_expected.rb

@@ -3,4 +3,17 @@ class << self
   end
 end
 
+# The moon beams white on the peach blossoms,
+# the Milky Way moored silvering at midnight.
+class MoonBeam
+  # I wonder if the nightingale has noticed
+  # the spring spirit already alive in the branch?
+  class << self
+    # I can hardly get to sleep
+    # as if tenderness were a sickness.
+    def show
+    end
+  end
+end
+
 Foo.machine

librubyfmt/rubyfmt_lib.rb

@@ -45,6 +45,7 @@ def initialize(file_data)
       "return" => [],
       "when" => [],
       "case" => [],
+      "class" => [],
       "yield" => [],
       "break" => [],
       "super" => [],
@@ -406,11 +407,11 @@ def on_defs(*args)
   end
 
   def on_class(*args)
-    with_lineno { super }
+    super + [start_end_for_keyword("class")]
   end
 
   def on_sclass(*args)
-    with_lineno { super }
+    super + [start_end_for_keyword("class")]
   end
 
   def on_module(*args)

librubyfmt/src/format.rs

@@ -3581,6 +3581,8 @@ pub fn format_sclass(ps: &mut dyn ConcreteParserState, sc: SClass) {
     let body = sc.2;
     let end_line = sc.3.end_line();
 
+    ps.on_line(sc.3.start_line());
+
     ps.with_start_of_line(
         false,
         Box::new(|ps| {
@@ -3589,29 +3591,9 @@ pub fn format_sclass(ps: &mut dyn ConcreteParserState, sc: SClass) {
             ps.emit_ident("<<".to_string());
             ps.emit_space();
             format_expression(ps, *expr);
-            ps.emit_newline();
-            ps.new_block(Box::new(|ps| {
-                ps.with_start_of_line(
-                    true,
-                    Box::new(|ps| {
-                        format_bodystmt(ps, body, end_line);
-                    }),
-                );
-            }));
+            format_constant_body(ps, body, end_line);
         }),
     );
-    ps.with_start_of_line(
-        true,
-        Box::new(|ps| {
-            ps.emit_end();
-        }),
-    );
-
-    ps.on_line(end_line);
-
-    if ps.at_start_of_line() {
-        ps.emit_newline();
-    }
 }
 
 pub fn format_stabby_lambda(ps: &mut dyn ConcreteParserState, sl: StabbyLambda) {