Don't allocate a Vec for non_null_positions (#746)

Author: reese

librubyfmt/src/format_prism.rs

@@ -4728,8 +4728,8 @@ fn handle_string_at_offset<'src>(ps: &mut ParserState<'src>, ident: &'src str, o
     ps.emit_ident(ident);
 }
 
-fn non_null_positions<'src>(params: &prism::ParametersNode<'src>) -> Vec<bool> {
-    vec![
+fn non_null_positions<'src>(params: &prism::ParametersNode<'src>) -> [bool; 7] {
+    [
         !params.requireds().is_empty(),
         !params.optionals().is_empty(),
         params.rest().is_some(),

librubyfmt/src/ripper_tree_types.rs

@@ -1264,8 +1264,8 @@ def_tag!(args_forward_tag, "args_forward");
 pub struct ArgsForward(pub args_forward_tag, pub StartEnd);
 
 impl Params {
-    pub fn non_null_positions(&self) -> Vec<bool> {
-        vec![
+    pub fn non_null_positions(&self) -> [bool; 7] {
+        [
             (self.1).is_some(),
             (self.2).is_some(),
             (self.3).is_some(),