Clarify indent calcs in compute_budget_for_args

Author: tdudziak

src/items.rs

@@ -136,11 +136,12 @@ impl<'a> FmtVisitor<'a> {
         debug!("rewrite_fn: one_line_budget: {}, multi_line_budget: {}, arg_indent: {}",
                one_line_budget, multi_line_budget, arg_indent);
 
+        // Check if vertical layout was forced by compute_budget_for_args.
         if one_line_budget <= 0 {
             if config!(fn_args_paren_newline) {
                 result.push('\n');
                 result.push_str(&make_indent(arg_indent));
-                arg_indent = arg_indent + 1;
+                arg_indent = arg_indent + 1; // extra space for `(`
                 result.push('(');
             } else {
                 result.push_str("(\n");
@@ -378,15 +379,14 @@ impl<'a> FmtVisitor<'a> {
 
         // Didn't work. we must force vertical layout and put args on a newline.
         if let None = budgets {
-            // 6 = new indent + `()`
-            let used_space = indent + 6;
+            let new_indent = indent + 4;
+            let used_space = new_indent + 2; // account for `(` and `)`
             let max_space = config!(ideal_width) + config!(leeway);
             if used_space > max_space {
                 // Whoops! bankrupt.
                 // TODO take evasive action, perhaps kill the indent or something.
             } else {
-                // 5 = new indent + `(`
-                budgets = Some((0, max_space - used_space, indent + 4));
+                budgets = Some((0, max_space - used_space, new_indent));
             }
         }