Disallow combining parens and brackets in impl

Author: topecongiro

src/items.rs

@@ -33,8 +33,8 @@ use types::join_bounds;
 use utils::{colon_spaces, contains_skip, first_line_width, format_abi, format_constness,
             format_defaultness, format_mutability, format_unsafety, format_visibility,
             is_attributes_extendable, last_line_contains_single_line_comment,
-            last_line_extendable, last_line_used_width, last_line_width, mk_sp,
-            semicolon_for_expr, starts_with_newline, stmt_expr, trimmed_last_line_width};
+            last_line_used_width, last_line_width, mk_sp, semicolon_for_expr, starts_with_newline,
+            stmt_expr, trimmed_last_line_width};
 use vertical::rewrite_with_alignment;
 use visitor::FmtVisitor;
 
@@ -631,8 +631,7 @@ pub fn format_impl(
         }
         result.push_str(&where_clause_str);
 
-        let need_newline = !last_line_extendable(&result)
-            && (last_line_contains_single_line_comment(&result) || result.contains('\n'));
+        let need_newline = last_line_contains_single_line_comment(&result) || result.contains('\n');
         match context.config.brace_style() {
             _ if need_newline => result.push_str(&sep),
             BraceStyle::AlwaysNextLine => result.push_str(&sep),