check struct lit ends with comma

Author: csmoe

src/expr.rs

@@ -20,7 +20,8 @@ use chains::rewrite_chain;
 use closures;
 use codemap::{LineRangeUtils, SpanUtils};
 use comment::{combine_strs_with_missing_comments, contains_comment, recover_comment_removed,
-              rewrite_comment, rewrite_missing_comment, FindUncommented};
+              rewrite_comment, rewrite_missing_comment, CharClasses, FindUncommented,
+              FullCodeCharKind};
 use config::{Config, ControlBraceStyle, IndentStyle};
 use lists::{definitive_tactic, itemize_list, shape_for_tactic, struct_lit_formatting,
             struct_lit_shape, struct_lit_tactic, write_list, ListFormatting, ListItem, Separator};
@@ -2365,12 +2366,11 @@ pub fn wrap_args_with_parens(
     }
 }
 
-/// Return true if a function call ,a method call or a struct represented by the given span ends with a
+/// Return true if a function call or a method call represented by the given span ends with a
 /// trailing comma. This function is used when rewriting macro, as adding or removing a trailing
 /// comma from macro can potentially break the code.
 fn span_ends_with_comma(context: &RewriteContext, span: Span) -> bool {
     let mut encountered_closing_paren = false;
-    let mut encountered_closing_braces = false;
     for c in context.snippet(span).chars().rev() {
         match c {
             ',' => return true,
@@ -2379,11 +2379,6 @@ fn span_ends_with_comma(context: &RewriteContext, span: Span) -> bool {
             } else {
                 encountered_closing_paren = true;
             },
-            '}' => if encountered_closing_braces {
-                return false;
-            } else {
-                encountered_closing_braces = true;
-            },
             _ if c.is_whitespace() => continue,
             _ => return false,
         }
@@ -2487,6 +2482,26 @@ fn struct_lit_can_be_aligned(fields: &[ast::Field], base: &Option<&ast::Expr>) -
     fields.iter().all(|field| !field.is_shorthand)
 }
 
+#[allow(dead_code)]
+/// Check if a struct representation ends with comma by match on the chars of struct
+/// snippet reversely, once a FullCodeCharKind::Normal comma matched, returns true
+fn struct_lit_ends_with_comma(context: &RewriteContext, span: Span) -> bool {
+    // FIXME: implement DoubleEndedIterator trait for CharClasses
+    //
+    // for (char_kind, c) in CharClasses::new(context.snippet(span).chars()).rev() {
+    //     match c {
+    //         ',' => match char_kind {
+    //             FullCodeCharKind::Normal => return true,
+    //             _ => continue,
+    //         },
+    //         _ => continue,
+    //     }
+    // }
+    //
+    // false
+    unimplemented!()
+}
+
 fn rewrite_struct_lit<'a>(
     context: &RewriteContext,
     path: &ast::Path,
@@ -2573,12 +2588,13 @@ fn rewrite_struct_lit<'a>(
         let tactic = struct_lit_tactic(h_shape, context, &item_vec);
         let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 
-        let ends_with_comma = span_ends_with_comma(context, span);
+        let ends_with_comma = struct_lit_ends_with_comma(context, span);
         let force_no_trailing_comma = if context.inside_macro && !ends_with_comma {
             true
         } else {
             false
         };
+
         let fmt = struct_lit_formatting(
             nested_shape,
             tactic,