Add count_newlines() utility function

src/comment.rs

@@ -18,7 +18,7 @@
 use rewrite::RewriteContext;
 use shape::{Indent, Shape};
 use string::{rewrite_string, StringFormat};
-use utils::{first_line_width, last_line_width};
+use utils::{count_newlines, first_line_width, last_line_width};
 
 fn is_custom_comment(comment: &str) -> bool {
     if !comment.starts_with("//") {
@@ -296,7 +296,7 @@ fn rewrite_comment_inner(
         config: config,
     };
 
-    let line_breaks = orig.trim_right().chars().filter(|&c| c == '\n').count();
+    let line_breaks = count_newlines(orig.trim_right());
     let lines = orig.lines()
         .enumerate()
         .map(|(i, mut line)| {

src/expr.rs

@@ -2712,12 +2712,8 @@ pub fn choose_rhs<R: Rewrite>(
 }
 
 fn prefer_next_line(orig_rhs: &str, next_line_rhs: &str) -> bool {
-    fn count_line_breaks(src: &str) -> usize {
-        src.chars().filter(|&x| x == '\n').count()
-    }
-
-    !next_line_rhs.contains('\n')
-        || count_line_breaks(orig_rhs) > count_line_breaks(next_line_rhs) + 1
+    use utils::count_newlines;
+    !next_line_rhs.contains('\n') || count_newlines(orig_rhs) > count_newlines(next_line_rhs) + 1
 }
 
 fn rewrite_expr_addrof(

src/lists.rs

@@ -17,7 +17,7 @@
 use config::{Config, IndentStyle};
 use rewrite::RewriteContext;
 use shape::{Indent, Shape};
-use utils::{first_line_width, last_line_width, mk_sp, starts_with_newline};
+use utils::{count_newlines, first_line_width, last_line_width, mk_sp, starts_with_newline};
 
 /// Formatting tactic for lists. This will be cast down to a
 /// `DefinitiveListTactic` depending on the number and length of the items and
@@ -651,7 +651,7 @@ fn next(&mut self) -> Option<Self::Item> {
                 // From the end of the first line of comments to the next non-whitespace char.
                 let test_snippet = &test_snippet[..first];
 
-                if test_snippet.chars().filter(|c| c == &'\n').count() > 1 {
+                if count_newlines(test_snippet) > 1 {
                     // There were multiple line breaks which got trimmed to nothing.
                     new_lines = true;
                 }

src/missed_spans.rs

@@ -16,7 +16,7 @@
 use comment::{rewrite_comment, CodeCharKind, CommentCodeSlices};
 use config::WriteMode;
 use shape::{Indent, Shape};
-use utils::mk_sp;
+use utils::{count_newlines, mk_sp};
 use visitor::FmtVisitor;
 
 impl<'a> FmtVisitor<'a> {
@@ -86,7 +86,7 @@ fn format_missing_inner<F: Fn(&mut FmtVisitor, &str, &str)>(
     }
 
     fn push_vertical_spaces(&mut self, original: &str) {
-        let mut newline_count = original.chars().filter(|&c| c == '\n').count();
+        let mut newline_count = count_newlines(original);
         let newline_upper_bound = self.config.blank_lines_upper_bound() + 1;
         let newline_lower_bound = self.config.blank_lines_lower_bound() + 1;
         if newline_count > newline_upper_bound {
@@ -171,7 +171,7 @@ fn replace_chars<'a>(string: &'a str) -> Cow<'a, str> {
 
                 let fix_indent = last_char.map_or(true, |rev_c| ['{', '\n'].contains(&rev_c));
 
-                let subslice_num_lines = subslice.chars().filter(|c| *c == '\n').count();
+                let subslice_num_lines = count_newlines(subslice);
 
                 if rewrite_next_comment
                     && !self.config.file_lines().intersects_range(

src/utils.rs

@@ -262,6 +262,11 @@ pub fn stmt_expr(stmt: &ast::Stmt) -> Option<&ast::Expr> {
     }
 }
 
+#[inline]
+pub fn count_newlines(input: &str) -> usize {
+    input.chars().filter(|&c| c == '\n').count()
+}
+
 #[inline]
 pub fn trim_newlines(input: &str) -> &str {
     match input.find(|c| c != '\n' && c != '\r') {

src/visitor.rs

@@ -31,7 +31,7 @@
 use regex::Regex;
 use rewrite::{Rewrite, RewriteContext};
 use shape::{Indent, Shape};
-use utils::{self, contains_skip, inner_attributes, mk_sp, ptr_vec_to_ref_vec};
+use utils::{self, contains_skip, count_newlines, inner_attributes, mk_sp, ptr_vec_to_ref_vec};
 
 fn is_use_item(item: &ast::Item) -> bool {
     match item.node {
@@ -833,7 +833,7 @@ fn take_while_with_pred<'a, P>(
             // Extract comments between two attributes.
             let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
             let snippet = context.snippet(span_between_attr);
-            if snippet.chars().filter(|c| *c == '\n').count() >= 2 || snippet.contains('/') {
+            if count_newlines(&snippet) >= 2 || snippet.contains('/') {
                 break;
             }
         }
@@ -886,7 +886,7 @@ fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
     // Look at before and after comment and see if there are any empty lines.
     let comment_begin = comment.chars().position(|c| c == '/');
     let len = comment_begin.unwrap_or_else(|| comment.len());
-    let mlb = comment.chars().take(len).filter(|c| *c == '\n').count() > 1;
+    let mlb = count_newlines(&comment[..len]) > 1;
     let mla = if comment_begin.is_none() {
         mlb
     } else {