From c49526aa18f13ff0fdd5f9b2cddc946692720792 Mon Sep 17 00:00:00 2001
From: Seiichi Uchida <seuchida@gmail.com>
Date: Sat, 2 Dec 2017 23:01:35 +0900
Subject: [PATCH 1/2] Add a test for #2197

---
 tests/target/issue-2197.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)
 create mode 100644 tests/target/issue-2197.rs

diff --git a/tests/target/issue-2197.rs b/tests/target/issue-2197.rs
new file mode 100644
index 00000000000..d26ca1a80e5
--- /dev/null
+++ b/tests/target/issue-2197.rs
@@ -0,0 +1,12 @@
+// rustfmt-max_width: 79
+// rustfmt-wrap_comments: true
+// rustfmt-error_on_line_overflow: false
+
+/// ```rust
+/// unsafe fn sum_sse2(x: i32x4) -> i32 {
+///     let x = vendor::_mm_add_epi32(x, vendor::_mm_srli_si128(x.into(), 8).into());
+///     let x = vendor::_mm_add_epi32(x, vendor::_mm_srli_si128(x.into(), 4).into());
+///     vendor::_mm_cvtsi128_si32(x)
+/// }
+/// ```
+fn foo() {}

From b9126fac82280f5a1ba9365957dce5bb8268ee15 Mon Sep 17 00:00:00 2001
From: Seiichi Uchida <seuchida@gmail.com>
Date: Sat, 2 Dec 2017 23:01:50 +0900
Subject: [PATCH 2/2] Do not format fenced code blocks in comment

---
 src/comment.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/comment.rs b/src/comment.rs
index 2e3dadd2066..9b9056c4170 100644
--- a/src/comment.rs
+++ b/src/comment.rs
@@ -319,6 +319,7 @@ fn rewrite_comment_inner(
 
     let mut result = opener.to_owned();
     let mut is_prev_line_multi_line = false;
+    let mut inside_code_block = false;
     let comment_line_separator = format!("\n{}{}", indent_str, line_start);
     for line in lines {
         if result == opener {
@@ -331,6 +332,14 @@ fn rewrite_comment_inner(
             result.push_str(&comment_line_separator);
         }
 
+        if line.starts_with("```") {
+            inside_code_block = !inside_code_block;
+        }
+        if inside_code_block {
+            result.push_str(line);
+            continue;
+        }
+
         if config.wrap_comments() && line.len() > fmt.shape.width && !has_url(line) {
             match rewrite_string(line, &fmt, Some(max_chars)) {
                 Some(ref s) => {