Fix code block whitespace handling

compiler/rustc_errors/src/markdown/parse.rs

@@ -220,7 +220,7 @@ fn parse_codeblock(buf: &[u8]) -> Parsed<'_> {
     let mut found = None;
     for idx in (0..working.len()).filter(|idx| working[*idx..].starts_with(&end_pat)) {
         let (eol_txt, rest) = parse_to_newline(&working[(idx + end_pat.len())..]);
-        if !eol_txt.iter().any(u8::is_ascii_whitespace) {
+        if eol_txt.iter().all(u8::is_ascii_whitespace) {
             found = Some((&working[..idx], rest));
             break;
         }

compiler/rustc_errors/src/markdown/tests/parse.rs

@@ -364,3 +364,16 @@ fn test_snake_case() {
     let res = entrypoint(SNAKE_CASE);
     assert_eq!(res, expected);
 }
+
+#[test]
+fn test_codeblock_trailing_whitespace() {
+    let buf = "```rust\ncode\n```	\nrest";
+    let (t, r) = parse_codeblock(buf.as_bytes());
+    assert_eq!(t, MdTree::CodeBlock { txt: "code", lang: Some("rust") });
+    assert_eq!(r, b"\nrest");
+
+    let buf = "```rust\ncode\n```abc\nrest";
+    let (t, r) = parse_codeblock(buf.as_bytes());
+    assert_eq!(t, MdTree::CodeBlock { txt: "code\n```abc\nrest", lang: Some("rust") });
+    assert_eq!(r, b"");
+}