Prefilter bidirectional Unicode checks by UTF-8 leading bytes (astral-sh#29561)

Author: MichaReiser

crates/ruff_linter/resources/test/fixtures/pylint/bidirectional_unicode.py

@@ -29,3 +29,6 @@ def subtract_funds(account: str, amount: int):
 
 # OK
 print("Hello World")
+
+# OK
+print("“مرحبا”")

crates/ruff_linter/src/rules/pylint/rules/bidirectional_unicode.rs

@@ -63,7 +63,12 @@ impl Violation for BidirectionalUnicode {
 
 /// PLE2502
 pub(crate) fn bidirectional_unicode(line: &Line, context: &LintContext) {
-    if line.contains(BIDI_UNICODE) {
+    let text = line.as_str();
+    // All characters in BIDI_UNICODE start with 0xD8 or 0xE2 in UTF-8. These are leading
+    // bytes, so the first match is a character boundary and the preceding text can be skipped.
+    if let Some(start) = memchr::memchr2(0xD8, 0xE2, text.as_bytes())
+        && text[start..].contains(BIDI_UNICODE)
+    {
         context.report_diagnostic(BidirectionalUnicode, line.full_range());
     }
 }