gh-17645 test for out of bounds read

TODO test fails with sanitize=address.

Author: hvds

t/lib/croak/toke

@@ -564,3 +564,12 @@ else {
 EXPECT
 OPTIONS regex
 Use of code point 0x80000000(00000000)? is not allowed; the permissible max is 0x7FFFFFFF(FFFFFFFF)? at - line \d+.
+########
+# TODO gh-17645: conflict marker detection should not read out of bounds
+m/$0[
+==0/
+EXPECT
+syntax error at - line 2, near "[
+=="
+  (Might be a runaway multi-line // string starting on line 1)
+Execution of - aborted due to compilation errors.