[GR-23348] make test_userstring pass

PullRequest: graalpython/1397

Author: qunaibit

graalpython/com.oracle.graal.python.test/src/tests/unittest_tags/test_userstring.txt

@@ -7,6 +7,7 @@
 *graalpython.lib-python.3.test.test_userstring.UserStringTest.test_count
 *graalpython.lib-python.3.test.test_userstring.UserStringTest.test_encode_default_args
 *graalpython.lib-python.3.test.test_userstring.UserStringTest.test_encode_explicit_none_args
+*graalpython.lib-python.3.test.test_userstring.UserStringTest.test_endswith
 *graalpython.lib-python.3.test.test_userstring.UserStringTest.test_expandtabs
 *graalpython.lib-python.3.test.test_userstring.UserStringTest.test_extended_getslice
 *graalpython.lib-python.3.test.test_userstring.UserStringTest.test_find

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/str/StringBuiltins.java

@@ -575,7 +575,7 @@ abstract static class PrefixSuffixBaseNode extends PythonQuaternaryBuiltinNode {
         @Specialization
         boolean doStringPrefixStartEnd(String self, String substr, int start, int end) {
             int len = self.length();
-            return doIt(self, substr, adjustStart(start, len), adjustStart(end, len));
+            return doIt(self, substr, adjustStart(start, len), adjustEnd(end, len));
         }
 
         @Specialization
@@ -592,7 +592,7 @@ boolean doStringPrefix(String self, String substr, @SuppressWarnings("unused") P
         @Specialization
         boolean doTuplePrefixStartEnd(String self, PTuple substrs, int start, int end) {
             int len = self.length();
-            return doIt(self, substrs, adjustStart(start, len), adjustStart(end, len));
+            return doIt(self, substrs, adjustStart(start, len), adjustEnd(end, len));
         }
 
         @Specialization