[ruby/prism] Update unterminated string error location

ruby/prism@33d12afa60

prism/prism.c

@@ -16878,6 +16878,7 @@ parse_strings(pm_parser_t *parser, pm_node_t *current) {
             // start with a single string content node.
             pm_string_t unescaped;
             pm_token_t content;
+
             if (match1(parser, PM_TOKEN_EOF)) {
                 unescaped = PM_STRING_EMPTY;
                 content = not_provided(parser);
@@ -16940,7 +16941,19 @@ parse_strings(pm_parser_t *parser, pm_node_t *current) {
             if (match2(parser, PM_TOKEN_STRING_END, PM_TOKEN_EOF)) {
                 node = (pm_node_t *) pm_string_node_create_unescaped(parser, &opening, &content, &parser->current, &unescaped);
                 pm_node_flag_set(node, parse_unescaped_encoding(parser));
-                expect1(parser, PM_TOKEN_STRING_END, PM_ERR_STRING_LITERAL_EOF);
+
+                // Kind of odd behavior, but basically if we have an
+                // unterminated string and it ends in a newline, we back up one
+                // character so that the error message is on the last line of
+                // content in the string.
+                if (!accept1(parser, PM_TOKEN_STRING_END)) {
+                    const uint8_t *location = parser->previous.end;
+                    if (location > parser->start && location[-1] == '\n') location--;
+                    pm_parser_err(parser, location, location, PM_ERR_STRING_LITERAL_EOF);
+
+                    parser->previous.start = parser->previous.end;
+                    parser->previous.type = PM_TOKEN_MISSING;
+                }
             } else if (accept1(parser, PM_TOKEN_LABEL_END)) {
                 node = (pm_node_t *) pm_symbol_node_create_unescaped(parser, &opening, &content, &parser->previous, &unescaped, parse_symbol_encoding(parser, &content, &unescaped, true));
             } else {