[PRISM] Fix up some error formatting edge cases

prism/prism.c

@@ -19588,7 +19588,7 @@ typedef struct {
 
 #define PM_COLOR_GRAY "\033[38;5;102m"
 #define PM_COLOR_RED "\033[1;31m"
-#define PM_COLOR_RESET "\033[0m"
+#define PM_COLOR_RESET "\033[m"
 
 static inline pm_error_t *
 pm_parser_errors_format_sort(const pm_parser_t *parser, const pm_list_t *error_list, const pm_newline_list_t *newline_list) {
@@ -19644,7 +19644,11 @@ pm_parser_errors_format_sort(const pm_parser_t *parser, const pm_list_t *error_l
 
 static inline void
 pm_parser_errors_format_line(const pm_parser_t *parser, const pm_newline_list_t *newline_list, const char *number_prefix, int32_t line, pm_buffer_t *buffer) {
-    size_t index = (size_t) (line - parser->start_line);
+    int32_t line_delta = line - parser->start_line;
+    assert(line_delta >= 0);
+
+    size_t index = (size_t) line_delta;
+    assert(index < newline_list->size);
 
     const uint8_t *start = &parser->start[newline_list->offsets[index]];
     const uint8_t *end;
@@ -19765,7 +19769,7 @@ pm_parser_errors_format(const pm_parser_t *parser, pm_buffer_t *buffer, bool col
     // the source before the error to give some context. We'll be careful not to
     // display the same line twice in case the errors are close enough in the
     // source.
-    int32_t last_line = 0;
+    int32_t last_line = parser->start_line - 1;
     const pm_encoding_t *encoding = parser->encoding;
 
     for (size_t index = 0; index < error_list->size; index++) {
@@ -19791,13 +19795,16 @@ pm_parser_errors_format(const pm_parser_t *parser, pm_buffer_t *buffer, bool col
         // the line that has the error in it.
         if ((index == 0) || (error->line != last_line)) {
             if (colorize) {
-                pm_buffer_append_string(buffer, PM_COLOR_RED "> " PM_COLOR_RESET, 13);
+                pm_buffer_append_string(buffer, PM_COLOR_RED "> " PM_COLOR_RESET, 12);
             } else {
                 pm_buffer_append_string(buffer, "> ", 2);
             }
             pm_parser_errors_format_line(parser, newline_list, error_format.number_prefix, error->line, buffer);
         }
 
+        const uint8_t *start = &parser->start[newline_list->offsets[error->line - start_line]];
+        if (start == parser->end) pm_buffer_append_byte(buffer, '\n');
+
         // Now we'll display the actual error message. We'll do this by first
         // putting the prefix to the line, then a bunch of blank spaces
         // depending on the column, then as many carets as we need to display
@@ -19811,13 +19818,11 @@ pm_parser_errors_format(const pm_parser_t *parser, pm_buffer_t *buffer, bool col
         pm_buffer_append_string(buffer, error_format.blank_prefix, error_format.blank_prefix_length);
 
         size_t column = 0;
-        const uint8_t *start = &parser->start[newline_list->offsets[error->line - start_line]];
-
         while (column < error->column_end) {
             if (column < error->column_start) {
                 pm_buffer_append_byte(buffer, ' ');
             } else if (colorize) {
-                pm_buffer_append_string(buffer, PM_COLOR_RED "^" PM_COLOR_RESET, 12);
+                pm_buffer_append_string(buffer, PM_COLOR_RED "^" PM_COLOR_RESET, 11);
             } else {
                 pm_buffer_append_byte(buffer, '^');
             }