expect method Null safety
If pattern
matches at the current position of the string, scans forward
until the end of the match.
If pattern
did not match, throws a FormatException describing the
position of the failure. name
is used in this error as the expected name
of the pattern being matched; if it's null
, the pattern itself is used
instead.
Implementation
void expect(Pattern pattern, {String? name}) {
if (scan(pattern)) return;
if (name == null) {
if (pattern is RegExp) {
final source = pattern.pattern;
name = '/$source/';
} else {
name =
pattern.toString().replaceAll('\\', '\\\\').replaceAll('"', '\\"');
name = '"$name"';
}
}
_fail(name);
}