equals method
Structural equality.
When ignoreSpans is true (the default), two ASTs from differently-
positioned sources compare equal as long as their structure matches —
useful for testing parser output against expected shapes regardless
of whitespace placement. Set false for a strict, position-aware
comparison that requires every Span to match.
Implementation
@override
bool equals(FluentNode other, {bool ignoreSpans = true}) {
if (other is! Variant) return false;
if (other.isDefault != isDefault) return false;
if (!key.equals(other.key, ignoreSpans: ignoreSpans)) return false;
if (!value.equals(other.value, ignoreSpans: ignoreSpans)) return false;
return _spansEqual(span, other.span, ignoreSpans: ignoreSpans);
}