Implement (non-negated) class desugaring

lib/desugar.c

@@ -9,6 +9,33 @@
 #include <stdlib.h>
 #include <string.h>
 
+static bool desugar_class(parse_term_t *term)
+{
+	if (term->class.negated)
+		return false;
+
+	const int count = term->class.count;
+	parse_sequence_t *alternatives
+	    = malloc(count * sizeof(parse_sequence_t));
+	if (NULL == alternatives)
+		return false;
+
+	for (int i = 0; i < count; ++i) {
+		parse_term_t *terms = malloc(sizeof(parse_term_t));
+		terms[0].quantifier = PARSE_QUANTIFIER_NONE;
+		terms[0].type = PARSE_TERM_LITERAL;
+		terms[0].literal = term->class.contents[i];
+		alternatives[i].count = alternatives[i].capacity = 1;
+		alternatives[i].contents = terms;
+	}
+
+	parse_free_class_children(&term->class);
+	term->type = PARSE_TERM_SUBEXPR;
+	term->subexpr.count = term->subexpr.capacity = count;
+	term->subexpr.contents = alternatives;
+
+	return true;
+}
 
 static bool deep_copy_term(parse_term_t *dst, parse_term_t *src);
 
@@ -104,6 +131,20 @@ static bool desugar_qmark(parse_term_t *term)
 
 static bool desugar_term(parse_term_t *term)
 {
+	switch (term->type) {
+	case PARSE_TERM_WILDCARD:
+		return false;
+	case PARSE_TERM_CLASS:
+		if (!desugar_class(term))
+			return false;
+		break;
+
+	case PARSE_TERM_LITERAL:
+	case PARSE_TERM_SUBEXPR:
+	case PARSE_TERM_EMPTY:
+		break;
+	}
+
 	switch (term->quantifier) {
 	case PARSE_QUANTIFIER_PLUS:
 		if (!desugar_plus(term))