Fix references when rules are unused, and fix missing cloneExpr

Fix references when unused rules are removed
Add missing cloneExpr when optimizing ZeroOrOneExpr

Improves situation for #70

Makefile

@@ -154,6 +154,18 @@ $(TEST_DIR)/issue_65/optimized/issue_65.go: $(TEST_DIR)/issue_65/issue_65.peg $(
 $(TEST_DIR)/issue_65/optimized-grammar/issue_65.go: $(TEST_DIR)/issue_65/issue_65.peg $(BINDIR)/pigeon
 	$(BINDIR)/pigeon -nolint -optimize-grammar $< > $@
 
+$(TEST_DIR)/issue_70/issue_70.go: $(TEST_DIR)/issue_70/issue_70.peg $(TEST_DIR)/issue_70/optimized/issue_70.go $(TEST_DIR)/issue_70/optimized-grammar/issue_70.go $(BINDIR)/pigeon
+	$(BINDIR)/pigeon -nolint $< > $@
+
+$(TEST_DIR)/issue_70/optimized/issue_70.go: $(TEST_DIR)/issue_70/issue_70.peg $(BINDIR)/pigeon
+	$(BINDIR)/pigeon -nolint -optimize-parser -optimize-basic-latin $< > $@
+
+$(TEST_DIR)/issue_70/optimized-grammar/issue_70.go: $(TEST_DIR)/issue_70/issue_70.peg $(BINDIR)/pigeon
+	$(BINDIR)/pigeon -nolint -optimize-grammar $< > $@
+
+$(TEST_DIR)/issue_70b/issue_70b.go: $(TEST_DIR)/issue_70b/issue_70b.peg $(BINDIR)/pigeon
+	$(BINDIR)/pigeon -nolint --optimize-grammar $< > $@
+
 $(TEST_DIR)/issue_80/issue_80.go: $(TEST_DIR)/issue_80/issue_80.peg $(BINDIR)/pigeon
 	$(BINDIR)/pigeon -nolint $< > $@
 

ast/ast_optimize.go

@@ -153,6 +153,20 @@ func (r *grammarOptimizer) optimize(expr0 Expression) Visitor {
 			_, protected := r.protectedRules[rule.Name.Val]
 			if !used && !protected {
 				expr.Rules = append(expr.Rules[:i], expr.Rules[i+1:]...)
+				// Compensate for the removed item
+				i--
+
+				for k, v := range r.ruleUsedByRules {
+					for kk := range v {
+						if kk == rule.Name.Val {
+							delete(r.ruleUsedByRules[k], kk)
+							if len(r.ruleUsedByRules[k]) == 0 {
+								delete(r.ruleUsedByRules, k)
+							}
+						}
+					}
+				}
+
 				r.optimized = true
 				continue
 			}
@@ -165,6 +179,7 @@ func (r *grammarOptimizer) optimize(expr0 Expression) Visitor {
 		expr.Expr = r.optimizeRule(expr.Expr)
 	case *Rule:
 		r.rule = expr.Name.Val
+		expr.Expr = r.optimizeRule(expr.Expr)
 	case *SeqExpr:
 		expr.Exprs = r.optimizeRules(expr.Exprs)
 
@@ -333,7 +348,7 @@ func cloneExpr(expr Expression) Expression {
 		}
 	case *ZeroOrOneExpr:
 		return &ZeroOrOneExpr{
-			Expr: expr.Expr,
+			Expr: cloneExpr(expr.Expr),
 			p:    expr.p,
 		}
 	}