replace restore_size_trail by more generic restore_vector

other updates:
- change signature of advance_qhead to simplify call sites
- have model reconstruction replay work on a tail of dependent_expr state, while adding formulas to the tail.

src/ast/converters/generic_model_converter.cpp

@@ -36,7 +36,6 @@ generic_model_converter::~generic_model_converter() {
 void generic_model_converter::add(func_decl * d, expr* e) {
     VERIFY(e);
     VERIFY(d->get_range() == e->get_sort());
-    m_first_idx.insert_if_not_there(d, m_entries.size());
     m_entries.push_back(entry(d, e, m, ADD));
 }
 

src/ast/converters/generic_model_converter.h

@@ -35,7 +35,6 @@ private:
     ast_manager& m;
     std::string  m_orig;
     vector<entry> m_entries;
-    obj_map<func_decl, unsigned> m_first_idx;
 
     expr_ref simplify_def(entry const& e);
 
@@ -71,6 +70,8 @@ public:
     void get_units(obj_map<expr, bool>& units) override;
 
     vector<entry> const& entries() const { return m_entries; }
+
+    void shrink(unsigned j) { m_entries.shrink(j); }
 };
 
 typedef ref<generic_model_converter> generic_model_converter_ref;

src/ast/converters/model_converter.h

@@ -101,6 +101,10 @@ typedef sref_buffer<model_converter> model_converter_ref_buffer;
 
 model_converter * concat(model_converter * mc1, model_converter * mc2);
 
+inline model_converter * concat(model_converter * mc1, model_converter * mc2, model_converter* mc3) {
+    return concat(mc1, concat(mc2, mc3));
+}
+
 model_converter * model2model_converter(model * m);
 
 model_converter * model_and_labels2model_converter(model * m, labels_vec const &r);