diff --git a/src/solvers/flattening/boolbv_struct.cpp b/src/solvers/flattening/boolbv_struct.cpp
index 9b49a69eb09..b418da6438f 100644
--- a/src/solvers/flattening/boolbv_struct.cpp
+++ b/src/solvers/flattening/boolbv_struct.cpp
@@ -12,7 +12,10 @@ Author: Daniel Kroening, kroening@kroening.com
 
 bvt boolbvt::convert_struct(const struct_exprt &expr)
 {
-  const struct_typet &struct_type=to_struct_type(ns.follow(expr.type()));
+  const struct_typet &struct_type =
+    expr.type().id() == ID_struct_tag
+      ? ns.follow_tag(to_struct_tag_type(expr.type()))
+      : to_struct_type(expr.type());
 
   std::size_t width=boolbv_width(struct_type);
 
diff --git a/src/solvers/flattening/boolbv_typecast.cpp b/src/solvers/flattening/boolbv_typecast.cpp
index 6f14f1c6d1a..3be48023153 100644
--- a/src/solvers/flattening/boolbv_typecast.cpp
+++ b/src/solvers/flattening/boolbv_typecast.cpp
@@ -538,17 +538,23 @@ bool boolbvt::type_conversion(
         return false;
       }
     }
-    else if(ns.follow(dest_type).id() == ID_struct)
+    else if(dest_type.id() == ID_struct || dest_type.id() == ID_struct_tag)
     {
-      const struct_typet &dest_struct = to_struct_type(ns.follow(dest_type));
+      const struct_typet &dest_struct =
+        dest_type.id() == ID_struct_tag
+          ? ns.follow_tag(to_struct_tag_type(dest_type))
+          : to_struct_type(dest_type);
 
-      if(ns.follow(src_type).id() == ID_struct)
+      if(src_type.id() == ID_struct || src_type.id() == ID_struct_tag)
       {
         // we do subsets
 
         dest.resize(dest_width, const_literal(false));
 
-        const struct_typet &op_struct = to_struct_type(ns.follow(src_type));
+        const struct_typet &op_struct =
+          src_type.id() == ID_struct_tag
+            ? ns.follow_tag(to_struct_tag_type(src_type))
+            : to_struct_type(src_type);
 
         const struct_typet::componentst &dest_comp = dest_struct.components();
 
diff --git a/src/solvers/flattening/boolbv_update.cpp b/src/solvers/flattening/boolbv_update.cpp
index 2a1ce9a5e23..5af9c09874a 100644
--- a/src/solvers/flattening/boolbv_update.cpp
+++ b/src/solvers/flattening/boolbv_update.cpp
@@ -107,9 +107,11 @@ void boolbvt::convert_update_rec(
   {
     const irep_idt &component_name=designator.get(ID_component_name);
 
-    if(ns.follow(type).id() == ID_struct)
+    if(type.id() == ID_struct || type.id() == ID_struct_tag)
     {
-      const struct_typet &struct_type = to_struct_type(ns.follow(type));
+      const struct_typet &struct_type =
+        type.id() == ID_struct_tag ? ns.follow_tag(to_struct_tag_type(type))
+                                   : to_struct_type(type);
 
       std::size_t struct_offset=0;
 
@@ -144,9 +146,11 @@ void boolbvt::convert_update_rec(
       convert_update_rec(
         designators, d+1, new_type, new_offset, new_value, bv);
     }
-    else if(ns.follow(type).id() == ID_union)
+    else if(type.id() == ID_union || type.id() == ID_union_tag)
     {
-      const union_typet &union_type = to_union_type(ns.follow(type));
+      const union_typet &union_type = type.id() == ID_union_tag
+                                        ? ns.follow_tag(to_union_tag_type(type))
+                                        : to_union_type(type);
 
       const union_typet::componentt &component=
         union_type.get_component(component_name);
diff --git a/src/solvers/flattening/bv_pointers.cpp b/src/solvers/flattening/bv_pointers.cpp
index e40162aa1f2..a022801df4b 100644
--- a/src/solvers/flattening/bv_pointers.cpp
+++ b/src/solvers/flattening/bv_pointers.cpp
@@ -312,7 +312,6 @@ std::optional<bvt> bv_pointerst::convert_address_of_rec(const exprt &expr)
   {
     const member_exprt &member_expr=to_member_expr(expr);
     const exprt &struct_op = member_expr.compound();
-    const typet &struct_op_type=ns.follow(struct_op.type());
 
     // recursive call
     auto bv_opt = convert_address_of_rec(struct_op);
@@ -320,10 +319,16 @@ std::optional<bvt> bv_pointerst::convert_address_of_rec(const exprt &expr)
       return {};
 
     bvt bv = std::move(*bv_opt);
-    if(struct_op_type.id()==ID_struct)
+    if(
+      struct_op.type().id() == ID_struct ||
+      struct_op.type().id() == ID_struct_tag)
     {
-      auto offset = member_offset(
-        to_struct_type(struct_op_type), member_expr.get_component_name(), ns);
+      const struct_typet &struct_op_type =
+        struct_op.type().id() == ID_struct_tag
+          ? ns.follow_tag(to_struct_tag_type(struct_op.type()))
+          : to_struct_type(struct_op.type());
+      auto offset =
+        member_offset(struct_op_type, member_expr.get_component_name(), ns);
       CHECK_RETURN(offset.has_value());
 
       // add offset
@@ -333,7 +338,8 @@ std::optional<bvt> bv_pointerst::convert_address_of_rec(const exprt &expr)
     else
     {
       INVARIANT(
-        struct_op_type.id() == ID_union,
+        struct_op.type().id() == ID_union ||
+          struct_op.type().id() == ID_union_tag,
         "member expression should operate on struct or union");
       // nothing to do, all members have offset 0
     }
@@ -551,21 +557,26 @@ bvt bv_pointerst::convert_pointer_type(const exprt &expr)
   else if(expr.id() == ID_field_address)
   {
     const auto &field_address_expr = to_field_address_expr(expr);
-    const typet &compound_type = ns.follow(field_address_expr.compound_type());
+    const typet &compound_type = field_address_expr.compound_type();
 
     // recursive call
     auto bv = convert_bitvector(field_address_expr.base());
 
-    if(compound_type.id() == ID_struct)
+    if(compound_type.id() == ID_struct || compound_type.id() == ID_struct_tag)
     {
-      auto offset = member_offset(
-        to_struct_type(compound_type), field_address_expr.component_name(), ns);
+      const struct_typet &struct_type =
+        compound_type.id() == ID_struct_tag
+          ? ns.follow_tag(to_struct_tag_type(compound_type))
+          : to_struct_type(compound_type);
+      auto offset =
+        member_offset(struct_type, field_address_expr.component_name(), ns);
       CHECK_RETURN(offset.has_value());
 
       // add offset
       bv = offset_arithmetic(field_address_expr.type(), bv, *offset);
     }
-    else if(compound_type.id() == ID_union)
+    else if(
+      compound_type.id() == ID_union || compound_type.id() == ID_union_tag)
     {
       // nothing to do, all fields have offset 0
     }
diff --git a/src/solvers/smt2/smt2_conv.cpp b/src/solvers/smt2/smt2_conv.cpp
index 0d63d2863c5..d132114cb22 100644
--- a/src/solvers/smt2/smt2_conv.cpp
+++ b/src/solvers/smt2/smt2_conv.cpp
@@ -846,7 +846,10 @@ void smt2_convt::convert_address_of_rec(
       struct_op_type.id() == ID_struct || struct_op_type.id() == ID_struct_tag,
       "member expression operand shall have struct type");
 
-    const struct_typet &struct_type = to_struct_type(ns.follow(struct_op_type));
+    const struct_typet &struct_type =
+      struct_op_type.id() == ID_struct_tag
+        ? ns.follow_tag(to_struct_tag_type(struct_op_type))
+        : to_struct_type(struct_op_type);
 
     const irep_idt &component_name = member_expr.get_component_name();
 
@@ -3159,7 +3162,10 @@ void smt2_convt::convert_floatbv_typecast(const floatbv_typecast_exprt &expr)
 
 void smt2_convt::convert_struct(const struct_exprt &expr)
 {
-  const struct_typet &struct_type = to_struct_type(ns.follow(expr.type()));
+  const struct_typet &struct_type =
+    expr.type().id() == ID_struct_tag
+      ? ns.follow_tag(to_struct_tag_type(expr.type()))
+      : to_struct_type(expr.type());
 
   const struct_typet::componentst &components=
     struct_type.components();
@@ -3262,10 +3268,9 @@ void smt2_convt::flatten_array(const exprt &expr)
 
 void smt2_convt::convert_union(const union_exprt &expr)
 {
-  const union_typet &union_type = to_union_type(ns.follow(expr.type()));
   const exprt &op=expr.op();
 
-  std::size_t total_width=boolbv_width(union_type);
+  std::size_t total_width = boolbv_width(expr.type());
 
   std::size_t member_width=boolbv_width(op.type());
 
@@ -4182,7 +4187,10 @@ void smt2_convt::convert_with(const with_exprt &expr)
   }
   else if(expr_type.id() == ID_struct || expr_type.id() == ID_struct_tag)
   {
-    const struct_typet &struct_type = to_struct_type(ns.follow(expr_type));
+    const struct_typet &struct_type =
+      expr_type.id() == ID_struct_tag
+        ? ns.follow_tag(to_struct_tag_type(expr_type))
+        : to_struct_type(expr_type);
 
     const exprt &index = expr.where();
     const exprt &value = expr.new_value();
@@ -4253,11 +4261,9 @@ void smt2_convt::convert_with(const with_exprt &expr)
   }
   else if(expr_type.id() == ID_union || expr_type.id() == ID_union_tag)
   {
-    const union_typet &union_type = to_union_type(ns.follow(expr_type));
-
     const exprt &value = expr.new_value();
 
-    std::size_t total_width=boolbv_width(union_type);
+    std::size_t total_width = boolbv_width(expr_type);
 
     std::size_t member_width=boolbv_width(value.type());
 
@@ -4399,7 +4405,10 @@ void smt2_convt::convert_member(const member_exprt &expr)
 
   if(struct_op_type.id() == ID_struct || struct_op_type.id() == ID_struct_tag)
   {
-    const struct_typet &struct_type = to_struct_type(ns.follow(struct_op_type));
+    const struct_typet &struct_type =
+      struct_op_type.id() == ID_struct_tag
+        ? ns.follow_tag(to_struct_tag_type(struct_op_type))
+        : to_struct_type(struct_op_type);
 
     INVARIANT(
       struct_type.has_component(name), "struct should have accessed component");
@@ -4496,7 +4505,9 @@ void smt2_convt::flatten2bv(const exprt &expr)
     if(use_datatypes)
     {
       // concatenate elements
-      const struct_typet &struct_type = to_struct_type(ns.follow(type));
+      const struct_typet &struct_type =
+        type.id() == ID_struct_tag ? ns.follow_tag(to_struct_tag_type(type))
+                                   : to_struct_type(type);
 
       const struct_typet::componentst &components=
         struct_type.components();
@@ -4622,7 +4633,9 @@ void smt2_convt::unflatten(
 
         out << "(mk-" << smt_typename;
 
-        const struct_typet &struct_type = to_struct_type(ns.follow(type));
+        const struct_typet &struct_type =
+          type.id() == ID_struct_tag ? ns.follow_tag(to_struct_tag_type(type))
+                                     : to_struct_type(type);
 
         const struct_typet::componentst &components=
           struct_type.components();
@@ -5501,8 +5514,11 @@ void smt2_convt::convert_type(const typet &type)
   else if(type.id() == ID_union || type.id() == ID_union_tag)
   {
     std::size_t width=boolbv_width(type);
+    const union_typet &union_type = type.id() == ID_union_tag
+                                      ? ns.follow_tag(to_union_tag_type(type))
+                                      : to_union_type(type);
     CHECK_RETURN_WITH_DIAGNOSTICS(
-      to_union_type(ns.follow(type)).components().empty() || width != 0,
+      union_type.components().empty() || width != 0,
       "failed to get width of union");
 
     out << "(_ BitVec " << width << ")";
diff --git a/src/solvers/smt2_incremental/encoding/struct_encoding.cpp b/src/solvers/smt2_incremental/encoding/struct_encoding.cpp
index f57b943ff81..7e8e946d86b 100644
--- a/src/solvers/smt2_incremental/encoding/struct_encoding.cpp
+++ b/src/solvers/smt2_incremental/encoding/struct_encoding.cpp
@@ -105,8 +105,7 @@ extricate_updates(const with_exprt &struct_expr)
 static exprt encode(const with_exprt &with, const namespacet &ns)
 {
   const auto tag_type = type_checked_cast<struct_tag_typet>(with.type());
-  const auto struct_type =
-    type_checked_cast<struct_typet>(ns.follow(with.type()));
+  const auto struct_type = ns.follow_tag(tag_type);
   const auto updates = extricate_updates(with);
   const auto components =
     make_range(struct_type.components())
@@ -194,11 +193,19 @@ static std::size_t count_trailing_bit_width(
 /// the combined width of the fields which follow the field being selected.
 exprt struct_encodingt::encode_member(const member_exprt &member_expr) const
 {
-  const auto &type = ns.get().follow(member_expr.compound().type());
+  const auto &compound_type = member_expr.compound().type();
   const auto offset_bits = [&]() -> std::size_t {
-    if(can_cast_type<union_typet>(type))
+    if(
+      can_cast_type<union_typet>(compound_type) ||
+      can_cast_type<union_tag_typet>(compound_type))
+    {
       return 0;
-    const auto &struct_type = type_checked_cast<struct_typet>(type);
+    }
+    const auto &struct_type =
+      compound_type.id() == ID_struct_tag
+        ? ns.get().follow_tag(
+            type_checked_cast<struct_tag_typet>(compound_type))
+        : type_checked_cast<struct_typet>(compound_type);
     return count_trailing_bit_width(
       struct_type, member_expr.get_component_name(), *boolbv_width);
   }();
diff --git a/src/solvers/strings/string_refinement.cpp b/src/solvers/strings/string_refinement.cpp
index d9e682ae64c..e1980bed5f4 100644
--- a/src/solvers/strings/string_refinement.cpp
+++ b/src/solvers/strings/string_refinement.cpp
@@ -341,7 +341,10 @@ static void add_equations_for_symbol_resolution(
     {
       if(rhs.type().id() == ID_struct || rhs.type().id() == ID_struct_tag)
       {
-        const struct_typet &struct_type = to_struct_type(ns.follow(rhs.type()));
+        const struct_typet &struct_type =
+          rhs.type().id() == ID_struct_tag
+            ? ns.follow_tag(to_struct_tag_type(rhs.type()))
+            : to_struct_type(rhs.type());
         for(const auto &comp : struct_type.components())
         {
           if(is_char_pointer_type(comp.type()))
@@ -377,7 +380,10 @@ extract_strings_from_lhs(const exprt &lhs, const namespacet &ns)
     result.push_back(lhs);
   else if(lhs.type().id() == ID_struct || lhs.type().id() == ID_struct_tag)
   {
-    const struct_typet &struct_type = to_struct_type(ns.follow(lhs.type()));
+    const struct_typet &struct_type =
+      lhs.type().id() == ID_struct_tag
+        ? ns.follow_tag(to_struct_tag_type(lhs.type()))
+        : to_struct_type(lhs.type());
     for(const auto &comp : struct_type.components())
     {
       const std::vector<exprt> strings_in_comp = extract_strings_from_lhs(
@@ -439,7 +445,9 @@ static void add_string_equation_to_symbol_resolution(
       eq.rhs().type().id() == ID_struct_tag)
     {
       const struct_typet &struct_type =
-        to_struct_type(ns.follow(eq.rhs().type()));
+        eq.rhs().type().id() == ID_struct_tag
+          ? ns.follow_tag(to_struct_tag_type(eq.rhs().type()))
+          : to_struct_type(eq.rhs().type());
       for(const auto &comp : struct_type.components())
       {
         const member_exprt lhs_data(eq.lhs(), comp.get_name(), comp.type());