SMV: catch variables that have the same identifier as an enum

regression/smv/define/define8.desc

@@ -0,0 +1,8 @@
+CORE
+define8.smv
+
+^file .* line 6: identifier x already used as enum$
+^EXIT=2$
+^SIGNAL=0$
+--
+--

regression/smv/define/define8.smv

@@ -0,0 +1,6 @@
+MODULE main
+
+VAR some_enum : {x, y, z};
+
+-- x is already defined as an enum
+DEFINE x := 123;

regression/smv/var/already_declared5.desc

@@ -1,8 +1,8 @@
-KNOWNBUG
+CORE
 already_declared5.smv
 
+^file .* line 6: identifier x already used as enum$
 ^EXIT=2$
 ^SIGNAL=0$
 --
 --
-This crashes.

src/smvlang/smv_typecheck.cpp

@@ -2137,13 +2137,23 @@ void smv_typecheckt::create_var_symbols(
 {
   const irep_idt mode = "SMV";
 
+  // to catch variables that have the same name as enums
+  std::unordered_set<irep_idt, irep_id_hash> enums;
+
   for(const auto &item : items)
   {
     if(item.is_var() || item.is_ivar())
     {
       irep_idt base_name = to_smv_identifier_expr(item.expr).identifier();
       irep_idt identifier = module + "::var::" + id2string(base_name);
 
+      // already used as enum?
+      if(enums.find(base_name) != enums.end())
+      {
+        throw errort{}.with_location(item.expr.source_location())
+          << "identifier " << base_name << " already used as enum";
+      }
+
       auto symbol_ptr = symbol_table.lookup(identifier);
       if(symbol_ptr != nullptr)
       {
@@ -2185,6 +2195,13 @@ void smv_typecheckt::create_var_symbols(
       irep_idt base_name = identifier_expr.identifier();
       irep_idt identifier = module + "::var::" + id2string(base_name);
 
+      // already used as enum?
+      if(enums.find(base_name) != enums.end())
+      {
+        throw errort{}.with_location(identifier_expr.source_location())
+          << "identifier " << base_name << " already used as enum";
+      }
+
       auto symbol_ptr = symbol_table.lookup(identifier);
       if(symbol_ptr != nullptr)
       {
@@ -2226,6 +2243,8 @@ void smv_typecheckt::create_var_symbols(
           << "enum " << base_name << " already declared, at "
           << symbol_ptr->location;
       }
+
+      enums.insert(base_name);
     }
   }
 }