Initialise symbol_exprt in the constructor

No need to delay initialisation - do proper RAII.

Author: tautschnig

src/goto-symex/slice_by_trace.cpp

@@ -31,10 +31,6 @@ void symex_slice_by_tracet::slice_by_trace(
 {
   std::cout << "Slicing by trace...\n";
 
-  merge_identifier="goto_symex::\\merge";
-  merge_symbol=symbol_exprt(typet(ID_bool));
-  merge_symbol.set_identifier(merge_identifier);
-
   std::vector<exprt> trace_conditions;
 
   size_t length=trace_files.length();

src/goto-symex/slice_by_trace.h

@@ -17,9 +17,11 @@ Author: Alex Groce ([email protected])
 class symex_slice_by_tracet
 {
 public:
-  explicit symex_slice_by_tracet(const namespacet &_ns):
-    ns(_ns),
-    alphabet_parity(false)
+  explicit symex_slice_by_tracet(const namespacet &_ns)
+    : ns(_ns),
+      alphabet_parity(false),
+      merge_symbol("goto_symex::\\merge", bool_typet())
+
   {
   }