Remove dead code around ID_function_call

Both bits of code would necessarily have triggered a failing invariant or an
exception. We continue to fail an invariant (UNREACHABLE), but don't keep around
the poorly maintained (dead) code.

Author: tautschnig

src/ansi-c/c_typecheck_expr.cpp

@@ -916,43 +916,13 @@ void c_typecheck_baset::typecheck_side_effect_statement_expression(
 
     expr.type()=op.type();
   }
-  else if(last_statement==ID_function_call)
+  else
   {
-    // this is suspected to be dead
-    UNREACHABLE;
-
-    // make the last statement an expression
-
-    code_function_callt &fc=to_code_function_call(last);
-
-    side_effect_expr_function_callt sideeffect(
-      fc.function(),
-      fc.arguments(),
-      to_code_type(fc.function().type()).return_type(),
-      fc.source_location());
+    // we used to do this, but don't expect it any longer
+    PRECONDITION(last_statement != ID_function_call);
 
-    expr.type()=sideeffect.type();
-
-    if(fc.lhs().is_nil())
-    {
-      code_expressiont code_expr(sideeffect);
-      code_expr.add_source_location() = fc.source_location();
-      last.swap(code_expr);
-    }
-    else
-    {
-      side_effect_exprt assign(
-        ID_assign, sideeffect.type(), fc.source_location());
-      assign.add_to_operands(fc.lhs(), std::move(sideeffect));
-
-      code_expressiont code_expr(assign);
-      code_expr.add_source_location() = fc.source_location();
-
-      last.swap(code_expr);
-    }
-  }
-  else
     expr.type()=typet(ID_empty);
+  }
 }
 
 void c_typecheck_baset::typecheck_expr_sizeof(exprt &expr)

src/goto-symex/symex_assign.cpp

@@ -40,26 +40,7 @@ void goto_symext::symex_assign(
     const side_effect_exprt &side_effect_expr=to_side_effect_expr(rhs);
     const irep_idt &statement=side_effect_expr.get_statement();
 
-    if(statement==ID_function_call)
-    {
-      const auto &function_call =
-        to_side_effect_expr_function_call(side_effect_expr);
-
-      DATA_INVARIANT(
-        !side_effect_expr.operands().empty(),
-        "function call statement expects non-empty list of side effects");
-
-      DATA_INVARIANT(
-        function_call.function().id() == ID_symbol,
-        "expected symbol as function");
-
-      const irep_idt &identifier =
-        to_symbol_expr(function_call.function()).get_identifier();
-
-      throw unsupported_operation_exceptiont(
-        "symex_assign: unexpected function call: " + id2string(identifier));
-    }
-    else if(
+    if(
       statement == ID_cpp_new || statement == ID_cpp_new_array ||
       statement == ID_java_new_array_data)
       symex_cpp_new(state, lhs, side_effect_expr);