Change type of 'actual' variable (#631)

Before the type of this variable was the same as the return type of executable under test. However, this could lead to undesired reflection usage: if a method returns 'A', but the real type of 'actual' variable is 'B' (subclass of A), then we will not be able to access fields that are declared in 'B' without reflection, because the variable is declared with type 'A'. For example, this can happen when we make assertions on field modifications and some of these fields are from 'B', but are not accessible, because type 'A' knows nothing about these new fields.

Author: ArsenHD

utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/constructor/tree/CgMethodConstructor.kt

@@ -1078,7 +1078,7 @@ internal class CgMethodConstructor(val context: CgContext) : CgContextOwner by c
                     emptyLineIfNeeded()
 
                     actual = newVar(
-                        CgClassId(executable.returnType, isNullable = result is UtNullModel),
+                        CgClassId(result.classId, isNullable = result is UtNullModel),
                         "actual"
                     ) {
                         thisInstance[executable](*methodArguments.toTypedArray())