rspec/rules/S2955/csharp/rule.adoc

== Why is this an issue?

When constraints have not been applied to restrict a generic type parameter to be a reference type, then a value type, such as a ``++struct++``, could also be passed. In such cases, comparing the type parameter to ``++null++`` would always be false, because a ``++struct++`` can be empty, but never ``++null++``. If a value type is truly what's expected, then the comparison should use ``++default()++``. If it's not, then constraints should be added so that no value type can be passed.


=== Noncompliant code example

[source,csharp]
----
private bool IsDefault<T>(T value) 
{
  if (value == null) // Noncompliant
  {
    // ...
  }
  // ...
}
----


=== Compliant solution

[source,csharp]
----
private bool IsDefault<T>(T value) 
{
  if(object.Equals(value, default(T)))
  {
    // ...
  }
  // ...
}
----
or

[source,csharp]
----
private bool IsDefault<T>(T value) where T : class
{
  if (value == null) 
  {
    // ...
  }
  // ...
}
----


ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Use a comparison to "default(xxx)" instead or add a constraint to "xxx" so that it can't be a value type.


'''
== Comments And Links
(visible only on this page)

=== on 22 May 2015, 10:04:25 Tamas Vajk wrote:
Fixed some minor wording issues, and the sample

=== on 22 May 2015, 12:07:32 Ann Campbell wrote:
Thanks [~tamas.vajk]. Looks good.

=== on 29 May 2015, 12:50:40 Tamas Vajk wrote:
\[~ann.campbell.2] Could you run through the description? I've change the wording "false negative" because it sounded strange.

=== on 29 May 2015, 14:50:44 Ann Campbell wrote:
looks good [~tamas.vajk]

endif::env-github,rspecator-view[]