Fix ConvertTypeCheckPatternToNullCheck
#110973
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Use null check pattern instead of a type check succeeding on any not-null value
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| @@ -301,7 +301,7 @@ private static Attribute[] InternalParamGetCustomAttributes(ParameterInfo param, | |||
| count = 0; | |||
| for (int i = 0; i < objAttr.Length; i++) | |||
| { | |||
| if (objAttr[i] is object attr) | |||
| if (objAttr[i] is { } attr) | |||
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This is not readable. In the initial version of pattern matching before is not null, is { } is rejected by many projects.
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We cannot use is not null with declaration pattern, i.e. if (objAttr[i] is not null attr) is invalid C#.
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| if (objAttr[i] is { } attr) | |
| if (objAttr[i] is not null and var attr) |
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Yes, it is unfortunate that there are number of more or less cryptic ways one can express a null check in modern C#. The choice between them is a matter of personal preference. My personal preference is the old fashioned:
object? attr = objAttr[i];
if (attr != null)I believe that it is the best balance of readable and succinct. (Except for the few types that overload operator==. It is fine to use more verbose is not null in those cases for performance reasons.)
Use null check pattern instead of a type check succeeding on any not-null value.