CSHARP-5563: Create AstExpression extension methods to make testing for constants easier.

[rstam]

Here's the pattern:

public static bool IsInt32Constant(this AstExpression expression)
public static bool IsInt32Constant(this AstExpression expression, int value)
public static bool IsInt32Constant(this AstExpression expression, out int value)

The first tests whether it is an integer constant (the value doesn't matter)
The second test whether it is an integer constant (of a particular value)
The third tests whether is it an integer constant (and returns the value in the out parameter)

[sanych-sun]

All such IsXXXConstant methods could be simplified by calling appropriate IsXXXConstant with out parameter. For example:

public static bool IsStringConstant(this AstExpression expression, string value)
  => expression.IsStringConstant(out var val) && val == value

[rstam]

That is true.

My thinking was that this was slightly more efficient than adding one more level of indirection with the additional bool return value and copying of out parameters.

I'm willing to make this change if you confirm that you still want it.

[rstam]

I totally agree that your suggestion is short and concise and elegant.

The only possible reason for not doing it would be performance, and any concerns about performance in this method might be premature optimization anyway.

[sanych-sun]

If we worried about the implications of calling the method instead of the executing the code itself, we can force compiler to inline the code whenever it's possible by marking the calling method with:
[MethodImplAttribute(MethodImplOptions.AggressiveInlining)}

[sanych-sun]

If we worried about the implications of calling the method instead of the executing the code itself, we can force compiler to inline the code whenever it's possible by marking the calling method with:
[MethodImplAttribute(MethodImplOptions.AggressiveInlining)}