Tuxedo

Tuxedo

Types that already know they are valid.

A source generator that turns a predicate into a refined type, so a value of that type has already passed the check.

dotnet add package tuxedo.sourcegenerator

Why?

A guard clause proves something about a value for the rest of a method, but the proof stops at the method boundary. Every nested call has to check again, and the same condition ends up repeated through the program as a precaution.

Tuxedo turns the predicate into a type. The generator writes a new type whose constructor runs the predicate, so a value of that type has already passed the check.

[Refinement("The float must be positive, but was '{value}'")]
public static bool Positive(float value) => value > 0;

public static float MyCustomDivide(float dividend, PositiveFloat divisor)
{
    return dividend / divisor;
}

PositiveFloat cannot be constructed with zero, so MyCustomDivide does not need a guard. The check happens at the point the value enters the program.

What it does not do

  • It is not a runtime validation library; the generated types are ordinary C# types with a validating constructor
  • It does not track values across I/O. A value read from a file or a network request has to be refined again when it is read
  • It does not add nullable or optional semantics; a refined type is a separate type

See also

Edit this page