Cometary.Macros

Cometary.Macros

This library provides macros the ability to allow methods to redefine themselves, based on the context of the caller.

Note:
Macros must be defined in another library in order for them to be properly expanded. Alternatively, the Cometary.Metaprogramming package must be installed.

Installation

Install-Package Cometary.Macros

Activation

[assembly: Macros]

Features

Note:
Some examples can be found in the tests library.

Macro expansion

All static methods marked with the Expand attribute are now considered "macros." They will be called during compilation with access to the static CallBinder class. From there, they'll be able to change the syntax of the statement or expression that led to this call.

Example

[Expand]
public static void Mixin(string expression)
{
    CallBinder.ExpressionSyntax = SyntaxFactory.ParseExpression(expression);
}

// Before:
Mixin("int i = 0;")

// After:
int i = 0;

Compile-Time Dynamic Binding

Any class can now define members that are dynamically resolved during compilation by declaring a static Bind method.

Example

public static class Numbers
{
    private static ExpressionSyntax Bind(MemberAccessExpressionSyntax node)
    {
        int number = ExampleClass.ParseNumber(node.Name.Identifier.Text);

        return SyntaxFactory.LiteralExpression(
            SyntaxKind.NumericLiteralExpression,
            SyntaxFactory.Literal(number)
        );
    }
}

// Before:
int i = Numbers.FiftyFive;

// After:
int i = 25;