2.1 KiB
Lambda discard parameters
Summary
Allow discards (_) to be used as parameters of lambdas and anonymous methods.
For example:
- lambdas:
(_, _) => 0,(int _, int _) => 0 - anonymous methods:
delegate(int _, int _) { return 0; }
Motivation
Unused parameters do not need to be named. The intent of discards is clear, i.e. they are unused/discarded.
Detailed design
Method parameters
In the parameter list of a lambda or anonymous method with more than one parameter named _, such parameters are discard parameters.
Note: if a single parameter is named _ then it is a regular parameter for backwards compatibility reasons.
Discard parameters do not introduce any names to any scopes.
Note this implies they do not cause any _ (underscore) names to be hidden.
Simple names
If K is zero and the simple_name appears within a block and if the block's (or an enclosing block's) local variable declaration space (Declarations) contains a local variable, parameter (with the exception of discard parameters) or constant with name I, then the simple_name refers to that local variable, parameter or constant and is classified as a variable or value.
Scopes With the exception of discard parameters, the scope of a parameter declared in a lambda_expression (Anonymous function expressions) is the anonymous_function_body of that lambda_expression With the exception of discard parameters, the scope of a parameter declared in an anonymous_method_expression (Anonymous function expressions) is the block of that anonymous_method_expression.