IsDef

Used to check whether there is a definition under a given name.

?? name<id> -> bool

Returns whether a lookup on the given name would result in a typed value.

If there is a symbol, function, macro, or type called name, returns true, otherwise false.

data Foo;

fnc main () () {
    sym x:i32;
    ?? x; # true

    ?? main; # true

    ?? c8; # true

    ?? Foo; # true

    ?? nonexistent; # false

    ?? sym; # false
};