Talking to the compiler (the :meta mechanism))

:meta expressions are created with macros. As an example, consider the implementation of the @inline macro:

gets turned into an expression like this:

To use the metadata, you have to parse these :meta expressions. If your implementation can be performed within Julia, Base.popmeta! is very handy: will scan a function body expression (one without the function signature) for the first :meta expression containing :symbol, extract any arguments, and return a tuple (found::Bool, args::Array{Any}). If the metadata did not have any arguments, or :symbol was not found, the args array will be empty.