Attribute Macro requires 

#[requires]

Tag SPs on an unsafe function item.

Syntax Example

#![feature(stmt_expr_attributes)]
#![feature(proc_macro_hygiene)]
#![feature(register_tool)]
#![register_tool(rapx)]

// Tag SPs:
#[requires { SP1 }] unsafe fn foo() {}
#[requires { SP1, SP2 }] unsafe fn bar() {}