We extend Kobayashi and Sumii's type system for the deadlock-free
pi-calculus and develop a type reconstruction algorithm.  Kobayashi
and Sumii's type system helps high-level reasoning about concurrent
programs by guaranteeing that communication on certain channels will
eventually succeed.  It can ensure, for example, that a process
implementing a function really behaves like a function.  However,
because it lacked a type reconstruction algorithm and required rather
complicated type annotations, applying it to real concurrent languages
was impractical.  We have therefore developed a type reconstruction
algorithm for an extension of the type system.  The key novelties that
made it possible are generalization of _usages_ (which specifies how
each communication channel is used) and a _subusage_ relation.