mozilla/rust — pull request #7204 by alexcrichton (2013-06-18 00:26:06+00:00)
Title: Expand the deriving(ToStr) implementation

Closes #7180 and #7179.

Before, the `deriving(ToStr)` attribute was essentially `fmt!("%?")`. This changes it to recursively invoke `to_str()` on fields instead of relying on `fmt!`-style things. This seems more natural to me and what should actually be expected.