This is primarily a bug fix release. Changes of interest are: Nix 1.6 accidentally changed the semantics of antiquoted paths in strings, such as "${/foo}/bar". This release reverts to the Nix 1.5.3 behaviour. Previously, Nix optimised expressions such as "${expr}" to expr. Thus it neither checked whether expr could be coerced to a string, nor applied such coercions. This meant that "${123}" evaluatued to 123, and "${./foo}" evaluated to ./foo (even though "${./foo} " evaluates to "/nix/store/hash-foo "). Nix now checks the type of antiquoted expressions and applies coercions. Nix now shows the exact position of undefined variables. In particular, undefined variable errors in a with previously didn't show any position information, so this makes it a lot easier to fix such errors. Undefined variables are now treated consistently. Previously, the tryEval function would catch undefined variables inside a with but not outside. Now tryEval never catches undefined variables. Bash completion in nix-shell now works correctly. Stack traces are less verbose: they no longer show calls to builtin functions and only show a single line for each derivation on the call stack. New built-in function: builtins.typeOf, which returns the type of its argument as a string.