Don't know how transformational it has been yet, but I feel the idea that all side effecting code needs to be specifically noted by the programmer, a la Haskell

Don't know how transformational it has been yet, but I feel the idea that all side effecting code needs to be specifically noted by the programmer, a la Haskell, will one day be seen as a watershed. We're only at the very early stages of the parallelisation of hardware, but as that trend intensifies, I can't imagine compiling efficient code without explicit compiler knowledge of what code might side effect.