Indeed, inspecting typed code, lowered code, llvm ir, and native code from the REPL is great. Combine that with @benchmark for microbenchmarking and it's amazing.

Note that the 'manual dispatch' is optimized out in a very early stage:

    julia> @code_typed foo(1)
    CodeInfo(
    1 ─     return 2
    ) => Int64

So, no need to look at assembly here.