nur0n parent
I love how easy it is to view the machine code for a function. Julia actually ships with a handful of these introspection macros: https://docs.julialang.org/en/v1/devdocs/reflection/#Interme.... They are invaluable when it comes to optimization.
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
Prof. Alan Edelman gave a nice lecture about this a couple of days ago https://www.youtube.com/watch?v=IuOXXQR7dAo