Show source code of function from repl

I would like to review the definition of a method in the REPL. I follow this link ( https://github.com/JuliaLang/julia/issues/2625 ) but it doesn't work:

julia> f(x) = x^2
f (generic function with 1 method)

julia> expand(f)
f (generic function with 1 method)

julia> methods(f)
# 1 method for generic function "f":
f(x) at REPL[155]:1

julia> implementation(f,1)
ERROR: UndefVarError: implementation not defined
 in eval_user_input(::Any, ::Base.REPL.REPLBackend) at ./REPL.jl:64
 in macro expansion at ./REPL.jl:95 [inlined]
 in (::Base.REPL.##3#4{Base.REPL.REPLBackend})() at ./event.jl:68

      

        
        
        
      

    

The method implementation

doesn't seem to exist.