fix check for iterability in Dict constructor

Author: JeffBezanson

base/dict.jl

@@ -144,8 +144,7 @@ function Dict(kv)
     try
         associative_with_eltype((K, V) -> Dict{K, V}, kv, eltype(kv))
     catch e
-        if any(x->isempty(methods(x, (typeof(kv),))), [start, next, done]) ||
-            !all(x->isa(x,Union{Tuple,Pair}),kv)
+        if !applicable(start, kv) || !all(x->isa(x,Union{Tuple,Pair}),kv)
             throw(ArgumentError("Dict(kv): kv needs to be an iterator of tuples or pairs"))
         else
             rethrow(e)