fix error check in WeakKeyDict constructor

Author: JeffBezanson

base/weakkeydict.jl

@@ -55,8 +55,7 @@ function WeakKeyDict(kv)
     try
         Base.associative_with_eltype((K, V) -> WeakKeyDict{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("WeakKeyDict(kv): kv needs to be an iterator of tuples or pairs"))
         else
             rethrow(e)

test/dict.jl

@@ -443,6 +443,11 @@ d = Dict(:a=>"a")
 @test_throws ArgumentError Dict([1])
 @test_throws ArgumentError Dict([(1,2),0])
 
+# test Dict constructor's argument checking (for an iterable of pairs or tuples)
+# make sure other errors can propagate when the nature of the iterator is not the problem
+@test_throws InexactError Dict(convert(Int,1.5) for i=1:1)
+@test_throws InexactError WeakKeyDict(convert(Int,1.5) for i=1:1)
+
 # ImmutableDict
 import Base.ImmutableDict
 let d = ImmutableDict{String, String}(),