diff --git a/base/abstractarray.jl b/base/abstractarray.jl
index 70d1fd4828d4e..8d0436441b096 100644
--- a/base/abstractarray.jl
+++ b/base/abstractarray.jl
@@ -486,7 +486,7 @@ argument or as a series of integer arguments.
 
 Custom AbstractArray subtypes may choose which specific array type is best-suited to return
 for the given element type and dimensionality. If they do not specialize this method, the
-default is an `Array{element_type}(dims...)`.
+default is an `Array{element_type}(uninitialized, dims...)`.
 
 For example, `similar(1:10, 1, 4)` returns an uninitialized `Array{Int,2}` since ranges are
 neither mutable nor support 2 dimensions:
@@ -525,7 +525,7 @@ similar(a::AbstractArray{T}, dims::DimOrInd...) where {T}          = similar(a,
 similar(a::AbstractArray, ::Type{T}, dims::DimOrInd...) where {T}  = similar(a, T, to_shape(dims))
 similar(a::AbstractArray, ::Type{T}, dims::NeedsShaping) where {T} = similar(a, T, to_shape(dims))
 # similar creates an Array by default
-similar(a::AbstractArray, ::Type{T}, dims::Dims{N}) where {T,N}    = Array{T,N}(dims)
+similar(a::AbstractArray, ::Type{T}, dims::Dims{N}) where {T,N}    = Array{T,N}(uninitialized, dims)
 
 to_shape(::Tuple{}) = ()
 to_shape(dims::Dims) = dims
@@ -550,7 +550,7 @@ argument. `storagetype` might be a type or a function.
 creates an array that "acts like" an `Array{Int}` (and might indeed be
 backed by one), but which is indexed identically to `A`. If `A` has
 conventional indexing, this will be identical to
-`Array{Int}(size(A))`, but if `A` has unconventional indexing then the
+`Array{Int}(uninitialized, size(A))`, but if `A` has unconventional indexing then the
 indices of the result will match `A`.
 
     similar(BitArray, (indices(A, 2),))
@@ -1078,10 +1078,10 @@ promote_eltype() = Bottom
 promote_eltype(v1, vs...) = promote_type(eltype(v1), promote_eltype(vs...))
 
 #TODO: ERROR CHECK
-cat(catdim::Integer) = Array{Any,1}(0)
+cat(catdim::Integer) = Vector{Any}()
 
-typed_vcat(::Type{T}) where {T} = Array{T,1}(0)
-typed_hcat(::Type{T}) where {T} = Array{T,1}(0)
+typed_vcat(::Type{T}) where {T} = Vector{T}()
+typed_hcat(::Type{T}) where {T} = Vector{T}()
 
 ## cat: special cases
 vcat(X::T...) where {T}         = T[ X[i] for i=1:length(X) ]
@@ -1089,10 +1089,10 @@ vcat(X::T...) where {T<:Number} = T[ X[i] for i=1:length(X) ]
 hcat(X::T...) where {T}         = T[ X[j] for i=1:1, j=1:length(X) ]
 hcat(X::T...) where {T<:Number} = T[ X[j] for i=1:1, j=1:length(X) ]
 
-vcat(X::Number...) = hvcat_fill(Vector{promote_typeof(X...)}(length(X)), X)
-hcat(X::Number...) = hvcat_fill(Matrix{promote_typeof(X...)}(1,length(X)), X)
-typed_vcat(::Type{T}, X::Number...) where {T} = hvcat_fill(Array{T,1}(length(X)), X)
-typed_hcat(::Type{T}, X::Number...) where {T} = hvcat_fill(Array{T,2}(1,length(X)), X)
+vcat(X::Number...) = hvcat_fill(Vector{promote_typeof(X...)}(uninitialized, length(X)), X)
+hcat(X::Number...) = hvcat_fill(Matrix{promote_typeof(X...)}(uninitialized, 1,length(X)), X)
+typed_vcat(::Type{T}, X::Number...) where {T} = hvcat_fill(Vector{T}(uninitialized, length(X)), X)
+typed_hcat(::Type{T}, X::Number...) where {T} = hvcat_fill(Matrix{T}(uninitialized, 1,length(X)), X)
 
 vcat(V::AbstractVector...) = typed_vcat(promote_eltype(V...), V...)
 vcat(V::AbstractVector{T}...) where {T} = typed_vcat(T, V...)
@@ -1184,7 +1184,7 @@ cat_size(A::AbstractArray, d) = size(A, d)
 cat_indices(A, d) = OneTo(1)
 cat_indices(A::AbstractArray, d) = indices(A, d)
 
-cat_similar(A, T, shape) = Array{T}(shape)
+cat_similar(A, T, shape) = Array{T}(uninitialized, shape)
 cat_similar(A::AbstractArray, T, shape) = similar(A, T, shape)
 
 cat_shape(dims, shape::Tuple) = shape
@@ -1233,7 +1233,7 @@ end
 
 function _cat(A, shape::NTuple{N}, catdims, X...) where N
     offsets = zeros(Int, N)
-    inds = Vector{UnitRange{Int}}(N)
+    inds = Vector{UnitRange{Int}}(uninitialized, N)
     concat = copy!(zeros(Bool, N), catdims)
     for x in X
         for i = 1:N
@@ -1457,13 +1457,13 @@ function typed_hvcat(::Type{T}, rows::Tuple{Vararg{Int}}, as::AbstractVecOrMat..
 end
 
 hvcat(rows::Tuple{Vararg{Int}}) = []
-typed_hvcat(::Type{T}, rows::Tuple{Vararg{Int}}) where {T} = Array{T,1}(0)
+typed_hvcat(::Type{T}, rows::Tuple{Vararg{Int}}) where {T} = Vector{T}()
 
 function hvcat(rows::Tuple{Vararg{Int}}, xs::T...) where T<:Number
     nr = length(rows)
     nc = rows[1]
 
-    a = Array{T,2}(nr, nc)
+    a = Matrix{T}(uninitialized, nr, nc)
     if length(a) != length(xs)
         throw(ArgumentError("argument count does not match specified shape (expected $(length(a)), got $(length(xs)))"))
     end
@@ -1507,12 +1507,12 @@ function typed_hvcat(::Type{T}, rows::Tuple{Vararg{Int}}, xs::Number...) where T
     if nr*nc != len
         throw(ArgumentError("argument count $(len) does not match specified shape $((nr,nc))"))
     end
-    hvcat_fill(Array{T,2}(nr, nc), xs)
+    hvcat_fill(Matrix{T}(uninitialized, nr, nc), xs)
 end
 
 function typed_hvcat(::Type{T}, rows::Tuple{Vararg{Int}}, as...) where T
     nbr = length(rows)  # number of block rows
-    rs = Array{Any,1}(nbr)
+    rs = Vector{Any}(uninitialized, nbr)
     a = 1
     for i = 1:nbr
         rs[i] = typed_hcat(T, as[a:a-1+rows[i]]...)
diff --git a/base/array.jl b/base/array.jl
index bd385c1e15464..b721b1b52ba9b 100644
--- a/base/array.jl
+++ b/base/array.jl
@@ -92,14 +92,14 @@ eltype(x) = eltype(typeof(x))
 
 import Core: arraysize, arrayset, arrayref
 
-vect() = Array{Any,1}(0)
+vect() = Vector{Any}()
 vect(X::T...) where {T} = T[ X[i] for i = 1:length(X) ]
 
 function vect(X...)
     T = promote_typeof(X...)
     #T[ X[i] for i=1:length(X) ]
     # TODO: this is currently much faster. should figure out why. not clear.
-    return copy!(Array{T,1}(length(X)), X)
+    return copy!(Vector{T}(uninitialized, length(X)), X)
 end
 
 size(a::Array, d) = arraysize(a, d)
@@ -244,13 +244,13 @@ end
 
 ## Constructors ##
 
-similar(a::Array{T,1}) where {T}                    = Array{T,1}(size(a,1))
-similar(a::Array{T,2}) where {T}                    = Array{T,2}(size(a,1), size(a,2))
-similar(a::Array{T,1}, S::Type) where {T}           = Array{S,1}(size(a,1))
-similar(a::Array{T,2}, S::Type) where {T}           = Array{S,2}(size(a,1), size(a,2))
-similar(a::Array{T}, m::Int) where {T}              = Array{T,1}(m)
-similar(a::Array, T::Type, dims::Dims{N}) where {N} = Array{T,N}(dims)
-similar(a::Array{T}, dims::Dims{N}) where {T,N}     = Array{T,N}(dims)
+similar(a::Array{T,1}) where {T}                    = Vector{T}(uninitialized, size(a,1))
+similar(a::Array{T,2}) where {T}                    = Matrix{T}(uninitialized, size(a,1), size(a,2))
+similar(a::Array{T,1}, S::Type) where {T}           = Vector{S}(uninitialized, size(a,1))
+similar(a::Array{T,2}, S::Type) where {T}           = Matrix{S}(uninitialized, size(a,1), size(a,2))
+similar(a::Array{T}, m::Int) where {T}              = Vector{T}(uninitialized, m)
+similar(a::Array, T::Type, dims::Dims{N}) where {N} = Array{T,N}(uninitialized, dims)
+similar(a::Array{T}, dims::Dims{N}) where {T,N}     = Array{T,N}(uninitialized, dims)
 
 # T[x...] constructs Array{T,1}
 """
@@ -275,26 +275,26 @@ julia> getindex(Int8, 1, 2, 3)
 ```
 """
 function getindex(::Type{T}, vals...) where T
-    a = Array{T,1}(length(vals))
+    a = Vector{T}(uninitialized, length(vals))
     @inbounds for i = 1:length(vals)
         a[i] = vals[i]
     end
     return a
 end
 
-getindex(::Type{T}) where {T} = (@_inline_meta; Array{T,1}(0))
-getindex(::Type{T}, x) where {T} = (@_inline_meta; a = Array{T,1}(1); @inbounds a[1] = x; a)
-getindex(::Type{T}, x, y) where {T} = (@_inline_meta; a = Array{T,1}(2); @inbounds (a[1] = x; a[2] = y); a)
-getindex(::Type{T}, x, y, z) where {T} = (@_inline_meta; a = Array{T,1}(3); @inbounds (a[1] = x; a[2] = y; a[3] = z); a)
+getindex(::Type{T}) where {T} = (@_inline_meta; Vector{T}())
+getindex(::Type{T}, x) where {T} = (@_inline_meta; a = Vector{T}(uninitialized, 1); @inbounds a[1] = x; a)
+getindex(::Type{T}, x, y) where {T} = (@_inline_meta; a = Vector{T}(uninitialized, 2); @inbounds (a[1] = x; a[2] = y); a)
+getindex(::Type{T}, x, y, z) where {T} = (@_inline_meta; a = Vector{T}(uninitialized, 3); @inbounds (a[1] = x; a[2] = y; a[3] = z); a)
 
 function getindex(::Type{Any}, @nospecialize vals...)
-    a = Array{Any,1}(length(vals))
+    a = Vector{Any}(uninitialized, length(vals))
     @inbounds for i = 1:length(vals)
         a[i] = vals[i]
     end
     return a
 end
-getindex(::Type{Any}) = Array{Any,1}(0)
+getindex(::Type{Any}) = Vector{Any}()
 
 function fill!(a::Union{Array{UInt8}, Array{Int8}}, x::Integer)
     ccall(:memset, Ptr{Void}, (Ptr{Void}, Cint, Csize_t), a, x, length(a))
@@ -329,8 +329,8 @@ julia> fill(1.0, (5,5))
 If `x` is an object reference, all elements will refer to the same object. `fill(Foo(),
 dims)` will return an array filled with the result of evaluating `Foo()` once.
 """
-fill(v, dims::Dims)       = fill!(Array{typeof(v)}(dims), v)
-fill(v, dims::Integer...) = fill!(Array{typeof(v)}(dims...), v)
+fill(v, dims::Dims)       = fill!(Array{typeof(v)}(uninitialized, dims), v)
+fill(v, dims::Integer...) = fill!(Array{typeof(v)}(uninitialized, dims...), v)
 
 """
     zeros([A::AbstractArray,] [T=eltype(A)::Type,] [dims=size(A)::Tuple])
@@ -420,7 +420,7 @@ function ones end
 
 for (fname, felt) in ((:zeros, :zero), (:ones, :one))
     @eval begin
-        $fname(::Type{T}, dims::NTuple{N, Any}) where {T, N} = fill!(Array{T,N}(Dims(dims)), $felt(T))
+        $fname(::Type{T}, dims::NTuple{N, Any}) where {T, N} = fill!(Array{T,N}(uninitialized, Dims(dims)), $felt(T))
         $fname(dims::Tuple) = ($fname)(Float64, dims)
         $fname(::Type{T}, dims...) where {T} = $fname(T, dims)
         $fname(dims...) = $fname(dims)
@@ -477,10 +477,10 @@ julia> collect(Float64, 1:2:5)
 """
 collect(::Type{T}, itr) where {T} = _collect(T, itr, iteratorsize(itr))
 
-_collect(::Type{T}, itr, isz::HasLength) where {T} = copy!(Array{T,1}(Int(length(itr)::Integer)), itr)
+_collect(::Type{T}, itr, isz::HasLength) where {T} = copy!(Vector{T}(uninitialized, Int(length(itr)::Integer)), itr)
 _collect(::Type{T}, itr, isz::HasShape) where {T}  = copy!(similar(Array{T}, indices(itr)), itr)
 function _collect(::Type{T}, itr, isz::SizeUnknown) where T
-    a = Array{T,1}(0)
+    a = Vector{T}()
     for x in itr
         push!(a,x)
     end
@@ -532,9 +532,9 @@ end
 
 _collect_indices(::Tuple{}, A) = copy!(Array{eltype(A)}(), A)
 _collect_indices(indsA::Tuple{Vararg{OneTo}}, A) =
-    copy!(Array{eltype(A)}(length.(indsA)), A)
+    copy!(Array{eltype(A)}(uninitialized, length.(indsA)), A)
 function _collect_indices(indsA, A)
-    B = Array{eltype(A)}(length.(indsA))
+    B = Array{eltype(A)}(uninitialized, length.(indsA))
     copy!(B, CartesianRange(indices(B)), A, CartesianRange(indsA))
 end
 
@@ -554,14 +554,14 @@ else
     end
 end
 
-_array_for(::Type{T}, itr, ::HasLength) where {T} = Array{T,1}(Int(length(itr)::Integer))
+_array_for(::Type{T}, itr, ::HasLength) where {T} = Vector{T}(uninitialized, Int(length(itr)::Integer))
 _array_for(::Type{T}, itr, ::HasShape) where {T} = similar(Array{T}, indices(itr))::Array{T}
 
 function collect(itr::Generator)
     isz = iteratorsize(itr.iter)
     et = @default_eltype(typeof(itr))
     if isa(isz, SizeUnknown)
-        return grow_to!(Array{et,1}(0), itr)
+        return grow_to!(Vector{et}(), itr)
     else
         st = start(itr)
         if done(itr,st)
@@ -1439,8 +1439,8 @@ end
 
 # concatenations of homogeneous combinations of vectors, horizontal and vertical
 
-vcat() = Array{Any,1}(0)
-hcat() = Array{Any,1}(0)
+vcat() = Vector{Any}()
+hcat() = Vector{Any}()
 
 function hcat(V::Vector{T}...) where T
     height = length(V[1])
@@ -1457,7 +1457,7 @@ function vcat(arrays::Vector{T}...) where T
     for a in arrays
         n += length(a)
     end
-    arr = Array{T,1}(n)
+    arr = Vector{T}(uninitialized, n)
     ptr = pointer(arr)
     if isbits(T)
         elsz = Core.sizeof(T)
@@ -1752,14 +1752,14 @@ julia> find(isodd, [2, 4])
 function find(testf::Function, A)
     # use a dynamic-length array to store the indexes, then copy to a non-padded
     # array for the return
-    tmpI = Array{Int,1}(0)
+    tmpI = Vector{Int}()
     inds = _index_remapper(A)
     for (i,a) = enumerate(A)
         if testf(a)
             push!(tmpI, inds[i])
         end
     end
-    I = Array{Int,1}(length(tmpI))
+    I = Vector{Int}(uninitialized, length(tmpI))
     copy!(I, tmpI)
     return I
 end
@@ -1790,7 +1790,7 @@ julia> find(falses(3))
 """
 function find(A)
     nnzA = count(t -> t != 0, A)
-    I = Vector{Int}(nnzA)
+    I = Vector{Int}(uninitialized, nnzA)
     cnt = 1
     inds = _index_remapper(A)
     warned = false
@@ -1807,8 +1807,8 @@ function find(A)
     return I
 end
 
-find(x::Bool) = x ? [1] : Array{Int,1}(0)
-find(testf::Function, x::Number) = !testf(x) ? Array{Int,1}(0) : [1]
+find(x::Bool) = x ? [1] : Vector{Int}()
+find(testf::Function, x::Number) = !testf(x) ? Vector{Int}() : [1]
 
 findn(A::AbstractVector) = find(A)
 
@@ -1876,7 +1876,7 @@ function findnz(A::AbstractMatrix{T}) where T
     nnzA = count(t -> t != 0, A)
     I = zeros(Int, nnzA)
     J = zeros(Int, nnzA)
-    NZs = Array{T,1}(nnzA)
+    NZs = Vector{T}(uninitialized, nnzA)
     cnt = 1
     if nnzA > 0
         for j=indices(A,2), i=indices(A,1)
@@ -2225,7 +2225,7 @@ function filter!(f, a::AbstractVector)
 end
 
 function filter(f, a::Vector)
-    r = Vector{eltype(a)}(0)
+    r = Vector{eltype(a)}()
     for ai in a
         if f(ai)
             push!(r, ai)
@@ -2238,7 +2238,7 @@ end
 # These are moderately efficient, preserve order, and remove dupes.
 
 function intersect(v1, vs...)
-    ret = Vector{promote_eltype(v1, vs...)}(0)
+    ret = Vector{promote_eltype(v1, vs...)}()
     for v_elem in v1
         inall = true
         for vsi in vs
@@ -2254,7 +2254,7 @@ function intersect(v1, vs...)
 end
 
 function union(vs...)
-    ret = Vector{promote_eltype(vs...)}(0)
+    ret = Vector{promote_eltype(vs...)}()
     seen = Set()
     for v in vs
         for v_elem in v
@@ -2287,7 +2287,7 @@ julia> setdiff([1,2,3],[3,4,5])
 function setdiff(a, b)
     args_type = promote_type(eltype(a), eltype(b))
     bset = Set(b)
-    ret = Array{args_type,1}(0)
+    ret = Vector{args_type}()
     seen = Set{eltype(a)}()
     for a_elem in a
         if !in(a_elem, seen) && !in(a_elem, bset)
diff --git a/base/associative.jl b/base/associative.jl
index 3e04c6adacf01..c3ed947a202eb 100644
--- a/base/associative.jl
+++ b/base/associative.jl
@@ -349,7 +349,7 @@ Dict{Int64,String} with 2 entries:
 ```
 """
 function filter!(f, d::Associative)
-    badkeys = Vector{keytype(d)}(0)
+    badkeys = Vector{keytype(d)}()
     try
         for (k,v) in d
             # don't delete!(d, k) here, since associative types
@@ -368,7 +368,7 @@ end
 function filter!_dict_deprecation(e, f, d::Associative)
     if isa(e, MethodError) && e.f === f
         depwarn("In `filter!(f, dict)`, `f` is now passed a single pair instead of two arguments.", :filter!)
-        badkeys = Vector{keytype(d)}(0)
+        badkeys = Vector{keytype(d)}()
         for (k,v) in d
             # don't delete!(d, k) here, since associative types
             # may not support mutation during iteration
@@ -495,7 +495,7 @@ See [`Dict`](@ref) for further help.
 mutable struct ObjectIdDict <: Associative{Any,Any}
     ht::Vector{Any}
     ndel::Int
-    ObjectIdDict() = new(Vector{Any}(32), 0)
+    ObjectIdDict() = new(Vector{Any}(uninitialized, 32), 0)
 
     function ObjectIdDict(itr)
         d = ObjectIdDict()
diff --git a/base/asyncmap.jl b/base/asyncmap.jl
index 297a4411d8487..f60ea5507de2c 100644
--- a/base/asyncmap.jl
+++ b/base/asyncmap.jl
@@ -246,7 +246,7 @@ end
 
 # Special handling for some types.
 function asyncmap(f, s::AbstractString; kwargs...)
-    s2 = Array{Char,1}(length(s))
+    s2 = Vector{Char}(uninitialized, length(s))
     asyncmap!(f, s2, s; kwargs...)
     return convert(String, s2)
 end