diff --git a/base/bitarray.jl b/base/bitarray.jl
index a6d94b2152a39..3d2267bc49f00 100644
--- a/base/bitarray.jl
+++ b/base/bitarray.jl
@@ -22,7 +22,7 @@ mutable struct BitArray{N} <: DenseArray{Bool, N}
             i += 1
         end
         nc = num_bit_chunks(n)
-        chunks = Vector{UInt64}(nc)
+        chunks = Vector{UInt64}(uninitialized, nc)
         nc > 0 && (chunks[end] = UInt64(0))
         b = new(chunks, n)
         N != 1 && (b.dims = dims)
@@ -348,7 +348,7 @@ similar(B::BitArray, dims::Dims) = BitArray(dims...)
 similar(B::BitArray, T::Type{Bool}, dims::Dims) = BitArray(dims)
 # changing type to a non-Bool returns an Array
 # (this triggers conversions like float(bitvector) etc.)
-similar(B::BitArray, T::Type, dims::Dims) = Array{T}(dims)
+similar(B::BitArray, T::Type, dims::Dims) = Array{T}(uninitialized, dims)
 
 function fill!(B::BitArray, x)
     y = convert(Bool, x)
@@ -502,7 +502,7 @@ end
 convert(::Type{Array{T}}, B::BitArray{N}) where {T,N} = convert(Array{T,N}, B)
 convert(::Type{Array{T,N}}, B::BitArray{N}) where {T,N} = _convert(Array{T,N}, B) # see #15801
 function _convert(::Type{Array{T,N}}, B::BitArray{N}) where {T,N}
-    A = Array{T}(size(B))
+    A = Array{T}(uninitialized, size(B))
     Bc = B.chunks
     @inbounds for i = 1:length(A)
         A[i] = unsafe_bitgetindex(Bc, i)
@@ -620,7 +620,7 @@ gen_bitarray(::IsInfinite, itr) =  throw(ArgumentError("infinite-size iterable u
 
 function gen_bitarray_from_itr(itr, st)
     B = empty!(BitArray(bitcache_size))
-    C = Vector{Bool}(bitcache_size)
+    C = Vector{Bool}(uninitialized, bitcache_size)
     Bc = B.chunks
     ind = 1
     cind = 1
@@ -645,7 +645,7 @@ end
 
 function fill_bitarray_from_itr!(B::BitArray, itr, st)
     n = length(B)
-    C = Vector{Bool}(bitcache_size)
+    C = Vector{Bool}(uninitialized, bitcache_size)
     Bc = B.chunks
     ind = 1
     cind = 1
@@ -1189,7 +1189,7 @@ end
 
 for f in (:+, :-)
     @eval function ($f)(A::BitArray, B::BitArray)
-        r = Array{Int}(promote_shape(size(A), size(B)))
+        r = Array{Int}(uninitialized, promote_shape(size(A), size(B)))
         ai = start(A)
         bi = start(B)
         ri = 1
@@ -1649,7 +1649,7 @@ end
 function find(B::BitArray)
     l = length(B)
     nnzB = count(B)
-    I = Vector{Int}(nnzB)
+    I = Vector{Int}(uninitialized, nnzB)
     nnzB == 0 && return I
     Bc = B.chunks
     Bcount = 1
@@ -1683,8 +1683,8 @@ findn(B::BitVector) = find(B)
 
 function findn(B::BitMatrix)
     nnzB = count(B)
-    I = Vector{Int}(nnzB)
-    J = Vector{Int}(nnzB)
+    I = Vector{Int}(uninitialized, nnzB)
+    J = Vector{Int}(uninitialized, nnzB)
     cnt = 1
     for j = 1:size(B,2), i = 1:size(B,1)
         if B[i,j]
diff --git a/base/broadcast.jl b/base/broadcast.jl
index f81b16672e788..ffa047e94c367 100644
--- a/base/broadcast.jl
+++ b/base/broadcast.jl
@@ -168,7 +168,7 @@ end
         @nexprs $N i->(A_{i+1} = Bs[i])
         @nexprs $nargs i->(keep_i = keeps[i])
         @nexprs $nargs i->(Idefault_i = Idefaults[i])
-        C = Vector{Bool}(bitcache_size)
+        C = Vector{Bool}(uninitialized, bitcache_size)
         Bc = B.chunks
         ind = 1
         cind = 1
diff --git a/base/channels.jl b/base/channels.jl
index c6cad87c5f369..b48a8d0cf91be 100644
--- a/base/channels.jl
+++ b/base/channels.jl
@@ -42,10 +42,10 @@ mutable struct Channel{T} <: AbstractChannel
         if sz < 0
             throw(ArgumentError("Channel size must be either 0, a positive integer or Inf"))
         end
-        ch = new(Condition(), Condition(), :open, Nullable{Exception}(), Vector{T}(0), sz, 0)
+        ch = new(Condition(), Condition(), :open, Nullable{Exception}(), Vector{T}(), sz, 0)
         if sz == 0
-            ch.takers = Vector{Task}(0)
-            ch.putters = Vector{Task}(0)
+            ch.takers = Vector{Task}()
+            ch.putters = Vector{Task}()
         end
         return ch
     end
diff --git a/base/combinatorics.jl b/base/combinatorics.jl
index ad38a7fd07538..7b8b79fc16bfd 100644
--- a/base/combinatorics.jl
+++ b/base/combinatorics.jl
@@ -2,13 +2,13 @@
 
 # Factorials
 
-const _fact_table64 = Vector{Int64}(20)
+const _fact_table64 = Vector{Int64}(uninitialized, 20)
 _fact_table64[1] = 1
 for n in 2:20
     _fact_table64[n] = _fact_table64[n-1] * n
 end
 
-const _fact_table128 = Vector{UInt128}(34)
+const _fact_table128 = Vector{UInt128}(uninitialized, 34)
 _fact_table128[1] = 1
 for n in 2:34
     _fact_table128[n] = _fact_table128[n-1] * n
diff --git a/base/deprecated.jl b/base/deprecated.jl
index 18e9ee6d93d41..e8cc748edfe32 100644
--- a/base/deprecated.jl
+++ b/base/deprecated.jl
@@ -792,7 +792,7 @@ function Math.frexp(A::Array{<:AbstractFloat})
                    "consider using dot-syntax to `broadcast` scalar `frexp` over `Array`s ",
                    "instead, for example `frexp.(rand(4))`."), :frexp)
     F = similar(A)
-    E = Array{Int}(size(A))
+    E = Array{Int}(uninitialized, size(A))
     for (iF, iE, iA) in zip(eachindex(F), eachindex(E), eachindex(A))
         F[iF], E[iE] = frexp(A[iA])
     end
@@ -931,15 +931,15 @@ iteratoreltype(::Type{Task}) = EltypeUnknown()
 isempty(::Task) = error("isempty not defined for Tasks")
 
 # Deprecate Array(T, dims...) in favor of proper type constructors
-@deprecate Array(::Type{T}, d::NTuple{N,Int}) where {T,N}               Array{T}(d)
-@deprecate Array(::Type{T}, d::Int...) where {T}                        Array{T}(d...)
-@deprecate Array(::Type{T}, m::Int) where {T}                           Array{T}(m)
-@deprecate Array(::Type{T}, m::Int,n::Int) where {T}                    Array{T}(m,n)
-@deprecate Array(::Type{T}, m::Int,n::Int,o::Int) where {T}             Array{T}(m,n,o)
-@deprecate Array(::Type{T}, d::Integer...) where {T}                    Array{T}(convert(Tuple{Vararg{Int}}, d))
-@deprecate Array(::Type{T}, m::Integer) where {T}                       Array{T}(Int(m))
-@deprecate Array(::Type{T}, m::Integer,n::Integer) where {T}            Array{T}(Int(m),Int(n))
-@deprecate Array(::Type{T}, m::Integer,n::Integer,o::Integer) where {T} Array{T}(Int(m),Int(n),Int(o))
+@deprecate Array(::Type{T}, d::NTuple{N,Int}) where {T,N}               Array{T}(uninitialized, d)
+@deprecate Array(::Type{T}, d::Int...) where {T}                        Array{T}(uninitialized, d...)
+@deprecate Array(::Type{T}, m::Int) where {T}                           Array{T}(uninitialized, m)
+@deprecate Array(::Type{T}, m::Int,n::Int) where {T}                    Array{T}(uninitialized, m,n)
+@deprecate Array(::Type{T}, m::Int,n::Int,o::Int) where {T}             Array{T}(uninitialized, m,n,o)
+@deprecate Array(::Type{T}, d::Integer...) where {T}                    Array{T}(uninitialized, convert(Tuple{Vararg{Int}}, d))
+@deprecate Array(::Type{T}, m::Integer) where {T}                       Array{T}(uninitialized, Int(m))
+@deprecate Array(::Type{T}, m::Integer,n::Integer) where {T}            Array{T}(uninitialized, Int(m),Int(n))
+@deprecate Array(::Type{T}, m::Integer,n::Integer,o::Integer) where {T} Array{T}(uninitialized, Int(m),Int(n),Int(o))
 
 @noinline function is_intrinsic_expr(@nospecialize(x))
     Base.depwarn("is_intrinsic_expr is deprecated. There are no intrinsic functions anymore.", :is_intrinsic_expr)
@@ -1062,14 +1062,14 @@ end
 ## end of FloatRange
 
 @noinline zero_arg_matrix_constructor(prefix::String) =
-    depwarn("$prefix() is deprecated, use $prefix(0, 0) instead.", :zero_arg_matrix_constructor)
+    depwarn("$prefix() is deprecated, use $prefix(uninitialized, 0, 0) instead.", :zero_arg_matrix_constructor)
 function Matrix{T}() where T
     zero_arg_matrix_constructor("Matrix{T}")
-    return Matrix{T}(0, 0)
+    return Matrix{T}(uninitialized, 0, 0)
 end
 function Matrix()
     zero_arg_matrix_constructor("Matrix")
-    return Matrix(0, 0)
+    return Matrix(uninitialized, 0, 0)
 end
 
 for name in ("alnum", "alpha", "cntrl", "digit", "number", "graph",
@@ -1129,9 +1129,9 @@ import .LinAlg: cond
 
 # PR #21359
 import .Random: srand
-@deprecate srand(r::MersenneTwister, filename::AbstractString, n::Integer=4) srand(r, read!(filename, Array{UInt32}(Int(n))))
-@deprecate srand(filename::AbstractString, n::Integer=4) srand(read!(filename, Array{UInt32}(Int(n))))
-@deprecate MersenneTwister(filename::AbstractString)  srand(MersenneTwister(0), read!(filename, Array{UInt32}(Int(4))))
+@deprecate srand(r::MersenneTwister, filename::AbstractString, n::Integer=4) srand(r, read!(filename, Vector{UInt32}(uninitialized, Int(n))))
+@deprecate srand(filename::AbstractString, n::Integer=4) srand(read!(filename, Vector{UInt32}(uninitialized, Int(n))))
+@deprecate MersenneTwister(filename::AbstractString)  srand(MersenneTwister(0), read!(filename, Vector{UInt32}(uninitialized, Int(4))))
 
 # PR #21974
 @deprecate versioninfo(verbose::Bool) versioninfo(verbose=verbose)
@@ -1343,9 +1343,9 @@ import .LinAlg: lufact, lufact!, qrfact, qrfact!, cholfact, cholfact!
 
 @deprecate read(s::IO, x::Ref) read!(s, x)
 
-@deprecate read(s::IO, t::Type, d1::Int, dims::Int...) read!(s, Array{t}(tuple(d1,dims...)))
-@deprecate read(s::IO, t::Type, d1::Integer, dims::Integer...) read!(s, Array{t}(convert(Tuple{Vararg{Int}},tuple(d1,dims...))))
-@deprecate read(s::IO, t::Type, dims::Dims) read!(s, Array{t}(dims))
+@deprecate read(s::IO, t::Type, d1::Int, dims::Int...) read!(s, Array{t}(uninitialized, tuple(d1,dims...)))
+@deprecate read(s::IO, t::Type, d1::Integer, dims::Integer...) read!(s, Array{t}(uninitialized, convert(Tuple{Vararg{Int}},tuple(d1,dims...))))
+@deprecate read(s::IO, t::Type, dims::Dims) read!(s, Array{t}(uninitialized, dims))
 
 function CartesianRange(start::CartesianIndex{N}, stop::CartesianIndex{N}) where N
     inds = map((f,l)->f:l, start.I, stop.I)
diff --git a/base/dict.jl b/base/dict.jl
index 1f8be1c375aee..4a3ed1352e5fa 100644
--- a/base/dict.jl
+++ b/base/dict.jl
@@ -101,7 +101,7 @@ mutable struct Dict{K,V} <: Associative{K,V}
 
     function Dict{K,V}() where V where K
         n = 16
-        new(zeros(UInt8,n), Array{K,1}(n), Array{V,1}(n), 0, 0, 0, 1, 0)
+        new(zeros(UInt8,n), Vector{K}(uninitialized, n), Vector{V}(uninitialized, n), 0, 0, 0, 1, 0)
     end
     function Dict{K,V}(d::Dict{K,V}) where V where K
         new(copy(d.slots), copy(d.keys), copy(d.vals), d.ndel, d.count, d.age,
@@ -227,8 +227,8 @@ function rehash!(h::Dict{K,V}, newsz = length(h.keys)) where V where K
     end
 
     slots = zeros(UInt8,newsz)
-    keys = Array{K,1}(newsz)
-    vals = Array{V,1}(newsz)
+    keys = Vector{K}(uninitialized, newsz)
+    vals = Vector{V}(uninitialized, newsz)
     age0 = h.age
     count = 0
     maxprobe = h.maxprobe
diff --git a/base/docs/core.jl b/base/docs/core.jl
index b096bf13173aa..b428ae7269ec5 100644
--- a/base/docs/core.jl
+++ b/base/docs/core.jl
@@ -7,7 +7,7 @@ import ..esc, ..push!, ..getindex, ..unsafe_load, ..Csize_t
 function doc!(source::LineNumberNode, mod::Module, str, ex)
     push!(DOCS, (mod, ex, str, source.file, source.line))
 end
-const DOCS = Array{Any, 1}()
+const DOCS = Array{Any,1}()
 
 isexpr(x, h) = isa(x, Expr) && x.head === h
 
diff --git a/base/docs/utils.jl b/base/docs/utils.jl
index 5daaa068a7893..b4a1f4eb947ec 100644
--- a/base/docs/utils.jl
+++ b/base/docs/utils.jl
@@ -271,7 +271,7 @@ function levenshtein(s1, s2)
     a, b = collect(s1), collect(s2)
     m = length(a)
     n = length(b)
-    d = Matrix{Int}(m+1, n+1)
+    d = Matrix{Int}(uninitialized, m+1, n+1)
 
     d[1:m+1, 1] = 0:m
     d[1, 1:n+1] = 0:n