add undef (#514)

README.md

@@ -243,9 +243,9 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 * Constructor for `Matrix` from `UniformScaling` ([#24372], [#24657]).
 
-* `Uninitialized` and `uninitialized` with corresponding `Array` constructors ([#24652]).
+* `UndefInitializer` and `undef` with corresponding `Array` constructors ([#24652], [#26316]).
 
-* `BitArray` constructors for `uninitialized` ([#24785]).
+* `BitArray` constructors for `undef` ([#24785], [#26316]).
 
 * `@compat finalizer(func, obj)` with the finalizer to run as the first argument and the object to be finalized
   as the second ([#24605]).
@@ -589,3 +589,4 @@ includes this fix. Find the minimum version from there.
 [#26089]: https://github.com/JuliaLang/julia/issues/26089
 [#26149]: https://github.com/JuliaLang/julia/issues/26149
 [#26156]: https://github.com/JuliaLang/julia/issues/26156
+[#26316]: https://github.com/JuliaLang/julia/issues/26316

src/Compat.jl

@@ -970,33 +970,31 @@ end
     Base.IOContext(io::IOContext, arg1::Pair, arg2::Pair) = IOContext(IOContext(io, arg1), arg2)
 end
 
-# 0.7.0-DEV.2581
-@static if !isdefined(Base, :Uninitialized)
-    if VERSION >= v"0.6.0"
-        include_string(@__MODULE__, """
-            struct Uninitialized end
-            Array{T}(::Uninitialized, args...) where {T} = Array{T}(args...)
-            Array{T,N}(::Uninitialized, args...) where {T,N} = Array{T,N}(args...)
-            Vector(::Uninitialized, args...) = Vector(args...)
-            Matrix(::Uninitialized, args...) = Matrix(args...)
-
-            BitArray{N}(::Uninitialized, args...) where {N} = BitArray{N}(args...)
-            BitArray(::Uninitialized, args...) = BitArray(args...)
-        """)
+# 0.7.0-DEV.4527
+@static if !isdefined(Base, :UndefInitializer)
+    import Base: Array, Matrix, Vector
+    @static if isdefined(Base, :Uninitialized)
+        useuninit(args) = (Base.uninitialized, args...)
     else
-        include_string(@__MODULE__, """
-            immutable Uninitialized end
-            (::Type{Array{T}}){T}(::Uninitialized, args...) = Array{T}(args...)
-            (::Type{Array{T,N}}){T,N}(::Uninitialized, args...) = Array{T,N}(args...)
-            (::Type{Vector})(::Uninitialized, args...) = Vector(args...)
-            (::Type{Matrix})(::Uninitialized, args...) = Matrix(args...)
-
-            (::Type{BitArray{N}}){N}(::Uninitialized, args...) = BitArray{N}(args...)
-            (::Type{BitArray})(::Uninitialized, args...) = BitArray(args...)
-        """)
-    end
-    const uninitialized = Uninitialized()
-    export Uninitialized, uninitialized
+        useuninit(args) = args
+    end
+    struct UndefInitializer end
+    const undef = UndefInitializer()
+    export undef, UndefInitializer
+    Base.show(io::IO, ::UndefInitializer) =
+        print(io, "array initializer with undefined values")
+    Array{T}(::UndefInitializer, args...) where {T} = Array{T}(useuninit(args)...)
+    Array{T,N}(::UndefInitializer, args...) where {T,N} = Array{T,N}(useuninit(args)...)
+    Vector(::UndefInitializer, args...) = Vector(useuninit(args)...)
+    Matrix(::UndefInitializer, args...) = Matrix(useuninit(args)...)
+
+    BitArray{N}(::UndefInitializer, args...) where {N} = BitArray{N}(useuninit(args)...)
+    BitArray(::UndefInitializer, args...) = BitArray(useuninit(args)...)
+end
+@static if VERSION < v"0.7.0-DEV.2581"
+    export uninitialized, Uninitialized
+    const uninitialized = undef
+    const Uninitialized = UndefInitializer
 end
 
 # 0.7.0-DEV.1499

test/runtests.jl

@@ -987,17 +987,17 @@ let a = [1 0 0; 0 1 0; 0 0 1]
     @test Matrix(2.0I, 3, 3)::Matrix{Float64} == Matrix(2.0I, (3, 3))::Matrix{Float64} == 2a
 end
 
-# 0.7.0-DEV.2581
-@test isa(Vector(uninitialized, 2), Vector{Any})
-@test isa(Vector{Float64}(uninitialized, 2), Vector{Float64})
-@test isa(Matrix(uninitialized, 2, 2), Matrix{Any})
-@test isa(Matrix{Float64}(uninitialized, 2, 2), Matrix{Float64})
-@test isa(Array{Float64}(uninitialized, 2, 2), Matrix{Float64})
-@test isa(Array{Float64,3}(uninitialized, 2, 2, 2), Array{Float64,3})
-
-# 0.7.0-DEV.2687
-@test isa(BitVector(uninitialized, 2), BitVector)
-@test isa(BitArray(uninitialized, 2, 2), BitMatrix)
+# 0.7.0-DEV.2581, 0.7.0-DEV.4527
+@test isa(Vector(undef, 2), Vector{Any})
+@test isa(Vector{Float64}(undef, 2), Vector{Float64})
+@test isa(Matrix(undef, 2, 2), Matrix{Any})
+@test isa(Matrix{Float64}(undef, 2, 2), Matrix{Float64})
+@test isa(Array{Float64}(undef, 2, 2), Matrix{Float64})
+@test isa(Array{Float64,3}(undef, 2, 2, 2), Array{Float64,3})
+
+# 0.7.0-DEV.2687, 0.7.0-DEV.4527
+@test isa(BitVector(undef, 2), BitVector)
+@test isa(BitArray(undef, 2, 2), BitMatrix)
 
 # 0.7.0-DEV.1472
 @test get(IOContext(IOBuffer(), :arg1=>true, :arg2=>true, :arg3=>true), :arg3, false)