deprecate convert-to-construct fallback

NEWS.md

@@ -17,6 +17,10 @@ Language changes
   * The syntax for parametric methods, `function f{T}(x::T)`, has been
     changed to `function f(x::T) where {T}` ([#11310]).
 
+  * The fallback constructor that calls `convert` is deprecated. Instead, new types should
+    prefer to define constructors, and add `convert` methods that call those constructors
+    only as necessary ([#15120]).
+
   * The syntax `1.+2` is deprecated, since it is ambiguous: it could mean either
     `1 .+ 2` (the current meaning) or `1. + 2` ([#19089]).
 

base/abstractarray.jl

@@ -11,6 +11,9 @@ Supertype for `N`-dimensional arrays (or array-like types) with elements of type
 """
 AbstractArray
 
+convert(::Type{T}, a::T) where {T<:AbstractArray} = a
+convert(::Type{T}, a::AbstractArray) where {T<:AbstractArray} = T(a)
+
 """
     size(A::AbstractArray, [dim...])
 
@@ -839,14 +842,6 @@ isempty(a::AbstractArray) = (_length(a) == 0)
 # keys with an IndexStyle
 keys(s::IndexStyle, A::AbstractArray, B::AbstractArray...) = eachindex(s, A, B...)
 
-## Conversions ##
-
-convert(::Type{AbstractArray{T,N}}, A::AbstractArray{T,N}) where {T,N  } = A
-convert(::Type{AbstractArray{T,N}}, A::AbstractArray{S,N}) where {T,S,N} = copy!(similar(A,T), A)
-convert(::Type{AbstractArray{T}},   A::AbstractArray{S,N}) where {T,S,N} = convert(AbstractArray{T,N}, A)
-
-convert(::Type{Array}, A::AbstractArray{T,N}) where {T,N} = convert(Array{T,N}, A)
-
 """
    of_indices(x, y)
 

base/array.jl

@@ -549,22 +549,15 @@ end
 one(x::AbstractMatrix{T}) where {T} = _one(one(T), x)
 oneunit(x::AbstractMatrix{T}) where {T} = _one(oneunit(T), x)
 
-## Conversions ##
-
-convert(::Type{Vector}, x::AbstractVector{T}) where {T} = convert(Vector{T}, x)
-convert(::Type{Matrix}, x::AbstractMatrix{T}) where {T} = convert(Matrix{T}, x)
-
-convert(::Type{Array{T}}, x::Array{T,n}) where {T,n} = x
-convert(::Type{Array{T,n}}, x::Array{T,n}) where {T,n} = x
-
-convert(::Type{Array{T}}, x::AbstractArray{S,n}) where {T,n,S} = convert(Array{T,n}, x)
-convert(::Type{Array{T,n}}, x::AbstractArray{S,n}) where {T,n,S} = copy!(Array{T,n}(size(x)), x)
-
 promote_rule(a::Type{Array{T,n}}, b::Type{Array{S,n}}) where {T,n,S} = el_same(promote_type(T,S), a, b)
 
-# constructors should make copies
+## Constructors ##
 
 if module_name(@__MODULE__) === :Base  # avoid method overwrite
+Array{T,N}(x::AbstractArray{S,N})         where {T,N,S} = copy!(Array{T,N}(size(x)), x)
+AbstractArray{T,N}(A::AbstractArray{S,N}) where {T,N,S} = copy!(similar(A,T), A)
+
+# constructors should make copies
 (::Type{T})(x::T) where {T<:Array} = copy(x)
 end
 

base/bitarray.jl

@@ -497,21 +497,21 @@ function _bitreshape(B::BitArray, dims::NTuple{N,Int}) where N
     return Br
 end
 
-## Conversions ##
+## Constructors ##
 
-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))
+#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 Array{T,N}(B::BitArray{N}) where {T,N}
+    A = Array{T,N}(size(B))
     Bc = B.chunks
     @inbounds for i = 1:length(A)
         A[i] = unsafe_bitgetindex(Bc, i)
     end
     return A
 end
 
-convert(::Type{BitArray}, A::AbstractArray{T,N}) where {T,N} = convert(BitArray{N}, A)
-function convert(::Type{BitArray{N}}, A::AbstractArray{T,N}) where N where T
+BitArray(A::AbstractArray{<:Any,N}) where {N} = BitArray{N}(A)
+function BitArray{N}(A::AbstractArray{T,N}) where N where T
     B = BitArray(size(A))
     Bc = B.chunks
     l = length(B)
@@ -536,7 +536,7 @@ function convert(::Type{BitArray{N}}, A::AbstractArray{T,N}) where N where T
     return B
 end
 
-function convert(::Type{BitArray{N}}, A::Array{Bool,N}) where N
+function BitArray{N}(A::Array{Bool,N}) where N
     B = BitArray(size(A))
     Bc = B.chunks
     l = length(B)
@@ -545,16 +545,9 @@ function convert(::Type{BitArray{N}}, A::Array{Bool,N}) where N
     return B
 end
 
-convert(::Type{BitArray{N}}, B::BitArray{N}) where {N} = B
-convert(::Type{AbstractArray{T,N}}, B::BitArray{N}) where {T,N} = convert(Array{T,N}, B)
-
 reinterpret(::Type{Bool}, B::BitArray, dims::NTuple{N,Int}) where {N} = reinterpret(B, dims)
 reinterpret(B::BitArray, dims::NTuple{N,Int}) where {N} = reshape(B, dims)
 
-## Constructors from generic iterables ##
-
-BitArray(A::AbstractArray{<:Any,N}) where {N} = convert(BitArray{N}, A)
-
 if module_name(@__MODULE__) === :Base  # avoid method overwrite
 (::Type{T})(x::T) where {T<:BitArray} = copy(x)
 end

base/boot.jl

@@ -382,6 +382,13 @@ Array{T}(m::Int, n::Int, o::Int) where {T} = Array{T,3}(m, n, o)
 
 Array{T,1}() where {T} = Array{T,1}(0)
 
+(::Type{Array{T,N} where T})(x::AbstractArray{S,N}) where {S,N} = Array{S,N}(x)
+
+Array(A::AbstractArray{T,N})    where {T,N}   = Array{T,N}(A)
+Array{T}(A::AbstractArray{S,N}) where {T,N,S} = Array{T,N}(A)
+
+AbstractArray{T}(A::AbstractArray{S,N}) where {T,S,N} = AbstractArray{T,N}(A)
+
 # primitive Symbol constructors
 function Symbol(s::String)
     return ccall(:jl_symbol_n, Ref{Symbol}, (Ptr{UInt8}, Int),

base/dates/periods.jl

@@ -403,6 +403,9 @@ function divexact(x, y)
     return q
 end
 
+convert(::Type{T}, p::T) where {T<:Period} = p
+convert(::Type{T}, p::Period) where {T<:Period} = T(p)
+
 # FixedPeriod conversions and promotion rules
 const fixedperiod_conversions = [(Week, 7), (Day, 24), (Hour, 60), (Minute, 60), (Second, 1000), (Millisecond, 1000), (Microsecond, 1000), (Nanosecond, 1)]
 for i = 1:length(fixedperiod_conversions)
@@ -413,15 +416,15 @@ for i = 1:length(fixedperiod_conversions)
         N *= nc
         vmax = typemax(Int64) ÷ N
         vmin = typemin(Int64) ÷ N
-        @eval function Base.convert(::Type{$T}, x::$Tc)
-            $vmin ≤ value(x) ≤ $vmax || throw(InexactError(:convert, $T, x))
+        @eval function $T(x::$Tc)
+            $vmin ≤ value(x) ≤ $vmax || throw(InexactError(($T).name.name, x))
             return $T(value(x) * $N)
         end
     end
     N = n
     for j = (i + 1):length(fixedperiod_conversions) # more-precise periods
         Tc, nc = fixedperiod_conversions[j]
-        @eval Base.convert(::Type{$T}, x::$Tc) = $T(divexact(value(x), $N))
+        @eval $T(x::$Tc) = $T(divexact(value(x), $N))
         @eval Base.promote_rule(::Type{$T}, ::Type{$Tc}) = $Tc
         N *= nc
     end
@@ -430,12 +433,12 @@ end
 # other periods with fixed conversions but which aren't fixed time periods
 const OtherPeriod = Union{Month, Year}
 let vmax = typemax(Int64) ÷ 12, vmin = typemin(Int64) ÷ 12
-    @eval function Base.convert(::Type{Month}, x::Year)
-        $vmin ≤ value(x) ≤ $vmax || throw(InexactError(:convert, Month, x))
+    @eval function Month(x::Year)
+        $vmin ≤ value(x) ≤ $vmax || throw(InexactError(:Month, x))
         Month(value(x) * 12)
     end
 end
-Base.convert(::Type{Year}, x::Month) = Year(divexact(value(x), 12))
+Year(x::Month) = Year(divexact(value(x), 12))
 Base.promote_rule(::Type{Year}, ::Type{Month}) = Month
 
 # disallow comparing fixed to other periods

base/deprecated.jl

@@ -1751,6 +1751,11 @@ import .Iterators.enumerate
 @deprecate enumerate(i::IndexLinear,    A::AbstractArray)  pairs(i, A)
 @deprecate enumerate(i::IndexCartesian, A::AbstractArray)  pairs(i, A)
 
+function (::Type{T})(arg) where {T}
+    depwarn("Constructors no longer fall back to `convert`. A constructor for `$T` should be defined instead.", :Type)
+    convert(T, arg)::T
+end
+
 # END 0.7 deprecations
 
 # BEGIN 1.0 deprecations

base/linalg/bidiag.jl

@@ -131,7 +131,7 @@ function Base.replace_in_print_matrix(A::Bidiagonal,i::Integer,j::Integer,s::Abs
 end
 
 #Converting from Bidiagonal to dense Matrix
-function convert(::Type{Matrix{T}}, A::Bidiagonal) where T
+function Matrix{T}(A::Bidiagonal) where T
     n = size(A, 1)
     B = zeros(T, n, n)
     for i = 1:n - 1
@@ -145,14 +145,14 @@ function convert(::Type{Matrix{T}}, A::Bidiagonal) where T
     B[n,n] = A.dv[n]
     return B
 end
-convert(::Type{Matrix}, A::Bidiagonal{T}) where {T} = convert(Matrix{T}, A)
-convert(::Type{Array}, A::Bidiagonal) = convert(Matrix, A)
-full(A::Bidiagonal) = convert(Array, A)
+Matrix(A::Bidiagonal{T}) where {T} = Matrix{T}(A)
+Array(A::Bidiagonal) = Matrix(A)
+full(A::Bidiagonal) = Array(A)
 promote_rule(::Type{Matrix{T}}, ::Type{<:Bidiagonal{S}}) where {T,S} = Matrix{promote_type(T,S)}
 
 #Converting from Bidiagonal to Tridiagonal
-Tridiagonal(M::Bidiagonal{T}) where {T} = convert(Tridiagonal{T}, M)
-function convert(::Type{Tridiagonal{T}}, A::Bidiagonal) where T
+Tridiagonal(M::Bidiagonal{T}) where {T} = Tridiagonal{T}(M)
+function Tridiagonal{T}(A::Bidiagonal) where T
     dv = convert(AbstractVector{T}, A.dv)
     ev = convert(AbstractVector{T}, A.ev)
     z = fill!(similar(ev), zero(T))
@@ -161,12 +161,12 @@ end
 promote_rule(::Type{<:Tridiagonal{T}}, ::Type{<:Bidiagonal{S}}) where {T,S} = Tridiagonal{promote_type(T,S)}
 
 # No-op for trivial conversion Bidiagonal{T} -> Bidiagonal{T}
-convert(::Type{Bidiagonal{T}}, A::Bidiagonal{T}) where {T} = A
+Bidiagonal{T}(A::Bidiagonal{T}) where {T} = A
 # Convert Bidiagonal to Bidiagonal{T} by constructing a new instance with converted elements
-convert(::Type{Bidiagonal{T}}, A::Bidiagonal) where {T} =
+Bidiagonal{T}(A::Bidiagonal) where {T} =
     Bidiagonal(convert(AbstractVector{T}, A.dv), convert(AbstractVector{T}, A.ev), A.uplo)
 # When asked to convert Bidiagonal to AbstractMatrix{T}, preserve structure by converting to Bidiagonal{T} <: AbstractMatrix{T}
-convert(::Type{AbstractMatrix{T}}, A::Bidiagonal) where {T} = convert(Bidiagonal{T}, A)
+AbstractMatrix{T}(A::Bidiagonal) where {T} = convert(Bidiagonal{T}, A)
 
 broadcast(::typeof(big), B::Bidiagonal) = Bidiagonal(big.(B.dv), big.(B.ev), B.uplo)
 

base/linalg/cholesky.jl

@@ -345,32 +345,32 @@ function cholfact(x::Number, uplo::Symbol=:U)
 end
 
 
-function convert(::Type{Cholesky{T}}, C::Cholesky) where T
+function Cholesky{T}(C::Cholesky) where T
     Cnew = convert(AbstractMatrix{T}, C.factors)
     Cholesky{T, typeof(Cnew)}(Cnew, C.uplo, C.info)
 end
-convert(::Type{Factorization{T}}, C::Cholesky{T}) where {T} = C
-convert(::Type{Factorization{T}}, C::Cholesky) where {T} = convert(Cholesky{T}, C)
-convert(::Type{CholeskyPivoted{T}},C::CholeskyPivoted{T}) where {T} = C
-convert(::Type{CholeskyPivoted{T}},C::CholeskyPivoted) where {T} =
+Factorization{T}(C::Cholesky{T}) where {T} = C
+Factorization{T}(C::Cholesky) where {T} = Cholesky{T}(C)
+CholeskyPivoted{T}(C::CholeskyPivoted{T}) where {T} = C
+CholeskyPivoted{T}(C::CholeskyPivoted) where {T} =
     CholeskyPivoted(AbstractMatrix{T}(C.factors),C.uplo,C.piv,C.rank,C.tol,C.info)
-convert(::Type{Factorization{T}}, C::CholeskyPivoted{T}) where {T} = C
-convert(::Type{Factorization{T}}, C::CholeskyPivoted) where {T} = convert(CholeskyPivoted{T}, C)
+Factorization{T}(C::CholeskyPivoted{T}) where {T} = C
+Factorization{T}(C::CholeskyPivoted) where {T} = CholeskyPivoted{T}(C)
 
-convert(::Type{AbstractMatrix}, C::Cholesky) = C.uplo == 'U' ? C[:U]'C[:U] : C[:L]*C[:L]'
-convert(::Type{AbstractArray}, C::Cholesky) = convert(AbstractMatrix, C)
-convert(::Type{Matrix}, C::Cholesky) = convert(Array, convert(AbstractArray, C))
-convert(::Type{Array}, C::Cholesky) = convert(Matrix, C)
-full(C::Cholesky) = convert(AbstractArray, C)
+AbstractMatrix(C::Cholesky) = C.uplo == 'U' ? C[:U]'C[:U] : C[:L]*C[:L]'
+AbstractArray(C::Cholesky) = AbstractMatrix(C)
+Matrix(C::Cholesky) = Array(AbstractArray(C))
+Array(C::Cholesky) = Matrix(C)
+full(C::Cholesky) = AbstractArray(C)
 
-function convert(::Type{AbstractMatrix}, F::CholeskyPivoted)
+function AbstractMatrix(F::CholeskyPivoted)
     ip = invperm(F[:p])
     (F[:L] * F[:U])[ip,ip]
 end
-convert(::Type{AbstractArray}, F::CholeskyPivoted) = convert(AbstractMatrix, F)
-convert(::Type{Matrix}, F::CholeskyPivoted) = convert(Array, convert(AbstractArray, F))
-convert(::Type{Array}, F::CholeskyPivoted) = convert(Matrix, F)
-full(F::CholeskyPivoted) = convert(AbstractArray, F)
+AbstractArray(F::CholeskyPivoted) = AbstractMatrix(F)
+Matrix(F::CholeskyPivoted) = Array(AbstractArray(F))
+Array(F::CholeskyPivoted) = Matrix(F)
+full(F::CholeskyPivoted) = AbstractArray(F)
 
 copy(C::Cholesky) = Cholesky(copy(C.factors), C.uplo, C.info)
 copy(C::CholeskyPivoted) = CholeskyPivoted(copy(C.factors), C.uplo, C.piv, C.rank, C.tol, C.info)

base/linalg/diagonal.jl

@@ -49,12 +49,12 @@ Diagonal(V::AbstractVector{T}) where {T} = Diagonal{T,typeof(V)}(V)
 Diagonal{T}(V::AbstractVector{T}) where {T} = Diagonal{T,typeof(V)}(V)
 Diagonal{T}(V::AbstractVector) where {T} = Diagonal{T}(convert(AbstractVector{T}, V))
 
-convert(::Type{Diagonal{T}}, D::Diagonal{T}) where {T} = D
-convert(::Type{Diagonal{T}}, D::Diagonal) where {T} = Diagonal{T}(convert(AbstractVector{T}, D.diag))
-convert(::Type{AbstractMatrix{T}}, D::Diagonal) where {T} = convert(Diagonal{T}, D)
-convert(::Type{Matrix}, D::Diagonal) = diagm(D.diag)
-convert(::Type{Array}, D::Diagonal) = convert(Matrix, D)
-full(D::Diagonal) = convert(Array, D)
+Diagonal{T}(D::Diagonal{T}) where {T} = D
+Diagonal{T}(D::Diagonal) where {T} = Diagonal{T}(convert(AbstractVector{T}, D.diag))
+AbstractMatrix{T}(D::Diagonal) where {T} = Diagonal{T}(D)
+Matrix(D::Diagonal) = diagm(D.diag)
+Array(D::Diagonal) = Matrix(D)
+full(D::Diagonal) = Array(D)
 
 function similar(D::Diagonal, ::Type{T}) where T
     return Diagonal{T}(similar(D.diag, T))

base/linalg/eigen.jl

@@ -433,8 +433,8 @@ eigvecs(A::AbstractMatrix, B::AbstractMatrix) = eigvecs(eigfact(A, B))
 # Conversion methods
 
 ## Can we determine the source/result is Real?  This is not stored in the type Eigen
-convert(::Type{AbstractMatrix}, F::Eigen) = F.vectors * Diagonal(F.values) / F.vectors
-convert(::Type{AbstractArray}, F::Eigen) = convert(AbstractMatrix, F)
-convert(::Type{Matrix}, F::Eigen) = convert(Array, convert(AbstractArray, F))
-convert(::Type{Array}, F::Eigen) = convert(Matrix, F)
-full(F::Eigen) = convert(AbstractArray, F)
+AbstractMatrix(F::Eigen) = F.vectors * Diagonal(F.values) / F.vectors
+AbstractArray(F::Eigen) = AbstractMatrix(F)
+Matrix(F::Eigen) = Array(AbstractArray(F))
+Array(F::Eigen) = Matrix(F)
+full(F::Eigen) = AbstractArray(F)

base/linalg/factorization.jl

@@ -45,8 +45,11 @@ function det(F::Factorization)
     return exp(d)*s
 end
 
+convert(::Type{T}, f::T) where {T<:Factorization} = f
+convert(::Type{T}, f::Factorization) where {T<:Factorization} = T(f)
+
 ### General promotion rules
-convert(::Type{Factorization{T}}, F::Factorization{T}) where {T} = F
+Factorization{T}(F::Factorization{T}) where {T} = F
 inv(F::Factorization{T}) where {T} = A_ldiv_B!(F, eye(T, size(F,1)))
 
 Base.hash(F::Factorization, h::UInt) = mapreduce(f -> hash(getfield(F, f)), hash, h, 1:nfields(F))

base/linalg/givens.jl

@@ -34,12 +34,12 @@ mutable struct Rotation{T} <: AbstractRotation{T}
     rotations::Vector{Givens{T}}
 end
 
-convert(::Type{Givens{T}}, G::Givens{T}) where {T} = G
-convert(::Type{Givens{T}}, G::Givens) where {T} = Givens(G.i1, G.i2, convert(T, G.c), convert(T, G.s))
-convert(::Type{Rotation{T}}, R::Rotation{T}) where {T} = R
-convert(::Type{Rotation{T}}, R::Rotation) where {T} = Rotation{T}([convert(Givens{T}, g) for g in R.rotations])
-convert(::Type{AbstractRotation{T}}, G::Givens) where {T} = convert(Givens{T}, G)
-convert(::Type{AbstractRotation{T}}, R::Rotation) where {T} = convert(Rotation{T}, R)
+Givens{T}(G::Givens{T}) where {T} = G
+Givens{T}(G::Givens) where {T} = Givens(G.i1, G.i2, convert(T, G.c), convert(T, G.s))
+Rotation{T}(R::Rotation{T}) where {T} = R
+Rotation{T}(R::Rotation) where {T} = Rotation{T}([Givens{T}(g) for g in R.rotations])
+AbstractRotation{T}(G::Givens) where {T} = Givens{T}(G)
+AbstractRotation{T}(R::Rotation) where {T} = Rotation{T}(R)
 
 adjoint(G::Givens) = Givens(G.i1, G.i2, conj(G.c), -G.s)
 adjoint(R::Rotation{T}) where {T} = Rotation{T}(reverse!([adjoint(r) for r in R.rotations]))

base/linalg/hessenberg.jl

@@ -77,14 +77,14 @@ function getindex(A::HessenbergQ, i::Integer, j::Integer)
 end
 
 ## reconstruct the original matrix
-convert(::Type{Matrix}, A::HessenbergQ{<:BlasFloat}) = LAPACK.orghr!(1, size(A.factors, 1), copy(A.factors), A.τ)
-convert(::Type{Array}, A::HessenbergQ) = convert(Matrix, A)
-full(A::HessenbergQ) = convert(Array, A)
-convert(::Type{AbstractMatrix}, F::Hessenberg) = (fq = Array(F[:Q]); (fq * F[:H]) * fq')
-convert(::Type{AbstractArray}, F::Hessenberg) = convert(AbstractMatrix, F)
-convert(::Type{Matrix}, F::Hessenberg) = convert(Array, convert(AbstractArray, F))
-convert(::Type{Array}, F::Hessenberg) = convert(Matrix, F)
-full(F::Hessenberg) = convert(AbstractArray, F)
+Matrix(A::HessenbergQ{<:BlasFloat}) = LAPACK.orghr!(1, size(A.factors, 1), copy(A.factors), A.τ)
+Array(A::HessenbergQ) = Matrix(A)
+full(A::HessenbergQ) = Array(A)
+AbstractMatrix(F::Hessenberg) = (fq = Array(F[:Q]); (fq * F[:H]) * fq')
+AbstractArray(F::Hessenberg) = AbstractMatrix(F)
+Matrix(F::Hessenberg) = Array(AbstractArray(F))
+Array(F::Hessenberg) = Matrix(F)
+full(F::Hessenberg) = AbstractArray(F)
 
 A_mul_B!(Q::HessenbergQ{T}, X::StridedVecOrMat{T}) where {T<:BlasFloat} =
     LAPACK.ormhr!('L', 'N', 1, size(Q.factors, 1), Q.factors, Q.τ, X)