Add constructors for Matrix from UniformScaling.

Author: Sacha0

base/linalg/uniformscaling.jl

@@ -351,3 +351,10 @@ UniformScaling{Float64}
 ```
 """
 chol(J::UniformScaling, args...) = ((C, info) = _chol!(J, nothing); @assertposdef C info)
+
+
+## Matrix construction from UniformScaling
+Matrix{T}(s::UniformScaling, dims::Dims{2}) where {T} = setindex!(zeros(T, dims), T(s.λ), diagind(dims...))
+Matrix{T}(s::UniformScaling, m::Integer, n::Integer) where {T} = Matrix{T}(s, Dims((m, n)))
+Matrix(s::UniformScaling, m::Integer, n::Integer) = Matrix(s, Dims((m, n)))
+Matrix(s::UniformScaling, dims::Dims{2}) = Matrix{eltype(s)}(s, dims)

test/linalg/uniformscaling.jl

@@ -188,3 +188,12 @@ end
         @test_throws LinAlg.PosDefException chol(-λ*I)
     end
 end
+
+@testset "Matrix construction from UniformScaling" begin
+    @test Matrix(2I, 3, 3)::Matrix{Int} == 2*eye(3)
+    @test Matrix(2I, 3, 4)::Matrix{Int} == 2*eye(3, 4)
+    @test Matrix(2I, 4, 3)::Matrix{Int} == 2*eye(4, 3)
+    @test Matrix(2.0I, 3, 3)::Matrix{Float64} == 2*eye(3)
+    @test Matrix{Real}(2I, 3, 3)::Matrix{Real} == 2*eye(3)
+    @test Matrix{Float64}(2I, 3, 3)::Matrix{Float64} == 2*eye(3)
+end