Add Matrix(I, dims) constructor (#438)

Author: ararslan

README.md

@@ -216,6 +216,8 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 * Constructors for `Matrix{T}`, `Array{T}`, and `SparseMatrixCSC{T}` from `UniformScaling` ([#24372], [#24657])
 
+* Constructor for `Matrix` from `UniformScaling` ([#24372], [#24657]).
+
 * `Uninitialized` and `uninitialized` with corresponding `Array` constructors ([#24652]).
 
 * `BitArray` constructors for `uninitialized` ([#24785]).

src/Compat.jl

@@ -922,6 +922,9 @@ end
     (::Type{Array{T}}){T}(s::UniformScaling, dims::Dims{2}) = Matrix{T}(s, dims)
     (::Type{Array{T}}){T}(s::UniformScaling, m::Integer, n::Integer) = Matrix{T}(s, m, n)
 end
+@static if VERSION < v"0.7.0-DEV.2541"
+    (::Type{Matrix})(s::UniformScaling{T}, dims...) where {T} = Matrix{T}(s, dims...)
+end
 
 # https://github.com/JuliaLang/julia/pull/23271
 @static if VERSION < v"0.7.0-DEV.1472"

test/runtests.jl

@@ -975,6 +975,9 @@ let a = [1 0 0; 0 1 0; 0 0 1]
     @test SparseMatrixCSC{Float64}(I, (3, 2))::SparseMatrixCSC{Float64,Int} == a[:,1:2]
     @test SparseMatrixCSC{Bool,Int16}(I, (3, 3))::SparseMatrixCSC{Bool,Int16} == a
     @test SparseMatrixCSC{ComplexF64,Int8}(I, 3, 2)::SparseMatrixCSC{ComplexF64,Int8} == a[:,1:2]
+
+    @test Matrix(2I, 3, 3)::Matrix{Int} == Matrix(2I, (3, 3))::Matrix{Int} == 2a
+    @test Matrix(2.0I, 3, 3)::Matrix{Float64} == Matrix(2.0I, (3, 3))::Matrix{Float64} == 2a
 end
 
 # 0.7.0-DEV.2581