Add missing convert(Vector, ...) and convert(Matrix, ...) methods (#17848)

This commit will allow a user to call:
convert(Vector, my_abstractvector_of_eltype_Foo)
convert(Matrix, my_abstractmatrix_of_eltype_Foo)

which is useful because
- for the case that the variable is a subarray of the same dimensionality
- for consistency with PR #17066

Author: Evizero

base/array.jl

@@ -226,6 +226,9 @@ end
 
 ## Conversions ##
 
+convert{T}(::Type{Vector}, x::AbstractVector{T}) = convert(Vector{T}, x)
+convert{T}(::Type{Matrix}, x::AbstractMatrix{T}) = convert(Matrix{T}, x)
+
 convert{T,n}(::Type{Array{T}}, x::Array{T,n}) = x
 convert{T,n}(::Type{Array{T,n}}, x::Array{T,n}) = x
 

test/abstractarray.jl

@@ -405,7 +405,19 @@ function test_primitives{T}(::Type{T}, shape, ::Type{TestAbstractArray})
 
     # convert{T, N}(::Type{Array}, A::AbstractArray{T, N})
     X = [1:10...]
+    Y = [1 2; 3 4]
     @test convert(Array, X) == X
+    @test convert(Array, Y) == Y
+
+    # convert{T}(::Type{Vector}, A::AbstractVector{T})
+    @test convert(Vector, X) == X
+    @test convert(Vector, view(X, 2:4)) == [2,3,4]
+    @test_throws MethodError convert(Vector, Y)
+
+    # convert{T}(::Type{Matrix}, A::AbstractMatrix{T})
+    @test convert(Matrix, Y) == Y
+    @test convert(Matrix, view(Y, 1:2, 1:2)) == Y
+    @test_throws MethodError convert(Matrix, X)
 end
 
 let