re-allow vector*(1-row matrix) and transpose (closes #20389)

Author: stevengj

base/linalg/matmul.jl

@@ -80,6 +80,7 @@ function (*){T,S}(A::AbstractMatrix{T}, x::AbstractVector{S})
     TS = promote_op(matprod, T, S)
     A_mul_B!(similar(x,TS,size(A,1)),A,x)
 end
+(*)(A::AbstractVector, B::AbstractMatrix) = reshape(A,length(A),1)*B
 
 A_mul_B!{T<:BlasFloat}(y::StridedVector{T}, A::StridedVecOrMat{T}, x::StridedVector{T}) = gemv!(y, 'N', A, x)
 for elty in (Float32,Float64)

base/linalg/rowvector.jl

@@ -154,12 +154,9 @@ end
     sum(@inbounds(return rowvec[i]*vec[i]) for i = 1:length(vec))
 end
 @inline *(rowvec::RowVector, mat::AbstractMatrix) = transpose(mat.' * transpose(rowvec))
-*(vec::AbstractVector, mat::AbstractMatrix) = throw(DimensionMismatch(
-    "Cannot left-multiply a matrix by a vector")) # Should become a deprecation
 *(::RowVector, ::RowVector) = throw(DimensionMismatch("Cannot multiply two transposed vectors"))
 @inline *(vec::AbstractVector, rowvec::RowVector) = vec .* rowvec
 *(vec::AbstractVector, rowvec::AbstractVector) = throw(DimensionMismatch("Cannot multiply two vectors"))
-*(mat::AbstractMatrix, rowvec::RowVector) = throw(DimensionMismatch("Cannot right-multiply matrix by transposed vector"))
 
 # Transposed forms
 A_mul_Bt(::RowVector, ::AbstractVector) = throw(DimensionMismatch("Cannot multiply two transposed vectors"))

test/linalg/rowvector.jl

@@ -104,7 +104,7 @@ end
 
     @test (rv*v) === 14
     @test (rv*mat)::RowVector == [1 4 9]
-    @test_throws DimensionMismatch [1]*reshape([1],(1,1)) # no longer permitted
+    @test [1]*reshape([1],(1,1)) == reshape([1],(1,1))
     @test_throws DimensionMismatch rv*rv
     @test (v*rv)::Matrix == [1 2 3; 2 4 6; 3 6 9]
     @test_throws DimensionMismatch v*v # Was previously a missing method error, now an error message
@@ -238,5 +238,10 @@ end
     @test_throws DimensionMismatch ut\rv
 end
 
+# issue #20389
+@testset "1 row/col vec*mat" begin
+    @test [1,2,3] * ones(1, 4) == [1,2,3] .* ones(1, 4)
+    @test ones(4,1) * RowVector([1,2,3]) == ones(4,1) .* RowVector([1,2,3])
+end
 
 end # @testset "RowVector"