Fix unitful 3-arg *

src/matmul.jl

@@ -605,7 +605,7 @@ function generic_syrk!(C::StridedMatrix{T}, A::StridedVecOrMat{T}, conjugate::Bo
         aA_11 = abs2(A[1,1])
         fill!(UpperTriangular(C), zero(aA_11 + aA_11))
     end
-    iszero(α) && return C
+    (iszero(α) || isempty(A)) && return C
     @inbounds if !conjugate
         if aat
             for k ∈ 1:n, j ∈ 1:m
@@ -1075,7 +1075,8 @@ function __generic_matvecmul!(::typeof(identity), C::AbstractVector, A::Abstract
             elseif length(B) == 0
                 C[i] = zero(eltype(C))
             else
-                C[i] = zero(A[i]*B[1] + A[i]*B[1])
+                ci   = @stable_muladdmul MulAddMul(alpha,false)(A[i]*B[1])
+                C[i] = zero(ci + ci)
             end
         end
         if !iszero(alpha)
@@ -1147,12 +1148,12 @@ function _generic_matmatmul_nonadjtrans!(C, A, B, alpha, beta)
         for j in axes(C, 2)
             B_1j = B[b1, j]
             for i in axes(C, 1)
-                C_ij = A[i, a1] * B_1j
+                C_ij = @stable_muladdmul MulAddMul(alpha, false)(A[i, a1] * B_1j)
                 C[i,j] = zero(C_ij + C_ij)
             end
         end
     end
-    iszero(alpha) && return C
+    (iszero(alpha) || isempty(A) || isempty(B)) && return C
     @inbounds for n in axes(B, 2), k in axes(B, 1)
         # Balpha = B[k,n] * alpha, but we skip the multiplication in case isone(alpha)
         Balpha = @stable_muladdmul MulAddMul(alpha, false)(B[k,n])
@@ -1167,21 +1168,21 @@ function _generic_matmatmul_adjtrans!(C, A, B, alpha, beta)
     t = _wrapperop(A)
     pB = parent(B)
     pA = parent(A)
-    if (!iszero(beta) || isempty(A) || isempty(B)) # return C*beta
+    if (!iszero(beta) || isempty(A) || isempty(B))
         _rmul_or_fill!(C, beta)
     else # iszero(beta) && A and B are non-empty
         a1 = firstindex(pA, 1)
         b1 = firstindex(pB, 2)
         for j in axes(C, 2)
             tB_1j = t(pB[j, b1])
             for i in axes(C, 1)
-                C_ij = t(pA[a1, i]) * tB_1j
+                C_ij = @stable_muladdmul MulAddMul(alpha, false)(t(pA[a1, i]) * tB_1j)
                 C[i,j] = zero(C_ij + C_ij)
             end
         end
     end
-    iszero(alpha) && return C
-    tmp = similar(C, axes(C, 2))
+    (iszero(alpha) || isempty(A) || isempty(B)) && return C
+    tmp = similar(C, promote_op(matprod, typeof(first(A)), typeof(first(B))), axes(C, 2))
     ci = firstindex(C, 1)
     ta = t(alpha)
     if isone(ta)
@@ -1434,7 +1435,7 @@ mat_vec_scalar(A::StridedMaybeAdjOrTransMat, x::StridedVector, γ) = _mat_vec_sc
 mat_vec_scalar(A::AdjOrTransAbsVec, x::StridedVector, γ) = (A * x) * γ
 
 function _mat_vec_scalar(A, x, γ)
-    T = promote_type(eltype(A), eltype(x), typeof(γ))
+    T = promote_op(*, promote_op(matprod, eltype(A), eltype(x)), typeof(γ))
     C = similar(A, T, axes(A,1))
     mul!(C, A, x, γ, false)
 end
@@ -1444,7 +1445,7 @@ mat_mat_scalar(A::StridedMaybeAdjOrTransMat, B::StridedMaybeAdjOrTransMat, γ) =
     _mat_mat_scalar(A, B, γ)
 
 function _mat_mat_scalar(A, B, γ)
-    T = promote_type(eltype(A), eltype(B), typeof(γ))
+    T = promote_op(*, promote_op(matprod, eltype(A), eltype(B)), typeof(γ))
     C = similar(A, T, axes(A,1), axes(B,2))
     mul!(C, A, B, γ, false)
 end

test/testhelpers/Furlongs.jl

@@ -76,6 +76,11 @@ end
 for op in (:(==), :(!=), :<, :<=, :isless, :isequal)
     @eval $op(x::Furlong{p}, y::Furlong{p}) where {p} = $op(x.val, y.val)::Bool
 end
+for op in (:(==), :isequal)
+    @eval $op(x::Furlong{p}, y::Furlong{q}) where {p,q} = false
+    @eval $op(x::Furlong, y::Number) = $op(x, convert(Furlong, y))
+    @eval $op(x::Number, y::Furlong) = $op(y, x)
+end
 for (f,op) in ((:_plus,:+),(:_minus,:-),(:_times,:*),(:_div,://))
     @eval function $f(v::T, ::Furlong{p}, ::Union{Furlong{q},Val{q}}) where {T,p,q}
         s = $op(p, q)

test/unitful.jl

@@ -202,4 +202,21 @@ end
     @test (C \ b)::Vector{<:Furlong{0}} == (D \ b)::Vector{<:Furlong{0}} == Furlong{0}.([5, -12])
 end
 
+@testset "unitful 3-arg *" begin
+    for n in (2, 3, 5)
+        λ = 5
+        A = rand(-10:10, n, n)
+        b = rand(-10:10, n)
+        λu = Furlong{1}(λ)
+        Au = Furlong{1}.(A)
+        bu = Furlong{1}.(b)
+        @test Furlong{3}.(A*A*λ) == Au*Au*λu
+        @test Furlong{3}.(A'*A*λ) == Au'*Au*λu
+        @test Furlong{3}.(A*A'*λ) == Au*Au'*λu
+        @test Furlong{3}.(A'*A'*λ) == Au'*Au'*λu
+        @test Furlong{3}.(A*b*λ) == Au*bu*λu
+        @test Furlong{3}.(A'*b*λ) == Au'*bu*λu
+    end
+end
+
 end # module TestUnitfulLinAlg