Destination zeros from eltype in zero-length generic_matvecmul

Author: jishnub

src/matmul.jl

@@ -955,7 +955,7 @@ function __generic_matvecmul!(::typeof(identity), C::AbstractVector, A::Abstract
             if !iszero(beta)
                 C[i] *= beta
             elseif length(B) == 0
-                C[i] = false
+                C[i] = zero(eltype(C))
             else
                 C[i] = zero(A[i]*B[1] + A[i]*B[1])
             end

test/matmul.jl

@@ -6,6 +6,11 @@ using Base: rtoldefault
 using Test, LinearAlgebra, Random
 using LinearAlgebra: mul!, Symmetric, Hermitian
 
+const BASE_TEST_PATH = joinpath(Sys.BINDIR, "..", "share", "julia", "test")
+
+isdefined(Main, :SizedArrays) || @eval Main include(joinpath($(BASE_TEST_PATH), "testhelpers", "SizedArrays.jl"))
+using .Main.SizedArrays
+
 ## Test Julia fallbacks to BLAS routines
 
 mul_wrappers = [
@@ -1168,4 +1173,13 @@ end
     end
 end
 
+@testset "zero-length generic matvec" begin
+    m = SizedArrays.SizedArray{(2,2)}(reshape(1:4, 2, 2))
+    A = fill(m, 2, 0)
+    v = fill(m, size(A,2))
+    w = similar(v, size(A,1))
+    mul!(w, A, v)
+    @test all(iszero, w)
+end
+
 end # module TestMatmul