Copy matrices in triu/tril if no zero exists for the eltype

src/generic.jl

@@ -466,6 +466,11 @@
 """
 function triu(M::AbstractMatrix, k::Integer = 0)
     d = similar(M)
+    if !haszero(eltype(M))
+        # since the zero would need to be evaluated from the elements,
+        # we copy the array to avoid undefined references in triu!
+        copy!(d, M)
+    end
     A = triu!(d,k)
     if iszero(k)
         copytrito!(A, M, 'U')
@@ -509,6 +514,11 @@
 """
 function tril(M::AbstractMatrix,k::Integer=0)
     d = similar(M)
+    if !haszero(eltype(M))
+        # since the zero would need to be evaluated from the elements,
+        # we copy the array to avoid undefined references in tril!
+        copy!(d, M)
+    end
     A = tril!(d,k)
     if iszero(k)
         copytrito!(A, M, 'L')

test/dense.jl

@@ -1408,4 +1408,13 @@ end
     @test 2^A == 2^Matrix(A)
 end
 
+@testset "triu/tril for block matrices" begin
+    O = ones(2,2)
+    Z = zero(O)
+    M = fill(O, 3, 3)
+    res = fill(Z, size(M))
+    res[1,2] = res[1,3] = res[2,3] = O
+    @test triu(GenericArray(M),1) == res
+end
+
 end # module TestDense