Fix some ad hoc binary methods

src/poly/poly.jl

@@ -575,6 +575,35 @@ function divexact(x::spoly, y::Rational)
    return divexact(x, base_ring(x)(y))
 end
 
+################################################################################
+#
+#   Ad hoc binary
+#
+################################################################################
+
+# We cannot use the promote_rule mechanism, since n_Q and fmpq have no and
+# should not have a promote_rule
+
+function +(x::spoly, y::fmpq)
+  return x + parent(x)(y)
+end
+
+function +(x::fmpq, y::spoly)
+  return parent(y)(x) + y
+end
+
+function *(x::spoly, y::fmpq)
+  return x * parent(x)(y)
+end
+
+function *(x::fmpq, y::spoly)
+  return parent(y)(x) * y
+end
+
+function divexact(x::spoly, y::fmpq)
+  return divexact(x, parent(x)(y))
+end
+
 ###############################################################################
 #
 #   Divisibility testing

test/poly/spoly-test.jl

@@ -304,6 +304,18 @@ end
    @test divexact(2a, BigInt(2)//3) == 3a
 end
 
+@testset "spoly.adhoc_binary_operation" begin
+   R, (x, ) = PolynomialRing(QQ, ["x", ])
+
+   a = x^2 + 3x + 1
+
+   @test Nemo.QQ(2)*a == 2*a
+   @test a*Nemo.QQ(2) == 2*a
+   @test Nemo.QQ(2) + a == 2 + a
+   @test a + Nemo.QQ(2) == 2 + a
+   @test divexact(2a, Nemo.QQ(2)) == a
+end
+
 @testset "spoly.euclidean_division" begin
    for k in [QQ, Nemo.QQ]
       R, (x, y) = PolynomialRing(k, ["x", "y"])