fix multiplication bug

Author: jishnub

src/Spaces/Ultraspherical/UltrasphericalOperators.jl

@@ -26,7 +26,7 @@ Base.stride(M::ConcreteMultiplication{U,V}) where {U<:Ultraspherical,V<:Chebyshe
 Base.stride(M::ConcreteMultiplication{U,V}) where {U<:Ultraspherical,V<:Ultraspherical} =
     stride(M.f)
 
-@inline function _Multiplication(f::Fun{<:Chebyshev}, sp::Ultraspherical)
+@inline function _Multiplication(f::Fun{<:Chebyshev}, sp::Ultraspherical{Int})
     if order(sp) == 1
         cfs = f.coefficients
         MultiplicationWrapper(f,
@@ -40,10 +40,10 @@ Base.stride(M::ConcreteMultiplication{U,V}) where {U<:Ultraspherical,V<:Ultrasph
     end
 end
 @static if VERSION >= v"1.8"
-    Base.@constprop aggressive Multiplication(f::Fun{<:Chebyshev}, sp::Ultraspherical) =
+    Base.@constprop aggressive Multiplication(f::Fun{<:Chebyshev}, sp::Ultraspherical{Int}) =
         _Multiplication(f, sp)
 else
-    Multiplication(f::Fun{<:Chebyshev}, sp::Ultraspherical) = _Multiplication(f, sp)
+    Multiplication(f::Fun{<:Chebyshev}, sp::Ultraspherical{Int}) = _Multiplication(f, sp)
 end
 
 

test/UltrasphericalTest.jl

@@ -153,4 +153,11 @@ using ApproxFunOrthogonalPolynomials: jacobip
             end
         end
     end
+
+    @testset "Multiplication" begin
+        M = Multiplication(Fun(), Ultraspherical(0.5))
+        f = Fun(Ultraspherical(0.5))
+        f2 = Fun(x->x^2, Ultraspherical(0.5))
+        @test M * f ≈ f2
+    end
 end