Fix conversion_type for NormalizedPolynomialSpace (#243)

* Fix conversion_type for NormalizedPolynomialSpace

* don't return nospace

* update test

Author: jishnub

src/Spaces/PolynomialSpace.jl

@@ -476,7 +476,13 @@ function Fun(::typeof(identity), S::NormalizedPolynomialSpace)
 end
 
 function conversion_rule(a::NormalizedPolynomialSpace{S}, b::S) where S<:PolynomialSpace
-    domainscompatible(domain(a), domain(b)) ? a : NoSpace()
+    asp = a.space
+    c = conversion_type(asp, b)
+    if c == asp
+        return a
+    else
+        return c
+    end
 end
 
 bandwidths(C::ConcreteConversion{NormalizedPolynomialSpace{S,D,R},S}) where {S,D,R} = (0, 0)

test/JacobiTest.jl

@@ -191,6 +191,11 @@ using Static
                 @test NormalizedPolynomialSpace(Ultraspherical(j)) ==
                     NormalizedUltraspherical(NormalizedPolynomialSpace(j))
             end
+
+            @test conversion_type(NormalizedLegendre(), Jacobi(1,1)) == NormalizedLegendre()
+            @test conversion_type(Jacobi(1,1), NormalizedLegendre()) == NormalizedLegendre()
+            @test conversion_type(Jacobi(1,1), NormalizedJacobi(2,2)) == Jacobi(1,1)
+            @test conversion_type(NormalizedJacobi(2,2), Jacobi(1,1)) == Jacobi(1,1)
         end
 
         @test ApproxFunOrthogonalPolynomials.normalization(ComplexF64, Jacobi(-0.5, -0.5), 0) ≈ pi