hasconversion Chebyshev->Ultraspherical, and maxspace domainscomatible (#235)

Author: jishnub

src/Spaces/Ultraspherical/Ultraspherical.jl

@@ -131,7 +131,9 @@ spacescompatible(a::Ultraspherical,b::Ultraspherical) =
     compare_orders(order(a), order(b)) && domainscompatible(a,b)
 hasfasttransform(::Ultraspherical) = true
 
-
+# these methods help with type-inference
+hasconversion(C::Chebyshev, U::Ultraspherical{<:Union{Int,StaticInt}}) = domainscompatible(C,U)
+hasconversion(U::Ultraspherical{<:Union{Int,StaticInt}}, C::Chebyshev) = false
 
 include("UltrasphericalOperators.jl")
 include("DirichletSpace.jl")

src/Spaces/Ultraspherical/UltrasphericalOperators.jl

@@ -191,6 +191,7 @@ function Conversion(A::Ultraspherical,B::Ultraspherical)
 end
 
 function maxspace_rule(A::Ultraspherical, B::Ultraspherical)
+    domainscompatible(A, B) || return NoSpace()
     isapproxinteger(order(A) - order(B)) || return NoSpace()
     order(A) > order(B) ? A : B
 end