Type-stable ChebyshevT multiplication (#537)

Author: jishnub

Project.toml

@@ -2,7 +2,7 @@ name = "Polynomials"
 uuid = "f27b6e38-b328-58d1-80ce-0feddd5e7a45"
 license = "MIT"
 author = "JuliaMath"
-version = "4.0.3"
+version = "4.0.4"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

src/polynomials/chebyshev.jl

@@ -174,7 +174,7 @@ function Base.:*(p1::MutableDensePolynomial{B,T,X}, p2::MutableDensePolynomial{B
     z2 = _c_to_z(coeffs(p2))
     prod = fastconv(z1, z2)
     cs = _z_to_c(prod)
-    ret = ChebyshevT(cs,X)
+    ret = ChebyshevT(cs, Var(X))
     return ret
 end
 

test/ChebyshevT.jl

@@ -124,7 +124,7 @@ end
     target[abs(i - j) + 1] += 0.5
     c1 = ChebyshevT(vcat(zeros(i), 1))
     c2 = ChebyshevT(vcat(zeros(j), 1))
-    @test c1 * c2 ≈ ChebyshevT(target)
+    @test @inferred(c1 * c2) ≈ ChebyshevT(target)
 
     # divrem
     target = c1 + c2