Merge pull request #532 from oscar-system/th/quograd

Fix coercion into quotient rings
oscar-system · Jul 7, 2021 · c9fde9d · c9fde9d
2 parents 209c89f + aa68a43
commit c9fde9d
Show file tree

Hide file tree

Showing 2 changed files with 11 additions and 3 deletions.
diff --git a/src/Rings/MPolyQuo.jl b/src/Rings/MPolyQuo.jl
@@ -652,16 +652,18 @@ function (Q::MPolyQuo)(a::MPolyQuoElem)
 end
 
 function (Q::MPolyQuo)(a::MPolyElem) 
-   @assert parent(a) == Q.R
-   return MPolyQuoElem(Q.R(a), Q)
+   if base_ring(Q) === parent(a)
+      return MPolyQuoElem(a, Q)
+   else
+      return MPolyQuoElem(Q.R(a), Q)
+   end
 end
 
 function (Q::MPolyQuo)(a::Singular.spoly)
    @assert singular_ring(Q) == parent(a)
    return MPolyQuoElem(Q.R(a), Q)
 end
 
-
 function (S::Singular.PolyRing)(a::MPolyQuoElem)
    Q = parent(a)
    @assert singular_ring(Q) == S

diff --git a/test/Rings/mpoly-graded-test.jl b/test/Rings/mpoly-graded-test.jl
@@ -157,6 +157,12 @@ end
   end
 end
 
+@testset "Coercion" begin
+  R, (x, y) = grade(PolynomialRing(QQ, ["x", "y"])[1]);
+  Q = quo(R, ideal([x^2, y]))[1];
+  @test parent(Q(x)) === Q
+  @test parent(Q(gens(R.R)[1])) === Q
+end
 @testset "Evaluation" begin
   R, (x,y) = grade(PolynomialRing(QQ, ["x", "y"])[1]);
   @test x(y, x) == y