Fix some finite field promotion (#1575)

Nemocas · Nov 4, 2023 · 04d5a3a · 04d5a3a · thofma · Nov 4, 2023
1 parent 1acb178
commit 04d5a3a
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Showing 3 changed files with 18 additions and 4 deletions.
diff --git a/Project.toml b/Project.toml
@@ -1,6 +1,6 @@
 name = "Nemo"
 uuid = "2edaba10-b0f1-5616-af89-8c11ac63239a"
-version = "0.37.3"
+version = "0.37.4"
 
 [deps]
 AbstractAlgebra = "c3fe647b-3220-5bb0-a1ea-a7954cac585d"

diff --git a/src/flint/fq_default_extended.jl b/src/flint/fq_default_extended.jl
@@ -837,15 +837,21 @@ end
 
 function _try_promote(K::FqField, a::FqFieldElem)
   L = parent(a)
-  if degree(K) == 1 && K !== L
-    return false, a
-  end
 
   if K === L
     return true, a
   end
 
+  if absolute_degree(L) == 1 && L === base_field(K)
+    return true, K(lift(ZZ, a))
+  end
+
+  if degree(K) == 1 && K !== L
+    return false, a
+  end
+
   fl, b = _try_promote(base_field(K), a)
+
   if fl
     return fl, K(a)::FqFieldElem
   else

diff --git a/test/flint/fq_default_extended-test.jl b/test/flint/fq_default_extended-test.jl
@@ -287,4 +287,12 @@ end
     end
     @test divexact(a, one(FF)) == divexact(FF(a), one(FF))
   end
+
+  F = Nemo._GF(3)
+  Fx, x = F["x"]
+  FF, = Nemo._residue_field(x - 2)
+  a = one(F) * one(FF)
+  @test parent(a) === FF && is_one(a)
+  a = one(FF) * one(F)
+  @test parent(a) === FF && is_one(a)
 end