Fix some type instability in fixed_field (#2993)

oscar-system · Nov 6, 2023 · 5766255 · 5766255
1 parent 9013fad
commit 5766255
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Showing 2 changed files with 7 additions and 2 deletions.
diff --git a/experimental/GaloisGrp/test/runtests.jl b/experimental/GaloisGrp/test/runtests.jl
@@ -10,5 +10,10 @@
   subfields(F)
   G, = galois_group(F)
   @test is_isomorphic(G, symmetric_group(3))
+
+  K, a = cyclotomic_field(3, "a", cached = false)
+  G, C = galois_group(K)
+  k = fixed_field(C, G)
+  @test degree(k) == 1 && k isa AnticNumberField
 end
 
diff --git a/src/NumberTheory/GaloisGrp/GaloisGrp.jl b/src/NumberTheory/GaloisGrp/GaloisGrp.jl
@@ -2314,8 +2314,8 @@ extension.
 """
 function fixed_field(GC::GaloisCtx, U::PermGroup, extra::Int = 5)
   G = GC.G
-  if index(G, U) == 1 # not type stable
-    return QQ
+  if index(G, U) == 1
+    return Hecke.rationals_as_number_field()[1]
   end
   #XXX: seems to be broken for reducible f, ie. intransitive groups
   a, T = relative_invariant(G, U)