Canonical subvs_fieldType K :=
  Eval hnf in FieldType (subvs_of K) (@subvs_fieldMixin K).Fact prodv_is_aspace E F : is_aspace (E * F).Canonical prodv_aspace E F : {subfield L} := ASpace (prodv_is_aspace E F).Canonical capv_aspace E F : {subfield L} := aspace_cap (field_mem_algid E F).

Lemma field_subvMr U F : (U <= U * F)%VS.