support deepcopy_internal for group elements

resolves issue #860

Author: ThomasBreuer

src/Groups/matrices/MatGrp.jl

@@ -125,6 +125,23 @@ parent_type(::Type{T}) where T<:MatrixGroupElem{RE,S} where {RE,S} = MatrixGroup
 parent_type(::T) where T<:MatrixGroupElem{RE,S} where {RE,S} = MatrixGroup{RE,S}
 
 
+function Base.deepcopy_internal(x::MatrixGroupElem, dict::IdDict)
+  if isdefined(x, :X)
+    X = Base.deepcopy_internal(x.X, dict)
+    if isdefined(x, :elm)
+      elm = Base.deepcopy_internal(x.elm, dict)
+      return MatrixGroupElem(x.parent, elm, X)
+    else
+      return MatrixGroupElem(x.parent, X)
+    end
+  elseif isdefined(x, :elm)
+    elm = Base.deepcopy_internal(x.elm, dict)
+    return MatrixGroupElem(x.parent, elm)
+  end
+  error("$x has neither :X nor :elm")
+end
+
+
 ########################################################################
 #
 # Basic

src/Groups/types.jl

@@ -61,6 +61,11 @@ struct BasicGAPGroupElem{T<:GAPGroup} <: GAPGroupElem{T}
    X::GapObj
 end
 
+function Base.deepcopy_internal(x::BasicGAPGroupElem, dict::IdDict)
+  X = Base.deepcopy_internal(x.X, dict)
+  return BasicGAPGroupElem(x.parent, X)
+end
+
 Base.hash(x::GAPGroup, h::UInt) = h # FIXME
 Base.hash(x::GAPGroupElem, h::UInt) = h # FIXME
 

test/Groups/elements.jl

@@ -131,3 +131,15 @@ end
    @test_throws ErrorException gen(G, 0)
 end
 
+@testset "deepcopy" begin
+   for g in [symmetric_group(5), free_group(2), small_group(8, 1),
+             automorphism_group(alternating_group(4))]
+     m = Oscar.BasicGAPGroupElem(g, gen(g, 1).X)
+     @test isdefined(m, :X)
+     c = deepcopy(m);
+     @test isdefined(c, :X)
+     @test c.X == m.X
+
+     @test deepcopy([one(g)]) == [one(g)]
+   end
+end

test/Groups/matrixgroups.jl

@@ -686,3 +686,34 @@ end
    g = -identity_matrix(K, 3)
    @test g in G
 end
+
+@testset "deepcopy" begin
+   g = general_linear_group(2, 4)
+
+   m = MatrixGroupElem(g, gen(g, 1).X);  # do not call `show`!
+   @test isdefined(m, :X)
+   @test ! isdefined(m, :elm)
+   c = deepcopy(m);
+   @test isdefined(c, :X)
+   @test ! isdefined(c, :elm)
+   @test c.X == m.X
+
+   m = MatrixGroupElem(g, gen(g, 1).elm, gen(g, 1).X)
+   @test isdefined(m, :X)
+   @test isdefined(m, :elm)
+   c = deepcopy(m);
+   @test isdefined(c, :X)
+   @test isdefined(c, :elm)
+   @test c.X == m.X
+   @test c.elm == m.elm
+
+   m = MatrixGroupElem(g, gen(g, 1).elm)
+   @test ! isdefined(m, :X)
+   @test isdefined(m, :elm)
+   c = deepcopy(m);
+   @test ! isdefined(c, :X)
+   @test isdefined(c, :elm)
+   @test c.elm == m.elm
+
+   @test deepcopy([one(g)]) == [one(g)]
+end