Removed a convert method for Cells that was causing cells to be copie…

…d when referenced. Added a test for this condition.

src/Cells.jl

@@ -103,11 +103,11 @@ type CellArray{S,T} <: CellRef{S,T}
     mag::Float64
     rot::Float64
 end
-convert{S,T}(::Type{CellArray{S,T}}, x::CellArray) =
-    CellArray(T(x.cell), convert(Point{S}, x.origin),
-                         convert(Point{S}, x.deltacol),
-                         convert(Point{S}, x.deltarow),
-                         x.col, x.row, x.xrefl, x.mag, x.rot)
+convert{S}(::Type{CellArray{S}}, x::CellArray) =
+    CellArray(x.cell, convert(Point{S}, x.origin),
+                      convert(Point{S}, x.deltacol),
+                      convert(Point{S}, x.deltarow),
+                      x.col, x.row, x.xrefl, x.mag, x.rot)
 
 """
 ```
@@ -154,10 +154,12 @@ type Cell{T<:Coordinate}
         c
     end
 end
-convert{T}(::Type{Cell{T}}, x::Cell) =
-    Cell{T}(x.name, convert(Vector{Polygon{T}}, x.elements),
-                    convert(Vector{CellRef}, x.refs),
-                    x.create)
+# Do NOT define a convert method like this or otherwise cells will
+# be copied when referenced by CellRefs!
+# convert{T}(::Type{Cell{T}}, x::Cell) =
+#     Cell{T}(x.name, convert(Vector{Polygon{T}}, x.elements),
+#                     convert(Vector{CellRef}, x.refs),
+#                     x.create)
 
 """
 ```

test/runtests.jl

@@ -286,6 +286,7 @@ end
     @test_throws Unitful.DimensionError render!(c3, Rectangle(5m,10m))
     render!(c3, r)
     c2ref = CellReference(c2, Point(-10.0,0.0); mag=1.0, rot=180°)
+    @test c2ref.cell === c2
     c3ref = CellReference(c3, Point(10.0,0.0); mag=2.0, rot=90°)
     push!(c.refs, c2ref)
     push!(c2.refs, c3ref)
@@ -308,8 +309,10 @@ end
     c = Cell("main")
     c2 = Cell("rect")
     render!(c2, Rectangle(5,5))
-    push!(c.refs, CellArray(c2, Point(0,0); dc=Point(10,0), dr=Point(0,10),
-        ncols=10, nrows=10))
+    arr = CellArray(c2, Point(0,0); dc=Point(10,0), dr=Point(0,10),
+        ncols=10, nrows=10)
+    @test arr.cell === c2
+    push!(c.refs, arr)
 
     # Test bounds with cell arrays
     @test bounds(c) == Rectangle(95,95)