Instead of multiple setter calls, set filters and attribute in one.

To avoid deductions changing the type all the time.

lib/coll.gi

@@ -3058,13 +3058,21 @@ InstallMethod( CanComputeIsSubset,"default: no, unless identical",
 InstallOtherMethod(SetSize,true,[IsObject and IsAttributeStoringRep,IsObject],
   100, # override system setter
 function(obj,sz)
-  if not HasSize(obj) then
-    SetIsEmpty(obj,sz=0);
-    SetIsTrivial(obj,sz=1);
-    SetIsNonTrivial(obj,sz<>1);
-    SetIsFinite(obj,sz<>infinity);
+local filt;
+  if HasSize(obj) and Size(obj)<>sz then
+    # Make this an ordinary error to enter break loop so that one can
+    # investigate call order for debugging
+    Error("size of ",obj," already set to ",Size(obj),
+      ", cannot be changed to ",sz);
   fi;
-  TryNextMethod(); # to enforce size setting
+  if sz=0 then filt:=IsEmpty;
+  elif sz=1 then filt:=IsTrivial;
+  elif sz=infinity then filt:=IsNonTrivial and HasIsFinite;
+  else filt:=IsNonTrivial and IsFinite;
+  fi;
+  filt:=filt and HasSize;
+  obj!.Size:=sz;
+  SetFilterObj(obj,filt);
 end);
 
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