Resolves: tdf#136364 treat svSep type with ocUnion as range type

So for RPN
sv...Ref(ocPush), sv...Ref(ocPush), svSep(ocUnion), sv...Ref(ocPush)
another svSep(ocUnion) instead of svSep(ocSep) is appended.

Regression from

    commit a6032ff541
    CommitDate: Thu Oct 11 11:26:37 2018 +0200

        Resolves: tdf#90698 catch list (1;2) of non-references as error

that introduced a conditional check on operands and operators.

Change-Id: If5da3a781f24f891ff12c4a8f32a2ec92c6b4c8a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/102276
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Jenkins

formula/source/core/api/FormulaCompiler.cxx

@@ -305,7 +305,7 @@ bool isRangeResultOpCode( OpCode eOp )
     @param  bRight
             If bRPN==false, bRight==false means opcodes for left side are
             checked, bRight==true means opcodes for right side. If bRPN==true
-            it doesn't matter.
+            it doesn't matter except for the ocSep converted to ocUnion case.
  */
 bool isPotentialRangeType( FormulaToken const * pToken, bool bRPN, bool bRight )
 {
@@ -326,6 +326,10 @@ bool isPotentialRangeType( FormulaToken const * pToken, bool bRPN, bool bRight )
         case svExternalDoubleRef:
         case svExternalName:        // could be range
             return true;
+        case svSep:
+            // A special case if a previous ocSep was converted to ocUnion it
+            // stays svSep instead of svByte.
+            return bRPN && !bRight && pToken->GetOpCode() == ocUnion;
         default:
             // Separators are not part of RPN and right opcodes need to be
             // other StackVar types or functions and thus svByte.
@@ -1407,6 +1411,7 @@ void FormulaCompiler::Factor()
                     if (p && isPotentialRangeType( p, true, true))
                     {
                         pFacToken->NewOpCode( ocUnion, FormulaToken::PrivateAccess());
+                        // XXX NOTE: the token's eType is still svSep here!
                         PutCode( pFacToken);
                     }
                 }