Before
```
Evaluated relational algebra for predicate TypeMention::RefTypeReprMention.resolveRootType/0#dispred#091b949a#fb@4bd8a49g with tuple counts:
            124419   ~0%    {1} r1 = RefTypeRepr::Generated::RefTypeRepr#422893fa AND NOT `RefTypeRepr::Generated::RefTypeRepr.isMut/0#dispred#e2b9988f`(FIRST 1)
        6621454761   ~1%    {3}    | JOIN WITH `Type::DataType.getTypeItem/0#dispred#83467854` CARTESIAN PRODUCT OUTPUT Rhs.0, Lhs.0, Rhs.1
         915101745   ~0%    {4}    | JOIN WITH `project#Type::DataType.getPositionalTypeParameter/1#dispred#3bf49cbe` ON FIRST 1 OUTPUT Lhs.2, _, Lhs.1, Lhs.0
         915101745   ~3%    {4}    | REWRITE WITH Out.1 := "Ref"
            124419   ~0%    {2}    | JOIN WITH `Builtins::BuiltinType.getName/0#dispred#8f62ab0a` ON FIRST 2 OUTPUT Lhs.2, Lhs.3

             76728   ~0%    {1} r2 = JOIN RefTypeRepr::Generated::RefTypeRepr#422893fa WITH `RefTypeRepr::Generated::RefTypeRepr.isMut/0#dispred#e2b9988f` ON FIRST 1 OUTPUT Lhs.0
        4083387432   ~1%    {3}    | JOIN WITH `Type::DataType.getTypeItem/0#dispred#83467854` CARTESIAN PRODUCT OUTPUT Rhs.0, Lhs.0, Rhs.1
         564334440   ~3%    {4}    | JOIN WITH `project#Type::DataType.getPositionalTypeParameter/1#dispred#3bf49cbe` ON FIRST 1 OUTPUT Lhs.2, _, Lhs.1, Lhs.0
         564334440   ~0%    {4}    | REWRITE WITH Out.1 := "RefMut"
             76728   ~2%    {2}    | JOIN WITH `Builtins::BuiltinType.getName/0#dispred#8f62ab0a` ON FIRST 2 OUTPUT Lhs.2, Lhs.3

            201147   ~1%    {2} r3 = r1 UNION r2
                            return r3
```

After
```
Evaluated relational algebra for predicate TypeMention::RefTypeReprMention.resolveRootType/0#dispred#091b949a#fb@8f12aa2a with tuple counts:
        124419   ~0%    {1} r1 = RefTypeRepr::Generated::RefTypeRepr#422893fa AND NOT `RefTypeRepr::Generated::RefTypeRepr.isMut/0#dispred#e2b9988f`(FIRST 1)
        124419   ~0%    {2}    | JOIN WITH Type::RefSharedType#090df68e CARTESIAN PRODUCT OUTPUT Rhs.0, Lhs.0
        124419   ~0%    {2}    | JOIN WITH `project#Type::DataType.getPositionalTypeParameter/1#dispred#3bf49cbe` ON FIRST 1 OUTPUT Lhs.1, Lhs.0

         76728   ~0%    {1} r2 = JOIN RefTypeRepr::Generated::RefTypeRepr#422893fa WITH `RefTypeRepr::Generated::RefTypeRepr.isMut/0#dispred#e2b9988f` ON FIRST 1 OUTPUT Lhs.0
         76728   ~0%    {2}    | JOIN WITH Type::RefMutType#c67a1837 CARTESIAN PRODUCT OUTPUT Rhs.0, Lhs.0
         76728   ~2%    {2}    | JOIN WITH `project#Type::DataType.getPositionalTypeParameter/1#dispred#3bf49cbe` ON FIRST 1 OUTPUT Lhs.1, Lhs.0

        201147   ~1%    {2} r3 = r1 UNION r2
                        return r3
```