IIUC, we have this structure:

             Type(i32)
            /         \
Global("g1", i32) Global("g2", i32)
           |     X     |
       Literal(1) Literal(2)

There is no unique least upper bound of the two literals and there is no unique greatest lower bound of the two globals. This is a problem because union and intersect are supposed to calculate unique least upper / greatest lower bounds.

I think there is a probably a way to solve this, but I'll have to think on it.

I ran into this while trying to simplify and complete the implementation of intersect as part of the investigation suggested here: https://github.com/WebAssembly/binaryen/pull/7538/files#r2054860951