Expansion requires all possible objects to have been declared

[ClementSparrow]

Context

We can declare two objects like that:

TAGS
T = A B

OBJECTS

Obj:A:B
transparent

Obj:B:A
transparent

And then use the following mappings in expansions:

MAPPINGS
T => Tbar
A B -> B A

So that we can expand Obj:T:Tbar with tag class parameter T to match our two objects.

Problem

The expansion code currently requires to have declared all four possible objects Obj:T:T, i.e. Obj:A:A, Obj:A:B, Obj:B:A, and Obj:B:B.

Solution

Checking the validity of a mapping-allowed identifier should use the expansion mechanism to check that all expansions lead to a valid expanded identifier. But this might be a complex modification of the code in identifiers.js.