Syntax error with expression starting with a reference including object accessor

This should work:

t = ((s: 1, 2, 3))
a = t.s[2] + 2

but produces this error:

Expected '.' or '[' or '<=' or '>=' or '>' or '<' or '!=' or '==' or 'if' or ':array' or ':columns' or ':name' or 'for' or 'on' or EOF

The workaround is a = 2 + t.s[2] as it was for expressions starting with a function calls (see this solved issue).

Maybe reordering the rules and/or some look-ahead to the expression rule?