DSL EXPRESSION:
@u[2] = @v


AST:
"block" [tt:block] [nt:StatementBlock]
    "=" [tt:equals] [nt:Assignment]
        "[]" [tt:[]] [nt:ArrayOrMapIndexAccess]
            "@u" [tt:oosvar_name] [nt:DirectOosvarValue]
            "2" [tt:int_literal] [nt:int_literal]
        "@v" [tt:oosvar_name] [nt:DirectOosvarValue]

