Thus, we do not need to look through two different namespaces.
The only difference w.r.t. the core namespace semantics is that
a program symbol (pvsymbol, psymbol, plsymbol, or xsymbol) may
be introduced in the scope of an lsymbol of the same name and
overshadow it in program expressions, though not in specifications.
For example, the following declarations allow to use (!) both in
programs and specifications:

    type ref 'a = {| mutable contents : 'a |}
    function (!) (x: ref 'a) : 'a = x.contents
    let (!) (r: ref 'a) = {} r.contents { result = !r }

Notice, however, that itsymbols cannot overshadow pure tsymbols.