17.20.2 Prerequisites for codes lifting

When arriving at this compiler pass the input recordised code is such that:

• All the clambda structs are wrapped into closure-maker structs.
• All the closure-maker structs appear as right–hand side expressions of bindings defined by fix structs.
• Bindings defined by fix structs are immutable and their right–hand side expressions are all closure-maker structs.
• Bindings defined by bind structs are immutable and their right–hand side expressions are of type different from closure-maker and clambda. These bindings are immutable because the assigned ones have been previously transformed into immutable references to mutable vector objects.
• If the right–hand side expression of a binding defined by bind is a var struct: such binding defines a synonym. For example:

  (bind ((a ?rhs))
    (bind ((b a))
      ?body))
  

  the binding b is immutable, so b is a synonym of a; it is perfectly all right to substitute all the occurrences of the var b in ?body with occurrences of the var a.