[isabelle-dev] Problem with code generation for non-executable types

[Johannes Hölzl]

Hi,

I want to introduce uniform spaces in HOL, for this I need to introduce
a type class of the form (see the attached bundle):

  class uniformity = 
    fixes uniformity :: "('a × 'a) filter"

Note that uniformity is a filter and not a function.

which sits between topological spaces and metric spaces, i.e. every
metric type is also in the following type classes:

  class open_uniformity = "open" + uniformity +
    assumes open_uniformity: "⋀U. open U ⟷ (∀x∈U. eventually (λ(x', y). x' = x ⟶ y ∈ U) uniformity)"

  class uniformity_dist = dist + uniformity +
    assumes uniformity_dist: "uniformity = (INF e:{0 <..}. principal {(x, y). dist x y < e})"

Everything works fine until Affinite_Arithmetic, there in
Intersection.thy the code generation fails with the following ML error:

  Error: Type mismatch in type constraint.
     Value: {uniformity = uniformity_proda} : {uniformity: 'a}
     Constraint: ('a * 'b) uniformity
     Reason:
        Can't unify 'a to (('a * 'b) * ('a * 'b)) filter
           (Type variable is free in surrounding scope)
  {uniformity = uniformity_proda} : ('a * 'b) uniformity
  At (line 1619 of "generated code")
  Exception- Fail "Static Errors" raised

I assume this is a strange interaction btw code_abort and the fact that
uniformity is a filter (datatype 'a filter = _EMPTY) and not a
function.

Does anybody know how to avoid such kind of errors? Do I need to
sprinkle more [code del] or code_abort annotations?

 - Johannes

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