[isabelle] Code generator forgets type constraint on literal integers



Dear experts of the code generator,

The code serialiser for Haskell forgets to print a type constraint on literal integers in a polymorphic context that requires a type class instance. I have attached a minimal example. The generated Haskell code does not compiler. Rather, it produces the following error message.

Generated_Code.hs:29:14:
    Ambiguous type variable `a0' in the constraints:
      (Prelude.Num a0)
        arising from the literal `42' at Generated_Code.hs:29:14-15
      (Foo a0) arising from a use of `bar' at Generated_Code.hs:29:10-12
    Probable fix: add a type signature that fixes these type variable(s)
    In the first argument of `bar', namely `42'
    In the expression: bar 42
    In an equation for `foobar': foobar = bar 42

How can I tell the code generator to print the type constraint for literal integers?

Andreas

Attachment: Test.thy
Description: application/extension-thy



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