Problem with sort inference

[lionelvillard]

This rule:

func AnalyzeCapturedAllVar(#env: LEnv, #vars: List) -> List<Core_cterm_sort>
→ Map((var)->cterm⟦ ⟨canno*: AnalyzeMayKeep(LEnvGetVarCount(#env, var), ())⟩ ⟨cvariable: var⟩ ⟧, #vars)

causes an error:

Error: undefined enumeration value Nil in type Region