Jira (PUP-6229) Non-Type expression within the RHS Type expression of a type alias gives unclear error

[Henrik Lindberg (JIRA)]

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Henrik Lindberg commented on PUP-6229   Re: Non-Type _expression_ within the RHS Type _expression_ of a type alias gives unclear error That is acceptable. There is a big difference between a definition like: type Foo = Enum[$x] and when a type is constructed dynamically: $t = Enum[$x] We cannot accept variables in the static case - then the entire typesystem becomes parameterized by the inputs at runtime. A pathologic example would be type T = Variant[type($x)] And now, there is no clue what T is unless you evaluate everything. Goodbye static type inference. We could introduce a type that is "variable" e.g. something like type NodeOsFamily = Variable['fact', 'os', 'family'] Then the type system would know that T must be what $fact[os][family] is. But it would not know if that is compatible with say Enum['windows'] or any static type except exactly itself. Since this probably is only really meaningful for facts, it is probably better to add the type Fact, and in the example it would then be used as Fact[os, family] with or without aliasing it. Add Comment   This message was sent by Atlassian JIRA (v6.4.13#64028-sha1:b7939e9) -- You received this message because you are subscribed to the Google Groups "Puppet Bugs" group. To unsubscribe from this group and stop receiving emails from it, send an email to puppet-bugs+unsubscr...@googlegroups.com. To post to this group, send email to puppet-bugs@googlegroups.com. Visit this group at https://groups.google.com/group/puppet-bugs. For more options, visit https://groups.google.com/d/optout.