Jira (PUP-6022) Need explanation for error message when using data types

[Henrik Lindberg (JIRA)]

Title: Message Title

Henrik Lindberg commented on PUP-6022   Re: Need explanation for error message when using data types Puppet does not (currently) support typing variables.So this: String $param1 = 'teststring' Is the same as if you had written: {code:puppet} String; $param1 = 'teststring' that is, two separate expressions. The error is telling you that the type String does not do anything, the _expression_ produces an instance of the String type, and then it throws it away. That is an "unproductive _expression_". It is as if you wrote: 1 + 1 $param1 = 'teststring' Since, you in puppet cannot change the value of variables we are not sure that the ability to type them is that valuable. If we introduce that we would probably need a keyword (var or similar) to resolve what would otherwise result in an ambiguous grammar. The best you can do, if you are assigning something complex to the variable (say the result of a function call) and you want to make sure that the value is what you expect it to be - use the assert_type function. (The example below will look silly because you can see that it is a string value, but it illustrates the principle). $param1 = String.assert_type('teststring') The assert_type will do automatic type mismatch error reporting (from 4.4.0 there are many improvements in how it describes the mismatch). The function returns the given value if it is ok, otherwise it will raise an error. (There are some extra stuff you can do if you want to provide another value, handle the error yourself etc. See the docimentation for assert_type for that). You can type parameters to defines, classes, functions, and lambdas, but not on variable assignments. I am closing this as a won't fix, as we currently have no plans to introduce typing of (non parameter) variables. Add Comment   This message was sent by Atlassian JIRA (v6.4.12#64027-sha1:e3691cc) -- 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.