Clojure

Functions with non-qualified return type hints force import of hinted classes when called from other namespace

Details

  • Type: Defect Defect
  • Status: Open Open
  • Priority: Major Major
  • Resolution: Unresolved
  • Affects Version/s: Release 1.5
  • Fix Version/s: None
  • Component/s: None
  • Labels:

Description

You can add a type hint to function arglists to indicate the return type of a function like so.

user> (import '(java.util List))
java.util.List
user> (defn linkedlist ^List [] (java.util.LinkedList.))
#'user/linkedlist
user> (.size (linkedlist))
0

The problem is that now when I call `linkedlist` exactly as above from another namespace, I'll get an exception because java.util.List is not imported in there.

user> (in-ns 'user2)
#<Namespace user2>
user2> (refer 'user)
nil
user2> (.size (linkedlist))
CompilerException java.lang.IllegalArgumentException: Unable to resolve classname: List, compiling:(NO_SOURCE_PATH:1:1)
user2> (import '(java.util List)) ;; Too bad, need to import List here, too.
java.util.List
user2> (.size (linkedlist))
0

There are two workarounds: You can import the hinted type also in the calling namespace, or you always use fully qualified class names for return type hints. Clearly, the latter is preferable.

But clearly, that's a bug that should be fixed. It's not in analogy to type hints on function parameters which may be simple-named without having any consequences for callers from other namespaces.

Activity

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Andy Fingerhut added a comment -

To make sure I understand, Nicola, in this ticket you are asking that the Clojure compiler change behavior so that the sample code works correctly with no exceptions, the same way as it would work correctly without exceptions if one of the workarounds were used?

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Andy Fingerhut added a comment - To make sure I understand, Nicola, in this ticket you are asking that the Clojure compiler change behavior so that the sample code works correctly with no exceptions, the same way as it would work correctly without exceptions if one of the workarounds were used?
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Tassilo Horn added a comment -

Hi Andy. Tassilo here, not Nicola. But yes, the example should work as-is. When I'm allowed to use type hints with simple imported class names for arguments, then doing so for return values should work, too.

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Tassilo Horn added a comment - Hi Andy. Tassilo here, not Nicola. But yes, the example should work as-is. When I'm allowed to use type hints with simple imported class names for arguments, then doing so for return values should work, too.

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Dates

  • Created:
    Updated: