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  1. CLJS-2928

Externs inference: Consider inheritance

    Details

    • Type: Improvement
    • Status: Open
    • Priority: Major
    • Resolution: Unresolved
    • Affects versions: None
    • Fix versions: None
    • Labels:
      None

      Description

      If a JavaScript type is inferred, "base" properties are not considered. A specific example is js/document, which gets inferred as js/HTMLDocument. If code makes use of any of the base properties, then an inference warning will get triggered, even though :advanced compilation is fine.

      src/test/infer.cljs
      (ns test.infer)
      
      (set! *warn-on-infer* true)
      
      (.-documentElement js/document)
      
      $ clj -m cljs.main -co '{:infer-externs true}' -c test.infer
      WARNING: Cannot resolve property documentElement for inferred type js/HTMLDocument in expression (. js/document -documentElement) at line 5 /Users/mfikes/Desktop/test-infer/src/test/infer.cljs
      

      If you add -O advanced you can confirm that documentElement survives into the compiled artifact without being mangled.

      Also, you can work around the issue by hinting the target as being the base type:

      (.-documentElement ^js/Document js/document)
      

      Perhaps there is some way to make use of the "extends" metadata in the externs in cases like these to check base types before emitting a warning (or by inferring the base type based on the property being accessed). Here is the extends metadata of interest in the example above: https://github.com/google/closure-compiler/blob/50713dceb16b369f8f317e5b49e8a9dec2b47496/externs/browser/w3c_dom2.js#L171

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            • Assignee:
              Unassigned
              Reporter:
              mfikes Mike Fikes
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              • Created:
                Updated: