License: Creative Commons Attribution 3.0 Unported license (CC BY 3.0)
When quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.ECOOP.2017.28
URN: urn:nbn:de:0030-drops-72640
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Williams, Jack ; Morris, J. Garrett ; Wadler, Philip ; Zalewski, Jakub

Mixed Messages: Measuring Conformance and Non-Interference in TypeScript

LIPIcs-ECOOP-2017-28.pdf (0.5 MB)


TypeScript participates in the recent trend among programming
languages to support gradual typing. The DefinitelyTyped Repository
for TypeScript supplies type definitions for over 2000 popular
JavaScript libraries. However, there is no guarantee that
implementations conform to their corresponding declarations.

We present a practical evaluation of gradual typing for TypeScript.
We have developed a tool for use with TypeScript, based on the
polymorphic blame calculus, for monitoring JavaScript libraries and
TypeScript clients against the TypeScript definition. We apply our
tool, TypeScript TPD, to those libraries in the DefinitelyTyped
Repository which had adequate test code to use. Of the 122 libraries
we checked, 62 had cases where either the library or its tests
failed to conform to the declaration.

Gradual typing should satisfy non-interference. Monitoring a program
should never change its behaviour, except to raise a type error
should a value not conform to its declared type. However, our
experience also suggests serious technical concerns with the use of
the JavaScript proxy mechanism for enforcing contracts. Of the 122
libraries we checked, 22 had cases where the library or its tests
violated non-interference.

BibTeX - Entry

  author =	{Jack Williams and J. Garrett Morris and Philip Wadler and Jakub Zalewski},
  title =	{{Mixed Messages: Measuring Conformance and Non-Interference in TypeScript}},
  booktitle =	{31st European Conference on Object-Oriented Programming (ECOOP 2017)},
  pages =	{28:1--28:29},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-035-4},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{74},
  editor =	{Peter M{\"u}ller},
  publisher =	{Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{},
  URN =		{urn:nbn:de:0030-drops-72640},
  doi =		{10.4230/LIPIcs.ECOOP.2017.28},
  annote =	{Keywords: Gradual Typing, TypeScript, JavaScript, Proxies}

Keywords: Gradual Typing, TypeScript, JavaScript, Proxies
Collection: 31st European Conference on Object-Oriented Programming (ECOOP 2017)
Issue Date: 2017
Date of publication: 16.06.2017

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