[issue18244] singledispatch: When virtual-inheriting ABCs at distinct points in MRO, composed MRO is dependent on haystack ordering

[Edward Catmur]

Edward Catmur added the comment:

Łukasz, thanks. When the most-derived class virtual-inherits two related ABCs U, V:

       object
      /   |  \
      A   W   V
      | .`  .`
      B`  U`
      | .`
      C`

The secondary `for` loop is necessary to ensure U and V are ordered correctly.  I'll upload a patch with an improved test that covers this case.

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Added file: http://bugs.python.org/file30646/singledispatch-mro-composition.patch

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<http://bugs.python.org/issue18244>
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