rustc/tests/ui/specialization/README.md

This directory contains the test for incorrect usage of specialization that should lead to compile failure. Those tests break down into a few categories:

• Feature gating

  • On use of the default keyword
  • On overlapping impls

• Overlap checking with specialization enabled

  • Basic overlap scenarios
    • Includes purely structural overlap
    • Includes purely trait-based overlap
    • Includes mix
  • Overlap with differing polarity

• Attempt to specialize without using default

• Attempt to change impl polarity in a specialization

• Attempt to rely on projection of a default type

  • Rely on it externally in both generic and monomorphic contexts
  • Rely on it both within an impl and outside it