[PATCH] D59932: [clang-tidy] **Prototype**: Add fix description to clang-tidy checks.

[Haojian Wu via Phabricator via cfe-commits]

hokein marked an inline comment as done.
hokein added a comment.

As discussed offline, the current approach only works for checks provide a single fix, providing such API is somehow misleading.

Instead, we'd emit the check fix and the fix description via diagnostic::Note, rather than attaching to the main diagnostic of the check:

- match the data model of the checks provide different semantic fixes depending on the context;
- align with the way how existing clang diagnostics emit alternative fixes (via diagnostic::Note);
- open a door to write clang-tidy checks that provide alternative fixes; we don't have these checks at the moment, but some clang diagnostics like `clang-diagnostic-parentheses` do (and our current implementation just aggregates all the fixes together, which is not correct);

It would require some changes in clang-tidy check side:

Before this patch:

  void MyCheck::check(...) {
     ...
     diag(loc, "my check warning") <<  FixtItHint::CreateReplacement(...);
  }

After this patch:

  void MyCheck::check(...) {
     ...
     diag(loc, "my check warning"); // Emit a check warning
     // We might want to introduce an utility method like `diagFix` to save some verbosed words.
     diag(loc, "fix description", DiagnosticIDs::Note) << FixtItHint::CreateReplacement(...); // Emit a diagnostic note and a fix
  }

An example of unused-using-decls check (clang-tidy command line output)

- before:

  1 warning generated.
  /tmp/test.cpp:8:12: warning: using decl 'Foo' is unused [misc-unused-using-decls]
  using foo::Foo;
  ~~~~~~~~~~~^~~~

- after:

  1 warning generated.
  /tmp/test.cpp:8:12: warning: using decl 'Foo' is unused [misc-unused-using-decls]
  using foo::Foo;
             ^
  /tmp/test.cpp:8:12: note: remove the using
  using foo::Foo;
  ~~~~~~~~~~~^~~~


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D59932/new/

https://reviews.llvm.org/D59932