Change default traversal in AST Matchers to ignore invisible nodes

[steveire]

Update

[steveire]

Update

[aaron.ballman]

LGTM aside from some documentation nits.

clang/docs/ReleaseNotes.rst

252

is -> are

Also, I think we typically use single spacing after the full stop in the release notes.

254–256

We also have release notes for clang-tools-extra that should be updated for the changes to clang-query.

[steveire]

Touch

[steveire]

Touch

[steveire]

Rebase

clang/docs/ReleaseNotes.rst

- clang-tidy and clang-include-fixer are no longer compiled into libclang by
   default. You can set ``LIBCLANG_INCLUDE_CLANG_TOOLS_EXTRA=ON`` to undo that,
   but it's expected that that setting will go away eventually. If this is
   something you need, please reach out to the mailing list to discuss possible
   ways forward.
 
 AST Matchers
 ------------
 
-- ...
+- Traversal in AST Matchers was simplified to use the
+  ``TK_IgnoreUnlessSpelledInSource`` mode by default, instead of ``TK_AsIs``.
+  This means that many uses of the ``ignoringImplicit()`` and similar matchers
+  is no longer necessary.  Clients of AST Matchers which wish to match on
+  implicit AST nodes can wrap their matcher in ``traverse(TK_AsIs, ...)`` or
+  use ``TraversalKindScope`` if appropriate.  The ``clang-query`` tool also
+  uses ``IgnoreUnlessSpelledInSource`` by default.  The mode can be changed
+  using ``set traversal AsIs`` in the ``clang-query`` environment.
 
 clang-format
 ------------
 
 - Option ``IndentExternBlock`` has been added to optionally apply indenting inside ``extern "C"`` and ``extern "C++"`` blocks.
 
 - ``IndentExternBlock`` option accepts ``AfterExternBlock`` to use the old behavior, as well as Indent and NoIndent options, which map to true and false, respectively.
 

clang/include/clang/AST/ParentMapContext.h

public:
 
   const Expr *traverseIgnored(const Expr *E) const;
   Expr *traverseIgnored(Expr *E) const;
   DynTypedNode traverseIgnored(const DynTypedNode &N) const;
 
 private:
   ASTContext &ASTCtx;
   class ParentMap;
-  TraversalKind Traversal = TK_AsIs;
+  TraversalKind Traversal = TK_IgnoreUnlessSpelledInSource;
   std::unique_ptr<ParentMap> Parents;
 };
 
 class TraversalKindScope {
   ParentMapContext &Ctx;
   TraversalKind TK = TK_AsIs;
 
 public: