docs: Convert some docs to reST.
Converts:
LanguageExtensions
LibASTMatchers
LibTooling
PCHInternals
ThreadSanitizer
Tooling
Patch by Mykhailo Pustovit!
(with minor edits by Dmitri Gribenko and Sean Silva)
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@170048 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/LibASTMatchers.rst b/docs/LibASTMatchers.rst
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+======================
+Matching the Clang AST
+======================
+
+This document explains how to use Clang's LibASTMatchers to match interesting
+nodes of the AST and execute code that uses the matched nodes. Combined with
+:doc:`LibTooling`, LibASTMatchers helps to write code-to-code transformation
+tools or query tools.
+
+We assume basic knowledge about the Clang AST. See the `Introduction to the
+Clang AST <IntroductionToTheClangAST.html>`_ if you want to learn more about
+how the AST is structured.
+
+.. FIXME: create tutorial and link to the tutorial
+
+Introduction
+------------
+
+LibASTMatchers provides a domain specific language to create predicates on
+Clang's AST. This DSL is written in and can be used from C++, allowing users
+to write a single program to both match AST nodes and access the node's C++
+interface to extract attributes, source locations, or any other information
+provided on the AST level.
+
+AST matchers are predicates on nodes in the AST. Matchers are created by
+calling creator functions that allow building up a tree of matchers, where
+inner matchers are used to make the match more specific.
+
+For example, to create a matcher that matches all class or union declarations
+in the AST of a translation unit, you can call `recordDecl()
+<LibASTMatchersReference.html#recordDecl0Anchor>`_. To narrow the match down,
+for example to find all class or union declarations with the name "``Foo``",
+insert a `hasName <LibASTMatchersReference.html#hasName0Anchor>`_ matcher: the
+call ``recordDecl(hasName("Foo"))`` returns a matcher that matches classes or
+unions that are named "``Foo``", in any namespace. By default, matchers that
+accept multiple inner matchers use an implicit `allOf()
+<LibASTMatchersReference.html#allOf0Anchor>`_. This allows further narrowing
+down the match, for example to match all classes that are derived from
+"``Bar``": ``recordDecl(hasName("Foo"), isDerivedFrom("Bar"))``.
+
+How to create a matcher
+-----------------------
+
+With more than a thousand classes in the Clang AST, one can quickly get lost
+when trying to figure out how to create a matcher for a specific pattern. This
+section will teach you how to use a rigorous step-by-step pattern to build the
+matcher you are interested in. Note that there will always be matchers missing
+for some part of the AST. See the section about :ref:`how to write your own
+AST matchers <astmatchers-writing>` later in this document.
+
+.. FIXME: why is it linking back to the same section?!
+
+The precondition to using the matchers is to understand how the AST for what you
+want to match looks like. The
+`Introduction to the Clang AST <IntroductionToTheClangAST.html>`_ teaches you
+how to dump a translation unit's AST into a human readable format.
+
+.. FIXME: Introduce link to ASTMatchersTutorial.html
+.. FIXME: Introduce link to ASTMatchersCookbook.html
+
+In general, the strategy to create the right matchers is:
+
+#. Find the outermost class in Clang's AST you want to match.
+#. Look at the `AST Matcher Reference <LibASTMatchersReference.html>`_ for
+ matchers that either match the node you're interested in or narrow down
+ attributes on the node.
+#. Create your outer match expression. Verify that it works as expected.
+#. Examine the matchers for what the next inner node you want to match is.
+#. Repeat until the matcher is finished.
+
+.. _astmatchers-bind:
+
+Binding nodes in match expressions
+----------------------------------
+
+Matcher expressions allow you to specify which parts of the AST are interesting
+for a certain task. Often you will want to then do something with the nodes
+that were matched, like building source code transformations.
+
+To that end, matchers that match specific AST nodes (so called node matchers)
+are bindable; for example, ``recordDecl(hasName("MyClass")).bind("id")`` will
+bind the matched ``recordDecl`` node to the string "``id``", to be later
+retrieved in the `match callback
+<http://clang.llvm.org/doxygen/classclang_1_1ast__matchers_1_1MatchFinder_1_1MatchCallback.html>`_.
+
+.. FIXME: Introduce link to ASTMatchersTutorial.html
+.. FIXME: Introduce link to ASTMatchersCookbook.html
+
+Writing your own matchers
+-------------------------
+
+There are multiple different ways to define a matcher, depending on its type
+and flexibility.
+
+``VariadicDynCastAllOfMatcher<Base, Derived>``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Those match all nodes of type *Base* if they can be dynamically casted to
+*Derived*. The names of those matchers are nouns, which closely resemble
+*Derived*. ``VariadicDynCastAllOfMatchers`` are the backbone of the matcher
+hierarchy. Most often, your match expression will start with one of them, and
+you can :ref:`bind <astmatchers-bind>` the node they represent to ids for later
+processing.
+
+``VariadicDynCastAllOfMatchers`` are callable classes that model variadic
+template functions in C++03. They take an aribtrary number of
+``Matcher<Derived>`` and return a ``Matcher<Base>``.
+
+``AST_MATCHER_P(Type, Name, ParamType, Param)``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Most matcher definitions use the matcher creation macros. Those define both
+the matcher of type ``Matcher<Type>`` itself, and a matcher-creation function
+named *Name* that takes a parameter of type *ParamType* and returns the
+corresponding matcher.
+
+There are multiple matcher definition macros that deal with polymorphic return
+values and different parameter counts. See `ASTMatchersMacros.h
+<http://clang.llvm.org/doxygen/ASTMatchersMacros_8h.html>`_.
+
+.. _astmatchers-writing:
+
+Matcher creation functions
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Matchers are generated by nesting calls to matcher creation functions. Most of
+the time those functions are either created by using
+``VariadicDynCastAllOfMatcher`` or the matcher creation macros (see below).
+The free-standing functions are an indication that this matcher is just a
+combination of other matchers, as is for example the case with `callee
+<LibASTMatchersReference.html#callee1Anchor>`_.
+
+.. FIXME: "... macros (see below)" --- there isn't anything below
+