Add a new AST matcher 'optionally'.

This matcher matches any node and at the same time executes all its
inner matchers to produce any possbile result bindings.

This is useful when a user wants certain supplementary information
that's not always present along with the main match result.

2 files changed, 28 insertions, 0 deletions

diff --git a/clang/lib/ASTMatchers/ASTMatchersInternal.cpp b/clang/lib/ASTMatchers/ASTMatchersInternal.cpp
index 75846ab2d4b..199a6d839e2 100644
--- a/clang/lib/ASTMatchers/ASTMatchersInternal.cpp
+++ b/clang/lib/ASTMatchers/ASTMatchersInternal.cpp
@@ -68,6 +68,11 @@ bool AnyOfVariadicOperator(const ast_type_traits::DynTypedNode &DynNode,
                            BoundNodesTreeBuilder *Builder,
                            ArrayRef<DynTypedMatcher> InnerMatchers);
 
+bool OptionallyVariadicOperator(const ast_type_traits::DynTypedNode &DynNode,
+                                ASTMatchFinder *Finder,
+                                BoundNodesTreeBuilder *Builder,
+                                ArrayRef<DynTypedMatcher> InnerMatchers);
+
 void BoundNodesTreeBuilder::visitMatches(Visitor *ResultVisitor) {
   if (Bindings.empty())
     Bindings.push_back(BoundNodesMap());
@@ -184,6 +189,11 @@ DynTypedMatcher DynTypedMatcher::constructVariadic(
         SupportedKind, RestrictKind,
         new VariadicMatcher<EachOfVariadicOperator>(std::move(InnerMatchers)));
 
+  case VO_Optionally:
+    return DynTypedMatcher(SupportedKind, RestrictKind,
+                           new VariadicMatcher<OptionallyVariadicOperator>(
+                               std::move(InnerMatchers)));
+
   case VO_UnaryNot:
     // FIXME: Implement the Not operator to take a single matcher instead of a
     // vector.
@@ -347,6 +357,20 @@ bool AnyOfVariadicOperator(const ast_type_traits::DynTypedNode &DynNode,
   return false;
 }
 
+bool OptionallyVariadicOperator(const ast_type_traits::DynTypedNode &DynNode,
+                                ASTMatchFinder *Finder,
+                                BoundNodesTreeBuilder *Builder,
+                                ArrayRef<DynTypedMatcher> InnerMatchers) {
+  BoundNodesTreeBuilder Result;
+  for (const DynTypedMatcher &InnerMatcher : InnerMatchers) {
+    BoundNodesTreeBuilder BuilderInner(*Builder);
+    if (InnerMatcher.matches(DynNode, Finder, &BuilderInner))
+      Result.addMatch(BuilderInner);
+  }
+  *Builder = std::move(Result);
+  return true;
+}
+
 inline static
 std::vector<std::string> vectorFromRefs(ArrayRef<const StringRef *> NameRefs) {
   std::vector<std::string> Names;
@@ -797,6 +821,9 @@ const internal::VariadicOperatorMatcherFunc<
 const internal::VariadicOperatorMatcherFunc<
     2, std::numeric_limits<unsigned>::max()>
     allOf = {internal::DynTypedMatcher::VO_AllOf};
+const internal::VariadicOperatorMatcherFunc<
+    1, std::numeric_limits<unsigned>::max()>
+    optionally = {internal::DynTypedMatcher::VO_Optionally};
 const internal::VariadicFunction<internal::Matcher<NamedDecl>, StringRef,
                                  internal::hasAnyNameFunc>
     hasAnyName = {};
diff --git a/clang/lib/ASTMatchers/Dynamic/Registry.cpp b/clang/lib/ASTMatchers/Dynamic/Registry.cpp
index 78b52d6fa2f..475818bc3ae 100644
--- a/clang/lib/ASTMatchers/Dynamic/Registry.cpp
+++ b/clang/lib/ASTMatchers/Dynamic/Registry.cpp
@@ -456,6 +456,7 @@ RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(on);
   REGISTER_MATCHER(onImplicitObjectArgument);
   REGISTER_MATCHER(opaqueValueExpr);
+  REGISTER_MATCHER(optionally);
   REGISTER_MATCHER(parameterCountIs);
   REGISTER_MATCHER(parenExpr);
   REGISTER_MATCHER(parenListExpr);