1 files changed, 58 insertions, 9 deletions

diff --git a/include/clang/ASTMatchers/Dynamic/Registry.h b/include/clang/ASTMatchers/Dynamic/Registry.h
index c113c1404ef0..faa9254bc2e7 100644
--- a/include/clang/ASTMatchers/Dynamic/Registry.h
+++ b/include/clang/ASTMatchers/Dynamic/Registry.h
@@ -21,20 +21,69 @@
 #include "clang/ASTMatchers/Dynamic/VariantValue.h"
 #include "clang/Basic/LLVM.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
 
 namespace clang {
 namespace ast_matchers {
 namespace dynamic {
 
+namespace internal {
+class MatcherDescriptor;
+}
+
+typedef const internal::MatcherDescriptor *MatcherCtor;
+
+struct MatcherCompletion {
+  MatcherCompletion() {}
+  MatcherCompletion(StringRef TypedText, StringRef MatcherDecl)
+      : TypedText(TypedText), MatcherDecl(MatcherDecl) {}
+
+  /// \brief The text to type to select this matcher.
+  std::string TypedText;
+
+  /// \brief The "declaration" of the matcher, with type information.
+  std::string MatcherDecl;
+
+  bool operator==(const MatcherCompletion &Other) const {
+    return TypedText == Other.TypedText && MatcherDecl == Other.MatcherDecl;
+  }
+};
+
 class Registry {
 public:
-  /// \brief Construct a matcher from the registry by name.
+  /// \brief Look up a matcher in the registry by name,
+  ///
+  /// \return An opaque value which may be used to refer to the matcher
+  /// constructor, or Optional<MatcherCtor>() if not found.
+  static llvm::Optional<MatcherCtor> lookupMatcherCtor(StringRef MatcherName);
+
+  /// \brief Compute the list of completions for \p Context.
   ///
-  /// Consult the registry of known matchers and construct the appropriate
-  /// matcher by name.
+  /// Each element of \p Context represents a matcher invocation, going from
+  /// outermost to innermost. Elements are pairs consisting of a reference to the
+  /// matcher constructor and the index of the next element in the argument list
+  /// of that matcher (or for the last element, the index of the completion
+  /// point in the argument list). An empty list requests completion for the
+  /// root matcher.
+  ///
+  /// The completions are ordered first by decreasing relevance, then
+  /// alphabetically.  Relevance is determined by how closely the matcher's
+  /// type matches that of the context. For example, if the innermost matcher
+  /// takes a FunctionDecl matcher, the FunctionDecl matchers are returned
+  /// first, followed by the ValueDecl matchers, then NamedDecl, then Decl, then
+  /// polymorphic matchers.
+  ///
+  /// Matchers which are technically convertible to the innermost context but
+  /// which would match either all or no nodes are excluded. For example,
+  /// namedDecl and varDecl are excluded in a FunctionDecl context, because
+  /// those matchers would match respectively all or no nodes in such a context.
+  static std::vector<MatcherCompletion>
+  getCompletions(ArrayRef<std::pair<MatcherCtor, unsigned> > Context);
+
+  /// \brief Construct a matcher from the registry.
   ///
-  /// \param MatcherName The name of the matcher to instantiate.
+  /// \param Ctor The matcher constructor to instantiate.
   ///
   /// \param NameRange The location of the name in the matcher source.
   ///   Useful for error reporting.
@@ -44,10 +93,10 @@ public:
   ///   will return an error.
   ///
   /// \return The matcher object constructed if no error was found.
-  ///   A null matcher if the matcher is not found, or if the number of
-  ///   arguments or argument types do not match the signature.
-  ///   In that case \c Error will contain the description of the error.
-  static VariantMatcher constructMatcher(StringRef MatcherName,
+  ///   A null matcher if the number of arguments or argument types do not match
+  ///   the signature.  In that case \c Error will contain the description of
+  ///   the error.
+  static VariantMatcher constructMatcher(MatcherCtor Ctor,
                                          const SourceRange &NameRange,
                                          ArrayRef<ParserValue> Args,
                                          Diagnostics *Error);
@@ -58,7 +107,7 @@ public:
   /// matcher to the specified \c BindID.
   /// If the matcher is not bindable, it sets an error in \c Error and returns
   /// a null matcher.
-  static VariantMatcher constructBoundMatcher(StringRef MatcherName,
+  static VariantMatcher constructBoundMatcher(MatcherCtor Ctor,
                                               const SourceRange &NameRange,
                                               StringRef BindID,
                                               ArrayRef<ParserValue> Args,