1 files changed, 683 insertions, 0 deletions
diff --git a/clang/lib/ASTMatchers/Dynamic/Parser.cpp b/clang/lib/ASTMatchers/Dynamic/Parser.cpp
new file mode 100644
index 000000000000..e3b00b46832c
--- /dev/null
+++ b/clang/lib/ASTMatchers/Dynamic/Parser.cpp
@@ -0,0 +1,683 @@
+//===- Parser.cpp - Matcher expression parser -----------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Recursive parser implementation for the matcher expression grammar.
+///
+//===----------------------------------------------------------------------===//
+
+#include "clang/ASTMatchers/Dynamic/Parser.h"
+#include "clang/ASTMatchers/ASTMatchersInternal.h"
+#include "clang/ASTMatchers/Dynamic/Diagnostics.h"
+#include "clang/ASTMatchers/Dynamic/Registry.h"
+#include "clang/Basic/CharInfo.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/ManagedStatic.h"
+#include <algorithm>
+#include <cassert>
+#include <cerrno>
+#include <cstddef>
+#include <cstdlib>
+#include <string>
+#include <utility>
+#include <vector>
+
+namespace clang {
+namespace ast_matchers {
+namespace dynamic {
+
+/// Simple structure to hold information for one token from the parser.
+struct Parser::TokenInfo {
+  /// Different possible tokens.
+  enum TokenKind {
+    TK_Eof,
+    TK_OpenParen,
+    TK_CloseParen,
+    TK_Comma,
+    TK_Period,
+    TK_Literal,
+    TK_Ident,
+    TK_InvalidChar,
+    TK_Error,
+    TK_CodeCompletion
+  };
+
+  /// Some known identifiers.
+  static const char* const ID_Bind;
+
+  TokenInfo() = default;
+
+  StringRef Text;
+  TokenKind Kind = TK_Eof;
+  SourceRange Range;
+  VariantValue Value;
+};
+
+const char* const Parser::TokenInfo::ID_Bind = "bind";
+
+/// Simple tokenizer for the parser.
+class Parser::CodeTokenizer {
+public:
+  explicit CodeTokenizer(StringRef MatcherCode, Diagnostics *Error)
+      : Code(MatcherCode), StartOfLine(MatcherCode), Error(Error) {
+    NextToken = getNextToken();
+  }
+
+  CodeTokenizer(StringRef MatcherCode, Diagnostics *Error,
+                unsigned CodeCompletionOffset)
+      : Code(MatcherCode), StartOfLine(MatcherCode), Error(Error),
+        CodeCompletionLocation(MatcherCode.data() + CodeCompletionOffset) {
+    NextToken = getNextToken();
+  }
+
+  /// Returns but doesn't consume the next token.
+  const TokenInfo &peekNextToken() const { return NextToken; }
+
+  /// Consumes and returns the next token.
+  TokenInfo consumeNextToken() {
+    TokenInfo ThisToken = NextToken;
+    NextToken = getNextToken();
+    return ThisToken;
+  }
+
+  TokenInfo::TokenKind nextTokenKind() const { return NextToken.Kind; }
+
+private:
+  TokenInfo getNextToken() {
+    consumeWhitespace();
+    TokenInfo Result;
+    Result.Range.Start = currentLocation();
+
+    if (CodeCompletionLocation && CodeCompletionLocation <= Code.data()) {
+      Result.Kind = TokenInfo::TK_CodeCompletion;
+      Result.Text = StringRef(CodeCompletionLocation, 0);
+      CodeCompletionLocation = nullptr;
+      return Result;
+    }
+
+    if (Code.empty()) {
+      Result.Kind = TokenInfo::TK_Eof;
+      Result.Text = "";
+      return Result;
+    }
+
+    switch (Code[0]) {
+    case '#':
+      Result.Kind = TokenInfo::TK_Eof;
+      Result.Text = "";
+      return Result;
+    case ',':
+      Result.Kind = TokenInfo::TK_Comma;
+      Result.Text = Code.substr(0, 1);
+      Code = Code.drop_front();
+      break;
+    case '.':
+      Result.Kind = TokenInfo::TK_Period;
+      Result.Text = Code.substr(0, 1);
+      Code = Code.drop_front();
+      break;
+    case '(':
+      Result.Kind = TokenInfo::TK_OpenParen;
+      Result.Text = Code.substr(0, 1);
+      Code = Code.drop_front();
+      break;
+    case ')':
+      Result.Kind = TokenInfo::TK_CloseParen;
+      Result.Text = Code.substr(0, 1);
+      Code = Code.drop_front();
+      break;
+
+    case '"':
+    case '\'':
+      // Parse a string literal.
+      consumeStringLiteral(&Result);
+      break;
+
+    case '0': case '1': case '2': case '3': case '4':
+    case '5': case '6': case '7': case '8': case '9':
+      // Parse an unsigned and float literal.
+      consumeNumberLiteral(&Result);
+      break;
+
+    default:
+      if (isAlphanumeric(Code[0])) {
+        // Parse an identifier
+        size_t TokenLength = 1;
+        while (true) {
+          // A code completion location in/immediately after an identifier will
+          // cause the portion of the identifier before the code completion
+          // location to become a code completion token.
+          if (CodeCompletionLocation == Code.data() + TokenLength) {
+            CodeCompletionLocation = nullptr;
+            Result.Kind = TokenInfo::TK_CodeCompletion;
+            Result.Text = Code.substr(0, TokenLength);
+            Code = Code.drop_front(TokenLength);
+            return Result;
+          }
+          if (TokenLength == Code.size() || !isAlphanumeric(Code[TokenLength]))
+            break;
+          ++TokenLength;
+        }
+        if (TokenLength == 4 && Code.startswith("true")) {
+          Result.Kind = TokenInfo::TK_Literal;
+          Result.Value = true;
+        } else if (TokenLength == 5 && Code.startswith("false")) {
+          Result.Kind = TokenInfo::TK_Literal;
+          Result.Value = false;
+        } else {
+          Result.Kind = TokenInfo::TK_Ident;
+          Result.Text = Code.substr(0, TokenLength);
+        }
+        Code = Code.drop_front(TokenLength);
+      } else {
+        Result.Kind = TokenInfo::TK_InvalidChar;
+        Result.Text = Code.substr(0, 1);
+        Code = Code.drop_front(1);
+      }
+      break;
+    }
+
+    Result.Range.End = currentLocation();
+    return Result;
+  }
+
+  /// Consume an unsigned and float literal.
+  void consumeNumberLiteral(TokenInfo *Result) {
+    bool isFloatingLiteral = false;
+    unsigned Length = 1;
+    if (Code.size() > 1) {
+      // Consume the 'x' or 'b' radix modifier, if present.
+      switch (toLowercase(Code[1])) {
+      case 'x': case 'b': Length = 2;
+      }
+    }
+    while (Length < Code.size() && isHexDigit(Code[Length]))
+      ++Length;
+
+    // Try to recognize a floating point literal.
+    while (Length < Code.size()) {
+      char c = Code[Length];
+      if (c == '-' || c == '+' || c == '.' || isHexDigit(c)) {
+        isFloatingLiteral = true;
+        Length++;
+      } else {
+        break;
+      }
+    }
+
+    Result->Text = Code.substr(0, Length);
+    Code = Code.drop_front(Length);
+
+    if (isFloatingLiteral) {
+      char *end;
+      errno = 0;
+      std::string Text = Result->Text.str();
+      double doubleValue = strtod(Text.c_str(), &end);
+      if (*end == 0 && errno == 0) {
+        Result->Kind = TokenInfo::TK_Literal;
+        Result->Value = doubleValue;
+        return;
+      }
+    } else {
+      unsigned Value;
+      if (!Result->Text.getAsInteger(0, Value)) {
+        Result->Kind = TokenInfo::TK_Literal;
+        Result->Value = Value;
+        return;
+      }
+    }
+
+    SourceRange Range;
+    Range.Start = Result->Range.Start;
+    Range.End = currentLocation();
+    Error->addError(Range, Error->ET_ParserNumberError) << Result->Text;
+    Result->Kind = TokenInfo::TK_Error;
+  }
+
+  /// Consume a string literal.
+  ///
+  /// \c Code must be positioned at the start of the literal (the opening
+  /// quote). Consumed until it finds the same closing quote character.
+  void consumeStringLiteral(TokenInfo *Result) {
+    bool InEscape = false;
+    const char Marker = Code[0];
+    for (size_t Length = 1, Size = Code.size(); Length != Size; ++Length) {
+      if (InEscape) {
+        InEscape = false;
+        continue;
+      }
+      if (Code[Length] == '\\') {
+        InEscape = true;
+        continue;
+      }
+      if (Code[Length] == Marker) {
+        Result->Kind = TokenInfo::TK_Literal;
+        Result->Text = Code.substr(0, Length + 1);
+        Result->Value = Code.substr(1, Length - 1);
+        Code = Code.drop_front(Length + 1);
+        return;
+      }
+    }
+
+    StringRef ErrorText = Code;
+    Code = Code.drop_front(Code.size());
+    SourceRange Range;
+    Range.Start = Result->Range.Start;
+    Range.End = currentLocation();
+    Error->addError(Range, Error->ET_ParserStringError) << ErrorText;
+    Result->Kind = TokenInfo::TK_Error;
+  }
+
+  /// Consume all leading whitespace from \c Code.
+  void consumeWhitespace() {
+    while (!Code.empty() && isWhitespace(Code[0])) {
+      if (Code[0] == '\n') {
+        ++Line;
+        StartOfLine = Code.drop_front();
+      }
+      Code = Code.drop_front();
+    }
+  }
+
+  SourceLocation currentLocation() {
+    SourceLocation Location;
+    Location.Line = Line;
+    Location.Column = Code.data() - StartOfLine.data() + 1;
+    return Location;
+  }
+
+  StringRef Code;
+  StringRef StartOfLine;
+  unsigned Line = 1;
+  Diagnostics *Error;
+  TokenInfo NextToken;
+  const char *CodeCompletionLocation = nullptr;
+};
+
+Parser::Sema::~Sema() = default;
+
+std::vector<ArgKind> Parser::Sema::getAcceptedCompletionTypes(
+    llvm::ArrayRef<std::pair<MatcherCtor, unsigned>> Context) {
+  return {};
+}
+
+std::vector<MatcherCompletion>
+Parser::Sema::getMatcherCompletions(llvm::ArrayRef<ArgKind> AcceptedTypes) {
+  return {};
+}
+
+struct Parser::ScopedContextEntry {
+  Parser *P;
+
+  ScopedContextEntry(Parser *P, MatcherCtor C) : P(P) {
+    P->ContextStack.push_back(std::make_pair(C, 0u));
+  }
+
+  ~ScopedContextEntry() {
+    P->ContextStack.pop_back();
+  }
+
+  void nextArg() {
+    ++P->ContextStack.back().second;
+  }
+};
+
+/// Parse expressions that start with an identifier.
+///
+/// This function can parse named values and matchers.
+/// In case of failure it will try to determine the user's intent to give
+/// an appropriate error message.
+bool Parser::parseIdentifierPrefixImpl(VariantValue *Value) {
+  const TokenInfo NameToken = Tokenizer->consumeNextToken();
+
+  if (Tokenizer->nextTokenKind() != TokenInfo::TK_OpenParen) {
+    // Parse as a named value.
+    if (const VariantValue NamedValue =
+            NamedValues ? NamedValues->lookup(NameToken.Text)
+                        : VariantValue()) {
+
+      if (Tokenizer->nextTokenKind() != TokenInfo::TK_Period) {
+        *Value = NamedValue;
+        return true;
+      }
+
+      std::string BindID;
+      if (!parseBindID(BindID))
+        return false;
+
+      assert(NamedValue.isMatcher());
+      llvm::Optional<DynTypedMatcher> Result =
+          NamedValue.getMatcher().getSingleMatcher();
+      if (Result.hasValue()) {
+        llvm::Optional<DynTypedMatcher> Bound = Result->tryBind(BindID);
+        if (Bound.hasValue()) {
+          *Value = VariantMatcher::SingleMatcher(*Bound);
+          return true;
+        }
+      }
+      return false;
+    }
+    // If the syntax is correct and the name is not a matcher either, report
+    // unknown named value.
+    if ((Tokenizer->nextTokenKind() == TokenInfo::TK_Comma ||
+         Tokenizer->nextTokenKind() == TokenInfo::TK_CloseParen ||
+         Tokenizer->nextTokenKind() == TokenInfo::TK_Eof) &&
+        !S->lookupMatcherCtor(NameToken.Text)) {
+      Error->addError(NameToken.Range, Error->ET_RegistryValueNotFound)
+          << NameToken.Text;
+      return false;
+    }
+    // Otherwise, fallback to the matcher parser.
+  }
+
+  // Parse as a matcher expression.
+  return parseMatcherExpressionImpl(NameToken, Value);
+}
+
+bool Parser::parseBindID(std::string &BindID) {
+  // Parse .bind("foo")
+  assert(Tokenizer->peekNextToken().Kind == TokenInfo::TK_Period);
+  Tokenizer->consumeNextToken(); // consume the period.
+  const TokenInfo BindToken = Tokenizer->consumeNextToken();
+  if (BindToken.Kind == TokenInfo::TK_CodeCompletion) {
+    addCompletion(BindToken, MatcherCompletion("bind(\"", "bind", 1));
+    return false;
+  }
+
+  const TokenInfo OpenToken = Tokenizer->consumeNextToken();
+  const TokenInfo IDToken = Tokenizer->consumeNextToken();
+  const TokenInfo CloseToken = Tokenizer->consumeNextToken();
+
+  // TODO: We could use different error codes for each/some to be more
+  //       explicit about the syntax error.
+  if (BindToken.Kind != TokenInfo::TK_Ident ||
+      BindToken.Text != TokenInfo::ID_Bind) {
+    Error->addError(BindToken.Range, Error->ET_ParserMalformedBindExpr);
+    return false;
+  }
+  if (OpenToken.Kind != TokenInfo::TK_OpenParen) {
+    Error->addError(OpenToken.Range, Error->ET_ParserMalformedBindExpr);
+    return false;
+  }
+  if (IDToken.Kind != TokenInfo::TK_Literal || !IDToken.Value.isString()) {
+    Error->addError(IDToken.Range, Error->ET_ParserMalformedBindExpr);
+    return false;
+  }
+  if (CloseToken.Kind != TokenInfo::TK_CloseParen) {
+    Error->addError(CloseToken.Range, Error->ET_ParserMalformedBindExpr);
+    return false;
+  }
+  BindID = IDToken.Value.getString();
+  return true;
+}
+
+/// Parse and validate a matcher expression.
+/// \return \c true on success, in which case \c Value has the matcher parsed.
+///   If the input is malformed, or some argument has an error, it
+///   returns \c false.
+bool Parser::parseMatcherExpressionImpl(const TokenInfo &NameToken,
+                                        VariantValue *Value) {
+  assert(NameToken.Kind == TokenInfo::TK_Ident);
+  const TokenInfo OpenToken = Tokenizer->consumeNextToken();
+  if (OpenToken.Kind != TokenInfo::TK_OpenParen) {
+    Error->addError(OpenToken.Range, Error->ET_ParserNoOpenParen)
+        << OpenToken.Text;
+    return false;
+  }
+
+  llvm::Optional<MatcherCtor> Ctor = S->lookupMatcherCtor(NameToken.Text);
+
+  if (!Ctor) {
+    Error->addError(NameToken.Range, Error->ET_RegistryMatcherNotFound)
+        << NameToken.Text;
+    // Do not return here. We need to continue to give completion suggestions.
+  }
+
+  std::vector<ParserValue> Args;
+  TokenInfo EndToken;
+
+  {
+    ScopedContextEntry SCE(this, Ctor ? *Ctor : nullptr);
+
+    while (Tokenizer->nextTokenKind() != TokenInfo::TK_Eof) {
+      if (Tokenizer->nextTokenKind() == TokenInfo::TK_CloseParen) {
+        // End of args.
+        EndToken = Tokenizer->consumeNextToken();
+        break;
+      }
+      if (!Args.empty()) {
+        // We must find a , token to continue.
+        const TokenInfo CommaToken = Tokenizer->consumeNextToken();
+        if (CommaToken.Kind != TokenInfo::TK_Comma) {
+          Error->addError(CommaToken.Range, Error->ET_ParserNoComma)
+              << CommaToken.Text;
+          return false;
+        }
+      }
+
+      Diagnostics::Context Ctx(Diagnostics::Context::MatcherArg, Error,
+                               NameToken.Text, NameToken.Range,
+                               Args.size() + 1);
+      ParserValue ArgValue;
+      ArgValue.Text = Tokenizer->peekNextToken().Text;
+      ArgValue.Range = Tokenizer->peekNextToken().Range;
+      if (!parseExpressionImpl(&ArgValue.Value)) {
+        return false;
+      }
+
+      Args.push_back(ArgValue);
+      SCE.nextArg();
+    }
+  }
+
+  if (EndToken.Kind == TokenInfo::TK_Eof) {
+    Error->addError(OpenToken.Range, Error->ET_ParserNoCloseParen);
+    return false;
+  }
+
+  std::string BindID;
+  if (Tokenizer->peekNextToken().Kind == TokenInfo::TK_Period) {
+    if (!parseBindID(BindID))
+      return false;
+  }
+
+  if (!Ctor)
+    return false;
+
+  // Merge the start and end infos.
+  Diagnostics::Context Ctx(Diagnostics::Context::ConstructMatcher, Error,
+                           NameToken.Text, NameToken.Range);
+  SourceRange MatcherRange = NameToken.Range;
+  MatcherRange.End = EndToken.Range.End;
+  VariantMatcher Result = S->actOnMatcherExpression(
+      *Ctor, MatcherRange, BindID, Args, Error);
+  if (Result.isNull()) return false;
+
+  *Value = Result;
+  return true;
+}
+
+// If the prefix of this completion matches the completion token, add it to
+// Completions minus the prefix.
+void Parser::addCompletion(const TokenInfo &CompToken,
+                           const MatcherCompletion& Completion) {
+  if (StringRef(Completion.TypedText).startswith(CompToken.Text) &&
+      Completion.Specificity > 0) {
+    Completions.emplace_back(Completion.TypedText.substr(CompToken.Text.size()),
+                             Completion.MatcherDecl, Completion.Specificity);
+  }
+}
+
+std::vector<MatcherCompletion> Parser::getNamedValueCompletions(
+    ArrayRef<ArgKind> AcceptedTypes) {
+  if (!NamedValues) return std::vector<MatcherCompletion>();
+  std::vector<MatcherCompletion> Result;
+  for (const auto &Entry : *NamedValues) {
+    unsigned Specificity;
+    if (Entry.getValue().isConvertibleTo(AcceptedTypes, &Specificity)) {
+      std::string Decl =
+          (Entry.getValue().getTypeAsString() + " " + Entry.getKey()).str();
+      Result.emplace_back(Entry.getKey(), Decl, Specificity);
+    }
+  }
+  return Result;
+}
+
+void Parser::addExpressionCompletions() {
+  const TokenInfo CompToken = Tokenizer->consumeNextToken();
+  assert(CompToken.Kind == TokenInfo::TK_CodeCompletion);
+
+  // We cannot complete code if there is an invalid element on the context
+  // stack.
+  for (ContextStackTy::iterator I = ContextStack.begin(),
+                                E = ContextStack.end();
+       I != E; ++I) {
+    if (!I->first)
+      return;
+  }
+
+  auto AcceptedTypes = S->getAcceptedCompletionTypes(ContextStack);
+  for (const auto &Completion : S->getMatcherCompletions(AcceptedTypes)) {
+    addCompletion(CompToken, Completion);
+  }
+
+  for (const auto &Completion : getNamedValueCompletions(AcceptedTypes)) {
+    addCompletion(CompToken, Completion);
+  }
+}
+
+/// Parse an <Expression>
+bool Parser::parseExpressionImpl(VariantValue *Value) {
+  switch (Tokenizer->nextTokenKind()) {
+  case TokenInfo::TK_Literal:
+    *Value = Tokenizer->consumeNextToken().Value;
+    return true;
+
+  case TokenInfo::TK_Ident:
+    return parseIdentifierPrefixImpl(Value);
+
+  case TokenInfo::TK_CodeCompletion:
+    addExpressionCompletions();
+    return false;
+
+  case TokenInfo::TK_Eof:
+    Error->addError(Tokenizer->consumeNextToken().Range,
+                    Error->ET_ParserNoCode);
+    return false;
+
+  case TokenInfo::TK_Error:
+    // This error was already reported by the tokenizer.
+    return false;
+
+  case TokenInfo::TK_OpenParen:
+  case TokenInfo::TK_CloseParen:
+  case TokenInfo::TK_Comma:
+  case TokenInfo::TK_Period:
+  case TokenInfo::TK_InvalidChar:
+    const TokenInfo Token = Tokenizer->consumeNextToken();
+    Error->addError(Token.Range, Error->ET_ParserInvalidToken) << Token.Text;
+    return false;
+  }
+
+  llvm_unreachable("Unknown token kind.");
+}
+
+static llvm::ManagedStatic<Parser::RegistrySema> DefaultRegistrySema;
+
+Parser::Parser(CodeTokenizer *Tokenizer, Sema *S,
+               const NamedValueMap *NamedValues, Diagnostics *Error)
+    : Tokenizer(Tokenizer), S(S ? S : &*DefaultRegistrySema),
+      NamedValues(NamedValues), Error(Error) {}
+
+Parser::RegistrySema::~RegistrySema() = default;
+
+llvm::Optional<MatcherCtor>
+Parser::RegistrySema::lookupMatcherCtor(StringRef MatcherName) {
+  return Registry::lookupMatcherCtor(MatcherName);
+}
+
+VariantMatcher Parser::RegistrySema::actOnMatcherExpression(
+    MatcherCtor Ctor, SourceRange NameRange, StringRef BindID,
+    ArrayRef<ParserValue> Args, Diagnostics *Error) {
+  if (BindID.empty()) {
+    return Registry::constructMatcher(Ctor, NameRange, Args, Error);
+  } else {
+    return Registry::constructBoundMatcher(Ctor, NameRange, BindID, Args,
+                                           Error);
+  }
+}
+
+std::vector<ArgKind> Parser::RegistrySema::getAcceptedCompletionTypes(
+    ArrayRef<std::pair<MatcherCtor, unsigned>> Context) {
+  return Registry::getAcceptedCompletionTypes(Context);
+}
+
+std::vector<MatcherCompletion> Parser::RegistrySema::getMatcherCompletions(
+    ArrayRef<ArgKind> AcceptedTypes) {
+  return Registry::getMatcherCompletions(AcceptedTypes);
+}
+
+bool Parser::parseExpression(StringRef Code, Sema *S,
+                             const NamedValueMap *NamedValues,
+                             VariantValue *Value, Diagnostics *Error) {
+  CodeTokenizer Tokenizer(Code, Error);
+  if (!Parser(&Tokenizer, S, NamedValues, Error).parseExpressionImpl(Value))
+    return false;
+  if (Tokenizer.peekNextToken().Kind != TokenInfo::TK_Eof) {
+    Error->addError(Tokenizer.peekNextToken().Range,
+                    Error->ET_ParserTrailingCode);
+    return false;
+  }
+  return true;
+}
+
+std::vector<MatcherCompletion>
+Parser::completeExpression(StringRef Code, unsigned CompletionOffset, Sema *S,
+                           const NamedValueMap *NamedValues) {
+  Diagnostics Error;
+  CodeTokenizer Tokenizer(Code, &Error, CompletionOffset);
+  Parser P(&Tokenizer, S, NamedValues, &Error);
+  VariantValue Dummy;
+  P.parseExpressionImpl(&Dummy);
+
+  // Sort by specificity, then by name.
+  llvm::sort(P.Completions,
+             [](const MatcherCompletion &A, const MatcherCompletion &B) {
+               if (A.Specificity != B.Specificity)
+                 return A.Specificity > B.Specificity;
+               return A.TypedText < B.TypedText;
+             });
+
+  return P.Completions;
+}
+
+llvm::Optional<DynTypedMatcher>
+Parser::parseMatcherExpression(StringRef Code, Sema *S,
+                               const NamedValueMap *NamedValues,
+                               Diagnostics *Error) {
+  VariantValue Value;
+  if (!parseExpression(Code, S, NamedValues, &Value, Error))
+    return llvm::Optional<DynTypedMatcher>();
+  if (!Value.isMatcher()) {
+    Error->addError(SourceRange(), Error->ET_ParserNotAMatcher);
+    return llvm::Optional<DynTypedMatcher>();
+  }
+  llvm::Optional<DynTypedMatcher> Result =
+      Value.getMatcher().getSingleMatcher();
+  if (!Result.hasValue()) {
+    Error->addError(SourceRange(), Error->ET_ParserOverloadedType)
+        << Value.getTypeAsString();
+  }
+  return Result;
+}
+
+} // namespace dynamic
+} // namespace ast_matchers
+} // namespace clang