Tooling/Transformer/MatchConsumer.h

0001 //===--- MatchConsumer.h - MatchConsumer abstraction ------------*- C++ -*-===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008 ///
0009 /// \file This file defines the *MatchConsumer* abstraction: a computation over
0010 /// match results, specifically the `ast_matchers::MatchFinder::MatchResult`
0011 /// class.
0012 ///
0013 //===----------------------------------------------------------------------===//
0014
0015 #ifndef LLVM_CLANG_TOOLING_TRANSFORMER_MATCHCONSUMER_H
0016 #define LLVM_CLANG_TOOLING_TRANSFORMER_MATCHCONSUMER_H
0017
0018 #include "clang/AST/ASTTypeTraits.h"
0019 #include "clang/ASTMatchers/ASTMatchFinder.h"
0020 #include "llvm/ADT/StringRef.h"
0021 #include "llvm/Support/Errc.h"
0022 #include "llvm/Support/Error.h"
0023
0024 namespace clang {
0025 namespace transformer {
0026 /// A failable computation over nodes bound by AST matchers.
0027 ///
0028 /// The computation should report any errors though its return value (rather
0029 /// than terminating the program) to enable usage in interactive scenarios like
0030 /// clang-query.
0031 ///
0032 /// This is a central abstraction of the Transformer framework.
0033 template <typename T>
0034 using MatchConsumer =
0035     std::function<Expected<T>(const ast_matchers::MatchFinder::MatchResult &)>;
0036
0037 /// Creates an error that signals that a `MatchConsumer` expected a certain node
0038 /// to be bound by AST matchers, but it was not actually bound.
0039 inline llvm::Error notBoundError(llvm::StringRef Id) {
0040   return llvm::make_error<llvm::StringError>(llvm::errc::invalid_argument,
0041                                              "Id not bound: " + Id);
0042 }
0043
0044 /// Chooses between the two consumers, based on whether \p ID is bound in the
0045 /// match.
0046 template <typename T>
0047 MatchConsumer<T> ifBound(std::string ID, MatchConsumer<T> TrueC,
0048                          MatchConsumer<T> FalseC) {
0049   return [=](const ast_matchers::MatchFinder::MatchResult &Result) {
0050     auto &Map = Result.Nodes.getMap();
0051     return (Map.find(ID) != Map.end() ? TrueC : FalseC)(Result);
0052   };
0053 }
0054
0055 /// A failable computation over nodes bound by AST matchers, with (limited)
0056 /// reflection via the `toString` method.
0057 ///
0058 /// The computation should report any errors though its return value (rather
0059 /// than terminating the program) to enable usage in interactive scenarios like
0060 /// clang-query.
0061 ///
0062 /// This is a central abstraction of the Transformer framework. It is a
0063 /// generalization of `MatchConsumer` and intended to replace it.
0064 template <typename T> class MatchComputation {
0065 public:
0066   virtual ~MatchComputation() = default;
0067
0068   /// Evaluates the computation and (potentially) updates the accumulator \c
0069   /// Result.  \c Result is undefined in the case of an error. `Result` is an
0070   /// out parameter to optimize case where the computation involves composing
0071   /// the result of sub-computation evaluations.
0072   virtual llvm::Error eval(const ast_matchers::MatchFinder::MatchResult &Match,
0073                            T *Result) const = 0;
0074
0075   /// Convenience version of `eval`, for the case where the computation is being
0076   /// evaluated on its own.
0077   llvm::Expected<T> eval(const ast_matchers::MatchFinder::MatchResult &R) const;
0078
0079   /// Constructs a string representation of the computation, for informational
0080   /// purposes. The representation must be deterministic, but is not required to
0081   /// be unique.
0082   virtual std::string toString() const = 0;
0083
0084 protected:
0085   MatchComputation() = default;
0086
0087   // Since this is an abstract class, copying/assigning only make sense for
0088   // derived classes implementing `clone()`.
0089   MatchComputation(const MatchComputation &) = default;
0090   MatchComputation &operator=(const MatchComputation &) = default;
0091 };
0092
0093 template <typename T>
0094 llvm::Expected<T> MatchComputation<T>::eval(
0095     const ast_matchers::MatchFinder::MatchResult &R) const {
0096   T Output;
0097   if (auto Err = eval(R, &Output))
0098     return std::move(Err);
0099   return Output;
0100 }
0101 } // namespace transformer
0102 } // namespace clang
0103 #endif // LLVM_CLANG_TOOLING_TRANSFORMER_MATCHCONSUMER_H