1//===--- MatchConsumer.h - MatchConsumer abstraction ------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8///
9/// \file This file defines the *MatchConsumer* abstraction: a computation over
10/// match results, specifically the `ast_matchers::MatchFinder::MatchResult`
11/// class.
12///
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_CLANG_TOOLING_TRANSFORMER_MATCHCONSUMER_H
16#define LLVM_CLANG_TOOLING_TRANSFORMER_MATCHCONSUMER_H
17
18#include "clang/AST/ASTTypeTraits.h"
19#include "clang/ASTMatchers/ASTMatchFinder.h"
20#include "llvm/ADT/StringRef.h"
21#include "llvm/Support/Errc.h"
22#include "llvm/Support/Error.h"
23
24namespace clang {
25namespace transformer {
26/// A failable computation over nodes bound by AST matchers.
27///
28/// The computation should report any errors though its return value (rather
29/// than terminating the program) to enable usage in interactive scenarios like
30/// clang-query.
31///
32/// This is a central abstraction of the Transformer framework.
33template <typename T>
34using MatchConsumer =
35 std::function<Expected<T>(const ast_matchers::MatchFinder::MatchResult &)>;
36
37/// Creates an error that signals that a `MatchConsumer` expected a certain node
38/// to be bound by AST matchers, but it was not actually bound.
39inline llvm::Error notBoundError(llvm::StringRef Id) {
40 return llvm::make_error<llvm::StringError>(Args: llvm::errc::invalid_argument,
41 Args: "Id not bound: " + Id);
42}
43
44/// Chooses between the two consumers, based on whether \p ID is bound in the
45/// match.
46template <typename T>
47MatchConsumer<T> ifBound(std::string ID, MatchConsumer<T> TrueC,
48 MatchConsumer<T> FalseC) {
49 return [=](const ast_matchers::MatchFinder::MatchResult &Result) {
50 auto &Map = Result.Nodes.getMap();
51 return (Map.find(x: ID) != Map.end() ? TrueC : FalseC)(Result);
52 };
53}
54
55/// A failable computation over nodes bound by AST matchers, with (limited)
56/// reflection via the `toString` method.
57///
58/// The computation should report any errors though its return value (rather
59/// than terminating the program) to enable usage in interactive scenarios like
60/// clang-query.
61///
62/// This is a central abstraction of the Transformer framework. It is a
63/// generalization of `MatchConsumer` and intended to replace it.
64template <typename T> class MatchComputation {
65public:
66 virtual ~MatchComputation() = default;
67
68 /// Evaluates the computation and (potentially) updates the accumulator \c
69 /// Result. \c Result is undefined in the case of an error. `Result` is an
70 /// out parameter to optimize case where the computation involves composing
71 /// the result of sub-computation evaluations.
72 virtual llvm::Error eval(const ast_matchers::MatchFinder::MatchResult &Match,
73 T *Result) const = 0;
74
75 /// Convenience version of `eval`, for the case where the computation is being
76 /// evaluated on its own.
77 llvm::Expected<T> eval(const ast_matchers::MatchFinder::MatchResult &R) const;
78
79 /// Constructs a string representation of the computation, for informational
80 /// purposes. The representation must be deterministic, but is not required to
81 /// be unique.
82 virtual std::string toString() const = 0;
83
84protected:
85 MatchComputation() = default;
86
87 // Since this is an abstract class, copying/assigning only make sense for
88 // derived classes implementing `clone()`.
89 MatchComputation(const MatchComputation &) = default;
90 MatchComputation &operator=(const MatchComputation &) = default;
91};
92
93template <typename T>
94llvm::Expected<T> MatchComputation<T>::eval(
95 const ast_matchers::MatchFinder::MatchResult &R) const {
96 T Output;
97 if (auto Err = eval(R, &Output))
98 return std::move(Err);
99 return Output;
100}
101} // namespace transformer
102} // namespace clang
103#endif // LLVM_CLANG_TOOLING_TRANSFORMER_MATCHCONSUMER_H
104