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//===--- RewriteRule.h - RewriteRule class ----------------------*- C++ -*-===//

//

// 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

///  Defines the RewriteRule class and related functions for creating,

///  modifying and interpreting RewriteRules.

///

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_TOOLING_TRANSFORMER_REWRITERULE_H

#define LLVM_CLANG_TOOLING_TRANSFORMER_REWRITERULE_H

#include "clang/ASTMatchers/ASTMatchFinder.h"

#include "clang/ASTMatchers/ASTMatchers.h"

#include "clang/ASTMatchers/ASTMatchersInternal.h"

#include "clang/Tooling/Refactoring/AtomicChange.h"

#include "clang/Tooling/Transformer/MatchConsumer.h"

#include "clang/Tooling/Transformer/RangeSelector.h"

#include "llvm/ADT/Any.h"

#include "llvm/ADT/STLExtras.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/Support/Error.h"

#include <functional>

#include <string>

#include <utility>

namespace clang {

namespace transformer {

// Specifies how to interpret an edit.

enum class EditKind {

  // Edits a source range in the file.

  Range,

  // Inserts an include in the file. The `Replacement` field is the name of the

  // newly included file.

  AddInclude,

};

/// A concrete description of a source edit, represented by a character range in

/// the source to be replaced and a corresponding replacement string.

struct Edit {

  EditKind Kind = EditKind::Range;

  CharSourceRange Range;

  std::string Replacement;

  std::string Note;

  llvm::Any Metadata;

};

/// Format of the path in an include directive -- angle brackets or quotes.

enum class IncludeFormat {

  Quoted,

  Angled,

};

/// Maps a match result to a list of concrete edits (with possible

/// failure). This type is a building block of rewrite rules, but users will

/// generally work in terms of `ASTEdit`s (below) rather than directly in terms

/// of `EditGenerator`.

using EditGenerator = MatchConsumer<llvm::SmallVector<Edit, 1>>;

template <typename T> using Generator = std::shared_ptr<MatchComputation<T>>;

using TextGenerator = Generator<std::string>;

using AnyGenerator = MatchConsumer<llvm::Any>;

// Description of a source-code edit, expressed in terms of an AST node.

// Includes: an ID for the (bound) node, a selector for source related to the

// node, a replacement and, optionally, an explanation for the edit.

//

// * Target: the source code impacted by the rule. This identifies an AST node,

//   or part thereof (\c Part), whose source range indicates the extent of the

//   replacement applied by the replacement term.  By default, the extent is the

//   node matched by the pattern term (\c NodePart::Node). Target's are typed

//   (\c Kind), which guides the determination of the node extent.

//

// * Replacement: a function that produces a replacement string for the target,

//   based on the match result.

//

// * Note: (optional) a note specifically for this edit, potentially referencing

//   elements of the match.  This will be displayed to the user, where possible;

//   for example, in clang-tidy diagnostics.  Use of notes should be rare --

//   explanations of the entire rewrite should be set in the rule

//   (`RewriteRule::Explanation`) instead.  Notes serve the rare cases wherein

//   edit-specific diagnostics are required.

//

// `ASTEdit` should be built using the `change` convenience functions. For

// example,

// \code

//   changeTo(name(fun), cat("Frodo"))

// \endcode

// Or, if we use Stencil for the TextGenerator:

// \code

//   using stencil::cat;

//   changeTo(statement(thenNode), cat("{", thenNode, "}"))

//   changeTo(callArgs(call), cat(x, ",", y))

// \endcode

// Or, if you are changing the node corresponding to the rule's matcher, you can

// use the single-argument override of \c change:

// \code

//   changeTo(cat("different_expr"))

// \endcode

struct ASTEdit {

  EditKind Kind = EditKind::Range;

  RangeSelector TargetRange;

  TextGenerator Replacement;

  TextGenerator Note;

  // Not all transformations will want or need to attach metadata and therefore

  // should not be required to do so.

  AnyGenerator Metadata = [](const ast_matchers::MatchFinder::MatchResult &)

      -> llvm::Expected<llvm::Any> {

    return llvm::Expected<llvm::Any>(llvm::Any());

  };

};

/// Generates a single (specified) edit.

EditGenerator edit(ASTEdit E);

/// Lifts a list of `ASTEdit`s into an `EditGenerator`.

///

/// The `EditGenerator` will return an empty vector if any of the edits apply to

/// portions of the source that are ineligible for rewriting (certain

/// interactions with macros, for example) and it will fail if any invariants

/// are violated relating to bound nodes in the match.  However, it does not

/// fail in the case of conflicting edits -- conflict handling is left to

/// clients.  We recommend use of the \c AtomicChange or \c Replacements classes

/// for assistance in detecting such conflicts.

EditGenerator editList(llvm::SmallVector<ASTEdit, 1> Edits);

/// Generates no edits.

inline EditGenerator noEdits() { return editList({}); }

/// Generates a single, no-op edit anchored at the start location of the

/// specified range. A `noopEdit` may be preferred over `noEdits` to associate a

/// diagnostic `Explanation` with the rule.

EditGenerator noopEdit(RangeSelector Anchor);

/// Generates a single, no-op edit with the associated note anchored at the

/// start location of the specified range.

ASTEdit note(RangeSelector Anchor, TextGenerator Note);

/// Version of `ifBound` specialized to `ASTEdit`.

inline EditGenerator ifBound(std::string ID, ASTEdit TrueEdit,

                             ASTEdit FalseEdit) {

  return ifBound(std::move(ID), edit(std::move(TrueEdit)),

                 edit(std::move(FalseEdit)));

}

/// Version of `ifBound` that has no "False" branch. If the node is not bound,

/// then no edits are produced.

inline EditGenerator ifBound(std::string ID, ASTEdit TrueEdit) {

  return ifBound(std::move(ID), edit(std::move(TrueEdit)), noEdits());

}

/// Flattens a list of generators into a single generator whose elements are the

/// concatenation of the results of the argument generators.

EditGenerator flattenVector(SmallVector<EditGenerator, 2> Generators);

namespace detail {

/// Helper function to construct an \c EditGenerator. Overloaded for common

/// cases so that user doesn't need to specify which factory function to

/// use. This pattern gives benefits similar to implicit constructors, while

/// maintaing a higher degree of explicitness.

inline EditGenerator injectEdits(ASTEdit E) { return edit(std::move(E)); }

inline EditGenerator injectEdits(EditGenerator G) { return G; }

} // namespace detail

template <typename... Ts> EditGenerator flatten(Ts &&...Edits) {

  return flattenVector({detail::injectEdits(std::forward<Ts>(Edits))...});

}

// Every rewrite rule is triggered by a match against some AST node.

// Transformer guarantees that this ID is bound to the triggering node whenever

// a rewrite rule is applied.

extern const char RootID[];

/// Replaces a portion of the source text with \p Replacement.

ASTEdit changeTo(RangeSelector Target, TextGenerator Replacement);

/// DEPRECATED: use \c changeTo.

inline ASTEdit change(RangeSelector Target, TextGenerator Replacement) {

  return changeTo(std::move(Target), std::move(Replacement));

}

/// Replaces the entirety of a RewriteRule's match with \p Replacement.  For

/// example, to replace a function call, one could write:

/// \code

///   makeRule(callExpr(callee(functionDecl(hasName("foo")))),

///            changeTo(cat("bar()")))

/// \endcode

inline ASTEdit changeTo(TextGenerator Replacement) {

  return changeTo(node(RootID), std::move(Replacement));

}

/// DEPRECATED: use \c changeTo.

inline ASTEdit change(TextGenerator Replacement) {

  return changeTo(std::move(Replacement));

}

/// Inserts \p Replacement before \p S, leaving the source selected by \S

/// unchanged.

inline ASTEdit insertBefore(RangeSelector S, TextGenerator Replacement) {

  return changeTo(before(std::move(S)), std::move(Replacement));

}

/// Inserts \p Replacement after \p S, leaving the source selected by \S

/// unchanged.

inline ASTEdit insertAfter(RangeSelector S, TextGenerator Replacement) {

  return changeTo(after(std::move(S)), std::move(Replacement));

}

/// Removes the source selected by \p S.

ASTEdit remove(RangeSelector S);

/// Adds an include directive for the given header to the file of `Target`. The

/// particular location specified by `Target` is ignored.

ASTEdit addInclude(RangeSelector Target, StringRef Header,

                   IncludeFormat Format = IncludeFormat::Quoted);

/// Adds an include directive for the given header to the file associated with

/// `RootID`. If `RootID` matches inside a macro expansion, will add the

/// directive to the file in which the macro was expanded (as opposed to the

/// file in which the macro is defined).

inline ASTEdit addInclude(StringRef Header,

                          IncludeFormat Format = IncludeFormat::Quoted) {

  return addInclude(expansion(node(RootID)), Header, Format);

}

// FIXME: If `Metadata` returns an `llvm::Expected<T>` the `AnyGenerator` will

// construct an `llvm::Expected<llvm::Any>` where no error is present but the

// `llvm::Any` holds the error. This is unlikely but potentially surprising.

// Perhaps the `llvm::Expected` should be unwrapped, or perhaps this should be a

// compile-time error. No solution here is perfect.

//

// Note: This function template accepts any type callable with a MatchResult

// rather than a `std::function` because the return-type needs to be deduced. If

// it accepted a `std::function<R(MatchResult)>`, lambdas or other callable

// types would not be able to deduce `R`, and users would be forced to specify

// explicitly the type they intended to return by wrapping the lambda at the

// call-site.

template <typename Callable>

inline ASTEdit withMetadata(ASTEdit Edit, Callable Metadata) {

  Edit.Metadata =

      [Gen = std::move(Metadata)](

          const ast_matchers::MatchFinder::MatchResult &R) -> llvm::Any {

    return Gen(R);

  };

  return Edit;

}

/// Assuming that the inner range is enclosed by the outer range, creates

/// precision edits to remove the parts of the outer range that are not included

/// in the inner range.

inline EditGenerator shrinkTo(RangeSelector outer, RangeSelector inner) {

  return editList({remove(enclose(before(outer), before(inner))),

                   remove(enclose(after(inner), after(outer)))});

}

/// Description of a source-code transformation.

//

// A *rewrite rule* describes a transformation of source code. A simple rule

// contains each of the following components:

//

// * Matcher: the pattern term, expressed as clang matchers (with Transformer

//   extensions).

//

// * Edits: a set of Edits to the source code, described with ASTEdits.

//

// However, rules can also consist of (sub)rules, where the first that matches

// is applied and the rest are ignored.  So, the above components together form

// a logical "case" and a rule is a sequence of cases.

//

// Rule cases have an additional, implicit, component: the parameters. These are

// portions of the pattern which are left unspecified, yet bound in the pattern

// so that we can reference them in the edits.

//

// The \c Transformer class can be used to apply the rewrite rule and obtain the

// corresponding replacements.

struct RewriteRuleBase {

  struct Case {

    ast_matchers::internal::DynTypedMatcher Matcher;

    EditGenerator Edits;

  };

  // We expect RewriteRules will most commonly include only one case.

  SmallVector<Case, 1> Cases;

};

/// A source-code transformation with accompanying metadata.

///

/// When a case of the rule matches, the \c Transformer invokes the

/// corresponding metadata generator and provides it alongside the edits.

template <typename MetadataT> struct RewriteRuleWith : RewriteRuleBase {

  SmallVector<Generator<MetadataT>, 1> Metadata;

};

template <> struct RewriteRuleWith<void> : RewriteRuleBase {};

using RewriteRule = RewriteRuleWith<void>;

namespace detail {

RewriteRule makeRule(ast_matchers::internal::DynTypedMatcher M,

                     EditGenerator Edits);

template <typename MetadataT>

RewriteRuleWith<MetadataT> makeRule(ast_matchers::internal::DynTypedMatcher M,

                                    EditGenerator Edits,

                                    Generator<MetadataT> Metadata) {

  RewriteRuleWith<MetadataT> R;

  R.Cases = {{std::move(M), std::move(Edits)}};

  R.Metadata = {std::move(Metadata)};

  return R;

}

inline EditGenerator makeEditGenerator(EditGenerator Edits) { return Edits; }

EditGenerator makeEditGenerator(llvm::SmallVector<ASTEdit, 1> Edits);

EditGenerator makeEditGenerator(ASTEdit Edit);

} // namespace detail

/// Constructs a simple \c RewriteRule. \c Edits can be an \c EditGenerator,

/// multiple \c ASTEdits, or a single \c ASTEdit.

/// @{

template <int &..., typename EditsT>

RewriteRule makeRule(ast_matchers::internal::DynTypedMatcher M,

                     EditsT &&Edits) {

  return detail::makeRule(

      std::move(M), detail::makeEditGenerator(std::forward<EditsT>(Edits)));

}

RewriteRule makeRule(ast_matchers::internal::DynTypedMatcher M,

                     std::initializer_list<ASTEdit> Edits);

/// @}

/// Overloads of \c makeRule that also generate metadata when matching.

/// @{

template <typename MetadataT, int &..., typename EditsT>

RewriteRuleWith<MetadataT> makeRule(ast_matchers::internal::DynTypedMatcher M,

                                    EditsT &&Edits,

                                    Generator<MetadataT> Metadata) {

  return detail::makeRule(

      std::move(M), detail::makeEditGenerator(std::forward<EditsT>(Edits)),

      std::move(Metadata));

}

template <typename MetadataT>

RewriteRuleWith<MetadataT> makeRule(ast_matchers::internal::DynTypedMatcher M,

                                    std::initializer_list<ASTEdit> Edits,

                                    Generator<MetadataT> Metadata) {

  return detail::makeRule(std::move(M),

                          detail::makeEditGenerator(std::move(Edits)),

                          std::move(Metadata));

}

/// @}

/// For every case in Rule, adds an include directive for the given header. The

/// common use is assumed to be a rule with only one case. For example, to

/// replace a function call and add headers corresponding to the new code, one

/// could write:

/// \code

///   auto R = makeRule(callExpr(callee(functionDecl(hasName("foo")))),

///            changeTo(cat("bar()")));

///   addInclude(R, "path/to/bar_header.h");

///   addInclude(R, "vector", IncludeFormat::Angled);

/// \endcode

void addInclude(RewriteRuleBase &Rule, llvm::StringRef Header,

                IncludeFormat Format = IncludeFormat::Quoted);

/// Applies the first rule whose pattern matches; other rules are ignored.  If

/// the matchers are independent then order doesn't matter. In that case,

/// `applyFirst` is simply joining the set of rules into one.

//

// `applyFirst` is like an `anyOf` matcher with an edit action attached to each

// of its cases. Anywhere you'd use `anyOf(m1.bind("id1"), m2.bind("id2"))` and

// then dispatch on those ids in your code for control flow, `applyFirst` lifts

// that behavior to the rule level.  So, you can write `applyFirst({makeRule(m1,

// action1), makeRule(m2, action2), ...});`

//

// For example, consider a type `T` with a deterministic serialization function,

// `serialize()`.  For performance reasons, we would like to make it

// non-deterministic.  Therefore, we want to drop the expectation that

// `a.serialize() = b.serialize() iff a = b` (although we'll maintain

// `deserialize(a.serialize()) = a`).

//

// We have three cases to consider (for some equality function, `eq`):

// ```

// eq(a.serialize(), b.serialize()) --> eq(a,b)

// eq(a, b.serialize())             --> eq(deserialize(a), b)

// eq(a.serialize(), b)             --> eq(a, deserialize(b))

// ```

//

// `applyFirst` allows us to specify each independently:

// ```

// auto eq_fun = functionDecl(...);

// auto method_call = cxxMemberCallExpr(...);

//

// auto two_calls = callExpr(callee(eq_fun), hasArgument(0, method_call),

//                           hasArgument(1, method_call));

// auto left_call =

//     callExpr(callee(eq_fun), callExpr(hasArgument(0, method_call)));

// auto right_call =

//     callExpr(callee(eq_fun), callExpr(hasArgument(1, method_call)));

//

// RewriteRule R = applyFirst({makeRule(two_calls, two_calls_action),

//                             makeRule(left_call, left_call_action),

//                             makeRule(right_call, right_call_action)});

// ```

/// @{

template <typename MetadataT>

RewriteRuleWith<MetadataT>

applyFirst(ArrayRef<RewriteRuleWith<MetadataT>> Rules) {

  RewriteRuleWith<MetadataT> R;

  for (auto &Rule : Rules) {

    assert(Rule.Cases.size() == Rule.Metadata.size() &&

           "mis-match in case and metadata array size");

    R.Cases.append(Rule.Cases.begin(), Rule.Cases.end());

    R.Metadata.append(Rule.Metadata.begin(), Rule.Metadata.end());

  }

  return R;

}

template <>

RewriteRuleWith<void> applyFirst(ArrayRef<RewriteRuleWith<void>> Rules);

template <typename MetadataT>

RewriteRuleWith<MetadataT>

applyFirst(const std::vector<RewriteRuleWith<MetadataT>> &Rules) {

  return applyFirst(llvm::ArrayRef(Rules));

}

template <typename MetadataT>

RewriteRuleWith<MetadataT>

applyFirst(std::initializer_list<RewriteRuleWith<MetadataT>> Rules) {

  return applyFirst(llvm::ArrayRef(Rules.begin(), Rules.end()));

}

/// @}

/// Converts a \c RewriteRuleWith<T> to a \c RewriteRule by stripping off the

/// metadata generators.

template <int &..., typename MetadataT>

std::enable_if_t<!std::is_same<MetadataT, void>::value, RewriteRule>

stripMetadata(RewriteRuleWith<MetadataT> Rule) {

  RewriteRule R;

  R.Cases = std::move(Rule.Cases);

  return R;

}

/// Applies `Rule` to all descendants of the node bound to `NodeId`. `Rule` can

/// refer to nodes bound by the calling rule. `Rule` is not applied to the node

/// itself.

///

/// For example,

/// ```

/// auto InlineX =

///     makeRule(declRefExpr(to(varDecl(hasName("x")))), changeTo(cat("3")));

/// makeRule(functionDecl(hasName("f"), hasBody(stmt().bind("body"))).bind("f"),

///          flatten(

///            changeTo(name("f"), cat("newName")),

///            rewriteDescendants("body", InlineX)));

/// ```

/// Here, we find the function `f`, change its name to `newName` and change all

/// appearances of `x` in its body to `3`.

EditGenerator rewriteDescendants(std::string NodeId, RewriteRule Rule);

/// The following three functions are a low-level part of the RewriteRule

/// API. We expose them for use in implementing the fixtures that interpret

/// RewriteRule, like Transformer and TransfomerTidy, or for more advanced

/// users.

//

// FIXME: These functions are really public, if advanced, elements of the

// RewriteRule API.  Recast them as such.  Or, just declare these functions

// public and well-supported and move them out of `detail`.

namespace detail {

/// The following overload set is a version of `rewriteDescendants` that

/// operates directly on the AST, rather than generating a Transformer

/// combinator. It applies `Rule` to all descendants of `Node`, although not

/// `Node` itself. `Rule` can refer to nodes bound in `Result`.

///

/// For example, assuming that "body" is bound to a function body in MatchResult

/// `Results`, this will produce edits to change all appearances of `x` in that

/// body to `3`.

/// ```

/// auto InlineX =

///     makeRule(declRefExpr(to(varDecl(hasName("x")))), changeTo(cat("3")));

/// const auto *Node = Results.Nodes.getNodeAs<Stmt>("body");

/// auto Edits = rewriteDescendants(*Node, InlineX, Results);

/// ```

/// @{

llvm::Expected<SmallVector<Edit, 1>>

rewriteDescendants(const Decl &Node, RewriteRule Rule,

                   const ast_matchers::MatchFinder::MatchResult &Result);

llvm::Expected<SmallVector<Edit, 1>>

rewriteDescendants(const Stmt &Node, RewriteRule Rule,

                   const ast_matchers::MatchFinder::MatchResult &Result);

llvm::Expected<SmallVector<Edit, 1>>

rewriteDescendants(const TypeLoc &Node, RewriteRule Rule,

                   const ast_matchers::MatchFinder::MatchResult &Result);

llvm::Expected<SmallVector<Edit, 1>>

rewriteDescendants(const DynTypedNode &Node, RewriteRule Rule,

                   const ast_matchers::MatchFinder::MatchResult &Result);

/// @}

/// Builds a single matcher for the rule, covering all of the rule's cases.

/// Only supports Rules whose cases' matchers share the same base "kind"

/// (`Stmt`, `Decl`, etc.)  Deprecated: use `buildMatchers` instead, which

/// supports mixing matchers of different kinds.

ast_matchers::internal::DynTypedMatcher

buildMatcher(const RewriteRuleBase &Rule);

/// Builds a set of matchers that cover the rule.

///

/// One matcher is built for each distinct node matcher base kind: Stmt, Decl,

/// etc. Node-matchers for `QualType` and `Type` are not permitted, since such

/// nodes carry no source location information and are therefore not relevant

/// for rewriting. If any such matchers are included, will return an empty

/// vector.

std::vector<ast_matchers::internal::DynTypedMatcher>

buildMatchers(const RewriteRuleBase &Rule);

/// Gets the beginning location of the source matched by a rewrite rule. If the

/// match occurs within a macro expansion, returns the beginning of the

/// expansion point. `Result` must come from the matching of a rewrite rule.

SourceLocation

getRuleMatchLoc(const ast_matchers::MatchFinder::MatchResult &Result);

/// Returns the index of the \c Case of \c Rule that was selected in the match

/// result. Assumes a matcher built with \c buildMatcher.

size_t findSelectedCase(const ast_matchers::MatchFinder::MatchResult &Result,

                        const RewriteRuleBase &Rule);

} // namespace detail

} // namespace transformer

} // namespace clang

#endif // LLVM_CLANG_TOOLING_TRANSFORMER_REWRITERULE_H