1 files changed, 200 insertions, 0 deletions
diff --git a/lib/Tooling/Refactoring/Stencil.cpp b/lib/Tooling/Refactoring/Stencil.cpp
new file mode 100644
index 0000000000..8fe589b098
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+++ b/lib/Tooling/Refactoring/Stencil.cpp
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+//===--- Stencil.cpp - Stencil implementation -------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Tooling/Refactoring/Stencil.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTTypeTraits.h"
+#include "clang/AST/Expr.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Lex/Lexer.h"
+#include "clang/Tooling/Refactoring/SourceCode.h"
+#include "llvm/Support/Errc.h"
+#include <atomic>
+#include <memory>
+#include <string>
+
+using namespace clang;
+using namespace tooling;
+
+using ast_matchers::MatchFinder;
+using llvm::Error;
+
+// A down_cast function to safely down cast a StencilPartInterface to a subclass
+// D. Returns nullptr if P is not an instance of D.
+template <typename D> const D *down_cast(const StencilPartInterface *P) {
+  if (P == nullptr || D::typeId() != P->typeId())
+    return nullptr;
+  return static_cast<const D *>(P);
+}
+
+static llvm::Expected<ast_type_traits::DynTypedNode>
+getNode(const ast_matchers::BoundNodes &Nodes, StringRef Id) {
+  auto &NodesMap = Nodes.getMap();
+  auto It = NodesMap.find(Id);
+  if (It == NodesMap.end())
+    return llvm::make_error<llvm::StringError>(llvm::errc::invalid_argument,
+                                               "Id not bound: " + Id);
+  return It->second;
+}
+
+namespace {
+// An arbitrary fragment of code within a stencil.
+struct RawTextData {
+  explicit RawTextData(std::string T) : Text(std::move(T)) {}
+  std::string Text;
+};
+
+// A debugging operation to dump the AST for a particular (bound) AST node.
+struct DebugPrintNodeOpData {
+  explicit DebugPrintNodeOpData(std::string S) : Id(std::move(S)) {}
+  std::string Id;
+};
+// Whether to associate a trailing semicolon with a node when identifying it's
+// text.  This flag is needed for expressions (clang::Expr), because their role
+// is ambiguous when they are also complete statements.  When this flag is
+// `Always`, an expression node will be treated like a statement, and will
+// therefore be associated with any trailing semicolon.
+enum class SemiAssociation : bool {
+  Always,
+  Inferred,
+};
+
+// A reference to a particular (bound) AST node.
+struct NodeRefData {
+  explicit NodeRefData(std::string S, SemiAssociation SA)
+      : Id(std::move(S)), SemiAssoc(SA) {}
+  std::string Id;
+  SemiAssociation SemiAssoc;
+};
+} // namespace
+
+bool isEqualData(const RawTextData &A, const RawTextData &B) {
+  return A.Text == B.Text;
+}
+
+bool isEqualData(const DebugPrintNodeOpData &A, const DebugPrintNodeOpData &B) {
+  return A.Id == B.Id;
+}
+
+bool isEqualData(const NodeRefData &A, const NodeRefData &B) {
+  return A.Id == B.Id && A.SemiAssoc == B.SemiAssoc;
+}
+
+// The `evalData()` overloads evaluate the given stencil data to a string, given
+// the match result, and append it to `Result`. We define an overload for each
+// type of stencil data.
+
+Error evalData(const RawTextData &Data, const MatchFinder::MatchResult &,
+               std::string *Result) {
+  Result->append(Data.Text);
+  return Error::success();
+}
+
+Error evalData(const DebugPrintNodeOpData &Data,
+               const MatchFinder::MatchResult &Match, std::string *Result) {
+  std::string Output;
+  llvm::raw_string_ostream Os(Output);
+  auto NodeOrErr = getNode(Match.Nodes, Data.Id);
+  if (auto Err = NodeOrErr.takeError())
+    return Err;
+  NodeOrErr->print(Os, PrintingPolicy(Match.Context->getLangOpts()));
+  *Result += Os.str();
+  return Error::success();
+}
+
+Error evalData(const NodeRefData &Data, const MatchFinder::MatchResult &Match,
+               std::string *Result) {
+  auto NodeOrErr = getNode(Match.Nodes, Data.Id);
+  if (auto Err = NodeOrErr.takeError())
+    return Err;
+  auto &Node = *NodeOrErr;
+  switch (Data.SemiAssoc) {
+  case SemiAssociation::Inferred:
+    // Include the semicolon for non-expression statements:
+    *Result += Node.get<Stmt>() != nullptr && Node.get<Expr>() == nullptr
+                   ? getExtendedText(NodeOrErr.get(), tok::TokenKind::semi,
+                                     *Match.Context)
+                   : getText(NodeOrErr.get(), *Match.Context);
+    break;
+  case SemiAssociation::Always:
+    *Result +=
+        getExtendedText(NodeOrErr.get(), tok::TokenKind::semi, *Match.Context);
+    break;
+  }
+  return Error::success();
+}
+
+template <typename T>
+class StencilPartImpl : public StencilPartInterface {
+  T Data;
+
+public:
+  template <typename... Ps>
+  explicit StencilPartImpl(Ps &&... Args)
+      : StencilPartInterface(StencilPartImpl::typeId()),
+        Data(std::forward<Ps>(Args)...) {}
+
+  // Generates a unique identifier for this class (specifically, one per
+  // instantiation of the template).
+  static const void* typeId() {
+    static bool b;
+    return &b;
+  }
+
+  Error eval(const MatchFinder::MatchResult &Match,
+             std::string *Result) const override {
+    return evalData(Data, Match, Result);
+  }
+
+  bool isEqual(const StencilPartInterface &Other) const override {
+    if (const auto *OtherPtr = down_cast<StencilPartImpl>(&Other))
+      return isEqualData(Data, OtherPtr->Data);
+    return false;
+  }
+};
+
+namespace {
+using RawText = StencilPartImpl<RawTextData>;
+using DebugPrintNodeOp = StencilPartImpl<DebugPrintNodeOpData>;
+using NodeRef = StencilPartImpl<NodeRefData>;
+} // namespace
+
+StencilPart Stencil::wrap(StringRef Text) {
+  return stencil::text(Text);
+}
+
+void Stencil::append(Stencil OtherStencil) {
+  for (auto &Part : OtherStencil.Parts)
+    Parts.push_back(std::move(Part));
+}
+
+llvm::Expected<std::string>
+Stencil::eval(const MatchFinder::MatchResult &Match) const {
+  std::string Result;
+  for (const auto &Part : Parts)
+    if (auto Err = Part.eval(Match, &Result))
+      return std::move(Err);
+  return Result;
+}
+
+StencilPart stencil::text(StringRef Text) {
+  return StencilPart(std::make_shared<RawText>(Text));
+}
+
+StencilPart stencil::node(StringRef Id) {
+  return StencilPart(std::make_shared<NodeRef>(Id, SemiAssociation::Inferred));
+}
+
+StencilPart stencil::sNode(StringRef Id) {
+  return StencilPart(std::make_shared<NodeRef>(Id, SemiAssociation::Always));
+}
+
+StencilPart stencil::dPrint(StringRef Id) {
+  return StencilPart(std::make_shared<DebugPrintNodeOp>(Id));
+}