[clang-tools-extra] [clangd] Add tweak to add pure virtual overrides (PR #139348)

[Marco Maia via cfe-commits]

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@@ -0,0 +1,296 @@
+//===--- OverridePureVirtuals.cpp --------------------------------*- 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 "refactor/Tweak.h"
+
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/AST/Type.h"
+#include "clang/AST/TypeLoc.h"
+#include "clang/Basic/LLVM.h"
+#include "clang/Basic/SourceLocation.h"
+#include "clang/Tooling/Core/Replacement.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/Support/FormatVariadic.h"
+#include <string>
+
+namespace clang {
+namespace clangd {
+namespace {
+
+class OverridePureVirtuals : public Tweak {
+public:
+  const char *id() const final; // defined by REGISTER_TWEAK.
+  bool prepare(const Selection &Sel) override;
+  Expected<Effect> apply(const Selection &Sel) override;
+  std::string title() const override { return "Override pure virtual methods"; }
+  llvm::StringLiteral kind() const override {
+    return CodeAction::QUICKFIX_KIND;
+  }
+
+private:
+  // Stores the CXXRecordDecl of the class being modified.
+  const CXXRecordDecl *CurrentDeclDef = nullptr;
+  // Stores pure virtual methods that need overriding, grouped by their original
+  // access specifier.
+  llvm::MapVector<AccessSpecifier, llvm::SmallVector<const CXXMethodDecl *>>
+      MissingMethodsByAccess;
+  // Stores the source locations of existing access specifiers in CurrentDecl.
+  llvm::MapVector<AccessSpecifier, SourceLocation> AccessSpecifierLocations;
+
+  // Helper function to gather information before applying the tweak.
+  void collectMissingPureVirtuals(const Selection &Sel);
+};
+
+REGISTER_TWEAK(OverridePureVirtuals)
+
+// Function to get all unique pure virtual methods from the entire
+// base class hierarchy of CurrentDeclDef.
+llvm::SmallVector<const clang::CXXMethodDecl *>
+getAllUniquePureVirtualsFromBaseHierarchy(
+    const clang::CXXRecordDecl *CurrentDeclDef) {
+  llvm::SmallVector<const clang::CXXMethodDecl *> AllPureVirtualsInHierarchy;
+  llvm::DenseSet<const clang::CXXMethodDecl *> CanonicalPureVirtualsSeen;
+
+  if (!CurrentDeclDef || !CurrentDeclDef->getDefinition())
+    return AllPureVirtualsInHierarchy;
+
+  const clang::CXXRecordDecl *Def = CurrentDeclDef->getDefinition();
+
+  Def->forallBases([&](const clang::CXXRecordDecl *BaseDefinition) {
+    for (const clang::CXXMethodDecl *Method : BaseDefinition->methods()) {
+      if (Method->isPureVirtual() &&
+          CanonicalPureVirtualsSeen.insert(Method->getCanonicalDecl()).second)
+        AllPureVirtualsInHierarchy.emplace_back(Method);
+    }
+    // Continue iterating through all bases.
+    return true;
+  });
+
+  return AllPureVirtualsInHierarchy;
+}
+
+// Gets canonical declarations of methods already overridden or implemented in
+// class D.
+llvm::SetVector<const CXXMethodDecl *>
+getImplementedOrOverriddenCanonicals(const CXXRecordDecl *D) {
+  llvm::SetVector<const CXXMethodDecl *> ImplementedSet;
+  for (const CXXMethodDecl *M : D->methods()) {
+    // If M provides an implementation for any virtual method it overrides.
+    // A method is an "implementation" if it's virtual and not pure.
+    // Or if it directly overrides a base method.
+    for (const CXXMethodDecl *OverriddenM : M->overridden_methods())
+      ImplementedSet.insert(OverriddenM->getCanonicalDecl());
+  }
+  return ImplementedSet;
+}
+
+// Get the location of every colon of the `AccessSpecifier`.
+llvm::MapVector<AccessSpecifier, SourceLocation>
+getSpecifierLocations(const CXXRecordDecl *D) {
+  llvm::MapVector<AccessSpecifier, SourceLocation> Locs;
+  for (auto *DeclNode : D->decls()) {
+    if (const auto *ASD = llvm::dyn_cast<AccessSpecDecl>(DeclNode))
+      Locs[ASD->getAccess()] = ASD->getColonLoc();
+  }
+  return Locs;
+}
+
+bool hasAbstractBaseAncestor(const clang::CXXRecordDecl *CurrentDecl) {
+  if (!CurrentDecl || !CurrentDecl->getDefinition())
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marcogmaia wrote:

Using assert now

https://github.com/llvm/llvm-project/pull/139348