ProTypeStaticCastDowncastCheck.cpp

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//===----------------------------------------------------------------------===//
//
// 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 "ProTypeStaticCastDowncastCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
 
using namespace clang::ast_matchers;
 
namespace clang::tidy::cppcoreguidelines {
 
ProTypeStaticCastDowncastCheck::ProTypeStaticCastDowncastCheck(
    StringRef Name, ClangTidyContext *Context)
    : ClangTidyCheck(Name, Context),
      StrictMode(Options.get("StrictMode", true)) {}
 
void ProTypeStaticCastDowncastCheck::storeOptions(
    ClangTidyOptions::OptionMap &Opts) {
  Options.store(Opts, "StrictMode", StrictMode);
}
 
void ProTypeStaticCastDowncastCheck::registerMatchers(MatchFinder *Finder) {
  Finder->addMatcher(
      cxxStaticCastExpr(hasCastKind(CK_BaseToDerived)).bind("cast"), this);
}
 
void ProTypeStaticCastDowncastCheck::check(
    const MatchFinder::MatchResult &Result) {
  const auto *MatchedCast = Result.Nodes.getNodeAs<CXXStaticCastExpr>("cast");
 
  QualType SourceType = MatchedCast->getSubExpr()->getType();
  const auto *SourceDecl = SourceType->getPointeeCXXRecordDecl();
  if (!SourceDecl) // The cast is from object to reference
    SourceDecl = SourceType->getAsCXXRecordDecl();
  if (!SourceDecl)
    return;
 
  if (SourceDecl->isPolymorphic()) {
    diag(MatchedCast->getOperatorLoc(),
         "do not use static_cast to downcast from a base to a derived class; "
         "use dynamic_cast instead")
        << FixItHint::CreateReplacement(MatchedCast->getOperatorLoc(),
                                        "dynamic_cast");
    return;
  }
 
  if (!StrictMode)
    return;
 
  diag(MatchedCast->getOperatorLoc(),
       "do not use static_cast to downcast from a base to a derived class");
}
 
} // namespace clang::tidy::cppcoreguidelines