[clang-tidy] add check to suggest replacement of nested std::min or std::max with initializer lists

clang-tools-extra/clang-tidy/modernize/CMakeLists.txt

@@ -16,6 +16,7 @@ add_clang_library(clangTidyModernizeModule
   MakeSharedCheck.cpp
   MakeSmartPtrCheck.cpp
   MakeUniqueCheck.cpp
+  MinMaxUseInitializerListCheck.cpp
   ModernizeTidyModule.cpp
   PassByValueCheck.cpp
   RawStringLiteralCheck.cpp

clang-tools-extra/clang-tidy/modernize/MinMaxUseInitializerListCheck.cpp

@@ -0,0 +1,271 @@
+//===--- MinMaxUseInitializerListCheck.cpp - clang-tidy -------------------===//
+//
+// 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 "MinMaxUseInitializerListCheck.h"
+#include "../utils/ASTUtils.h"
+#include "../utils/LexerUtils.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang;
+
+namespace {
+
+struct FindArgsResult {
+  const Expr *First;
+  const Expr *Last;
+  const Expr *Compare;
+  SmallVector<const clang::Expr *, 2> Args;
+};
+
+} // anonymous namespace
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::modernize {
+
+static FindArgsResult findArgs(const CallExpr *Call) {
+  FindArgsResult Result;
+  Result.First = nullptr;
+  Result.Last = nullptr;
+  Result.Compare = nullptr;
+
+  //   check if the function has initializer list argument
+  if (Call->getNumArgs() < 3) {
+    auto ArgIterator = Call->arguments().begin();
+
+    const auto *InitListExpr =
+        dyn_cast<CXXStdInitializerListExpr>(*ArgIterator);
+    const auto *InitList =
+        InitListExpr != nullptr
+            ? dyn_cast<clang::InitListExpr>(
+                  InitListExpr->getSubExpr()->IgnoreImplicit())
+            : nullptr;
+
+    if (InitList) {
+      Result.Args.append(InitList->inits().begin(), InitList->inits().end());
+      Result.First = *ArgIterator;
+      Result.Last = *ArgIterator;
+
+      // check if there is a comparison argument
+      std::advance(ArgIterator, 1);
+      if (ArgIterator != Call->arguments().end())
+        Result.Compare = *ArgIterator;
+
+      return Result;
+    }
+    Result.Args = SmallVector<const Expr *>(Call->arguments());
+  } else {
+    // if it has 3 arguments then the last will be the comparison
+    Result.Compare = *(std::next(Call->arguments().begin(), 2));
+    Result.Args = SmallVector<const Expr *>(llvm::drop_end(Call->arguments()));
+  }
+  Result.First = Result.Args.front();
+  Result.Last = Result.Args.back();
+
+  return Result;
+}
+
+static SmallVector<FixItHint>
+generateReplacements(const MatchFinder::MatchResult &Match,
+                     const CallExpr *TopCall, const FindArgsResult &Result,
+                     const bool IgnoreNonTrivialTypes,
+                     const std::uint64_t IgnoreTrivialTypesOfSizeAbove) {
+  SmallVector<FixItHint> FixItHints;
+  const SourceManager &SourceMngr = *Match.SourceManager;
+  const LangOptions &LanguageOpts = Match.Context->getLangOpts();
+
+  const QualType ResultType = TopCall->getDirectCallee()
+                                  ->getReturnType()
+                                  .getCanonicalType()
+                                  .getNonReferenceType()
+                                  .getUnqualifiedType();
+
+  // check if the type is trivial
+  const bool IsResultTypeTrivial = ResultType.isTrivialType(*Match.Context);
+
+  if ((!IsResultTypeTrivial && IgnoreNonTrivialTypes))
+    return FixItHints;
+
+  if (IsResultTypeTrivial &&
+      static_cast<std::uint64_t>(
+          Match.Context->getTypeSizeInChars(ResultType).getQuantity()) >
+          IgnoreTrivialTypesOfSizeAbove)
+    return FixItHints;
+
+  for (const Expr *Arg : Result.Args) {
+    const auto *InnerCall = dyn_cast<CallExpr>(Arg->IgnoreParenImpCasts());
+
+    // If the argument is not a nested call
+    if (!InnerCall) {
+      // check if typecast is required
+      const QualType ArgType = Arg->IgnoreParenImpCasts()
+                                   ->getType()
+                                   .getCanonicalType()
+                                   .getUnqualifiedType();
+
+      if (ArgType == ResultType)
+        continue;
+
+      const StringRef ArgText = Lexer::getSourceText(
+          CharSourceRange::getTokenRange(Arg->getSourceRange()), SourceMngr,
+          LanguageOpts);
+
+      const auto Replacement = Twine("static_cast<")
+                                   .concat(ResultType.getAsString(LanguageOpts))
+                                   .concat(">(")
+                                   .concat(ArgText)
+                                   .concat(")")
+                                   .str();
+
+      FixItHints.push_back(
+          FixItHint::CreateReplacement(Arg->getSourceRange(), Replacement));
+      continue;
+    }
+
+    const FindArgsResult InnerResult = findArgs(InnerCall);
+
+    // if the nested call doesn't have arguments skip it
+    if (!InnerResult.First || !InnerResult.Last)
+      continue;
+
+    // if the nested call is not the same as the top call
+    if (InnerCall->getDirectCallee()->getQualifiedNameAsString() !=
+        TopCall->getDirectCallee()->getQualifiedNameAsString())
+      continue;
+
+    // if the nested call doesn't have the same compare function
+    if ((Result.Compare || InnerResult.Compare) &&
+        !utils::areStatementsIdentical(Result.Compare, InnerResult.Compare,
+                                       *Match.Context))
+      continue;
+
+    // remove the function call
+    FixItHints.push_back(
+        FixItHint::CreateRemoval(InnerCall->getCallee()->getSourceRange()));
+
+    // remove the parentheses
+    const auto LParen = utils::lexer::findNextTokenSkippingComments(
+        InnerCall->getCallee()->getEndLoc(), SourceMngr, LanguageOpts);
+    if (LParen.has_value() && LParen->is(tok::l_paren))
+      FixItHints.push_back(
+          FixItHint::CreateRemoval(SourceRange(LParen->getLocation())));
+    FixItHints.push_back(
+        FixItHint::CreateRemoval(SourceRange(InnerCall->getRParenLoc())));
+
+    // if the inner call has an initializer list arg
+    if (InnerResult.First == InnerResult.Last) {
+      // remove the initializer list braces
+      FixItHints.push_back(FixItHint::CreateRemoval(
+          CharSourceRange::getTokenRange(InnerResult.First->getBeginLoc())));
+      FixItHints.push_back(FixItHint::CreateRemoval(
+          CharSourceRange::getTokenRange(InnerResult.First->getEndLoc())));
+    }
+
+    const SmallVector<FixItHint> InnerReplacements = generateReplacements(
+        Match, InnerCall, InnerResult, IgnoreNonTrivialTypes,
+        IgnoreTrivialTypesOfSizeAbove);
+
+    FixItHints.append(InnerReplacements);
+
+    if (InnerResult.Compare) {
+      // find the comma after the value arguments
+      const auto Comma = utils::lexer::findNextTokenSkippingComments(
+          InnerResult.Last->getEndLoc(), SourceMngr, LanguageOpts);
+
+      // remove the comma and the comparison
+      if (Comma.has_value() && Comma->is(tok::comma))
+        FixItHints.push_back(
+            FixItHint::CreateRemoval(SourceRange(Comma->getLocation())));
+
+      FixItHints.push_back(
+          FixItHint::CreateRemoval(InnerResult.Compare->getSourceRange()));
+    }
+  }
+
+  return FixItHints;
+}
+
+MinMaxUseInitializerListCheck::MinMaxUseInitializerListCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      IgnoreNonTrivialTypes(Options.get("IgnoreNonTrivialTypes", true)),
+      IgnoreTrivialTypesOfSizeAbove(
+          Options.get("IgnoreTrivialTypesOfSizeAbove", 32L)),
+      Inserter(Options.getLocalOrGlobal("IncludeStyle",
+                                        utils::IncludeSorter::IS_LLVM),
+               areDiagsSelfContained()) {}
+
+void MinMaxUseInitializerListCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "IgnoreNonTrivialTypes", IgnoreNonTrivialTypes);
+  Options.store(Opts, "IgnoreTrivialTypesOfSizeAbove",
+                IgnoreTrivialTypesOfSizeAbove);
+  Options.store(Opts, "IncludeStyle", Inserter.getStyle());
+}
+
+void MinMaxUseInitializerListCheck::registerMatchers(MatchFinder *Finder) {
+  auto CreateMatcher = [](const StringRef FunctionName) {
+    auto FuncDecl = functionDecl(hasName(FunctionName));
+    auto Expression = callExpr(callee(FuncDecl));
+
+    return callExpr(callee(FuncDecl),
+                    anyOf(hasArgument(0, Expression),
+                          hasArgument(1, Expression),
+                          hasArgument(0, cxxStdInitializerListExpr())),
+                    unless(hasParent(Expression)))
+        .bind("topCall");
+  };
+
+  Finder->addMatcher(CreateMatcher("::std::max"), this);
+  Finder->addMatcher(CreateMatcher("::std::min"), this);
+}
+
+void MinMaxUseInitializerListCheck::registerPPCallbacks(
+    const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) {
+  Inserter.registerPreprocessor(PP);
+}
+
+void MinMaxUseInitializerListCheck::check(
+    const MatchFinder::MatchResult &Match) {
+
+  const auto *TopCall = Match.Nodes.getNodeAs<CallExpr>("topCall");
+
+  const FindArgsResult Result = findArgs(TopCall);
+  const SmallVector<FixItHint> Replacements =
+      generateReplacements(Match, TopCall, Result, IgnoreNonTrivialTypes,
+                           IgnoreTrivialTypesOfSizeAbove);
+
+  if (Replacements.empty())
+    return;
+
+  const DiagnosticBuilder Diagnostic =
+      diag(TopCall->getBeginLoc(),
+           "do not use nested 'std::%0' calls, use an initializer list instead")
+      << TopCall->getDirectCallee()->getName()
+      << Inserter.createIncludeInsertion(
+             Match.SourceManager->getFileID(TopCall->getBeginLoc()),
+             "<algorithm>");
+
+  // if the top call doesn't have an initializer list argument
+  if (Result.First != Result.Last) {
+    // add { and } insertions
+    Diagnostic << FixItHint::CreateInsertion(Result.First->getBeginLoc(), "{");
+
+    Diagnostic << FixItHint::CreateInsertion(
+        Lexer::getLocForEndOfToken(Result.Last->getEndLoc(), 0,
+                                   *Match.SourceManager,
+                                   Match.Context->getLangOpts()),
+        "}");
+  }
+
+  Diagnostic << Replacements;
+}
+
+} // namespace clang::tidy::modernize

clang-tools-extra/clang-tidy/modernize/MinMaxUseInitializerListCheck.h

@@ -0,0 +1,56 @@
+//===--- MinMaxUseInitializerListCheck.h - clang-tidy -----------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_MINMAXUSEINITIALIZERLISTCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_MINMAXUSEINITIALIZERLISTCHECK_H
+
+#include "../ClangTidyCheck.h"
+#include "../utils/IncludeInserter.h"
+
+namespace clang::tidy::modernize {
+
+/// Replaces nested ``std::min`` and ``std::max`` calls with an initializer list
+/// where applicable.
+///
+/// For example:
+///
+/// \code
+///   int a = std::max(std::max(i, j), k);
+/// \endcode
+///
+/// This code is transformed to:
+///
+/// \code
+///   int a = std::max({i, j, k});
+/// \endcode
+class MinMaxUseInitializerListCheck : public ClangTidyCheck {
+public:
+  MinMaxUseInitializerListCheck(StringRef Name, ClangTidyContext *Context);
+
+  void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void registerPPCallbacks(const SourceManager &SM, Preprocessor *PP,
+                           Preprocessor *ModuleExpanderPP) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Match) override;
+
+  bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+    return LangOpts.CPlusPlus11;
+  }
+  std::optional<TraversalKind> getCheckTraversalKind() const override {
+    return TK_IgnoreUnlessSpelledInSource;
+  }
+
+private:
+  bool IgnoreNonTrivialTypes;
+  std::uint64_t IgnoreTrivialTypesOfSizeAbove;
+  utils::IncludeInserter Inserter;
+};
+
+} // namespace clang::tidy::modernize
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_MINMAXUSEINITIALIZERLISTCHECK_H

clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp

@@ -18,6 +18,7 @@
 #include "MacroToEnumCheck.h"
 #include "MakeSharedCheck.h"
 #include "MakeUniqueCheck.h"
+#include "MinMaxUseInitializerListCheck.h"
 #include "PassByValueCheck.h"
 #include "RawStringLiteralCheck.h"
 #include "RedundantVoidArgCheck.h"
@@ -68,6 +69,8 @@ class ModernizeModule : public ClangTidyModule {
     CheckFactories.registerCheck<MacroToEnumCheck>("modernize-macro-to-enum");
     CheckFactories.registerCheck<MakeSharedCheck>("modernize-make-shared");
     CheckFactories.registerCheck<MakeUniqueCheck>("modernize-make-unique");
+    CheckFactories.registerCheck<MinMaxUseInitializerListCheck>(
+        "modernize-min-max-use-initializer-list");
     CheckFactories.registerCheck<PassByValueCheck>("modernize-pass-by-value");
     CheckFactories.registerCheck<UseDesignatedInitializersCheck>(
         "modernize-use-designated-initializers");

clang-tools-extra/docs/ReleaseNotes.rst

@@ -117,6 +117,12 @@ New checks
   to reading out-of-bounds data due to inadequate or incorrect string null
   termination.
 
+- New :doc:`modernize-min-max-use-initializer-list
+  <clang-tidy/checks/modernize/min-max-use-initializer-list>` check.
+
+  Replaces nested ``std::min`` and ``std::max`` calls with an initializer list
+  where applicable.
+
 - New :doc:`modernize-use-designated-initializers
   <clang-tidy/checks/modernize/use-designated-initializers>` check.
 

clang-tools-extra/docs/clang-tidy/checks/list.rst

@@ -275,6 +275,7 @@ Clang-Tidy Checks
    :doc:`modernize-macro-to-enum <modernize/macro-to-enum>`, "Yes"
    :doc:`modernize-make-shared <modernize/make-shared>`, "Yes"
    :doc:`modernize-make-unique <modernize/make-unique>`, "Yes"
+   :doc:`modernize-min-max-use-initializer-list <modernize/min-max-use-initializer-list>`, "Yes"
    :doc:`modernize-pass-by-value <modernize/pass-by-value>`, "Yes"
    :doc:`modernize-raw-string-literal <modernize/raw-string-literal>`, "Yes"
    :doc:`modernize-redundant-void-arg <modernize/redundant-void-arg>`, "Yes"