[clang-tools-extra] [clang-tidy] add check to suggest replacement of nested std::min or std::max with initializer lists (PR #85572)

[via cfe-commits]

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+//===--- 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 (InitListExpr && InitList) {
+      Result.Args.insert(Result.Args.begin(), 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;
+    }
+    // if it has 3 arguments then the last will be the comparison
+  } else {
+    Result.Compare = *(std::next(Call->arguments().begin(), 2));
+  }
+
+  for (const Expr *Arg : Call->arguments()) {
+    if (!Result.First)
+      Result.First = Arg;
+
+    if (Arg == Result.Compare)
+      continue;
+
+    Result.Args.push_back(Arg);
+    Result.Last = Arg;
+  }
+
+  return Result;
+}
+
+static SmallVector<FixItHint>
+generateReplacement(const MatchFinder::MatchResult &Match,
+                    const CallExpr *TopCall, const FindArgsResult &Result) {
+  SmallVector<FixItHint> FixItHints;
+
+  const QualType ResultType = TopCall->getDirectCallee()
+                                  ->getReturnType()
+                                  .getNonReferenceType()
+                                  .getUnqualifiedType()
+                                  .getCanonicalType();
+  const auto &SourceMngr = *Match.SourceManager;
+  const auto LanguageOpts = Match.Context->getLangOpts();
+  const bool IsInitializerList = Result.First == Result.Last;
+
+  // add { and } if the top call doesn't have an initializer list arg
+  if (!IsInitializerList) {
+    FixItHints.push_back(
+        FixItHint::CreateInsertion(Result.First->getBeginLoc(), "{"));
+
+    if (Result.Compare)
+      FixItHints.push_back(FixItHint::CreateInsertion(
+          Lexer::getLocForEndOfToken(Result.Last->getEndLoc(), 0, SourceMngr,
+                                     LanguageOpts),
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sopyb wrote:

I even went ahead and debugged it to make sure Result.Last is the correct Expr and it is. I was unable to figure out why it is happening

https://github.com/llvm/llvm-project/pull/85572