[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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@@ -0,0 +1,138 @@
+//===--- 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 "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::modernize {
+
+MinMaxUseInitializerListCheck::MinMaxUseInitializerListCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      Inserter(Options.getLocalOrGlobal("IncludeStyle",
+                                        utils::IncludeSorter::IS_LLVM),
+               areDiagsSelfContained()) {}
+
+void MinMaxUseInitializerListCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "IncludeStyle", Inserter.getStyle());
+}
+
+void MinMaxUseInitializerListCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      callExpr(
+          callee(functionDecl(hasName("::std::max"))),
+          hasAnyArgument(callExpr(callee(functionDecl(hasName("::std::max"))))),
+          unless(
+              hasParent(callExpr(callee(functionDecl(hasName("::std::max")))))))
+          .bind("maxCall"),
+      this);
+
+  Finder->addMatcher(
+      callExpr(
+          callee(functionDecl(hasName("::std::min"))),
+          hasAnyArgument(callExpr(callee(functionDecl(hasName("::std::min"))))),
+          unless(
+              hasParent(callExpr(callee(functionDecl(hasName("::std::min")))))))
+          .bind("minCall"),
+      this);
+}
+
+void MinMaxUseInitializerListCheck::registerPPCallbacks(
+    const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) {
+  Inserter.registerPreprocessor(PP);
+}
+
+void MinMaxUseInitializerListCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *MaxCall = Result.Nodes.getNodeAs<CallExpr>("maxCall");
+  const auto *MinCall = Result.Nodes.getNodeAs<CallExpr>("minCall");
+
+  const CallExpr *TopCall = MaxCall ? MaxCall : MinCall;
+  if (!TopCall) {
+    return;
+  }
+  const QualType ResultType =
+      TopCall->getDirectCallee()->getReturnType().getNonReferenceType();
+
+  const Expr *FirstArg = nullptr;
+  const Expr *LastArg = nullptr;
+  std::vector<const Expr *> Args;
+  findArgs(TopCall, &FirstArg, &LastArg, Args);
+
+  if (!FirstArg || !LastArg || Args.size() <= 2) {
+    return;
+  }
+
+  std::string ReplacementText = "{";
+  for (const Expr *Arg : Args) {
+    QualType ArgType = Arg->getType();
+    bool CastNeeded =
+        ArgType.getCanonicalType() != ResultType.getCanonicalType();
+
+    if (CastNeeded)
+      ReplacementText += "static_cast<" + ResultType.getAsString() + ">(";
----------------
sopyb wrote:

I am unsure if a type cast may even be needed over here since the method declaration for std::{max, min} would require the first 2 parameters being compared would be type casted to the correct type already or it wouldn't compile.

```cpp
template< class T >
const T& max( const T& a, const T& b );

template< class T, class Compare >
const T& max( const T& a, const T& b, Compare comp );

template< class T >
const T& min( const T& a, const T& b );

template< class T, class Compare >
const T& min( const T& a, const T& b, Compare comp );
```

Source: 
 - https://en.cppreference.com/w/cpp/algorithm/min
 - https://en.cppreference.com/w/cpp/algorithm/max

Let me know if I am misunderstanding the intended purpose of the typecast in this case.

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