[clang-tools-extra] [clang-tidy]Add new check readability-avoid-nested-conditional-operator (PR #78022)

[Congcong Cai via cfe-commits]

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@@ -0,0 +1,56 @@
+//===--- AvoidNestedConditionalOperatorCheck.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 "AvoidNestedConditionalOperatorCheck.h"
+#include "clang/AST/Expr.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Basic/DiagnosticIDs.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+namespace {
+constexpr const char *Description = "don't use nested conditional operator";
+constexpr const char *OutSideConditionalOperatorNote =
+    "outside conditional operator here";
+} // namespace
+
+void AvoidNestedConditionalOperatorCheck::registerMatchers(
+    MatchFinder *Finder) {
+  Finder->addMatcher(
+      conditionalOperator(
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HerrCai0907 wrote:

`BinaryConditionalOperator` is a GNU extension and I don't find any code guide to rule its usage.
And it is a binary operator, like other normal binary operator, It's not worth being limited. 

https://github.com/llvm/llvm-project/pull/78022