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

[Congcong Cai via cfe-commits]

================
@@ -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(
+          anyOf(
+              hasCondition(ignoringParenCasts(
----------------
HerrCai0907 wrote:

Yes, It want to ignore the `ParenExpr` because this check want to detect `A ? B : (C ? D : E)` also.

```c++
/// Matches expressions that match InnerMatcher after parentheses and
/// casts are stripped off.
///
/// Implicit and non-C Style casts are also discarded.
/// Given
/// \code
///   int a = 0;
///   char b = (0);
///   void* c = reinterpret_cast<char*>(0);
///   char d = char(0);
/// \endcode
/// The matcher
///    varDecl(hasInitializer(ignoringParenCasts(integerLiteral())))
/// would match the declarations for a, b, c, and d.
/// while
///    varDecl(hasInitializer(integerLiteral()))
/// only match the declaration for a.
AST_MATCHER_P(Expr, ignoringParenCasts, internal::Matcher<Expr>, InnerMatcher) {
  return InnerMatcher.matches(*Node.IgnoreParenCasts(), Finder, Builder);
}
```

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