[clang-tools-extra] [clang-tidy] Add readability-redundant-lambda-parentheses check (PR #190438)

[Victor Chernyakin via cfe-commits]

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@@ -0,0 +1,99 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "RedundantLambdaParenthesesCheck.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace {
+
+AST_MATCHER(clang::LambdaExpr, hasNoParameters) {
+  return Node.getCallOperator()->getNumParams() == 0;
+}
+
+AST_MATCHER(clang::LambdaExpr, hasExplicitOrGenericParameters) {
+  return Node.hasExplicitParameters() || Node.isGenericLambda();
+}
+
+AST_MATCHER(clang::LambdaExpr, isGenericLambdaInCxx20OrLater) {
+  return !Node.isGenericLambda() ||
+         Finder->getASTContext().getLangOpts().CPlusPlus20;
+}
+
+} // namespace
+
+namespace clang::tidy::readability {
+
+void RedundantLambdaParenthesesCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(lambdaExpr(hasExplicitOrGenericParameters(),
+                                hasNoParameters(),
+                                isGenericLambdaInCxx20OrLater())
+                         .bind("lambda"),
+                     this);
+}
+
+void RedundantLambdaParenthesesCheck::check(
----------------
localspook wrote:

I think a lot of the manual parsing here can be avoided; you can do:
```cpp
Lambda->getCallOperator()-getFunctionTypeLoc();
```
to get a `FunctionTypeLoc`, which provides `getLParenLoc` and `getRParenLoc` functions for you.

https://github.com/llvm/llvm-project/pull/190438