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

[via cfe-commits]

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@@ -0,0 +1,101 @@
+//===----------------------------------------------------------------------===//
+//
+// 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(
+    const MatchFinder::MatchResult &Result) {
+  const auto *Lambda = Result.Nodes.getNodeAs<LambdaExpr>("lambda");
+
+
+  if (Lambda->getBeginLoc().isMacroID())
+    return;
+
+  const LangOptions &LangOpts = getLangOpts();
+
+  const SourceLocation ScanFrom =
+      Lambda->isGenericLambda()
+          ? Lexer::getLocForEndOfToken(
+                Lambda->getTemplateParameterList()->getRAngleLoc(), 0,
+                *Result.SourceManager, LangOpts)
+          : Lexer::getLocForEndOfToken(
+                Lambda->getIntroducerRange().getEnd(), 0,
+                *Result.SourceManager, LangOpts);
+
+  Token Tok;
+  if (Lexer::getRawToken(ScanFrom, Tok, *Result.SourceManager, LangOpts,
+                         /*IgnoreWhiteSpace=*/true))
+    return;
+
+  if (Tok.isNot(tok::l_paren))
+    return;
+
+  const SourceLocation LParenLoc = Tok.getLocation();
+  const SourceLocation RParenLoc = Lexer::findLocationAfterToken(
+      LParenLoc, tok::r_paren, *Result.SourceManager, LangOpts,
+      /*SkipTrailingWhitespaceAndNewLine=*/false);
+
+  if (LParenLoc.isInvalid() || RParenLoc.isInvalid())
+    return;
+
+  if (!LangOpts.CPlusPlus23) {
+    std::optional<Token> RParen =
+        Lexer::findNextToken(LParenLoc, *Result.SourceManager, LangOpts);
+    if (!RParen || RParen->isNot(tok::r_paren))
+      return;
+    std::optional<Token> NextTok = Lexer::findNextToken(
+        RParen->getLocation(), *Result.SourceManager, LangOpts);
+    if (NextTok && NextTok->is(tok::raw_identifier)) {
+      StringRef Id = NextTok->getRawIdentifier();
+      if (Id == "constexpr" || Id == "consteval" || Id == "mutable" ||
+          Id == "noexcept")
+        return;
+    }
+    if (NextTok && NextTok->is(tok::arrow))
+      return;
+  }
+
+  const CharSourceRange ParenRange =
+      CharSourceRange::getCharRange(LParenLoc, RParenLoc);
+
+  diag(LParenLoc, "redundant empty parameter list in lambda expression")
+      << FixItHint::CreateRemoval(ParenRange);
+}
+
+} // namespace clang::tidy::readability
----------------
EugeneZelenko wrote:

Please add newline.

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