[clang] [clang-tools-extra] [clang-tidy] Add readability-default-lambda-capture (PR #160150)

[via cfe-commits]

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@@ -0,0 +1,94 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "AvoidDefaultLambdaCaptureCheck.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Basic/Lambda.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+namespace {
+AST_MATCHER(LambdaExpr, hasDefaultCapture) {
+  return Node.getCaptureDefault() != LCD_None;
+}
+
+std::optional<std::string>
+generateImplicitCaptureText(const LambdaCapture &Capture) {
+  if (Capture.capturesThis()) {
+    return Capture.getCaptureKind() == LCK_StarThis ? "*this" : "this";
+  }
+
+  if (Capture.capturesVariable()) {
+    std::string Result;
+    if (Capture.getCaptureKind() == LCK_ByRef) {
+      Result += "&";
+    }
+    Result += Capture.getCapturedVar()->getName().str();
+    return Result;
+  }
+
+  if (Capture.capturesVLAType()) {
+    // VLA captures are rare and complex - for now we skip them
+    // A full implementation would need to handle the VLA type properly
+    return std::nullopt;
+  }
+
+  return std::nullopt;
+}
+
+} // namespace
+
+void AvoidDefaultLambdaCaptureCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(lambdaExpr(hasDefaultCapture()).bind("lambda"), this);
+}
+
+void AvoidDefaultLambdaCaptureCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *Lambda = Result.Nodes.getNodeAs<LambdaExpr>("lambda");
+  assert(Lambda);
+
+  const SourceLocation DefaultCaptureLoc = Lambda->getCaptureDefaultLoc();
+  if (DefaultCaptureLoc.isInvalid())
+    return;
+
+  auto Diag = diag(DefaultCaptureLoc,
+                   "lambda default captures are discouraged; "
+                   "prefer to capture specific variables explicitly");
+
+  std::vector<std::string> AllCaptures;
+
+  for (const auto &Capture : Lambda->explicit_captures()) {
+    if (const auto CaptureText = generateImplicitCaptureText(Capture)) {
+      AllCaptures.push_back(CaptureText.value());
+    }
+  }
+
+  for (const auto &Capture : Lambda->implicit_captures()) {
+    if (const auto CaptureText = generateImplicitCaptureText(Capture)) {
+      AllCaptures.push_back(CaptureText.value());
+    }
+  }
----------------
flovent wrote:

Is there a reason spliting implicit and explicit catures? otherwise you can use `Lambda->captures()` directly to get all the captures.

https://github.com/llvm/llvm-project/pull/160150