https://github.com/vbvictor updated
https://github.com/llvm/llvm-project/pull/135383
>From 29d9181db668ca200c04072821e7c6ce7e532f5c Mon Sep 17 00:00:00 2001
From: Victor Baranov <bar.victor.2...@gmail.com>
Date: Thu, 5 Jun 2025 18:17:16 +0300
Subject: [PATCH] [clang-tidy] add support for lambdas in
use-trailing-return-type
---
.../modernize/UseTrailingReturnTypeCheck.cpp | 173 ++++++++++++++++--
.../modernize/UseTrailingReturnTypeCheck.h | 11 +-
clang-tools-extra/docs/ReleaseNotes.rst | 7 +
.../modernize/use-trailing-return-type.rst | 26 ++-
...ng-return-type-transform-lambdas-cxx14.cpp | 24 +++
...ng-return-type-transform-lambdas-cxx20.cpp | 35 ++++
...trailing-return-type-transform-lambdas.cpp | 89 +++++++++
.../use-trailing-return-type-wrong-config.cpp | 5 +
.../modernize/use-trailing-return-type.cpp | 2 -
9 files changed, 352 insertions(+), 20 deletions(-)
create mode 100644
clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-transform-lambdas-cxx14.cpp
create mode 100644
clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-transform-lambdas-cxx20.cpp
create mode 100644
clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-transform-lambdas.cpp
create mode 100644
clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-wrong-config.cpp
diff --git
a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
index 4e5c6a798be98..61565d469023c 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
@@ -17,6 +17,30 @@
#include <cctype>
#include <optional>
+namespace clang::tidy {
+
+template <>
+struct OptionEnumMapping<
+ modernize::UseTrailingReturnTypeCheck::TransformLambda> {
+ static llvm::ArrayRef<std::pair<
+ modernize::UseTrailingReturnTypeCheck::TransformLambda, StringRef>>
+ getEnumMapping() {
+ static constexpr std::pair<
+ modernize::UseTrailingReturnTypeCheck::TransformLambda, StringRef>
+ Mapping[] = {
+ {modernize::UseTrailingReturnTypeCheck::TransformLambda::All,
+ "all"},
+ {modernize::UseTrailingReturnTypeCheck::TransformLambda::
+ AllExceptAuto,
+ "all_except_auto"},
+ {modernize::UseTrailingReturnTypeCheck::TransformLambda::None,
+ "none"}};
+ return Mapping;
+ }
+};
+
+} // namespace clang::tidy
+
using namespace clang::ast_matchers;
namespace clang::tidy::modernize {
@@ -111,10 +135,17 @@ struct UnqualNameVisitor : public
RecursiveASTVisitor<UnqualNameVisitor> {
private:
const FunctionDecl &F;
};
+
+AST_MATCHER(LambdaExpr, hasExplicitResultType) {
+ return Node.hasExplicitResultType();
+}
+
} // namespace
-constexpr llvm::StringLiteral ErrorMessageOnFunction =
+constexpr llvm::StringLiteral MessageFunction =
"use a trailing return type for this function";
+constexpr llvm::StringLiteral MessageLambda =
+ "use a trailing return type for this lambda";
static SourceLocation expandIfMacroId(SourceLocation Loc,
const SourceManager &SM) {
@@ -285,7 +316,6 @@ findReturnTypeAndCVSourceRange(const FunctionDecl &F, const
TypeLoc &ReturnLoc,
return {};
}
-
// If the return type has no local qualifiers, it's source range is accurate.
if (!hasAnyNestedLocalQualifiers(F.getReturnType()))
return ReturnTypeRange;
@@ -329,6 +359,48 @@ findReturnTypeAndCVSourceRange(const FunctionDecl &F,
const TypeLoc &ReturnLoc,
return ReturnTypeRange;
}
+static SourceLocation findLambdaTrailingReturnInsertLoc(
+ const CXXMethodDecl *Method, const SourceManager &SM,
+ const LangOptions &LangOpts, const ASTContext &Ctx) {
+ // 'requires' keyword is present in lambda declaration
+ if (Method->getTrailingRequiresClause()) {
+ SourceLocation ParamEndLoc;
+ if (Method->param_empty())
+ ParamEndLoc = Method->getBeginLoc();
+ else
+ ParamEndLoc = Method->getParametersSourceRange().getEnd();
+
+ std::pair<FileID, unsigned> ParamEndLocInfo =
+ SM.getDecomposedLoc(ParamEndLoc);
+ StringRef Buffer = SM.getBufferData(ParamEndLocInfo.first);
+
+ Lexer Lexer(SM.getLocForStartOfFile(ParamEndLocInfo.first), LangOpts,
+ Buffer.begin(), Buffer.data() + ParamEndLocInfo.second,
+ Buffer.end());
+
+ Token Token;
+ while (!Lexer.LexFromRawLexer(Token)) {
+ if (Token.is(tok::raw_identifier)) {
+ IdentifierInfo &Info = Ctx.Idents.get(StringRef(
+ SM.getCharacterData(Token.getLocation()), Token.getLength()));
+ Token.setIdentifierInfo(&Info);
+ Token.setKind(Info.getTokenID());
+ }
+
+ if (Token.is(tok::kw_requires))
+ return Token.getLocation().getLocWithOffset(-1);
+ }
+
+ return {};
+ }
+
+ // If no requires clause, insert before the body
+ if (const Stmt *Body = Method->getBody())
+ return Body->getBeginLoc().getLocWithOffset(-1);
+
+ return {};
+}
+
static void keepSpecifiers(std::string &ReturnType, std::string &Auto,
SourceRange ReturnTypeCVRange, const FunctionDecl
&F,
const FriendDecl *Fr, const ASTContext &Ctx,
@@ -382,14 +454,43 @@ static void keepSpecifiers(std::string &ReturnType,
std::string &Auto,
}
}
+UseTrailingReturnTypeCheck::UseTrailingReturnTypeCheck(
+ StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context),
+ TransformFunctions(Options.get("TransformFunctions", true)),
+ TransformLambdas(Options.get("TransformLambdas", TransformLambda::All)) {
+
+ if (TransformFunctions == false && TransformLambdas == TransformLambda::None)
+ this->configurationDiag(
+ "The check 'modernize-use-trailing-return-type' will not perform any "
+ "analysis because 'TransformFunctions' and 'TransformLambdas' are "
+ "disabled.");
+}
+
+void UseTrailingReturnTypeCheck::storeOptions(
+ ClangTidyOptions::OptionMap &Opts) {
+ Options.store(Opts, "TransformFunctions", TransformFunctions);
+ Options.store(Opts, "TransformLambdas", TransformLambdas);
+}
+
void UseTrailingReturnTypeCheck::registerMatchers(MatchFinder *Finder) {
- auto F = functionDecl(
- unless(anyOf(hasTrailingReturn(), returns(voidType()),
- cxxConversionDecl(), cxxMethodDecl(isImplicit()))))
- .bind("Func");
+ auto F =
+ functionDecl(
+ unless(anyOf(
+ hasTrailingReturn(), returns(voidType()), cxxConversionDecl(),
+ cxxMethodDecl(
+ anyOf(isImplicit(),
+ hasParent(cxxRecordDecl(hasParent(lambdaExpr()))))))))
+ .bind("Func");
+
+ if (TransformFunctions) {
+ Finder->addMatcher(F, this);
+ Finder->addMatcher(friendDecl(hasDescendant(F)).bind("Friend"), this);
+ }
- Finder->addMatcher(F, this);
- Finder->addMatcher(friendDecl(hasDescendant(F)).bind("Friend"), this);
+ if (TransformLambdas != TransformLambda::None)
+ Finder->addMatcher(
+ lambdaExpr(unless(hasExplicitResultType())).bind("Lambda"), this);
}
void UseTrailingReturnTypeCheck::registerPPCallbacks(
@@ -401,8 +502,13 @@ void UseTrailingReturnTypeCheck::check(const
MatchFinder::MatchResult &Result) {
assert(PP && "Expected registerPPCallbacks() to have been called before so "
"preprocessor is available");
- const auto *F = Result.Nodes.getNodeAs<FunctionDecl>("Func");
+ if (const auto *Lambda = Result.Nodes.getNodeAs<LambdaExpr>("Lambda")) {
+ diagOnLambda(Lambda, Result);
+ return;
+ }
+
const auto *Fr = Result.Nodes.getNodeAs<FriendDecl>("Friend");
+ const auto *F = Result.Nodes.getNodeAs<FunctionDecl>("Func");
assert(F && "Matcher is expected to find only FunctionDecls");
// Three-way comparison operator<=> is syntactic sugar and generates implicit
@@ -422,7 +528,7 @@ void UseTrailingReturnTypeCheck::check(const
MatchFinder::MatchResult &Result) {
if (F->getDeclaredReturnType()->isFunctionPointerType() ||
F->getDeclaredReturnType()->isMemberFunctionPointerType() ||
F->getDeclaredReturnType()->isMemberPointerType()) {
- diag(F->getLocation(), ErrorMessageOnFunction);
+ diag(F->getLocation(), MessageFunction);
return;
}
@@ -439,14 +545,14 @@ void UseTrailingReturnTypeCheck::check(const
MatchFinder::MatchResult &Result) {
// FIXME: This may happen if we have __attribute__((...)) on the function.
// We abort for now. Remove this when the function type location gets
// available in clang.
- diag(F->getLocation(), ErrorMessageOnFunction);
+ diag(F->getLocation(), MessageFunction);
return;
}
SourceLocation InsertionLoc =
findTrailingReturnTypeSourceLocation(*F, FTL, Ctx, SM, LangOpts);
if (InsertionLoc.isInvalid()) {
- diag(F->getLocation(), ErrorMessageOnFunction);
+ diag(F->getLocation(), MessageFunction);
return;
}
@@ -456,7 +562,7 @@ void UseTrailingReturnTypeCheck::check(const
MatchFinder::MatchResult &Result) {
SourceRange ReturnTypeCVRange = findReturnTypeAndCVSourceRange(
*F, FTL.getReturnLoc(), Ctx, SM, LangOpts, PP);
if (ReturnTypeCVRange.isInvalid()) {
- diag(F->getLocation(), ErrorMessageOnFunction);
+ diag(F->getLocation(), MessageFunction);
return;
}
@@ -471,7 +577,7 @@ void UseTrailingReturnTypeCheck::check(const
MatchFinder::MatchResult &Result) {
UnqualNameVisitor UNV{*F};
UNV.TraverseTypeLoc(FTL.getReturnLoc());
if (UNV.Collision) {
- diag(F->getLocation(), ErrorMessageOnFunction);
+ diag(F->getLocation(), MessageFunction);
return;
}
@@ -490,9 +596,46 @@ void UseTrailingReturnTypeCheck::check(const
MatchFinder::MatchResult &Result) {
keepSpecifiers(ReturnType, Auto, ReturnTypeCVRange, *F, Fr, Ctx, SM,
LangOpts,
PP);
- diag(F->getLocation(), ErrorMessageOnFunction)
+ diag(F->getLocation(), MessageFunction)
<< FixItHint::CreateReplacement(ReturnTypeCVRange, Auto)
<< FixItHint::CreateInsertion(InsertionLoc, " -> " + ReturnType);
}
+void UseTrailingReturnTypeCheck::diagOnLambda(
+ const LambdaExpr *Lambda,
+ const ast_matchers::MatchFinder::MatchResult &Result) {
+
+ const CXXMethodDecl *Method = Lambda->getCallOperator();
+ if (!Method || Lambda->hasExplicitResultType())
+ return;
+
+ const ASTContext *Ctx = Result.Context;
+ const QualType ReturnType = Method->getReturnType();
+
+ // We can't write 'auto' in C++11 mode, try to write generic msg and bail
out.
+ if (ReturnType->isDependentType() &&
+ Ctx->getLangOpts().LangStd == LangStandard::lang_cxx11) {
+ if (TransformLambdas == TransformLambda::All)
+ diag(Lambda->getBeginLoc(), MessageLambda);
+ return;
+ }
+
+ if (ReturnType->isUndeducedAutoType() &&
+ TransformLambdas == TransformLambda::AllExceptAuto)
+ return;
+
+ const SourceLocation TrailingReturnInsertLoc =
+ findLambdaTrailingReturnInsertLoc(Method, *Result.SourceManager,
+ getLangOpts(), *Result.Context);
+
+ if (TrailingReturnInsertLoc.isValid())
+ diag(Lambda->getBeginLoc(), "use a trailing return type for this lambda")
+ << FixItHint::CreateInsertion(
+ TrailingReturnInsertLoc,
+ " -> " +
+
ReturnType.getAsString(Result.Context->getPrintingPolicy()));
+ else
+ diag(Lambda->getBeginLoc(), MessageLambda);
+}
+
} // namespace clang::tidy::modernize
diff --git
a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h
b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h
index 7f20674d15a5c..91369919c5d36 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h
@@ -26,18 +26,25 @@ struct ClassifiedToken {
///
http://clang.llvm.org/extra/clang-tidy/checks/modernize/use-trailing-return-type.html
class UseTrailingReturnTypeCheck : public ClangTidyCheck {
public:
- UseTrailingReturnTypeCheck(StringRef Name, ClangTidyContext *Context)
- : ClangTidyCheck(Name, Context) {}
+ UseTrailingReturnTypeCheck(StringRef Name, ClangTidyContext *Context);
bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
return LangOpts.CPlusPlus11;
}
+ void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
void registerMatchers(ast_matchers::MatchFinder *Finder) override;
void registerPPCallbacks(const SourceManager &SM, Preprocessor *PP,
Preprocessor *ModuleExpanderPP) override;
void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+ enum TransformLambda { All, AllExceptAuto, None };
+
private:
Preprocessor *PP = nullptr;
+ const bool TransformFunctions;
+ const TransformLambda TransformLambdas;
+
+ void diagOnLambda(const LambdaExpr *Lambda,
+ const ast_matchers::MatchFinder::MatchResult &Result);
};
} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst
b/clang-tools-extra/docs/ReleaseNotes.rst
index b7d0a223ce5bb..a275d2ccfa004 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -236,6 +236,13 @@ Changes in existing checks
<clang-tidy/checks/modernize/use-std-numbers>` check to support math
functions of different precisions.
+- Improved :doc:`modernize-use-trailing-return-type
+ <clang-tidy/checks/modernize/use-trailing-return-type>` check by adding
+ support to modernize lambda signatures to use trailing return type and adding
+ two new options: `TransformFunctions` and `TransformLambdas` to control
+ whether function declarations and lambdas should be transformed by the check.
+ Fixed false positives when lambda was matched as a function in C++11 mode.
+
- Improved :doc:`performance-move-const-arg
<clang-tidy/checks/performance/move-const-arg>` check by fixing false
negatives on ternary operators calling ``std::move``.
diff --git
a/clang-tools-extra/docs/clang-tidy/checks/modernize/use-trailing-return-type.rst
b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-trailing-return-type.rst
index 0593a35326aaa..ed2a11a65f69a 100644
---
a/clang-tools-extra/docs/clang-tidy/checks/modernize/use-trailing-return-type.rst
+++
b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-trailing-return-type.rst
@@ -3,7 +3,7 @@
modernize-use-trailing-return-type
==================================
-Rewrites function signatures to use a trailing return type
+Rewrites function and lambda signatures to use a trailing return type
(introduced in C++11). This transformation is purely stylistic.
The return type before the function name is replaced by ``auto``
and inserted after the function parameter list (and qualifiers).
@@ -16,6 +16,7 @@ Example
int f1();
inline int f2(int arg) noexcept;
virtual float f3() const && = delete;
+ auto lambda = []() {};
transforms to:
@@ -24,6 +25,7 @@ transforms to:
auto f1() -> int;
inline auto f2(int arg) -> int noexcept;
virtual auto f3() const && -> float = delete;
+ auto lambda = []() -> void {};
Known Limitations
-----------------
@@ -66,3 +68,25 @@ a careless rewrite would produce the following output:
This code fails to compile because the S in the context of f refers to the
equally named function parameter.
Similarly, the S in the context of m refers to the equally named class member.
The check can currently only detect and avoid a clash with a function
parameter name.
+
+Options
+-------
+
+.. option:: TransformFunctions
+
+ When set to `true`, function declarations will be transformed to use trailing
+ return. Default is `true`.
+
+.. option:: TransformLambdas
+
+ Controls how lambda expressions are transformed to use trailing
+ return type. Possible values are:
+
+ * `all` - Transform all lambda expressions without an explicit return type
+ to use trailing return type. If type can not be deduced, ``auto`` will be
+ used in since C++14 and generic message will be emitted otherwise.
+ * `all_except_auto` - Transform all lambda expressions except those whose
return
+ type can not be deduced.
+ * `none` - Do not transform any lambda expressions.
+
+ Default is `all`.
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-transform-lambdas-cxx14.cpp
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-transform-lambdas-cxx14.cpp
new file mode 100644
index 0000000000000..33051c63e4f17
--- /dev/null
+++
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-transform-lambdas-cxx14.cpp
@@ -0,0 +1,24 @@
+// RUN: %check_clang_tidy -std=c++14-or-later %s
modernize-use-trailing-return-type %t -- -- -fno-delayed-template-parsing
+
+namespace std {
+ template <typename T>
+ class vector {};
+
+ class string {};
+} // namespace std
+
+void test_lambda_positive() {
+ auto l1 = [](auto x) { return x; };
+ // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: use a trailing return type for
this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES: {{^}} auto l1 = [](auto x) -> auto { return x; };{{$}}
+}
+
+template <template <typename> class C>
+void test_lambda_positive_template() {
+ auto l1 = []() { return C<int>{}; };
+ // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: use a trailing return type for
this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES: {{^}} auto l1 = []() -> auto { return C<int>{}; };{{$}}
+ auto l2 = []() { return 0; };
+ // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: use a trailing return type for
this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES: {{^}} auto l2 = []() -> auto { return 0; };{{$}}
+}
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-transform-lambdas-cxx20.cpp
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-transform-lambdas-cxx20.cpp
new file mode 100644
index 0000000000000..521b5c6d36184
--- /dev/null
+++
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-transform-lambdas-cxx20.cpp
@@ -0,0 +1,35 @@
+// RUN: %check_clang_tidy -std=c++20-or-later %s
modernize-use-trailing-return-type %t -- -- -fno-delayed-template-parsing
+
+namespace std {
+template <typename T, typename U>
+struct is_same { static constexpr auto value = false; };
+
+template <typename T>
+struct is_same<T, T> { static constexpr auto value = true; };
+
+template <typename T>
+concept floating_point = std::is_same<T, float>::value || std::is_same<T,
double>::value || std::is_same<T, long double>::value;
+}
+
+void test_lambda_positive() {
+ auto l1 = []<typename T, typename U>(T x, U y) { return x + y; };
+ // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: use a trailing return type for
this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES: {{^}} auto l1 = []<typename T, typename U>(T x, U y) ->
auto { return x + y; };{{$}}
+ auto l2 = [](auto x) requires requires { x + x; } { return x; };
+ // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: use a trailing return type for
this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES: {{^}} auto l2 = [](auto x) -> auto requires requires { x +
x; } { return x; };{{$}}
+ auto l3 = [](auto x) requires std::floating_point<decltype(x)> { return x; };
+ // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: use a trailing return type for
this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES: {{^}} auto l3 = [](auto x) -> auto requires
std::floating_point<decltype(x)> { return x; };{{$}}
+ auto l4 = [](int x) consteval { return x; };
+ // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: use a trailing return type for
this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES: {{^}} auto l4 = [](int x) consteval -> int { return x;
};{{$}}
+ // Complete complex example
+ auto l5 = []<typename T, typename U>(T x, U y) constexpr noexcept
+ requires std::floating_point<T> && std::floating_point<U>
+ { return x * y; };
+ // CHECK-MESSAGES: :[[@LINE-3]]:13: warning: use a trailing return type for
this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES: {{^}} auto l5 = []<typename T, typename U>(T x, U y)
constexpr noexcept{{$}}
+ // CHECK-FIXES: {{^}} -> auto requires std::floating_point<T> &&
std::floating_point<U>{{$}}
+ // CHECK-FIXES: {{^}} { return x * y; };{{$}}
+}
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-transform-lambdas.cpp
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-transform-lambdas.cpp
new file mode 100644
index 0000000000000..0b7e7a15b2f1b
--- /dev/null
+++
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-transform-lambdas.cpp
@@ -0,0 +1,89 @@
+// RUN: %check_clang_tidy -check-suffix=ALL -std=c++11-or-later %s
modernize-use-trailing-return-type %t --\
+// RUN: -config="{CheckOptions:
{modernize-use-trailing-return-type.TransformLambdas: all, \
+// RUN:
modernize-use-trailing-return-type.TransformFunctions: false}}" \
+// RUN: -- -fno-delayed-template-parsing
+// RUN: %check_clang_tidy -check-suffix=NOAUTO -std=c++11-or-later %s
modernize-use-trailing-return-type %t --\
+// RUN: -config="{CheckOptions:
{modernize-use-trailing-return-type.TransformLambdas: all_except_auto, \
+// RUN:
modernize-use-trailing-return-type.TransformFunctions: false}}" \
+// RUN: -- -fno-delayed-template-parsing
+// RUN: %check_clang_tidy -check-suffix=NONE -std=c++11-or-later %s
modernize-use-trailing-return-type %t --\
+// RUN: -config="{CheckOptions:
{modernize-use-trailing-return-type.TransformLambdas: none, \
+// RUN:
modernize-use-trailing-return-type.TransformFunctions: true}}" \
+// RUN: -- -fno-delayed-template-parsing
+
+namespace std {
+ template <typename T>
+ class vector {};
+
+ class string {};
+} // namespace std
+
+void test_lambda_positive() {
+ auto l01 = [] {};
+ // CHECK-MESSAGES-ALL: :[[@LINE-1]]:14: warning: use a trailing return type
for this lambda [modernize-use-trailing-return-type]
+ // CHECK-MESSAGES-NOAUTO: :[[@LINE-2]]:14: warning: use a trailing return
type for this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES-ALL: {{^}} auto l01 = [] -> void {};{{$}}
+ auto l1 = []() {};
+ // CHECK-MESSAGES-ALL: :[[@LINE-1]]:13: warning: use a trailing return type
for this lambda [modernize-use-trailing-return-type]
+ // CHECK-MESSAGES-NOAUTO: :[[@LINE-2]]:13: warning: use a trailing return
type for this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES-ALL: {{^}} auto l1 = []() -> void {};{{$}}
+ auto l2 = []() { return 42; };
+ // CHECK-MESSAGES-ALL: :[[@LINE-1]]:13: warning: use a trailing return type
for this lambda [modernize-use-trailing-return-type]
+ // CHECK-MESSAGES-NOAUTO: :[[@LINE-2]]:13: warning: use a trailing return
type for this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES-ALL: {{^}} auto l2 = []() -> int { return 42; };{{$}}
+ auto l3 = [](int x, double y) { return x * y; };
+ // CHECK-MESSAGES-ALL: :[[@LINE-1]]:13: warning: use a trailing return type
for this lambda [modernize-use-trailing-return-type]
+ // CHECK-MESSAGES-NOAUTO: :[[@LINE-2]]:13: warning: use a trailing return
type for this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES-ALL: {{^}} auto l3 = [](int x, double y) -> double { return
x * y; };{{$}}
+
+ int capture_int = 10;
+ double capture_double = 3.14;
+ int* capture_ptr = nullptr;
+
+ auto l4 = [capture_int]() { return capture_int; };
+ // CHECK-MESSAGES-ALL: :[[@LINE-1]]:13: warning: use a trailing return type
for this lambda [modernize-use-trailing-return-type]
+ // CHECK-MESSAGES-NOAUTO: :[[@LINE-2]]:13: warning: use a trailing return
type for this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES-ALL: {{^}} auto l4 = [capture_int]() -> int { return
capture_int; };{{$}}
+ auto l5 = [capture_int, &capture_double](char c) { return capture_int +
capture_double + c; };
+ // CHECK-MESSAGES-ALL: :[[@LINE-1]]:13: warning: use a trailing return type
for this lambda [modernize-use-trailing-return-type]
+ // CHECK-MESSAGES-NOAUTO: :[[@LINE-2]]:13: warning: use a trailing return
type for this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES-ALL: {{^}} auto l5 = [capture_int, &capture_double](char c)
-> double { return capture_int + capture_double + c; };{{$}}
+ auto l6 = [capture_int]() constexpr mutable noexcept { return ++capture_int;
};
+ // CHECK-MESSAGES-ALL: :[[@LINE-1]]:13: warning: use a trailing return type
for this lambda [modernize-use-trailing-return-type]
+ // CHECK-MESSAGES-NOAUTO: :[[@LINE-2]]:13: warning: use a trailing return
type for this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES-ALL: {{^}} auto l6 = [capture_int]() constexpr mutable
noexcept -> int { return ++capture_int; };{{$}}
+ auto l7 = [&capture_ptr]() { return capture_ptr; };
+ // CHECK-MESSAGES-ALL: :[[@LINE-1]]:13: warning: use a trailing return type
for this lambda [modernize-use-trailing-return-type]
+ // CHECK-MESSAGES-NOAUTO: :[[@LINE-2]]:13: warning: use a trailing return
type for this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES-ALL: {{^}} auto l7 = [&capture_ptr]() -> int * { return
capture_ptr; };{{$}}
+ auto l8 = [&capture_int]() { return capture_int; };
+ // CHECK-MESSAGES-ALL: :[[@LINE-1]]:13: warning: use a trailing return type
for this lambda [modernize-use-trailing-return-type]
+ // CHECK-MESSAGES-NOAUTO: :[[@LINE-2]]:13: warning: use a trailing return
type for this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES-ALL: {{^}} auto l8 = [&capture_int]() -> int { return
capture_int; };{{$}}
+ auto l9 = [] { return std::vector<std::vector<int>>{}; };
+ // CHECK-MESSAGES-ALL: :[[@LINE-1]]:13: warning: use a trailing return type
for this lambda [modernize-use-trailing-return-type]
+ // CHECK-MESSAGES-NOAUTO: :[[@LINE-2]]:13: warning: use a trailing return
type for this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES-ALL: {{^}} auto l9 = [] -> std::vector<std::vector<int>> {
return std::vector<std::vector<int>>{}; };{{$}}
+ auto l10 = [] { const char* const * const * const ptr = nullptr; return ptr;
};
+ // CHECK-MESSAGES-ALL: :[[@LINE-1]]:14: warning: use a trailing return type
for this lambda [modernize-use-trailing-return-type]
+ // CHECK-MESSAGES-NOAUTO: :[[@LINE-2]]:14: warning: use a trailing return
type for this lambda [modernize-use-trailing-return-type]
+ // CHECK-FIXES-ALL: {{^}} auto l10 = [] -> const char *const *const * {
const char* const * const * const ptr = nullptr; return ptr; };{{$}}
+}
+
+// In c++11 mode we can not write 'auto' type, see *-cxx14.cpp for fixes.
+template <template <typename> class C>
+void test_lambda_positive_template() {
+ auto l1 = []() { return C<int>{}; };
+ // CHECK-MESSAGES-ALL: :[[@LINE-1]]:13: warning: use a trailing return type
for this lambda [modernize-use-trailing-return-type]
+ auto l2 = []() { return 0; };
+ // CHECK-MESSAGES-ALL: :[[@LINE-1]]:13: warning: use a trailing return type
for this lambda [modernize-use-trailing-return-type]
+}
+
+void test_lambda_negative() {
+ auto l1_good = [](int arg) -> int { return 0; };
+}
+
+// this function is solely used to not to get "wrong config error" from the
check.
+int f();
+// CHECK-MESSAGES-NONE: :[[@LINE-1]]:5: warning: use a trailing return type
for this function [modernize-use-trailing-return-type]
+// CHECK-FIXES-NONE: {{^}}auto f() -> int;{{$}}
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-wrong-config.cpp
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-wrong-config.cpp
new file mode 100644
index 0000000000000..167e355f9fea7
--- /dev/null
+++
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type-wrong-config.cpp
@@ -0,0 +1,5 @@
+// RUN: %check_clang_tidy -std=c++11-or-later %s
modernize-use-trailing-return-type %t \
+// RUN: -config="{CheckOptions:
{modernize-use-trailing-return-type.TransformLambdas: none, \
+// RUN:
modernize-use-trailing-return-type.TransformFunctions: false}}"
+
+// CHECK-MESSAGES: warning: The check 'modernize-use-trailing-return-type'
will not perform any analysis because 'TransformFunctions' and
'TransformLambdas' are disabled. [clang-tidy-config]
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type.cpp
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type.cpp
index e1f36c52a7c01..c16c033f0b016 100644
---
a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type.cpp
+++
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-trailing-return-type.cpp
@@ -594,5 +594,3 @@ struct D2 : B {
operator double();
};
-auto l1 = [](int arg) {};
-auto l2 = [](int arg) -> double { return 0; };
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