Rakete1111 created this revision.
Rakete1111 added a reviewer: rsmith.
This change rejects the shadowing of a capture by a parameter in lambdas in
C++17.
int main() {
int a;
auto f = [a](int a) { return a; };
}
results in:
main.cpp:3:20: error: a lambda parameter cannot shadow an explicitly captured
entity
auto f = [a](int a) { return a; };
^
main.cpp:3:13: note: variable a is explicitly captured here
auto f = [a](int a) { return a; };
^
Repository:
rC Clang
https://reviews.llvm.org/D53595
Files:
include/clang/Basic/DiagnosticSemaKinds.td
include/clang/Sema/Sema.h
lib/Sema/SemaLambda.cpp
test/SemaCXX/warn-shadow-in-lambdas.cpp
Index: test/SemaCXX/warn-shadow-in-lambdas.cpp
===================================================================
--- test/SemaCXX/warn-shadow-in-lambdas.cpp
+++ test/SemaCXX/warn-shadow-in-lambdas.cpp
@@ -1,6 +1,7 @@
// RUN: %clang_cc1 -std=c++14 -verify -fsyntax-only -Wshadow -D AVOID %s
// RUN: %clang_cc1 -std=c++14 -verify -fsyntax-only -Wshadow -Wshadow-uncaptured-local %s
// RUN: %clang_cc1 -std=c++14 -verify -fsyntax-only -Wshadow-all %s
+// RUN: %clang_cc1 -std=c++17 -verify -fsyntax-only -Wshadow-all %s
void foo(int param) { // expected-note 1+ {{previous declaration is here}}
int var = 0; // expected-note 1+ {{previous declaration is here}}
@@ -78,8 +79,15 @@
auto f1 = [var] () { // expected-note {{variable 'var' is explicitly captured here}}
int var = 1; // expected-warning {{declaration shadows a local variable}}
};
- auto f2 = [param] // expected-note {{variable 'param' is explicitly captured here}}
- (int param) { ; }; // expected-warning {{declaration shadows a local variable}}
+ auto f2 = [param]
+ (int param) { ; };
+#if __cplusplus < 201703L
+ // expected-note@-3{{variable 'param' is explicitly captured here}}
+ // expected-warning@-3{{declaration shadows a local variable}}
+#else
+ // expected-error@-5{{a lambda parameter cannot shadow an explicitly captured entity}}
+ // expected-note@-7{{variable param is explicitly captured here}}
+#endif
}
// Warn for variables defined in the capture list.
@@ -134,8 +142,16 @@
auto g1 = [](auto param) { ; }; // expected-warning {{declaration shadows a local variable}}
auto g2 = [=](auto param) { ; }; // expected-warning {{declaration shadows a local variable}}
#endif
- auto g3 = [param] // expected-note {{variable 'param' is explicitly captured here}}
- (auto param) { ; }; // expected-warning {{declaration shadows a local variable}}
+ auto g3 = [param]
+ (auto param) { ; };
+#if __cplusplus < 201703L
+ // expected-note@-3{{variable 'param' is explicitly captured here}}
+ // expected-warning@-3{{declaration shadows a local variable}}
+#else
+ // expected-error@-5{{a lambda parameter cannot shadow an explicitly captured entity}}
+ // expected-note@-7{{variable param is explicitly captured here}}
+#endif
+
}
void avoidWarningWhenRedefining() {
@@ -145,3 +161,20 @@
int b = 0; // expected-error {{redefinition of 'b'}}
};
}
+
+void parameterShadowCapture() {
+#if __cplusplus >= 201703L
+ int var = 1; // expected-note{{previous declaration is here}}
+ auto f1 = [var](int var) { return var; }; // expected-error{{a lambda parameter cannot shadow an explicitly captured entity}}
+ // expected-note@-1{{variable var is explicitly captured here}}
+
+ auto f2 = [var = 1](int var) { return var; }; // expected-error{{a lambda parameter cannot shadow an explicitly captured entity}}
+ // expected-note@-1{{variable var is explicitly captured here}}
+ // expected-error@-2{{reference to 'var' is ambiguous}}
+ // expected-note@-3{{candidate found by name lookup is 'var'}}
+ // expected-note@-4{{candidate found by name lookup is 'var'}}
+
+ auto f3 = [=](int var) { return var; };
+ // expected-warning@-1{{declaration shadows a local variable}}
+#endif
+}
Index: lib/Sema/SemaLambda.cpp
===================================================================
--- lib/Sema/SemaLambda.cpp
+++ lib/Sema/SemaLambda.cpp
@@ -493,15 +493,30 @@
LSI->finishedExplicitCaptures();
}
-void Sema::addLambdaParameters(CXXMethodDecl *CallOperator, Scope *CurScope) {
+void Sema::addLambdaParameters(
+ const SmallVectorImpl<LambdaIntroducer::LambdaCapture> &Captures,
+ CXXMethodDecl *CallOperator, Scope *CurScope) {
// Introduce our parameters into the function scope
for (unsigned p = 0, NumParams = CallOperator->getNumParams();
p < NumParams; ++p) {
ParmVarDecl *Param = CallOperator->getParamDecl(p);
// If this has an identifier, add it to the scope stack.
if (CurScope && Param->getIdentifier()) {
- CheckShadow(CurScope, Param);
+ bool Error = false;
+ if (getLangOpts().CPlusPlus17) {
+ // Resolution of CWG 2211 in C++17 renders shadowing ill-formed.
+ for (const auto &Capture: Captures) {
+ if (Capture.Id && Capture.Id->getName() == Param->getName()) {
+ Error = true;
+ Diag(Param->getLocation(), diag::err_parameter_shadow_capture);
+ Diag(Capture.Loc, diag::note_var_explicitly_captured_here)
+ << Capture.Id->getName() << true;
+ }
+ }
+ }
+ if (!Error)
+ CheckShadow(CurScope, Param);
PushOnScopeChains(Param, CurScope);
}
@@ -1142,7 +1157,7 @@
LSI->ContainsUnexpandedParameterPack = ContainsUnexpandedParameterPack;
// Add lambda parameters into scope.
- addLambdaParameters(Method, CurScope);
+ addLambdaParameters(Intro.Captures, Method, CurScope);
// Enter a new evaluation context to insulate the lambda from any
// cleanups from the enclosing full-expression.
Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h
+++ include/clang/Sema/Sema.h
@@ -5580,7 +5580,9 @@
void finishLambdaExplicitCaptures(sema::LambdaScopeInfo *LSI);
/// Introduce the lambda parameters into scope.
- void addLambdaParameters(CXXMethodDecl *CallOperator, Scope *CurScope);
+ void addLambdaParameters(
+ const SmallVectorImpl<LambdaIntroducer::LambdaCapture> &Captures,
+ CXXMethodDecl *CallOperator, Scope *CurScope);
/// Deduce a block or lambda's return type based on the return
/// statements present in the body.
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -6630,6 +6630,10 @@
def ext_star_this_lambda_capture_cxx17 : ExtWarn<
"capture of '*this' by copy is a C++17 extension">, InGroup<CXX17>;
+ // C++17 shadow capture parameter
+ def err_parameter_shadow_capture : Error<
+ "a lambda parameter cannot shadow an explicitly captured entity">;
+
// C++2a [=, this] captures.
def warn_cxx17_compat_equals_this_lambda_capture : Warning<
"explicit capture of 'this' with a capture default of '=' is incompatible "
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
