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https://bugs.llvm.org/show_bug.cgi?id=40858
CheckShadow is now called for each binding in the structured binding to make
sure it does not shadow any other variable in scope. This does use a custom
implementation of getShadowedDeclaration though because a BindingDecl is not a
VarDecl
Added a few unit tests for this. In theory though all the other shadow unit
tests should be duplicated for the structured binding variables too but whether
it is probably not worth it as they use common code. The MyTuple and std
interface code has been copied from live-bindings-test.cpp
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D96147
Files:
clang/docs/ReleaseNotes.rst
clang/include/clang/Sema/Sema.h
clang/lib/Sema/SemaDecl.cpp
clang/lib/Sema/SemaDeclCXX.cpp
clang/test/SemaCXX/warn-shadow.cpp
Index: clang/test/SemaCXX/warn-shadow.cpp
===================================================================
--- clang/test/SemaCXX/warn-shadow.cpp
+++ clang/test/SemaCXX/warn-shadow.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -verify -fsyntax-only -std=c++11 -Wshadow-all %s
+// RUN: %clang_cc1 -verify -fsyntax-only -std=c++17 -Wshadow-all %s
namespace {
int i; // expected-note {{previous declaration is here}}
@@ -265,3 +265,86 @@
PR24718_1 // Does not shadow a type.
};
};
+
+// MyTuple and std code is copied from live-bindings-test.cpp
+
+//#define USE_STD
+
+#ifndef USE_STD
+// Machinery required for custom structured bindings decomposition.
+typedef unsigned long size_t;
+
+namespace std {
+template <class T> class tuple_size;
+template <class T>
+constexpr size_t tuple_size_v = tuple_size<T>::value;
+template <size_t I, class T> class tuple_element;
+
+template <class T, T v>
+struct integral_constant {
+ static constexpr T value = v;
+ typedef T value_type;
+ typedef integral_constant type;
+ constexpr operator value_type() const noexcept { return value; }
+};
+} // namespace std
+
+struct MyTuple {
+ int a;
+ int b;
+
+ template <size_t N>
+ int get() const {
+ if constexpr (N == 0)
+ return a;
+ else if constexpr (N == 1)
+ return b;
+ }
+};
+
+namespace std {
+template <>
+struct tuple_size<MyTuple>
+ : std::integral_constant<size_t, 2> {};
+
+template <size_t N>
+struct tuple_element<N, MyTuple> {
+ using type = int;
+};
+} // namespace std
+
+MyTuple getMyTuple();
+#else
+
+#include <tuple>
+std::tuple<int, int> getMyTuple();
+#endif
+
+
+namespace structured_binding_tests {
+int x; // expected-note {{previous declaration is here}}
+int y; // expected-note {{previous declaration is here}}
+
+void test1() {
+ const auto [x, y] = getMyTuple(); // expected-warning 2 {{declaration shadows a variable in namespace 'structured_binding_tests'}}
+}
+
+void test2() {
+ int a; // expected-note {{previous declaration is here}}
+ bool b; // expected-note {{previous declaration is here}}
+ {
+ auto [a, b] = getMyTuple(); // expected-warning 2 {{declaration shadows a local variable}}
+ }
+}
+
+class A
+{
+ int m_a; // expected-note {{previous declaration is here}}
+ int m_b; // expected-note {{previous declaration is here}}
+
+ void test3() {
+ auto [m_a, m_b] = getMyTuple(); // expected-warning 2 {{declaration shadows a field of 'structured_binding_tests::A'}}
+ }
+};
+
+}; // namespace structured_binding_tests
\ No newline at end of file
Index: clang/lib/Sema/SemaDeclCXX.cpp
===================================================================
--- clang/lib/Sema/SemaDeclCXX.cpp
+++ clang/lib/Sema/SemaDeclCXX.cpp
@@ -857,17 +857,28 @@
Previous.clear();
}
+ auto *BD = BindingDecl::Create(Context, DC, B.NameLoc, B.Name);
+
+ // Find the shadowed declaration before filtering for scope.
+ NamedDecl *ShadowedDecl = D.getCXXScopeSpec().isEmpty()
+ ? getShadowedDeclaration(BD, Previous)
+ : nullptr;
+
bool ConsiderLinkage = DC->isFunctionOrMethod() &&
DS.getStorageClassSpec() == DeclSpec::SCS_extern;
FilterLookupForScope(Previous, DC, S, ConsiderLinkage,
/*AllowInlineNamespace*/false);
+
+ // Diagnose shadowed variables if this isn't a redeclaration.
+ if (ShadowedDecl && !D.isRedeclaration())
+ CheckShadow(BD, ShadowedDecl, Previous);
+
if (!Previous.empty()) {
auto *Old = Previous.getRepresentativeDecl();
Diag(B.NameLoc, diag::err_redefinition) << B.Name;
Diag(Old->getLocation(), diag::note_previous_definition);
}
- auto *BD = BindingDecl::Create(Context, DC, B.NameLoc, B.Name);
PushOnScopeChains(BD, S, true);
Bindings.push_back(BD);
ParsingInitForAutoVars.insert(BD);
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -7557,6 +7557,19 @@
return isa<TypedefNameDecl>(ShadowedDecl) ? ShadowedDecl : nullptr;
}
+/// Return the declaration shadowed by the given variable \p D, or null
+/// if it doesn't shadow any declaration or shadowing warnings are disabled.
+NamedDecl *Sema::getShadowedDeclaration(const BindingDecl *D,
+ const LookupResult &R) {
+ if (!shouldWarnIfShadowedDecl(Diags, R))
+ return nullptr;
+
+ NamedDecl *ShadowedDecl = R.getFoundDecl();
+ return isa<VarDecl>(ShadowedDecl) || isa<FieldDecl>(ShadowedDecl)
+ ? ShadowedDecl
+ : nullptr;
+}
+
/// Diagnose variable or built-in function shadowing. Implements
/// -Wshadow.
///
Index: clang/include/clang/Sema/Sema.h
===================================================================
--- clang/include/clang/Sema/Sema.h
+++ clang/include/clang/Sema/Sema.h
@@ -2595,6 +2595,7 @@
NamedDecl *getShadowedDeclaration(const TypedefNameDecl *D,
const LookupResult &R);
NamedDecl *getShadowedDeclaration(const VarDecl *D, const LookupResult &R);
+ NamedDecl *getShadowedDeclaration(const BindingDecl *D, const LookupResult &R);
void CheckShadow(NamedDecl *D, NamedDecl *ShadowedDecl,
const LookupResult &R);
void CheckShadow(Scope *S, VarDecl *D);
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -71,7 +71,7 @@
Modified Compiler Flags
-----------------------
-- ...
+- -Wshadow now also checks for shadowed structured bindings
Removed Compiler Flags
-------------------------
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