shylie/llvm-project
1
0
Fork 0
Code Issues Pull Requests Actions 6 Packages Projects Releases Wiki Activity

Revert "[clang] Fix conflicting declaration error with using_if_exists" (#190441)

Browse Source 
Reverts llvm/llvm-project#167646
This commit is contained in:
Petr Hosek 2026-04-03 19:25:34 -07:00 committed by GitHub
parent 5cd98f966e
commit 3080198cc3
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
3 changed files with 44 additions and 86 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
clang/lib/Sema/SemaDeclCXX.cpp
View File

@ -12926,11 +12926,19 @@ bool Sema::CheckUsingShadowDecl(BaseUsingDecl *BUD, NamedDecl *Orig,
if (FoundEquivalentDecl)
return false;
// This using_if_exists decl cannot be a subsitute for the original decl,
// so do not create a shadow decl for this case.
// Always emit a diagnostic for a mismatch between an unresolved
// using_if_exists and a resolved using declaration in either direction.
if (isa<UnresolvedUsingIfExistsDecl>(Target) !=
(isa_and_nonnull<UnresolvedUsingIfExistsDecl>(NonTag)))
return false;
(isa_and_nonnull<UnresolvedUsingIfExistsDecl>(NonTag))) {
if (!NonTag && !Tag)
return false;
Diag(BUD->getLocation(), diag::err_using_decl_conflict);
Diag(Target->getLocation(), diag::note_using_decl_target);
Diag((NonTag ? NonTag : Tag)->getLocation(),
diag::note_using_decl_conflict);
BUD->setInvalidDecl();
return true;
}
if (FunctionDecl *FD = Target->getAsFunction()) {
NamedDecl *OldDecl = nullptr;

33
clang/lib/Sema/SemaLookup.cpp
View File

@ -521,15 +521,11 @@ void LookupResult::resolveKind() {
llvm::SmallVector<const NamedDecl *, 4> EquivalentNonFunctions;
llvm::BitVector RemovedDecls(N);
llvm::BitVector UnresolvedUsingDecls(N);
for (unsigned I = 0; I < N; I++) {
const NamedDecl *D = Decls[I]->getUnderlyingDecl();
D = cast<NamedDecl>(D->getCanonicalDecl());
if (isa<UnresolvedUsingIfExistsDecl>(D))
UnresolvedUsingDecls.set(I);
// Ignore an invalid declaration unless it's the only one left.
// Also ignore HLSLBufferDecl which not have name conflict with other Decls.
if ((D->isInvalidDecl() || isa<HLSLBufferDecl>(D)) &&
@ -637,31 +633,6 @@ void LookupResult::resolveKind() {
getSema().diagnoseEquivalentInternalLinkageDeclarations(
getNameLoc(), HasNonFunction, EquivalentNonFunctions);
// A lookup can be ambiguous if we find multiple declarations that cannot
// coexist. This occurs if:
//
// 1. We have a non-function (like a variable or namespace), which cannot
// be overloaded, and either a function or an unresolved using declaration.
bool ConflictWithNonFunction =
HasNonFunction && (HasFunction || HasUnresolved);
// 2. We have a hidden tag (struct or enum) and another declaration, and
// Because they both remain in the results, they must be from different
// scopes. If they were in the same scope, the tag would have been hidden
// and removed prior.
bool HiddenTagConflict =
HideTags && HasTag && (HasFunction || HasNonFunction || HasUnresolved);
if (ConflictWithNonFunction || HiddenTagConflict)
Ambiguous = true;
if (Ambiguous && UnresolvedUsingDecls.count()) {
// If we would have an ambiguous reference but any of them are
// using_if_exist decls, ignore them since they are unresolved.
RemovedDecls |= UnresolvedUsingDecls;
Ambiguous = false;
}
// Remove decls by replacing them with decls from the end (which
// means that we need to iterate from the end) and then truncating
// to the new size.
@ -669,6 +640,10 @@ void LookupResult::resolveKind() {
Decls[I] = Decls[--N];
Decls.truncate(N);
if ((HasNonFunction && (HasFunction || HasUnresolved)) ||
(HideTags && HasTag && (HasFunction || HasNonFunction || HasUnresolved)))
Ambiguous = true;
if (Ambiguous && ReferenceToPlaceHolderVariable)
setAmbiguous(LookupAmbiguityKind::AmbiguousReferenceToPlaceholderVariable);
else if (Ambiguous)

81
clang/test/SemaCXX/using-if-exists.cpp
View File

@ -22,28 +22,28 @@ using NS::x UIE;
namespace NS1 {}
namespace NS2 {}
namespace NS3 {
int A();
struct B {};
int C();
struct D {};
int A(); // expected-note{{target of using declaration}}
struct B {}; // expected-note{{target of using declaration}}
int C(); // expected-note{{conflicting declaration}}
struct D {}; // expected-note{{conflicting declaration}}
} // namespace NS3
using NS1::A UIE; // OK since this declaration shouldn't exist since `A` is not in `NS1`
using NS2::A UIE; // OK since this declaration shouldn't exist since `A` is not in `NS2`
using NS3::A UIE; // OK since prior UIEs of `A` shouldn't have declare anything since they don't exist
int i = A(); // OK since `A` resolved to the single UIE in the previous line
using NS1::A UIE;
using NS2::A UIE; // expected-note{{using declaration annotated with 'using_if_exists' here}} expected-note{{conflicting declaration}}
using NS3::A UIE; // expected-error{{target of using declaration conflicts with declaration already in scope}}
int i = A(); // expected-error{{reference to unresolved using declaration}}
using NS1::B UIE; // OK since this declaration shouldn't exist since `B` is not in `NS1`
using NS2::B UIE; // OK since this declaration shouldn't exist since `B` is not in `NS2
using NS3::B UIE; // OK since prior UIEs of `B` shouldn't have declare anything since they don't exist
B myB; // OK since `B` resolved to the single UIE in the previous line
using NS1::B UIE;
using NS2::B UIE; // expected-note{{conflicting declaration}} expected-note{{using declaration annotated with 'using_if_exists' here}}
using NS3::B UIE; // expected-error{{target of using declaration conflicts with declaration already in scope}}
B myB; // expected-error{{reference to unresolved using declaration}}
using NS3::C UIE;
using NS2::C UIE; // OK since NS2::C doesn't exist
using NS2::C UIE; // expected-error{{target of using declaration conflicts with declaration already in scope}} expected-note{{target of using declaration}}
int j = C();
using NS3::D UIE;
using NS2::D UIE; // OK since NS2::D doesn't exist
using NS2::D UIE; // expected-error{{target of using declaration conflicts with declaration already in scope}} expected-note{{target of using declaration}}
D myD;
} // namespace test_redecl
@ -113,12 +113,7 @@ struct NonDep : BaseEmpty {
namespace test_using_pack {
template <class... Ts>
struct S : Ts... {
// We don't expect any errors with conflicting targets for variables `a`, `b`, `c`,
// and `d` below this. For `a`, `x` will not be declared because neither E1 nor E2
// defines it. For `b`, `x` is the same type so there won't be any conflicts. For
// `c` and `d`, only one of the template parameters has a class that defines it,
// so there's no conflict.
using typename Ts::x... UIE;
using typename Ts::x... UIE; // expected-error 2 {{target of using declaration conflicts with declaration already in scope}} expected-note{{conflicting declaration}} expected-note{{target of using declaration}}
};
struct E1 {};
@ -126,23 +121,21 @@ struct E2 {};
S<E1, E2> a;
struct F1 {
typedef int x;
typedef int x; // expected-note 2 {{conflicting declaration}}
};
struct F2 {
typedef int x;
typedef int x; // expected-note 2 {{target of using declaration}}
};
S<F1, F2> b;
S<E1, F2> c;
S<F1, E2> d;
S<E1, F2> c; // expected-note{{in instantiation of template class}}
S<F1, E2> d; // expected-note{{in instantiation of template class}}
template <class... Ts>
struct S2 : Ts... {
// OK for the same reasons listed in `struct S` above. We don't expect any conflicts w.r.t
// redefinitions of `x` but we still expect errors when using `x` for cases it's not available.
using typename Ts::x... UIE; // expected-note 4 {{using declaration annotated with 'using_if_exists' here}}
using typename Ts::x... UIE; // expected-error 2 {{target of using declaration conflicts with declaration already in scope}} expected-note 3 {{using declaration annotated with 'using_if_exists' here}} expected-note{{conflicting declaration}} expected-note{{target of using declaration}}
x mem(); // expected-error 4 {{reference to unresolved using declaration}}
x mem(); // expected-error 3 {{reference to unresolved using declaration}}
};
S2<E1, E2> e; // expected-note{{in instantiation of template class}}
@ -152,15 +145,14 @@ S2<F1, E2> h; // expected-note{{in instantiation of template class}}
template <class... Ts>
struct S3 : protected Ts... {
// No errors for conflicting declarations because only one of the parent classes declares `m`.
using Ts::m... UIE;
using Ts::m... UIE; // expected-error{{target of using declaration conflicts with declaration already in scope}} expected-note{{target of using declaration}}
};
struct B1 {
enum { m };
enum { m }; // expected-note{{conflicting declaration}}
};
struct B2 {};
S3<B1, B2> i;
S3<B1, B2> i; // expected-note{{in instantiation of template}}
S<B2, B1> j;
} // namespace test_using_pack
@ -178,9 +170,9 @@ NS2::x y; // expected-error {{reference to unresolved using declaration}}
} // namespace test_nested
namespace test_scope {
int x;
int x; // expected-note{{conflicting declaration}}
void f() {
int x;
int x; // expected-note{{conflicting declaration}}
{
using ::x UIE; // expected-note {{using declaration annotated with 'using_if_exists' here}}
(void)x; // expected-error {{reference to unresolved using declaration}}
@ -188,13 +180,13 @@ void f() {
{
using test_scope::x;
using ::x UIE; // OK since there's no `x` in the global namespace, so this wouldn't be any declaration
using ::x UIE; // expected-error{{target of using declaration conflicts with declaration already in scope}} expected-note{{target of using declaration}}
(void)x;
}
(void)x;
using ::x UIE; // OK since there's no `x` in the global namespace, so this wouldn't be any declaration
using ::x UIE; // expected-error{{target of using declaration conflicts with declaration already in scope}} expected-note{{target of using declaration}}
(void)x;
}
} // namespace test_scope
@ -232,20 +224,3 @@ int main() {
size = fake_printf();
size = std::fake_printf();
}
// Regression test for https://github.com/llvm/llvm-project/issues/85335.
// No errors should be reported here.
namespace PR85335 {
void foo();
namespace N {
void bar();
using ::foo __attribute__((__using_if_exists__));
using ::bar __attribute__((__using_if_exists__));
}
void baz() {
N::bar();
}
} // namespace PR85335