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[Clang] Add test for CWG2285 "Issues with structured bindings" #126421

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Merged
merged 4 commits into from
Mar 7, 2025
Merged

[Clang] Add test for CWG2285 "Issues with structured bindings" #126421

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92c075a
Add test for cwg2285
zwuis Feb 9, 2025
17f8c3b
Modify comment mentioned in cwg2285
zwuis Feb 10, 2025
7c07f2b
Improve diagnostic messages
zwuis Feb 25, 2025
37d5afb
Add note in test file
zwuis Feb 25, 2025
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7 changes: 5 additions & 2 deletions clang/lib/Sema/SemaDeclCXX.cpp
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Expand Up @@ -733,8 +733,11 @@ Sema::ActOnDecompositionDeclarator(Scope *S, Declarator &D,
}

if (!TemplateParamLists.empty()) {
// FIXME: There's no rule against this, but there are also no rules that
// would actually make it usable, so we reject it for now.
// C++17 [temp]/1:
// A template defines a family of class, functions, or variables, or an
// alias for a family of types.
//
// Structured bindings are not included.
Diag(TemplateParamLists.front()->getTemplateLoc(),
diag::err_decomp_decl_template);
return nullptr;
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18 changes: 14 additions & 4 deletions clang/test/CXX/drs/cwg22xx.cpp
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@@ -1,10 +1,10 @@
// RUN: %clang_cc1 -std=c++98 -triple x86_64-unknown-unknown %s -verify=expected -fexceptions -fcxx-exceptions -pedantic-errors
// RUN: %clang_cc1 -std=c++11 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx11 -fexceptions -fcxx-exceptions -pedantic-errors
// RUN: %clang_cc1 -std=c++14 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx11 -fexceptions -fcxx-exceptions -pedantic-errors
// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx11 -fexceptions -fcxx-exceptions -pedantic-errors
// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx11 -fexceptions -fcxx-exceptions -pedantic-errors
// RUN: %clang_cc1 -std=c++23 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx11 -fexceptions -fcxx-exceptions -pedantic-errors
// RUN: %clang_cc1 -std=c++2c -triple x86_64-unknown-unknown %s -verify=expected,since-cxx11 -fexceptions -fcxx-exceptions -pedantic-errors
// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx11,since-cxx17 -fexceptions -fcxx-exceptions -pedantic-errors
// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx11,since-cxx17 -fexceptions -fcxx-exceptions -pedantic-errors
// RUN: %clang_cc1 -std=c++23 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx11,since-cxx17 -fexceptions -fcxx-exceptions -pedantic-errors
// RUN: %clang_cc1 -std=c++2c -triple x86_64-unknown-unknown %s -verify=expected,since-cxx11,since-cxx17 -fexceptions -fcxx-exceptions -pedantic-errors


namespace cwg2211 { // cwg2211: 8
Expand Down Expand Up @@ -196,6 +196,16 @@ void g() {
#endif
} // namespace cwg2277

namespace cwg2285 { // cwg2285: 4
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@Endilll Endilll Feb 10, 2025

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It seems that Clang 5 was the first release which exhibits the correct behavior: https://godbolt.org/z/qabGrdvPq

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@zwuis zwuis Feb 10, 2025

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It seems that Clang 5 was the first release which exhibits the correct behavior: https://godbolt.org/z/qabGrdvPq

-std=c++1z set __cplusplus to 201406L in Clang 4. It was changed to 201703L in 4b0cad0 (Clang 5). We need to remove the #if condition to test corresponding behaviour in Clang 4.

Do I need to add this note in test file?

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@Endilll Endilll Feb 24, 2025

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You're right, Clang 4 behaves as expected without #if __cplusplus.

Do I need to add this note in test file?

Yes, leave a comment somewhere that Clang 4 doesn't pass the test because of the wrong value of __cplusplus, even though it implements the DR.

#if __cplusplus >= 201703L
void test() {
using T = int[1];
auto [a] = T{a};
// since-cxx17-error@-1 {{binding 'a' cannot appear in the initializer of its own decomposition declaration}}
}
#endif
} // namespace cwg2285

namespace cwg2292 { // cwg2292: 9
#if __cplusplus >= 201103L
template<typename T> using id = T;
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2 changes: 1 addition & 1 deletion clang/test/Parser/cxx1z-decomposition.cpp
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Expand Up @@ -136,7 +136,7 @@ namespace MultiDeclarator {

namespace Template {
int n[3];
// FIXME: There's no actual rule against this...
// Structured binding template is not allowed.
template<typename T> auto [a, b, c] = n; // expected-error {{decomposition declaration template not supported}}
}

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2 changes: 1 addition & 1 deletion clang/www/cxx_dr_status.html
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Expand Up @@ -13537,7 +13537,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
<td><a href="https://cplusplus.github.io/CWG/issues/2285.html">2285</a></td>
<td>CD5</td>
<td>Issues with structured bindings</td>
<td class="unknown" align="center">Unknown</td>
<td class="full" align="center">Clang 4</td>
</tr>
<tr id="2286">
<td><a href="https://cplusplus.github.io/CWG/issues/2286.html">2286</a></td>
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