This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG07008a8df57f: CWG2635: Disallow constrained structured
bindings. (authored by erichkeane).
Herald added a project: clang.
Changed prior to commit:
https://reviews.llvm.org/D138852?vs=478351&id=478381#toc
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D138852/new/
https://reviews.llvm.org/D138852
Files:
clang/docs/ReleaseNotes.rst
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/Sema/SemaDeclCXX.cpp
clang/test/CXX/drs/dr26xx.cpp
clang/test/FixIt/fixit-constrained-structured-binding.cpp
clang/www/cxx_dr_status.html
Index: clang/www/cxx_dr_status.html
===================================================================
--- clang/www/cxx_dr_status.html
+++ clang/www/cxx_dr_status.html
@@ -15618,7 +15618,7 @@
<td><a href="https://wg21.link/cwg2635";>2635</a></td>
<td>DR</td>
<td>Constrained structured bindings</td>
- <td class="none" align="center">Unknown</td>
+ <td class="unreleased" align="center">Clang 16</td>
</tr>
<tr id="2636">
<td><a href="https://wg21.link/cwg2636";>2636</a></td>
Index: clang/test/FixIt/fixit-constrained-structured-binding.cpp
===================================================================
--- /dev/null
+++ clang/test/FixIt/fixit-constrained-structured-binding.cpp
@@ -0,0 +1,33 @@
+// RUN: not %clang_cc1 -std=c++20 -fdiagnostics-parseable-fixits -x c++ %s 2> %t
+// RUN: FileCheck %s < %t
+
+template<typename T>
+concept UnaryC = true;
+template<typename T, typename U>
+concept BinaryC = true;
+
+struct S{ int i, j; };
+S get_S();
+
+template<typename T>
+T get_T();
+
+void use() {
+ UnaryC auto [a, b] = get_S();
+ // CHECK: error: decomposition declaration cannot be declared with constrained 'auto'
+ // CHECK: fix-it:{{.*}}:{16:3-16:10}:""
+ BinaryC<int> auto [c, d] = get_S();
+ // CHECK: error: decomposition declaration cannot be declared with constrained 'auto'
+ // CHECK: fix-it:{{.*}}:{19:3-19:16}:""
+}
+
+template<typename T>
+void TemplUse() {
+ UnaryC auto [a, b] = get_T<T>();
+ // CHECK: error: decomposition declaration cannot be declared with constrained 'auto'
+ // XCHECK: fix-it:{{.*}}:{26:3-26:10}:""
+ BinaryC<T> auto [c, d] = get_T<T>();
+ // CHECK: error: decomposition declaration cannot be declared with constrained 'auto'
+ // XCHECK: fix-it:{{.*}}:{29:3-29:14}:""
+}
+
Index: clang/test/CXX/drs/dr26xx.cpp
===================================================================
--- clang/test/CXX/drs/dr26xx.cpp
+++ clang/test/CXX/drs/dr26xx.cpp
@@ -27,6 +27,34 @@
// expected-note@#DR2628_CTOR {{marked deleted here}}
}
+}
+
+namespace dr2635 { // dr2635: yes
+template<typename T>
+concept UnaryC = true;
+template<typename T, typename U>
+concept BinaryC = true;
+
+struct S{ int i, j; };
+S get_S();
+
+template<typename T>
+T get_T();
+
+void use() {
+ // expected-error@+1{{decomposition declaration cannot be declared with constrained 'auto'}}
+ UnaryC auto [a, b] = get_S();
+ // expected-error@+1{{decomposition declaration cannot be declared with constrained 'auto'}}
+ BinaryC<int> auto [c, d] = get_S();
+}
+
+template<typename T>
+void TemplUse() {
+ // expected-error@+1{{decomposition declaration cannot be declared with constrained 'auto'}}
+ UnaryC auto [a, b] = get_T<T>();
+ // expected-error@+1{{decomposition declaration cannot be declared with constrained 'auto'}}
+ BinaryC<T> auto [c, d] = get_T<T>();
+}
}
// dr2636: na
Index: clang/lib/Sema/SemaDeclCXX.cpp
===================================================================
--- clang/lib/Sema/SemaDeclCXX.cpp
+++ clang/lib/Sema/SemaDeclCXX.cpp
@@ -760,11 +760,16 @@
// C++17 [dcl.dcl]/8:
// The decl-specifier-seq shall contain only the type-specifier auto
// and cv-qualifiers.
- // C++2a [dcl.dcl]/8:
+ // C++20 [dcl.dcl]/8:
// If decl-specifier-seq contains any decl-specifier other than static,
// thread_local, auto, or cv-qualifiers, the program is ill-formed.
+ // C++2b [dcl.pre]/6:
+ // Each decl-specifier in the decl-specifier-seq shall be static,
+ // thread_local, auto (9.2.9.6 [dcl.spec.auto]), or a cv-qualifier.
auto &DS = D.getDeclSpec();
{
+ // Note: While constrained-auto needs to be checked, we do so separately so
+ // we can emit a better diagnostic.
SmallVector<StringRef, 8> BadSpecifiers;
SmallVector<SourceLocation, 8> BadSpecifierLocs;
SmallVector<StringRef, 8> CPlusPlus20Specifiers;
@@ -791,6 +796,7 @@
BadSpecifiers.push_back("inline");
BadSpecifierLocs.push_back(DS.getInlineSpecLoc());
}
+
if (!BadSpecifiers.empty()) {
auto &&Err = Diag(BadSpecifierLocs.front(), diag::err_decomp_decl_spec);
Err << (int)BadSpecifiers.size()
@@ -851,6 +857,20 @@
D.setInvalidType();
}
+ // Constrained auto is prohibited by [decl.pre]p6, so check that here.
+ if (DS.isConstrainedAuto()) {
+ TemplateIdAnnotation *TemplRep = DS.getRepAsTemplateId();
+ assert(TemplRep->Kind == TNK_Concept_template &&
+ "No other template kind should be possible for a constrained auto");
+
+ SourceRange TemplRange{TemplRep->TemplateNameLoc,
+ TemplRep->RAngleLoc.isValid()
+ ? TemplRep->RAngleLoc
+ : TemplRep->TemplateNameLoc};
+ Diag(TemplRep->TemplateNameLoc, diag::err_decomp_decl_constraint)
+ << TemplRange << FixItHint::CreateRemoval(TemplRange);
+ }
+
// Build the BindingDecls.
SmallVector<BindingDecl*, 8> Bindings;
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -492,6 +492,8 @@
def err_decomp_decl_type : Error<
"decomposition declaration cannot be declared with type %0; "
"declared type must be 'auto' or reference to 'auto'">;
+def err_decomp_decl_constraint : Error<
+ "decomposition declaration cannot be declared with constrained 'auto'">;
def err_decomp_decl_parens : Error<
"decomposition declaration cannot be declared with parentheses">;
def err_decomp_decl_template : Error<
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -655,6 +655,7 @@
- Do not hide templated base members introduced via using-decl in derived class
(useful specially for constrained members). Fixes `GH50886 <https://github.com/llvm/llvm-project/issues/50886>`_.
+- Implemented CWG2635 as a Defect Report, which prohibits structured bindings from being constrained.
C++2b Feature Support
^^^^^^^^^^^^^^^^^^^^^
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