[Clang] Implement CWG 2707 "Deduction guides cannot have a trailing requires-clause" #110473

zyn0217 · 2024-09-30T09:05:18Z

Closes #98595

…equires-clause"

llvmbot · 2024-09-30T12:52:48Z

@llvm/pr-subscribers-clang

Author: Younan Zhang (zyn0217)

Changes

Closes #98595

Full diff: https://github.com/llvm/llvm-project/pull/110473.diff

9 Files Affected:

(modified) clang/docs/ReleaseNotes.rst (+3)
(modified) clang/include/clang/AST/DeclCXX.h (+6-3)
(modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (-2)
(modified) clang/lib/AST/DeclCXX.cpp (+5-4)
(modified) clang/lib/Sema/SemaDecl.cpp (+4-7)
(modified) clang/lib/Sema/SemaTemplateInstantiateDecl.cpp (+1-1)
(modified) clang/test/CXX/dcl/dcl.decl/p3.cpp (+1-1)
(modified) clang/test/CXX/drs/cwg27xx.cpp (+28)
(modified) clang/www/cxx_dr_status.html (+2-2)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 35c31452cef411..9fd1cb09062059 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -205,6 +205,9 @@ Resolutions to C++ Defect Reports
 - Reject explicit object parameters with type ``void`` (``this void``).
   (`CWG2915: Explicit object parameters of type void <https://cplusplus.github.io/CWG/issues/2915.html>`_).
 
+- Clang now allows trailing requires clause on explicit deduction guides.
+  (`CWG2707: Deduction guides cannot have a trailing requires-clause <https://cplusplus.github.io/CWG/issues/2707.html>`_).
+
 C Language Changes
 ------------------
 
diff --git a/clang/include/clang/AST/DeclCXX.h b/clang/include/clang/AST/DeclCXX.h
index 252e6e92564142..2693cc0e95b4b2 100644
--- a/clang/include/clang/AST/DeclCXX.h
+++ b/clang/include/clang/AST/DeclCXX.h
@@ -1965,9 +1965,11 @@ class CXXDeductionGuideDecl : public FunctionDecl {
                         ExplicitSpecifier ES,
                         const DeclarationNameInfo &NameInfo, QualType T,
                         TypeSourceInfo *TInfo, SourceLocation EndLocation,
-                        CXXConstructorDecl *Ctor, DeductionCandidate Kind)
+                        CXXConstructorDecl *Ctor, DeductionCandidate Kind,
+                        Expr *TrailingRequiresClause)
       : FunctionDecl(CXXDeductionGuide, C, DC, StartLoc, NameInfo, T, TInfo,
-                     SC_None, false, false, ConstexprSpecKind::Unspecified),
+                     SC_None, false, false, ConstexprSpecKind::Unspecified,
+                     TrailingRequiresClause),
         Ctor(Ctor), ExplicitSpec(ES) {
     if (EndLocation.isValid())
       setRangeEnd(EndLocation);
@@ -1987,7 +1989,8 @@ class CXXDeductionGuideDecl : public FunctionDecl {
          ExplicitSpecifier ES, const DeclarationNameInfo &NameInfo, QualType T,
          TypeSourceInfo *TInfo, SourceLocation EndLocation,
          CXXConstructorDecl *Ctor = nullptr,
-         DeductionCandidate Kind = DeductionCandidate::Normal);
+         DeductionCandidate Kind = DeductionCandidate::Normal,
+         Expr *TrailingRequiresClause = nullptr);
 
   static CXXDeductionGuideDecl *CreateDeserialized(ASTContext &C,
                                                    GlobalDeclID ID);
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 9e8f152852fd1e..0f591022e68541 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3050,8 +3050,6 @@ def note_is_deducible_constraint_evaluated_to_false : Note<
   "cannot deduce template arguments for %0 from %1">;
 def err_constrained_virtual_method : Error<
   "virtual function cannot have a requires clause">;
-def err_trailing_requires_clause_on_deduction_guide : Error<
-  "deduction guide cannot have a requires clause">;
 def err_constrained_non_templated_function
     : Error<"non-templated function cannot have a requires clause">;
 def err_non_temp_spec_requires_clause : Error<
diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index 01143391edab40..f5a0aa8f82512e 100644
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -2211,9 +2211,10 @@ CXXDeductionGuideDecl *CXXDeductionGuideDecl::Create(
     ASTContext &C, DeclContext *DC, SourceLocation StartLoc,
     ExplicitSpecifier ES, const DeclarationNameInfo &NameInfo, QualType T,
     TypeSourceInfo *TInfo, SourceLocation EndLocation, CXXConstructorDecl *Ctor,
-    DeductionCandidate Kind) {
-  return new (C, DC) CXXDeductionGuideDecl(C, DC, StartLoc, ES, NameInfo, T,
-                                           TInfo, EndLocation, Ctor, Kind);
+    DeductionCandidate Kind, Expr *TrailingRequiresClause) {
+  return new (C, DC)
+      CXXDeductionGuideDecl(C, DC, StartLoc, ES, NameInfo, T, TInfo,
+                            EndLocation, Ctor, Kind, TrailingRequiresClause);
 }
 
 CXXDeductionGuideDecl *
@@ -2221,7 +2222,7 @@ CXXDeductionGuideDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) CXXDeductionGuideDecl(
       C, nullptr, SourceLocation(), ExplicitSpecifier(), DeclarationNameInfo(),
       QualType(), nullptr, SourceLocation(), nullptr,
-      DeductionCandidate::Normal);
+      DeductionCandidate::Normal, nullptr);
 }
 
 RequiresExprBodyDecl *RequiresExprBodyDecl::Create(
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 1bf0e800a36228..0e536f71a2f70d 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -9293,15 +9293,12 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
         TrailingRequiresClause);
 
   } else if (Name.getNameKind() == DeclarationName::CXXDeductionGuideName) {
-    if (TrailingRequiresClause)
-      SemaRef.Diag(TrailingRequiresClause->getBeginLoc(),
-                   diag::err_trailing_requires_clause_on_deduction_guide)
-          << TrailingRequiresClause->getSourceRange();
     if (SemaRef.CheckDeductionGuideDeclarator(D, R, SC))
       return nullptr;
-    return CXXDeductionGuideDecl::Create(SemaRef.Context, DC, D.getBeginLoc(),
-                                         ExplicitSpecifier, NameInfo, R, TInfo,
-                                         D.getEndLoc());
+    return CXXDeductionGuideDecl::Create(
+        SemaRef.Context, DC, D.getBeginLoc(), ExplicitSpecifier, NameInfo, R,
+        TInfo, D.getEndLoc(), /*Ctor=*/nullptr,
+        /*Kind=*/DeductionCandidate::Normal, TrailingRequiresClause);
   } else if (DC->isRecord()) {
     // If the name of the function is the same as the name of the record,
     // then this must be an invalid constructor that has a return type.
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index c3cb9d5d8c2c3d..1c35c7d288e325 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2233,7 +2233,7 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(
         SemaRef.Context, DC, D->getInnerLocStart(),
         InstantiatedExplicitSpecifier, NameInfo, T, TInfo,
         D->getSourceRange().getEnd(), DGuide->getCorrespondingConstructor(),
-        DGuide->getDeductionCandidateKind());
+        DGuide->getDeductionCandidateKind(), TrailingRequiresClause);
     Function->setAccess(D->getAccess());
   } else {
     Function = FunctionDecl::Create(
diff --git a/clang/test/CXX/dcl/dcl.decl/p3.cpp b/clang/test/CXX/dcl/dcl.decl/p3.cpp
index f141568ba6c221..b082e1c122a09e 100644
--- a/clang/test/CXX/dcl/dcl.decl/p3.cpp
+++ b/clang/test/CXX/dcl/dcl.decl/p3.cpp
@@ -65,4 +65,4 @@ struct R {
 };
 
 template<typename T>
-R(T) -> R<T> requires true; // expected-error{{deduction guide cannot have a requires clause}}
+R(T) -> R<T> requires true;
diff --git a/clang/test/CXX/drs/cwg27xx.cpp b/clang/test/CXX/drs/cwg27xx.cpp
index 2b57dbc60aed70..581e2af822d556 100644
--- a/clang/test/CXX/drs/cwg27xx.cpp
+++ b/clang/test/CXX/drs/cwg27xx.cpp
@@ -201,3 +201,31 @@ static_assert(false, f().s);
 #endif
 } // namespace cwg2798
 
+namespace cwg2707 { // cwg2707: 20
+
+#if __cplusplus >= 202002L
+
+template <class T, unsigned N> struct A {
+  T value[N];
+};
+
+template <typename... T>
+A(T...) -> A<int, sizeof...(T)> requires (sizeof...(T) == 2);
+
+// Brace elision is not allowed for synthesized CTAD guides if the array size
+// is value-dependent.
+// So this should pick up our explicit deduction guide.
+A a = {1, 2};
+
+A b = {3, 4, 5};
+// expected-error@-1 {{no viable constructor or deduction guide}} \
+// expected-note@-13 {{candidate function template not viable}} \
+// expected-note@-13 {{implicit deduction guide}} \
+// expected-note@-8 {{constraints not satisfied}} \
+// expected-note@-8 {{because 'sizeof...(T) == 2' (3 == 2) evaluated to false}} \
+// expected-note@-13 {{candidate function template not viable}} \
+// expected-note@-13 {{implicit deduction guide}}
+
+#endif
+
+} // namespace cwg2707
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index e5c5e50104fdaf..978351716ce33d 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -16089,7 +16089,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/2707.html">2707</a></td>
     <td>DRWP</td>
     <td>Deduction guides cannot have a trailing <I>requires-clause</I></td>
-    <td class="unknown" align="center">Unknown</td>
+    <td class="unreleased" align="center">Clang 20</td>
   </tr>
   <tr id="2708">
     <td><a href="https://cplusplus.github.io/CWG/issues/2708.html">2708</a></td>
@@ -17334,7 +17334,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/2913.html">2913</a></td>
     <td>tentatively ready</td>
     <td>Grammar for <I>deduction-guide</I> has <I>requires-clause</I> in the wrong position</td>
-    <td align="center">Not resolved</td>
+    <td class="unreleased" align="center">Clang 20</td>
   </tr>
   <tr class="open" id="2914">
     <td><a href="https://cplusplus.github.io/CWG/issues/2914.html">2914</a></td>

hokein

Thanks, looks good.

Endilll

You can use 2789 or other tests as a reference for how expected directives are written in DR tests.

Endilll · 2024-10-01T09:23:23Z

clang/test/CXX/drs/cwg27xx.cpp

@@ -201,3 +201,31 @@ static_assert(false, f().s);
 #endif
 } // namespace cwg2798

+namespace cwg2707 { // cwg2707: 20


Given the number of the Core issue, this test should've been placed towards the beginning of the file. We keep them in the ascending order.

Endilll · 2024-10-01T09:24:37Z

clang/test/CXX/drs/cwg27xx.cpp

+A a = {1, 2};
+
+A b = {3, 4, 5};
+// expected-error@-1 {{no viable constructor or deduction guide}} \


Expected directives should reflect the #if __cplusplus >= 202002L, i.e. since-cxx20-error.

Endilll · 2024-10-01T09:26:51Z

clang/test/CXX/drs/cwg27xx.cpp

+
+A b = {3, 4, 5};
+// expected-error@-1 {{no viable constructor or deduction guide}} \
+// expected-note@-13 {{candidate function template not viable}} \


DR tests indeed use relative offsets, but they very intentionally avoid making readers count lines to figure out which line the diagnostic is attached to. This should be converted to bookmarks.

Endilll · 2024-10-01T09:27:26Z

clang/test/CXX/drs/cwg27xx.cpp

+A b = {3, 4, 5};
+// expected-error@-1 {{no viable constructor or deduction guide}} \
+// expected-note@-13 {{candidate function template not viable}} \
+// expected-note@-13 {{implicit deduction guide}} \


Notes should be indented relative to the error directive they attach to.

zyn0217 · 2024-10-02T13:45:10Z

@Endilll Filed #110842 for your comments. PTAL, thanks!

@Endilll

This addresses comments from @Endilll in the post commit review of #110473.

…equires-clause" (llvm#110473) Closes llvm#98595

@Endilll

) This addresses comments from @Endilll in the post commit review of llvm#110473.

zyn0217 requested review from mizvekov, erichkeane and cor3ntin September 30, 2024 09:05

[Clang] Implement CWG 2707 "Deduction guides cannot have a trailing r…

f0692e1

…equires-clause"

zyn0217 force-pushed the cwg2707 branch from 0a06549 to f0692e1 Compare September 30, 2024 09:14

Merge branch 'main' into cwg2707

ea8f5b5

zyn0217 marked this pull request as ready for review September 30, 2024 12:52

zyn0217 requested a review from Endilll as a code owner September 30, 2024 12:52

zyn0217 requested a review from hokein September 30, 2024 12:52

llvmbot added clang Clang issues not falling into any other category clang:frontend Language frontend issues, e.g. anything involving "Sema" labels Sep 30, 2024

erichkeane approved these changes Sep 30, 2024

View reviewed changes

hokein approved these changes Sep 30, 2024

View reviewed changes

zyn0217 merged commit 915df1a into llvm:main Sep 30, 2024
13 checks passed

zyn0217 deleted the cwg2707 branch September 30, 2024 23:27

Endilll reviewed Oct 1, 2024

View reviewed changes

zyn0217 added a commit to zyn0217/llvm-project that referenced this pull request Oct 2, 2024

[Clang][NFC] Rearrange tests for CWG 2707 after llvm#110473

5660d1e

zyn0217 mentioned this pull request Oct 2, 2024

[Clang][NFC] Rearrange tests for CWG 2707 after #110473 #110842

Merged

zyn0217 added a commit that referenced this pull request Oct 2, 2024

[Clang][NFC] Rearrange tests for CWG 2707 after #110473 (#110842)

9b53a6e

This addresses comments from @Endilll in the post commit review of #110473.

Sterling-Augustine pushed a commit to Sterling-Augustine/llvm-project that referenced this pull request Oct 3, 2024

[Clang] Implement CWG 2707 "Deduction guides cannot have a trailing r…

dc6bb28

…equires-clause" (llvm#110473) Closes llvm#98595

Sterling-Augustine pushed a commit to Sterling-Augustine/llvm-project that referenced this pull request Oct 3, 2024

[Clang][NFC] Rearrange tests for CWG 2707 after llvm#110473 (llvm#110842

c174be8

) This addresses comments from @Endilll in the post commit review of llvm#110473.

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