[clang] [Clang] Fix unexpanded packs in NTTP type constraints (PR #121296)
Younan Zhang via cfe-commits
cfe-commits at lists.llvm.org
Fri Jan 3 03:10:26 PST 2025
https://github.com/zyn0217 updated https://github.com/llvm/llvm-project/pull/121296
>From 102e031cae56c130f48f08bcb316b6f451facf49 Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Sun, 29 Dec 2024 23:13:52 +0800
Subject: [PATCH 1/6] [Clang] Diagnose unexpanded packs for NTTP type
constraints
---
clang/docs/ReleaseNotes.rst | 1 +
clang/lib/Sema/SemaTemplate.cpp | 12 +++++--
clang/test/SemaCXX/cxx2c-fold-exprs.cpp | 43 +++++++++++++++++++++++++
3 files changed, 54 insertions(+), 2 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 8b984ecaefecaf..78ae4c8cab3a9e 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -885,6 +885,7 @@ Bug Fixes to C++ Support
- Fixed recognition of ``std::initializer_list`` when it's surrounded with ``extern "C++"`` and exported
out of a module (which is the case e.g. in MSVC's implementation of ``std`` module). (#GH118218)
- Fixed a pack expansion issue in checking unexpanded parameter sizes. (#GH17042)
+- Clang now identifies unexpanded parameter packs within the type constraint on a non-type template parameter. (#GH88866)
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 5e7a3c8484c88f..eac184d468ce9a 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -1530,9 +1530,17 @@ NamedDecl *Sema::ActOnNonTypeTemplateParameter(Scope *S, Declarator &D,
Param->setAccess(AS_public);
if (AutoTypeLoc TL = TInfo->getTypeLoc().getContainedAutoTypeLoc())
- if (TL.isConstrained())
- if (AttachTypeConstraint(TL, Param, Param, D.getEllipsisLoc()))
+ if (TL.isConstrained()) {
+ if (const ASTTemplateArgumentListInfo *ArgumentList =
+ TL.getConceptReference()->getTemplateArgsAsWritten())
+ for (const TemplateArgumentLoc &Loc : ArgumentList->arguments()) {
+ Invalid |= DiagnoseUnexpandedParameterPack(
+ Loc, UnexpandedParameterPackContext::UPPC_TypeConstraint);
+ }
+ if (!Invalid &&
+ AttachTypeConstraint(TL, Param, Param, D.getEllipsisLoc()))
Invalid = true;
+ }
if (Invalid)
Param->setInvalidDecl();
diff --git a/clang/test/SemaCXX/cxx2c-fold-exprs.cpp b/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
index 0674135aac483f..00236a8a839135 100644
--- a/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
+++ b/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
@@ -305,3 +305,46 @@ static_assert(__is_same_as(_Three_way_comparison_result_with_tuple_like<tuple<in
static_assert(__is_same_as(_Three_way_comparison_result_with_tuple_like<tuple<int>, 0>::type, long));
}
+
+namespace GH88866 {
+
+template <typename...Ts> struct index_by;
+
+template <typename T, typename Indices>
+concept InitFunc = true;
+
+namespace Invalid {
+
+template <typename Indices, InitFunc<Indices> auto... init>
+struct LazyLitMatrix;
+
+template <
+ typename...Indices,
+ InitFunc<index_by<Indices>> auto... init
+ // expected-error at -1 {{type constraint contains unexpanded parameter pack 'Indices'}}
+>
+struct LazyLitMatrix<index_by<Indices...>, init...> {
+};
+
+static_assert(
+ !__is_same(LazyLitMatrix<index_by<int, char>, 42, 43>, LazyLitMatrix<index_by<int, char>, 42, 43>));
+// expected-error at -1 {{static assertion failed}}
+}
+
+namespace Valid {
+
+template <typename Indices, InitFunc<Indices> auto... init>
+struct LazyLitMatrix;
+
+template <
+ typename...Indices,
+ InitFunc<index_by<Indices...>> auto... init
+>
+struct LazyLitMatrix<index_by<Indices...>, init...> {
+};
+
+static_assert(__is_same(LazyLitMatrix<index_by<int, char>, 42, 43>,
+ LazyLitMatrix<index_by<int, char>, 42, 43>));
+}
+
+}
>From 111d1002e081322fdb5f3fa8e94b15b99817b3b9 Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Sun, 29 Dec 2024 23:30:57 +0800
Subject: [PATCH 2/6] Simplify the test
---
clang/test/SemaCXX/cxx2c-fold-exprs.cpp | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/clang/test/SemaCXX/cxx2c-fold-exprs.cpp b/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
index 00236a8a839135..509922c0a8f4fe 100644
--- a/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
+++ b/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
@@ -326,9 +326,8 @@ template <
struct LazyLitMatrix<index_by<Indices...>, init...> {
};
-static_assert(
- !__is_same(LazyLitMatrix<index_by<int, char>, 42, 43>, LazyLitMatrix<index_by<int, char>, 42, 43>));
-// expected-error at -1 {{static assertion failed}}
+using T = LazyLitMatrix<index_by<int, char>, 42, 43>;
+
}
namespace Valid {
@@ -343,8 +342,8 @@ template <
struct LazyLitMatrix<index_by<Indices...>, init...> {
};
-static_assert(__is_same(LazyLitMatrix<index_by<int, char>, 42, 43>,
- LazyLitMatrix<index_by<int, char>, 42, 43>));
+using T = LazyLitMatrix<index_by<int, char>, 42, 43>;
+
}
}
>From 144f3c997def0a4d746edb111f2e7f90797b153e Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Tue, 31 Dec 2024 16:13:46 +0800
Subject: [PATCH 3/6] Let ... expand NTTP constraints
---
clang/lib/AST/ASTContext.cpp | 2 +-
clang/lib/Sema/SemaTemplate.cpp | 14 +++-----------
clang/lib/Sema/SemaTemplateDeduction.cpp | 3 ++-
3 files changed, 6 insertions(+), 13 deletions(-)
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 8b4ae58e8427a9..a9ecb4ee9c76b2 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -6376,7 +6376,7 @@ ASTContext::getAutoType(QualType DeducedType, AutoTypeKeyword Keyword,
}
QualType ASTContext::getUnconstrainedType(QualType T) const {
- QualType CanonT = T.getCanonicalType();
+ QualType CanonT = T.getNonPackExpansionType().getCanonicalType();
// Remove a type-constraint from a top-level auto or decltype(auto).
if (auto *AT = CanonT->getAs<AutoType>()) {
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index eac184d468ce9a..2e4a3060c0b391 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -1228,7 +1228,7 @@ bool Sema::AttachTypeConstraint(AutoTypeLoc TL,
NonTypeTemplateParmDecl *NewConstrainedParm,
NonTypeTemplateParmDecl *OrigConstrainedParm,
SourceLocation EllipsisLoc) {
- if (NewConstrainedParm->getType() != TL.getType() ||
+ if (NewConstrainedParm->getType().getNonPackExpansionType() != TL.getType() ||
TL.getAutoKeyword() != AutoTypeKeyword::Auto) {
Diag(NewConstrainedParm->getTypeSourceInfo()->getTypeLoc().getBeginLoc(),
diag::err_unsupported_placeholder_constraint)
@@ -1530,17 +1530,9 @@ NamedDecl *Sema::ActOnNonTypeTemplateParameter(Scope *S, Declarator &D,
Param->setAccess(AS_public);
if (AutoTypeLoc TL = TInfo->getTypeLoc().getContainedAutoTypeLoc())
- if (TL.isConstrained()) {
- if (const ASTTemplateArgumentListInfo *ArgumentList =
- TL.getConceptReference()->getTemplateArgsAsWritten())
- for (const TemplateArgumentLoc &Loc : ArgumentList->arguments()) {
- Invalid |= DiagnoseUnexpandedParameterPack(
- Loc, UnexpandedParameterPackContext::UPPC_TypeConstraint);
- }
- if (!Invalid &&
- AttachTypeConstraint(TL, Param, Param, D.getEllipsisLoc()))
+ if (TL.isConstrained())
+ if (AttachTypeConstraint(TL, Param, Param, D.getEllipsisLoc()))
Invalid = true;
- }
if (Invalid)
Param->setInvalidDecl();
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index fad20b37a7d9a2..b4a4ab35478a1b 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -857,7 +857,8 @@ class PackDeductionScope {
if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(
TemplateParams->getParam(Index))) {
if (!NTTP->isExpandedParameterPack())
- if (auto *Expansion = dyn_cast<PackExpansionType>(NTTP->getType()))
+ if (auto *Expansion = dyn_cast<PackExpansionType>(
+ S.Context.getUnconstrainedType(NTTP->getType())))
ExtraDeductions.push_back(Expansion->getPattern());
}
// FIXME: Also collect the unexpanded packs in any type and template
>From 2cb3e542e431f23e7827e939a066217524b9f0ae Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Tue, 31 Dec 2024 16:44:56 +0800
Subject: [PATCH 4/6] Additional tests
---
clang/lib/Sema/SemaTemplate.cpp | 14 ++++++-
clang/test/SemaCXX/cxx2c-fold-exprs.cpp | 49 ++++++++++++++++++++++---
2 files changed, 55 insertions(+), 8 deletions(-)
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 2e4a3060c0b391..20ec2fbeaa6a8b 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -1530,9 +1530,19 @@ NamedDecl *Sema::ActOnNonTypeTemplateParameter(Scope *S, Declarator &D,
Param->setAccess(AS_public);
if (AutoTypeLoc TL = TInfo->getTypeLoc().getContainedAutoTypeLoc())
- if (TL.isConstrained())
- if (AttachTypeConstraint(TL, Param, Param, D.getEllipsisLoc()))
+ if (TL.isConstrained()) {
+ if (D.getEllipsisLoc().isInvalid() &&
+ T->containsUnexpandedParameterPack()) {
+ assert(TL.getConceptReference()->getTemplateArgsAsWritten());
+ for (auto &Loc :
+ TL.getConceptReference()->getTemplateArgsAsWritten()->arguments())
+ Invalid |= DiagnoseUnexpandedParameterPack(
+ Loc, UnexpandedParameterPackContext::UPPC_TypeConstraint);
+ }
+ if (!Invalid &&
+ AttachTypeConstraint(TL, Param, Param, D.getEllipsisLoc()))
Invalid = true;
+ }
if (Invalid)
Param->setInvalidDecl();
diff --git a/clang/test/SemaCXX/cxx2c-fold-exprs.cpp b/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
index 509922c0a8f4fe..48061439941f23 100644
--- a/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
+++ b/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
@@ -313,24 +313,26 @@ template <typename...Ts> struct index_by;
template <typename T, typename Indices>
concept InitFunc = true;
-namespace Invalid {
+namespace ExpandsBoth {
template <typename Indices, InitFunc<Indices> auto... init>
-struct LazyLitMatrix;
+struct LazyLitMatrix; // expected-note {{here}}
template <
typename...Indices,
InitFunc<index_by<Indices>> auto... init
- // expected-error at -1 {{type constraint contains unexpanded parameter pack 'Indices'}}
>
struct LazyLitMatrix<index_by<Indices...>, init...> {
};
-using T = LazyLitMatrix<index_by<int, char>, 42, 43>;
+// FIXME: Explain why we didn't pick up the partial specialization - pack sizes don't match.
+template struct LazyLitMatrix<index_by<int, char>, 42>;
+// expected-error at -1 {{instantiation of undefined template}}
+template struct LazyLitMatrix<index_by<int, char>, 42, 43>;
}
-namespace Valid {
+namespace ExpandsRespectively {
template <typename Indices, InitFunc<Indices> auto... init>
struct LazyLitMatrix;
@@ -342,7 +344,42 @@ template <
struct LazyLitMatrix<index_by<Indices...>, init...> {
};
-using T = LazyLitMatrix<index_by<int, char>, 42, 43>;
+template struct LazyLitMatrix<index_by<int, char>, 42>;
+template struct LazyLitMatrix<index_by<int, char>, 42, 43>;
+
+}
+
+namespace TypeParameter {
+
+template <typename Indices, InitFunc<Indices>... init>
+struct LazyLitMatrix; // expected-note {{here}}
+
+template <
+ typename...Indices,
+ InitFunc<index_by<Indices>>... init
+>
+struct LazyLitMatrix<index_by<Indices...>, init...> {
+};
+
+// FIXME: Explain why we didn't pick up the partial specialization - pack sizes don't match.
+template struct LazyLitMatrix<index_by<int, char>, float>;
+// expected-error at -1 {{instantiation of undefined template}}
+template struct LazyLitMatrix<index_by<int, char>, unsigned, float>;
+
+}
+
+namespace Invalid {
+
+template <typename Indices, InitFunc<Indices>... init>
+struct LazyLitMatrix;
+
+template <
+ typename...Indices,
+ InitFunc<index_by<Indices>> init
+ // expected-error at -1 {{unexpanded parameter pack 'Indices'}}
+>
+struct LazyLitMatrix<index_by<Indices...>, init> {
+};
}
>From 88beac3af22b8f5a5ea58a31f4f0d13aafe1f0fc Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Fri, 3 Jan 2025 13:22:36 +0800
Subject: [PATCH 5/6] Add a note for CWG2982
---
clang/lib/Sema/SemaTemplateDeduction.cpp | 2 ++
1 file changed, 2 insertions(+)
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index b4a4ab35478a1b..1c1f6e30ab7b83 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -857,6 +857,8 @@ class PackDeductionScope {
if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(
TemplateParams->getParam(Index))) {
if (!NTTP->isExpandedParameterPack())
+ // FIXME: CWG2982 suggests a type-constraint forms a non-deduced
+ // context, however it is not yet resolved.
if (auto *Expansion = dyn_cast<PackExpansionType>(
S.Context.getUnconstrainedType(NTTP->getType())))
ExtraDeductions.push_back(Expansion->getPattern());
>From 7780ed619afe174a8d67eaf5818ff592c5d85c8c Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Fri, 3 Jan 2025 19:10:15 +0800
Subject: [PATCH 6/6] Remove extra \n
---
clang/docs/ReleaseNotes.rst | 1 -
1 file changed, 1 deletion(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index f5da5330bc6436..61d6aa2216cd06 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -889,7 +889,6 @@ Bug Fixes to C++ Support
- Clang now identifies unexpanded parameter packs within the type constraint on a non-type template parameter. (#GH88866)
- Fixed an issue while resolving type of expression indexing into a pack of values of non-dependent type (#GH121242)
-
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
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