[Clang] Fix unexpanded packs in NTTP type constraints #121296
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zyn0217
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cor3ntin and
erichkeane
and removed request for
cor3ntin
llvmbot
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@llvm/pr-subscribers-clang Author: Younan Zhang (zyn0217) ChangesOtherwise, the invalid unexpanded type would be passed to getAutoType and lead to a crash. Fixes #88866 Full diff: https://github.com/llvm/llvm-project/pull/121296.diff 3 Files Affected:
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 983c1da20ed4c8..db40a722ce1ed8 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -886,6 +886,7 @@ Bug Fixes to C++ Support
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)
- Fixed a bug where captured structured bindings were modifiable inside non-mutable lambda (#GH95081)
+- 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..509922c0a8f4fe 100644
--- a/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
+++ b/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
@@ -305,3 +305,45 @@ 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@-1 {{type constraint contains unexpanded parameter pack 'Indices'}}
+>
+struct LazyLitMatrix<index_by<Indices...>, init...> {
+};
+
+using T = LazyLitMatrix<index_by<int, char>, 42, 43>;
+
+}
+
+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...> {
+};
+
+using T = LazyLitMatrix<index_by<int, char>, 42, 43>;
+
+}
+
+}
|
cor3ntin
reviewed
Dec 30, 2024
zyn0217
commented
Dec 31, 2024
Comment on lines
860
to
861
| if (auto *Expansion = dyn_cast<PackExpansionType>(NTTP->getType())) | ||
| if (auto *Expansion = dyn_cast<PackExpansionType>( | ||
| S.Context.getUnconstrainedType(NTTP->getType()))) |
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@cor3ntin I assume we are unable to deduce template arguments in the type constraint, right? This logic would otherwise end up matching the NTTP argument against the NTTP constraint
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Unclear. @zygoloid asked that exact question last year (https://lists.isocpp.org/core/2023/03/14099.php) but there are no replies yet
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Sigh. Looks like having run into another dark corner of C++ :/
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https://cplusplus.github.io/CWG/issues/2982.html
I'd say lets do that and if it changes we can revisit. how does that sound?
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That always works :) I can definitely leave a FIXME here
zyn0217
changed the title
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/88/builds/6349 Here is the relevant piece of the build log for the reference |
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/73/builds/11096 Here is the relevant piece of the build log for the reference |
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In the case where a type-constraint on an NTTP contains a pack, we form a PackExpansionType to model it. However, there are a few places expecting it to be a non-pack expansion, and luckily only small changes could make them work.
Fixes #88866