[llvm-branch-commits] [clang] 09831f2 - [Clang] SFINAE on mismatching pack length during constraint satisfaction checking (#101879)

[Tobias Hieta via llvm-branch-commits]

Author: cor3ntin
Date: 2024-08-10T11:57:16+02:00
New Revision: 09831f28cf1e7630569dc672701fde1be90f8950

URL: https://github.com/llvm/llvm-project/commit/09831f28cf1e7630569dc672701fde1be90f8950
DIFF: https://github.com/llvm/llvm-project/commit/09831f28cf1e7630569dc672701fde1be90f8950.diff

LOG: [Clang] SFINAE on mismatching pack length during constraint satisfaction checking (#101879)

If a fold expanded constraint would expand packs of different size, it
is not a valid pack expansion and it is not satisfied. This should not
produce an error.

Fixes #99430

(cherry picked from commit da380b26e4748ade5a8dba85b7df5e1c4eded8bc)

Added: 
    

Modified: 
    clang/lib/Sema/SemaConcept.cpp
    clang/test/SemaCXX/cxx2c-fold-exprs.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index 9e16b67284be45..c34d32002b5ad7 100644
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -531,6 +531,10 @@ static ExprResult calculateConstraintSatisfaction(
 
     std::optional<unsigned>
     EvaluateFoldExpandedConstraintSize(const CXXFoldExpr *FE) const {
+
+      // We should ignore errors in the presence of packs of 
diff erent size.
+      Sema::SFINAETrap Trap(S);
+
       Expr *Pattern = FE->getPattern();
 
       SmallVector<UnexpandedParameterPack, 2> Unexpanded;

diff  --git a/clang/test/SemaCXX/cxx2c-fold-exprs.cpp b/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
index 1e0bc7bcfb4e7c..0674135aac483f 100644
--- a/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
+++ b/clang/test/SemaCXX/cxx2c-fold-exprs.cpp
@@ -275,3 +275,33 @@ static_assert(S<int>::g<int>() == 2); // expected-error {{call to 'g' is ambiguo
 
 
 }
+
+namespace GH99430 {
+
+template <class _Ty1, class _Ty2>
+using _Synth_three_way_result = int;
+
+template <class... _Types>
+class tuple;
+
+template <int _Index>
+struct tuple_element;
+
+template <class, int...>
+struct _Three_way_comparison_result_with_tuple_like {
+  using type = int;
+};
+
+template <class... _TTypes, int... _Indices>
+  requires(requires {
+    typename _Synth_three_way_result<_TTypes, tuple_element<_Indices>>;
+  } && ...)
+
+struct _Three_way_comparison_result_with_tuple_like<tuple<_TTypes...>, _Indices...>{
+    using type = long;
+};
+
+static_assert(__is_same_as(_Three_way_comparison_result_with_tuple_like<tuple<int>, 0, 1>::type, int));
+static_assert(__is_same_as(_Three_way_comparison_result_with_tuple_like<tuple<int>, 0>::type, long));
+
+}