Author: Richard Smith Date: 2020-01-15T16:21:08-08:00 New Revision: e8f198dd9e9dabed8d50276465906e7c8827cada
URL: https://github.com/llvm/llvm-project/commit/e8f198dd9e9dabed8d50276465906e7c8827cada DIFF: https://github.com/llvm/llvm-project/commit/e8f198dd9e9dabed8d50276465906e7c8827cada.diff LOG: Fix pack deduction to only deduce the arity of packs that are actually expanded by the deduced pack. We recently started also deducing the arity of separately-expanded packs that are merely mentioned within the pack in question, which is incorrect. Added: Modified: clang/lib/Sema/SemaTemplateDeduction.cpp clang/test/SemaTemplate/deduction.cpp Removed: ################################################################################ diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp index 1b9f1b2144d1..048a50a741e4 100644 --- a/clang/lib/Sema/SemaTemplateDeduction.cpp +++ b/clang/lib/Sema/SemaTemplateDeduction.cpp @@ -724,38 +724,48 @@ class PackDeductionScope { // Compute the set of template parameter indices that correspond to // parameter packs expanded by the pack expansion. llvm::SmallBitVector SawIndices(TemplateParams->size()); + llvm::SmallVector<TemplateArgument, 4> ExtraDeductions; auto AddPack = [&](unsigned Index) { if (SawIndices[Index]) return; SawIndices[Index] = true; addPack(Index); + + // Deducing a parameter pack that is a pack expansion also constrains the + // packs appearing in that parameter to have the same deduced arity. Also, + // in C++17 onwards, deducing a non-type template parameter deduces its + // type, so we need to collect the pending deduced values for those packs. + if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>( + TemplateParams->getParam(Index))) { + if (auto *Expansion = dyn_cast<PackExpansionType>(NTTP->getType())) + ExtraDeductions.push_back(Expansion->getPattern()); + } + // FIXME: Also collect the unexpanded packs in any type and template + // parameter packs that are pack expansions. }; - // First look for unexpanded packs in the pattern. - SmallVector<UnexpandedParameterPack, 2> Unexpanded; - S.collectUnexpandedParameterPacks(Pattern, Unexpanded); - for (unsigned I = 0, N = Unexpanded.size(); I != N; ++I) { - unsigned Depth, Index; - std::tie(Depth, Index) = getDepthAndIndex(Unexpanded[I]); - if (Depth == Info.getDeducedDepth()) - AddPack(Index); - } + auto Collect = [&](TemplateArgument Pattern) { + SmallVector<UnexpandedParameterPack, 2> Unexpanded; + S.collectUnexpandedParameterPacks(Pattern, Unexpanded); + for (unsigned I = 0, N = Unexpanded.size(); I != N; ++I) { + unsigned Depth, Index; + std::tie(Depth, Index) = getDepthAndIndex(Unexpanded[I]); + if (Depth == Info.getDeducedDepth()) + AddPack(Index); + } + }; + + // Look for unexpanded packs in the pattern. + Collect(Pattern); assert(!Packs.empty() && "Pack expansion without unexpanded packs?"); unsigned NumNamedPacks = Packs.size(); - // We can also have deduced template parameters that do not actually - // appear in the pattern, but can be deduced by it (the type of a non-type - // template parameter pack, in particular). These won't have prevented us - // from partially expanding the pack. - llvm::SmallBitVector Used(TemplateParams->size()); - MarkUsedTemplateParameters(S.Context, Pattern, /*OnlyDeduced*/true, - Info.getDeducedDepth(), Used); - for (int Index = Used.find_first(); Index != -1; - Index = Used.find_next(Index)) - if (TemplateParams->getParam(Index)->isParameterPack()) - AddPack(Index); + // Also look for unexpanded packs that are indirectly deduced by deducing + // the sizes of the packs in this pattern. + while (!ExtraDeductions.empty()) + Collect(ExtraDeductions.pop_back_val()); return NumNamedPacks; } diff --git a/clang/test/SemaTemplate/deduction.cpp b/clang/test/SemaTemplate/deduction.cpp index 1f1c30a8b4ab..7268912dd6c5 100644 --- a/clang/test/SemaTemplate/deduction.cpp +++ b/clang/test/SemaTemplate/deduction.cpp @@ -546,3 +546,21 @@ namespace designators { static_assert(f({.a = 1, .b = 2}) == 3, ""); // expected-error {{no matching function}} } + +namespace nested_packs { + template<typename ...T, typename ...U> void f(T (*...f)(U...)); // expected-note {{deduced packs of diff erent lengths for parameter 'U' (<> vs. <int>)}} + void g() { f(g); f(g, g); f(g, g, g); } + void h(int) { f(h); f(h, h); f(h, h, h); } + void i() { f(g, h); } // expected-error {{no matching function}} + +#if __cplusplus >= 201703L + template<auto ...A> struct Q {}; + template<typename ...T, T ...A, T ...B> void q(Q<A...>, Q<B...>); // #q + void qt(Q<> q0, Q<1, 2> qii, Q<1, 2, 3> qiii) { + q(q0, q0); + q(qii, qii); + q(qii, qiii); // expected-error {{no match}} expected-note@#q {{deduced packs of diff erent lengths for parameter 'T' (<int, int> vs. <int, int, int>)}} + q(q0, qiii); // expected-error {{no match}} expected-note@#q {{deduced packs of diff erent lengths for parameter 'T' (<> vs. <int, int, int>)}} + } +#endif +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
