Hi Hans, Please consider this bugfix for the Clang 10 release branch.
On Wed, 15 Jan 2020 at 16:21, Richard Smith via cfe-commits < cfe-commits@lists.llvm.org> wrote: > > 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 >
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