fhahn added inline comments.
================ Comment at: clang/lib/Sema/SemaTemplateDeduction.cpp:2112 + llvm::APSInt ArgRows(S.Context.getTypeSize(S.Context.IntTy), + ConstantMatrixArg->getNumRows()); + Result = DeduceNonTypeTemplateArgument( ---------------- rjmccall wrote: > fhahn wrote: > > rjmccall wrote: > > > Oh, and this needs to use `size_t`; not just the value but the type of a > > > non-type template parameter can be deduced, so you should use an > > > appropriate type. Test case for this deduction is `template <auto R> > > > void foo(matrix<int, R, 10>);` or something like that, with a check that > > > `decltype(R)` is `size_t` (which you can do in any number of ways). > > Could we be even more permissive? If we fix it to size_t, template > > arguments with integer types like int or unsigned would be rejected. Could > > we relax that to NTTP type, to allow different integer types that are > > implicitly convertible? We might need an extra check that the known number > > of rows/columns does not exceed the bit width of NTTP's type. > Unfortunately, template argument deduction requires the template parameter > type to match the type of the argument value exactly, so you get exactly one > type. Given that language rule, the natural type to use is `size_t`, which > is the same type that constant array bounds are considered to have. If C++ > wants to weaken this language rule, they should do so uniformly; it does not > make sense for us to use a weaker rule just for this specific extension. Thanks for the explanation! I've updated the code to just allow size_t. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D72281/new/ https://reviews.llvm.org/D72281 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
