diff options
| -rw-r--r-- | clang/lib/Sema/SemaTemplate.cpp | 13 | ||||
| -rw-r--r-- | clang/test/SemaTemplate/temp_arg_template_cxx1z.cpp | 13 |
2 files changed, 20 insertions, 6 deletions
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp index ad7b9e54f90..f6c6ccbd410 100644 --- a/clang/lib/Sema/SemaTemplate.cpp +++ b/clang/lib/Sema/SemaTemplate.cpp @@ -5666,6 +5666,19 @@ ExprResult Sema::CheckTemplateArgument(NonTypeTemplateParmDecl *Param, // If the parameter type somehow involves auto, deduce the type now. if (getLangOpts().CPlusPlus1z && ParamType->isUndeducedType()) { + // During template argument deduction, we allow 'decltype(auto)' to + // match an arbitrary dependent argument. + // FIXME: The language rules don't say what happens in this case. + // FIXME: We get an opaque dependent type out of decltype(auto) if the + // expression is merely instantiation-dependent; is this enough? + if (CTAK == CTAK_Deduced && Arg->isTypeDependent()) { + auto *AT = dyn_cast<AutoType>(ParamType); + if (AT && AT->isDecltypeAuto()) { + Converted = TemplateArgument(Arg); + return Arg; + } + } + // When checking a deduced template argument, deduce from its type even if // the type is dependent, in order to check the types of non-type template // arguments line up properly in partial ordering. diff --git a/clang/test/SemaTemplate/temp_arg_template_cxx1z.cpp b/clang/test/SemaTemplate/temp_arg_template_cxx1z.cpp index 703935dcd5c..e3f228e7efb 100644 --- a/clang/test/SemaTemplate/temp_arg_template_cxx1z.cpp +++ b/clang/test/SemaTemplate/temp_arg_template_cxx1z.cpp @@ -103,12 +103,13 @@ namespace Auto { TDecltypeAuto<Int> dai; // expected-error {{different template parameters}} TDecltypeAuto<IntPtr> daip; // expected-error {{different template parameters}} - // FIXME: It's completely unclear what should happen here. A case can be made - // that 'auto' is more specialized, because it's always a prvalue, whereas - // 'decltype(auto)' could have any value category. Under that interpretation, - // we get the following results entirely backwards: - TAuto<DecltypeAuto> ada; // expected-error {{different template parameters}} - TAutoPtr<DecltypeAuto> apda; // expected-error {{different template parameters}} + // FIXME: It's completely unclear what should happen here, but these results + // seem at least plausible: + TAuto<DecltypeAuto> ada; + TAutoPtr<DecltypeAuto> apda; + // Perhaps this case should be invalid, as there are valid 'decltype(auto)' + // parameters (such as 'user-defined-type &') that are not valid 'auto' + // parameters. TDecltypeAuto<Auto> daa; TDecltypeAuto<AutoPtr> daa; // expected-error {{different template parameters}} |
