The following snippet code fails with similar reason as PR101402, but it cannot be fixed with similar way of using *resolve_typename_type* without further improvement of itself. template<class TA> struct A{ template<class TB> using Type=TB[3]; }; template<class TA, class TB> void f(const typename A<TA>::template Type<TB>){} template <> void f<int, char>(const typename A<int>::template Type<char>){} error: template-id 'f<int, char>' for 'void f(const char*)' does not match any template declaration 9 | void f<int, char>(const typename A<int>::template Type<char>){} | ^~~~~~~~~~~~ array-using.cpp:7:6: note: candidate is: 'template<class TA, class TB> void f(typename A<TA>::Type<TB>)' 7 | void f(const typename A<TA>::template Type<TB>){} | ^
Confirmed, looks like an array is not decaying to a pointer issue or decaying too early really.
*** Bug 102034 has been marked as a duplicate of this bug. ***
I can give tons of similar cases with even more complicated template levels combined with using/typedefs/default arguments. i.e. template<class TA> struct A{ template<class TB> struct B{ using TB_Alias=TB; template<class TC=TB_Alias> struct C{ typedef TC Arr3[3]; }; }; }; template<class TA, class TB> void f(const typename A<TA>::template B<TB>::template C<>::Arr3){} template <> void f<int, char>(const typename A<int>::template B<char>::template C<>::Arr3){} The fix are all can be done similarly at point to calculating function parameter "cv-qualifier" value by passing its result into call *cp_build_qualified_type* at decl.c:grokparms. for example: diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c index 3414cbdc876..473c7b7d75c 100644 --- a/gcc/cp/decl.c +++ b/gcc/cp/decl.c @@ -14493,7 +14493,16 @@ grokparms (tree parmlist, tree *parms) /* Top-level qualifiers on the parameters are ignored for function types. */ - type = cp_build_qualified_type (type, 0); + int type_quals = 0; + /* Top-level qualifiers are reserved for array type. PR101402 */ + if (TREE_CODE (type) == TYPENAME_TYPE) + { + tree resolved_type = resolve_typename_type(type, false); + if (resolved_type && TREE_CODE(resolved_type) == ARRAY_TYPE) + type_quals = CP_TYPE_CONST_P(type); + } + type = cp_build_qualified_type (type, type_quals); + if (TREE_CODE (type) == METHOD_TYPE) { error ("parameter %qD invalidly declared method type", decl); However, original *resolve_typename_type* function is not working well to cover all cases. I only fixed one "non-recursive" case with diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index 020a4bf2f6d..1944bf4a6ea 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -27989,7 +27989,12 @@ resolve_typename_type (tree type, bool only_current_p) /* If we failed to resolve it, return the original typename. */ if (!result) - return type; + { + if (TREE_CODE (fullname) == TEMPLATE_ID_EXPR + && TREE_CODE (decl) == TEMPLATE_DECL) + return TREE_TYPE(decl); + return type; + } /* If lookup found a typename type, resolve that too. */ if (TREE_CODE (result) == TYPENAME_TYPE && !TYPENAME_IS_RESOLVING_P (result)) And then I give up because it requires almost a new *resolve_typename_type* function to cover all possible cases. And I have no GCC write access and the code is extremely difficult to maintain.
> And I have no GCC write access and the code is extremely difficult to maintain. We don't just give people write access as soon as they propose a patch (does any serious software proejct do that?!) The contribution process is documented at https://gcc.gnu.org/contribute.html#patches and write access policies at https://gcc.gnu.org/gitwrite.html#policies
*** Bug 102038 has been marked as a duplicate of this bug. ***
*** Bug 102042 has been marked as a duplicate of this bug. ***
The master branch has been updated by Jason Merrill <jason@gcc.gnu.org>: https://gcc.gnu.org/g:79802c5dcc043a515f429bb2bec7573b8537c32a commit r12-4453-g79802c5dcc043a515f429bb2bec7573b8537c32a Author: Jason Merrill <jason@redhat.com> Date: Tue Sep 28 10:02:04 2021 -0400 c++: array cv-quals and template specialization [PR101402] PRs 101402, 102033, etc. demonstrated that the fix for PR92010 wasn't handling all cases of the CWG1001/1322 issue with parameter type qual stripping and arrays with templates. The problem turned out to be in determine_specialization, which did an extra substitution without the 92010 fix and then complained that the result didn't match. But just removing that wrong/redundant code meant that we were accepting specializations with different numbers of parameters, because the code in fn_type_unification that compares types in this case wasn't checking for length mismatch. After fixing that, I realized that fn_type_unification couldn't tell the difference between variadic and non-variadic function types, because the args array doesn't include the terminal void we use to indicate non-variadic function type. So I added it, and made the necessary adjustments. Thanks to qingzhe "nick" huang <nickhuang99@hotmail.com> for the patch that led me to dig more into this, and the extensive testcases. PR c++/51851 PR c++/101402 PR c++/102033 PR c++/102034 PR c++/102039 PR c++/102044 gcc/cp/ChangeLog: * pt.c (determine_specialization): Remove redundant code. (fn_type_unification): Check for mismatched length. (type_unification_real): Ignore terminal void. (get_bindings): Don't stop at void_list_node. * class.c (resolve_address_of_overloaded_function): Likewise. gcc/testsuite/ChangeLog: * g++.dg/template/fnspec2.C: New test. * g++.dg/template/parm-cv1.C: New test. * g++.dg/template/parm-cv2.C: New test. * g++.dg/template/parm-cv3.C: New test.
fixed by patch under PR101402