[Bug c++/101988] New: Accepts invalid new-expression of array of deduced class template

[ed at catmur dot uk]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101988

            Bug ID: 101988
           Summary: Accepts invalid new-expression of array of deduced
                    class template
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ed at catmur dot uk
  Target Milestone: ---

template<class T> struct A { A(T); };
auto p = new A[]{1};

g++
(Compiler-Explorer-Build-gcc-f0fca213bc52644ba896da622b35842a6157bd98-binutils-2.36.1)
12.0.0 20210818 (experimental) accepts (it allocates and constructs a single
`A<int>`.

gcc 11.2 and below rejects, correctly: error: creating array of 'A<...auto...>'

Per [expr.new]/2 the invented declaration should be:
A[] x{1};
which is ill-formed.

nb. clang ICEs on this (https://bugs.llvm.org/show_bug.cgi?id=51547)