[Bug c++/88020] New: Template argument deduction fails inside sizeof

[toe-ger at web dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88020

            Bug ID: 88020
           Summary: Template argument deduction fails inside sizeof
           Product: gcc
           Version: 8.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: toe-ger at web dot de
  Target Milestone: ---

*Minimal example*:
template <class T>
struct S{
    S(T){}
};
static_assert(sizeof(S{0}));

*Expected output*:
*Actual output*:
<source>:5:22: error: missing template arguments after 'S'
 static_assert(sizeof(S{0}));
                      ^
<source>:2:8: note: 'template<class T> struct S' declared here
 struct S{
        ^
*Reproduction*:
https://godbolt.org/z/9XLvfT
(currently also fails on trunk)
Note: Deduction guides are a C++17 feature and requires -std=c++17.
S s{0}; compiles.