[Bug c++/98735] New: ICE with -std=c++20 -fmodules-ts -fsanitize=undefined

[webrown.cpp at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98735

            Bug ID: 98735
           Summary: ICE with -std=c++20 -fmodules-ts -fsanitize=undefined
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: webrown.cpp at gmail dot com
  Target Milestone: ---

Using gcc version 11.0.0 20210116 (experimental) (Homebrew GCC HEAD-2c356f2_2)
and compiling with flags:
   -std=c++20 -fmodules-ts -fsanitize=undefined
produces:
  internal compiler error: in tree_node, at cp/module.cc:9125
pointing at the module keyword (line 1) in the following innocuous program:

  export module X;

  export
    inline constexpr bool f( ) noexcept
    { return true; }

Removing -fsanitize=undefined permits successful compilation.