[Bug c++/82899] *this in constructors could not alias with reference input parameters of the same type

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82899

--- Comment #15 from Marc Glisse <glisse at gcc dot gnu.org> ---
Created attachment 44112
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44112&action=edit
Untested patch

Something like this, but I haven't tested, and other calls to build_this_parm
need auditing to check if "being a constructor" is set before.