commit b4e53e9b3c963b1c0fe9637618dec8042764f599
author Jason Merrill <jason@redhat.com> Mon Mar 02 14:42:47 2020 -0500
committer Jason Merrill <jason@redhat.com> Mon Mar 02 15:49:58 2020 -0500
tree 0032767bbbe11287e921f5bc1f0c57867ebfa7b5
parent f137a7c6b122e524294fb792bb97d5f3b0600c4f

c++: Allow parm of empty class type in constexpr.

Since copying a class object is defined in terms of the copy constructor,
copying an empty class is OK even if it would otherwise not be usable in a
constant expression.  Relatedly, using a parameter as an lvalue is no more
problematic than a local variable, and calling a member function uses the
object as an lvalue.

gcc/cp/ChangeLog
2020-03-02  Jason Merrill  <jason@redhat.com>

	PR c++/91953
	* constexpr.c (potential_constant_expression_1) [PARM_DECL]: Allow
	empty class type.
	[COMPONENT_REF]: A member function reference doesn't use the object
	as an rvalue.