c++: Partially revert fix for PR c++/95497 [PR96132]

I was mistaken to assume that a dependent type is necessarily
incomplete, and indeed there are multiple places in the frontend where
we check a type for both dependency and completeness.  So this patch
partially reverts the fix for PR95497, restoring the dependent_type_p
check that guarded the call to is_really_empty_class below.

gcc/cp/ChangeLog:

	PR c++/96132
	* constexpr.c (potential_constant_expression_1) <case PARM_DECL>:
	Restore dependent_type_p check that guarded the call to
	is_really_empty_class.

gcc/testsuite/ChangeLog:

	PR c++/96132
	* g++.dg/template/incomplete12.C: New test.

diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index ff78ebda2dc9fb83e9ff36d62aa8621d3aa32c67..97dcc1b1d1057567b1c099f691c8b19d6452d2ac 100644 (file)
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -7444,6 +7444,7 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now,
        {
          tree type = TREE_TYPE (t);
          if ((processing_template_decl && !COMPLETE_TYPE_P (type))
+             || dependent_type_p (type)
              || is_really_empty_class (type, /*ignore_vptr*/false))
            /* An empty class has no data to read.  */
            return true;

diff --git a/gcc/testsuite/g++.dg/template/incomplete12.C b/gcc/testsuite/g++.dg/template/incomplete12.C
new file mode 100644 (file)
index 0000000..335e535
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/incomplete12.C
@@ -0,0 +1,9 @@
+// PR c++/96132
+// { dg-do compile }
+
+template <int> class a;
+
+template <int b> class c {
+  a<b> e;
+  void operator=(c d) { e = d; }
+};