PR c++/93280 - ICE with aggregate assignment and DMI.

I recently added an assert to cp-gimplify to catch any
TARGET_EXPR_DIRECT_INIT_P being expanded without a target object, and this
testcase found one.  We started out with a TARGET_EXPR around the
CONSTRUCTOR, which would normally mean that the member initializer would be
used to directly initialize the appropriate member of whatever object the
TARGET_EXPR ends up initializing.  But then gimplify_modify_expr_rhs
stripped the TARGET_EXPR in order to assign directly from the elements of
the CONSTRUCTOR, leaving no object for the TARGET_EXPR_DIRECT_INIT_P to
initialize.  I considered setting CONSTRUCTOR_PLACEHOLDER_BOUNDARY in that
case, which implies TARGET_EXPR_NO_ELIDE, but decided that there's no
particular reason the A initializer needs to initialize a member of a B
rather than a distinct A object, so let's only set TARGET_EXPR_DIRECT_INIT_P
when we're using the DMI in a constructor.

	* init.c (get_nsdmi): Set TARGET_EXPR_DIRECT_INIT_P here.
	* typeck2.c (digest_nsdmi_init): Not here.

gcc/cp/ChangeLog

+2020-01-16  Jason Merrill  <jason@redhat.com>
+
+	PR c++/93280 - ICE with aggregate assignment and DMI.
+	* init.c (get_nsdmi): Set TARGET_EXPR_DIRECT_INIT_P here.
+	* typeck2.c (digest_nsdmi_init): Not here.
+
 2020-01-15  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/91073

gcc/cp/init.c

@@ -655,6 +655,10 @@ get_nsdmi (tree member, bool in_ctor, tsubst_flags_t complain)
   if (simple_target)
     init = TARGET_EXPR_INITIAL (init);
   init = break_out_target_exprs (init, /*loc*/true);
+  if (in_ctor && init && TREE_CODE (init) == TARGET_EXPR)
+    /* This expresses the full initialization, prevent perform_member_init from
+       calling another constructor (58162).  */
+    TARGET_EXPR_DIRECT_INIT_P (init) = true;
   if (simple_target && TREE_CODE (init) != CONSTRUCTOR)
     /* Now put it back so C++17 copy elision works.  */
     init = get_target_expr (init);

gcc/cp/typeck2.c

@@ -1369,9 +1369,6 @@ digest_nsdmi_init (tree decl, tree init, tsubst_flags_t complain)
       && CP_AGGREGATE_TYPE_P (type))
     init = reshape_init (type, init, complain);
   init = digest_init_flags (type, init, flags, complain);
-  if (TREE_CODE (init) == TARGET_EXPR)
-    /* This represents the whole initialization.  */
-    TARGET_EXPR_DIRECT_INIT_P (init) = true;
   return init;
 }