[C++ PATCH] Fix ICE in maybe_explain_implicit_delete (PR c++/88122)

[Jakub Jelinek]

Hi!

On the following testcase we ICE in maybe_explain_implicit_delete, because
FUNCTION_FIRST_USER_PARMTYPE (decl) is NULL - there are no user parameters
and ...
>From what I understood, const_p is used only in certain cases like const vs.
non-const copy constructor or assignment operator, if the sfk has no user
parameters, usually parm_type is just the void_type terminating the argument
list and also not really interesting for const_p computation.
So, this patch just arranges to pass false as const_p in this case.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2018-11-21  Jakub Jelinek  <jakub@redhat.com>

	PR c++/88122
	* method.c (maybe_explain_implicit_delete): If
	FUNCTION_FIRST_USER_PARMTYPE (decl) is NULL, set const_p to false
	instead of ICEing.

	* g++.dg/cpp0x/implicit15.C: New test.

--- gcc/cp/method.c.jj	2018-11-16 10:22:18.668258171 +0100
+++ gcc/cp/method.c	2018-11-21 15:42:08.441785625 +0100
@@ -1821,8 +1821,12 @@ maybe_explain_implicit_delete (tree decl
       if (!informed)
 	{
 	  tree parms = FUNCTION_FIRST_USER_PARMTYPE (decl);
-	  tree parm_type = TREE_VALUE (parms);
-	  bool const_p = CP_TYPE_CONST_P (non_reference (parm_type));
+	  bool const_p = false;
+	  if (parms)
+	    {
+	      tree parm_type = TREE_VALUE (parms);
+	      const_p = CP_TYPE_CONST_P (non_reference (parm_type));
+	    }
 	  tree raises = NULL_TREE;
 	  bool deleted_p = false;
 	  tree scope = push_scope (ctype);
--- gcc/testsuite/g++.dg/cpp0x/implicit15.C.jj	2018-11-21 15:59:29.849741499 +0100
+++ gcc/testsuite/g++.dg/cpp0x/implicit15.C	2018-11-21 15:58:00.912197089 +0100
@@ -0,0 +1,11 @@
+// PR c++/88122
+// { dg-do compile { target c++11 } }
+
+struct A {
+  A (...);	// { dg-message "candidate" }
+  A ();		// { dg-message "candidate" }
+};
+struct B : A {
+  using A::A;	// { dg-error "is ambiguous" }
+		// { dg-message "is implicitly deleted because the default definition would be ill-formed" "" { target *-*-* } .-1 }
+} b{3};		// { dg-error "use of deleted function" }

	Jakub