c++: "'decltype_type' not supported" in diagnostic [PR85278]

This fixes a garbled concepts diagnostic by moving the handling of DECLTYPE_TYPE
from pp_cxx_type_specifier_seq to cxx_pretty_printer::simple_type_specifier, a
move which also seems to be more consistent with the language grammar.

This patch also fixes pretty printing of rvalue reference types via
cxx_pretty_printer::type_id, which eventually calls pp_c_pointer which currently
doesn't distinguish between lvalue and rvalue references.

gcc/c-family/ChangeLog:

	PR c++/85278
	* c-pretty-print.c (pp_c_pointer) <case REFERENCE_TYPE>: Print a double
	ampersand if it's an rvalue reference type.

gcc/cp/ChangeLog:

	PR c++/85278
	* cxx-pretty-print.c (cxx_pretty_printer:simple_type_specifier)
	<case DECLTYPE_TYPE>: Handle DECLTYPE_TYPE here instead of ...
	(pp_cxx_type_specifier_seq) <case DECLTYPE_TYPE>: ... here.
	(cxx_pretty_printer::direct_abstract_declarator) <case DECLTYPE_TYPE>:
	New no-op case.

gcc/testsuite/ChangeLog:

	PR c++/85278
	* g++.dg/concepts/diagnostic9.C: New test.

6 files changed, 42 insertions, 8 deletions

diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index d0569d7..66f4873 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,9 @@
+2020-04-14  Patrick Palka  <ppalka@redhat.com>
+
+	PR c++/85278
+	* c-pretty-print.c (pp_c_pointer) <case REFERENCE_TYPE>: Print a double
+	ampersand if it's an rvalue reference type.
+
 2020-04-13  Martin Sebor  <msebor@redhat.com>
 
 	PR c/92326
diff --git a/gcc/c-family/c-pretty-print.c b/gcc/c-family/c-pretty-print.c
index eccb630..32f30f2 100644
--- a/gcc/c-family/c-pretty-print.c
+++ b/gcc/c-family/c-pretty-print.c
@@ -278,7 +278,11 @@ pp_c_pointer (c_pretty_printer *pp, tree t)
       if (TREE_CODE (t) == POINTER_TYPE)
 	pp_c_star (pp);
       else
-	pp_c_ampersand (pp);
+	{
+	  pp_c_ampersand (pp);
+	  if (TYPE_REF_IS_RVALUE (t))
+	    pp_c_ampersand (pp);
+	}
       pp_c_type_qualifier_list (pp, t);
       break;
 
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index ce39093..e34ef93 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,12 @@
 2020-04-14  Patrick Palka  <ppalka@redhat.com>
 
+	PR c++/85278
+	* cxx-pretty-print.c (cxx_pretty_printer:simple_type_specifier)
+	<case DECLTYPE_TYPE>: Handle DECLTYPE_TYPE here instead of ...
+	(pp_cxx_type_specifier_seq) <case DECLTYPE_TYPE>: ... here.
+	(cxx_pretty_printer::direct_abstract_declarator) <case DECLTYPE_TYPE>:
+	New no-op case.
+
 	PR c++/94034
 	* constexpr.c (replace_result_decl_data): New struct.
 	(replace_result_decl_data_r): New function.
diff --git a/gcc/cp/cxx-pretty-print.c b/gcc/cp/cxx-pretty-print.c
index 840b5a8..a26291e 100644
--- a/gcc/cp/cxx-pretty-print.c
+++ b/gcc/cp/cxx-pretty-print.c
@@ -1325,6 +1325,7 @@ cxx_pretty_printer::declaration_specifiers (tree t)
 /* simple-type-specifier:
       ::(opt) nested-name-specifier(opt) type-name
       ::(opt) nested-name-specifier(opt) template(opt) template-id
+      decltype-specifier
       char
       wchar_t
       bool
@@ -1363,6 +1364,13 @@ cxx_pretty_printer::simple_type_specifier (tree t)
       pp_cxx_unqualified_id (this, TYPENAME_TYPE_FULLNAME (t));
       break;
 
+    case DECLTYPE_TYPE:
+      pp_cxx_ws_string (this, "decltype");
+      pp_cxx_left_paren (this);
+      this->expression (DECLTYPE_TYPE_EXPR (t));
+      pp_cxx_right_paren (this);
+      break;
+
     default:
       c_pretty_printer::simple_type_specifier (t);
       break;
@@ -1389,6 +1397,7 @@ pp_cxx_type_specifier_seq (cxx_pretty_printer *pp, tree t)
     case TEMPLATE_TEMPLATE_PARM:
     case TYPE_DECL:
     case BOUND_TEMPLATE_TEMPLATE_PARM:
+    case DECLTYPE_TYPE:
       pp_cxx_cv_qualifier_seq (pp, t);
       pp->simple_type_specifier (t);
       break;
@@ -1399,13 +1408,6 @@ pp_cxx_type_specifier_seq (cxx_pretty_printer *pp, tree t)
       pp_cxx_nested_name_specifier (pp, TYPE_METHOD_BASETYPE (t));
       break;
 
-    case DECLTYPE_TYPE:
-      pp_cxx_ws_string (pp, "decltype");
-      pp_cxx_left_paren (pp);
-      pp->expression (DECLTYPE_TYPE_EXPR (t));
-      pp_cxx_right_paren (pp);
-      break;
-
     case RECORD_TYPE:
       if (TYPE_PTRMEMFUNC_P (t))
 	{
@@ -1799,6 +1801,7 @@ cxx_pretty_printer::direct_abstract_declarator (tree t)
     case TEMPLATE_TEMPLATE_PARM:
     case BOUND_TEMPLATE_TEMPLATE_PARM:
     case UNBOUND_CLASS_TEMPLATE:
+    case DECLTYPE_TYPE:
       break;
 
     default:
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3fec84e..cb4b23c 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
 2020-04-14  Patrick Palka  <ppalka@redhat.com>
 
+	PR c++/85278
+	* g++.dg/concepts/diagnostic9.C: New test.
+
 	PR c++/94034
 	* g++.dg/cpp0x/constexpr-empty15.C: New test.
 	* g++.dg/cpp1y/constexpr-nsdmi6a.C: New test.
diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic9.C b/gcc/testsuite/g++.dg/concepts/diagnostic9.C
new file mode 100644
index 0000000..414b924
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/diagnostic9.C
@@ -0,0 +1,11 @@
+// PR c++/85278
+// { dg-do compile { target concepts } }
+
+template<typename T>
+void f2(T a)
+  requires requires (const decltype(a) &&x) { -x; }
+{ }
+
+int main() {
+  f2<void*>(nullptr); // { dg-error "use of function .*const decltype\\(f2::a\\)&&" }
+}