c++: Fix printing of decltype(nullptr) [PR97517]

The C++ printer doesn't handle NULLPTR_TYPE, so we issue the ugly
"'nullptr_type' not supported by...".  Since NULLPTR_TYPE is
decltype(nullptr), it seemed reasonable to handle it where we
handle DECLTYPE_TYPE, that is, in the simple-type-specifier handler.

gcc/cp/ChangeLog:

	PR c++/97517
	* cxx-pretty-print.c (cxx_pretty_printer::simple_type_specifier): Handle
	NULLPTR_TYPE.
	(pp_cxx_type_specifier_seq): Likewise.
	(cxx_pretty_printer::type_id): Likewise.

gcc/testsuite/ChangeLog:

	PR c++/97517
	* g++.dg/diagnostic/nullptr.C: New test.

diff --git a/gcc/cp/cxx-pretty-print.c b/gcc/cp/cxx-pretty-print.c
index b97f70e2bd0e4e9fb44b01b942492e26ba623937..e18927008edd901ecc826e7f1efb0bda73132057 100644 (file)
--- a/gcc/cp/cxx-pretty-print.c
+++ b/gcc/cp/cxx-pretty-print.c
@@ -1381,6 +1381,10 @@ cxx_pretty_printer::simple_type_specifier (tree t)
       pp_cxx_right_paren (this);
       break;
 
+    case NULLPTR_TYPE:
+      pp_cxx_ws_string (this, "std::nullptr_t");
+      break;
+
     default:
       c_pretty_printer::simple_type_specifier (t);
       break;
@@ -1408,6 +1412,7 @@ pp_cxx_type_specifier_seq (cxx_pretty_printer *pp, tree t)
     case TYPE_DECL:
     case BOUND_TEMPLATE_TEMPLATE_PARM:
     case DECLTYPE_TYPE:
+    case NULLPTR_TYPE:
       pp_cxx_cv_qualifier_seq (pp, t);
       pp->simple_type_specifier (t);
       break;
@@ -1873,6 +1878,7 @@ cxx_pretty_printer::type_id (tree t)
     case TYPEOF_TYPE:
     case UNDERLYING_TYPE:
     case DECLTYPE_TYPE:
+    case NULLPTR_TYPE:
     case TEMPLATE_ID_EXPR:
     case OFFSET_TYPE:
       pp_cxx_type_specifier_seq (this, t);

diff --git a/gcc/testsuite/g++.dg/diagnostic/nullptr.C b/gcc/testsuite/g++.dg/diagnostic/nullptr.C
new file mode 100644 (file)
index 0000000..bc0d829
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/nullptr.C
@@ -0,0 +1,8 @@
+// PR c++/97517
+// { dg-do compile { target c++20 } }
+// Test that we print "decltype(nullptr)" correctly.
+
+template<typename T> struct Trait { static constexpr bool value = false; };
+template<typename T> concept Concept = Trait<T>::value; // { dg-message {\[with T = std::nullptr_t\]} }
+static_assert( Concept<decltype(nullptr)> ); // { dg-error "static assertion failed" }
+// { dg-message "constraints not satisfied" "" { target *-*-* } .-1 }