[PATCH] c++: handle decltype in nested-name-spec printing [PR118139]

[Marek Polacek]

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

-- >8 --
Compiling this test, we emit:

  error: 'static void CW<T>::operator=(int) requires 
requires(typename'decltype_type' not supported by pp_cxx_unqualified_id::type 
x) {x;}' must be a non-static member function

where the DECLTYPE_TYPE isn't printed properly.  This patch fixes that
to print:

error: 'static void CW<T>::operator=(int) requires requires(typename 
decltype(T())::type x) {x;}' must be a non-static member function

        PR c++/118139

gcc/cp/ChangeLog:

        * cxx-pretty-print.cc (pp_cxx_nested_name_specifier): Handle
        a computed-type-specifier.

gcc/testsuite/ChangeLog:

        * g++.dg/diagnostic/decltype1.C: New test.
---
 gcc/cp/cxx-pretty-print.cc                  | 14 +++++++++++---
 gcc/testsuite/g++.dg/diagnostic/decltype1.C |  8 ++++++++
 2 files changed, 19 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/diagnostic/decltype1.C

diff --git a/gcc/cp/cxx-pretty-print.cc b/gcc/cp/cxx-pretty-print.cc
index 4104c6863c7..caa74e3b86f 100644
--- a/gcc/cp/cxx-pretty-print.cc
+++ b/gcc/cp/cxx-pretty-print.cc
@@ -234,8 +234,12 @@ pp_cxx_template_keyword_if_needed (cxx_pretty_printer *pp, 
tree scope, tree t)
 }
 
 /* nested-name-specifier:
-      class-or-namespace-name :: nested-name-specifier(opt)
-      class-or-namespace-name :: template nested-name-specifier   */
+      ::
+      type-name ::
+      namespace-name ::
+      computed-type-specifier ::
+      nested-name-specifier identifier ::
+      nested-name-specifier templateopt simple-template-id ::  */
 
 static void
 pp_cxx_nested_name_specifier (cxx_pretty_printer *pp, tree t)
@@ -252,7 +256,11 @@ pp_cxx_nested_name_specifier (cxx_pretty_printer *pp, tree 
t)
       tree scope = get_containing_scope (t);
       pp_cxx_nested_name_specifier (pp, scope);
       pp_cxx_template_keyword_if_needed (pp, scope, t);
-      pp_cxx_unqualified_id (pp, t);
+      /* This is a computed-type-specifier.  */
+      if (TREE_CODE (t) == PACK_INDEX_TYPE || TREE_CODE (t) == DECLTYPE_TYPE)
+       pp->type_id (t);
+      else
+       pp_cxx_unqualified_id (pp, t);
       pp_cxx_colon_colon (pp);
     }
 }
diff --git a/gcc/testsuite/g++.dg/diagnostic/decltype1.C 
b/gcc/testsuite/g++.dg/diagnostic/decltype1.C
new file mode 100644
index 00000000000..8b57b165603
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/decltype1.C
@@ -0,0 +1,8 @@
+// PR c++/118139
+// { dg-do compile { target c++20 } }
+
+template<class T>
+struct CW {
+  using V = typename decltype(T())::type;
+  static void operator=(int) requires requires(V x) { x; } {} // { dg-error 
{requires requires\(typename decltype\(T\(\)\)::type x\)} }
+};

base-commit: 219ddae16f9d724baeff86934f8981aa5ef7b95f
-- 
2.47.1