c++: Some improvements to concept diagnostics

This patch improves our concept diagnostics in two ways.  First, it sets a more
precise location for the constraint expressions built in
finish_constraint_binary_op.  As a result, when a disjunction is unsatisfied we
now print e.g.

.../include/bits/range_access.h:467:2: note: neither operand of the disjunction is satisfied
  466 |  requires is_bounded_array_v<remove_reference_t<_Tp>> || __member_end<_Tp>
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  467 |  || __adl_end<_Tp>
      |  ^~~~~~~~~~~~~~~~~

instead of

.../include/bits/range_access.h:467:2: note: neither operand of the disjunction is satisfied
  467 |  || __adl_end<_Tp>
      |  ^~

Second, this patch changes diagnose_atomic_constraint to print unsatisfied
atomic constraint expressions with their template arguments.  So e.g. we now
print

cpp2a/concepts-pr67719.C:9:8: note: the expression ‘(... &&(C<Tx>)()) [with Tx = {int, long int, void}]’ evaluated to ‘false’

instead of

cpp2a/concepts-pr67719.C:9:8: note: the expression ‘(... &&(C<Tx>)())’ evaluated to ‘false’

Tested on x86_64-pc-linux-gnu, and verified that all the diagnostics emitted in
our concept tests are no worse with this patch.

gcc/cp/ChangeLog:

	* constraint.cc (finish_constraint_binary_op): Set expr's location range
	to the range of its operands.
	(satisfy_atom): Pass MAP instead of ARGS to diagnose_atomic_constraint.
	(diagnose_trait_expr): Take the instantiated parameter mapping MAP
	instead of the corresponding template arguments ARGS and adjust body
	accordingly.
	(diagnose_requires_expr): Likewise.
	(diagnose_atomic_constraint): Likewise.  When printing an atomic
	constraint expression, print the instantiated parameter mapping
	alongside it.
	* cxx-pretty-print.cc (cxx_pretty_printer::expression)
	[NONTYPE_ARGUMENT_PACK]: Print braces around a NONTYPE_ARGUMENT_PACK.
	(cxx_pretty_printer::type_id): Handle TYPE_ARGUMENT_PACK.

gcc/testsuite/ChangeLog:

	* g++.dg/concepts/diagnostic2.C: New test.
	* g++.dg/concepts/diagnostic3.C: New test.

1 files changed, 17 insertions, 0 deletions

diff --git a/gcc/cp/cxx-pretty-print.c b/gcc/cp/cxx-pretty-print.c
index 9e0c5fc..397bdbf 100644
--- a/gcc/cp/cxx-pretty-print.c
+++ b/gcc/cp/cxx-pretty-print.c
@@ -1214,12 +1214,14 @@ cxx_pretty_printer::expression (tree t)
       {
 	tree args = ARGUMENT_PACK_ARGS (t);
 	int i, len = TREE_VEC_LENGTH (args);
+	pp_cxx_left_brace (this);
 	for (i = 0; i < len; ++i)
 	  {
 	    if (i > 0)
 	      pp_cxx_separate_with (this, ',');
 	    expression (TREE_VEC_ELT (args, i));
 	  }
+	pp_cxx_right_brace (this);
       }
       break;
 
@@ -1839,6 +1841,21 @@ cxx_pretty_printer::type_id (tree t)
       pp_cxx_ws_string (this, "...");
       break;
 
+    case TYPE_ARGUMENT_PACK:
+      {
+	tree args = ARGUMENT_PACK_ARGS (t);
+	int len = TREE_VEC_LENGTH (args);
+	pp_cxx_left_brace (this);
+	for (int i = 0; i < len; ++i)
+	  {
+	    if (i > 0)
+	      pp_cxx_separate_with (this, ',');
+	    type_id (TREE_VEC_ELT (args, i));
+	  }
+	pp_cxx_right_brace (this);
+      }
+      break;
+
     default:
       c_pretty_printer::type_id (t);
       break;