re PR c++/45330 (Suggest likely nested-name-specifiers for undeclared identifiers.)

gcc/
	PR c++/45330
	* params.def (CXX_MAX_NAMESPACES_FOR_DIAGNOSTIC_HELP): New parameter.
	* doc/invoke.texi (cxx-max-namespaces-for-diagnostic-help): Document.

gcc/cp/
	PR c++/45330
	* cp-tree.h (suggest_alternatives_for, location_of): Declare.
	* error.c (dump_expr): Handle TYPE_DECL.
	(location_of): Unstaticize.
	* name-lookup.c (suggest_alternatives_for): New function.
	* lex.c (unqualified_name_lookup_error): Call it.

gcc/testsuite/
	PR c++/45330
	* g++.dg/pr45330.C: New test.
	* g++.dg/ext/builtin3.C: Adjust.
	* g++.dg/lookup/error1.C: Adjust.
	* g++.dg/lookup/koenig5.C: Adjust.
	* g++.dg/overload/koenig1.C: Adjust.
	* g++.dg/parse/decl-specifier-1.C: Adjust.
	* g++.dg/template/static10.C: Adjust.
	* g++.old-deja/g++.mike/ns5.C: Adjust.
	* g++.old-deja/g++.mike/ns7.C: Adjust.
	* g++.old-deja/g++.ns/koenig5.C: Adjust.
	* g++.old-deja/g++.ns/koenig9.C: Adjust.
	* g++.old-deja/g++.other/lineno5.C: Adjust.

From-SVN: r167536

1 files changed, 67 insertions, 0 deletions

diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index 3d19c08..4cf1380 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -29,8 +29,10 @@ along with GCC; see the file COPYING3.  If not see
 #include "name-lookup.h"
 #include "timevar.h"
 #include "diagnostic-core.h"
+#include "intl.h"
 #include "debug.h"
 #include "c-family/c-pragma.h"
+#include "params.h"
 
 /* The bindings for a particular name in a particular scope.  */
 
@@ -3916,6 +3918,71 @@ remove_hidden_names (tree fns)
   return fns;
 }
 
+/* Suggest alternatives for NAME, an IDENTIFIER_NODE for which name
+   lookup failed.  Search through all available namespaces and print out
+   possible candidates.  */
+
+void
+suggest_alternatives_for (tree name)
+{
+  VEC(tree,heap) *candidates = NULL;
+  VEC(tree,heap) *namespaces_to_search = NULL;
+  int max_to_search = PARAM_VALUE (CXX_MAX_NAMESPACES_FOR_DIAGNOSTIC_HELP);
+  int n_searched = 0;
+  tree t;
+  unsigned ix;
+  location_t name_location;
+
+  VEC_safe_push (tree, heap, namespaces_to_search, global_namespace);
+
+  while (!VEC_empty (tree, namespaces_to_search)
+	 && n_searched < max_to_search)
+    {
+      tree scope = VEC_pop (tree, namespaces_to_search);
+      struct scope_binding binding = EMPTY_SCOPE_BINDING;
+      struct cp_binding_level *level = NAMESPACE_LEVEL (scope);
+
+      /* Look in this namespace.  */
+      qualified_lookup_using_namespace (name, scope, &binding, 0);
+
+      n_searched++;
+
+      if (binding.value)
+	VEC_safe_push (tree, heap, candidates, binding.value);
+
+      /* Add child namespaces.  */
+      for (t = level->namespaces; t; t = DECL_CHAIN (t))
+	VEC_safe_push (tree, heap, namespaces_to_search, t);
+    }
+
+  name_location = location_of (name);
+
+  /* If we stopped before we could examine all namespaces, inform the
+     user.  Do this even if we don't have any candidates, since there
+     might be more candidates further down that we weren't able to
+     find.  */
+  if (n_searched >= max_to_search
+      && !VEC_empty (tree, namespaces_to_search))
+    inform (name_location,
+	    "maximum limit of %d namespaces searched for %qE",
+	    max_to_search, name);
+
+  VEC_free (tree, heap, namespaces_to_search);
+
+  /* Nothing useful to report.  */
+  if (VEC_empty (tree, candidates))
+    return;
+
+  inform_n (name_location, VEC_length (tree, candidates),
+	    "suggested alternative:",
+	    "suggested alternatives:");
+
+  FOR_EACH_VEC_ELT (tree, candidates, ix, t)
+    inform (location_of (t), "  %qE", t);
+
+  VEC_free (tree, heap, candidates);
+}
+
 /* Unscoped lookup of a global: iterate over current namespaces,
    considering using-directives.  */