Give #include hints for <complex>.

	* name-lookup.c (get_std_name_hint): Add <complex>.
	* parser.c (cp_parser_diagnose_invalid_type_name): Call
	suggest_alternative_in_explicit_scope.
	(cp_parser_namespace_name): Likewise.

From-SVN: r255336

gcc/cp/ChangeLog

 2017-12-01  Jason Merrill  <jason@redhat.com>
 
+	Give #include hints for <complex>.
+	* name-lookup.c (get_std_name_hint): Add <complex>.
+	* parser.c (cp_parser_diagnose_invalid_type_name): Call
+	suggest_alternative_in_explicit_scope.
+	(cp_parser_namespace_name): Likewise.
+
 	PR c++/79228 - extensions hide C++14 complex literal operators
 	* parser.c (cp_parser_userdef_numeric_literal): Be helpful about
 	'i' in C++14 and up.

gcc/cp/name-lookup.c

@@ -5414,6 +5414,9 @@ get_std_name_hint (const char *name)
   static const std_name_hint hints[] = {
     /* <array>.  */
     {"array", "<array>"}, // C++11
+    /* <complex>.  */
+    {"complex", "<complex>"},
+    {"complex_literals", "<complex>"},
     /* <deque>.  */
     {"deque", "<deque>"},
     /* <forward_list>.  */

gcc/cp/parser.c

@@ -3365,6 +3365,9 @@ cp_parser_diagnose_invalid_type_name (cp_parser *parser, tree id,
 		      id, parser->scope);
 	  if (DECL_P (decl))
 	    inform (DECL_SOURCE_LOCATION (decl), "%qD declared here", decl);
+	  else if (decl == error_mark_node)
+	    suggest_alternative_in_explicit_scope (location, id,
+						   parser->scope);
 	}
       else if (CLASS_TYPE_P (parser->scope)
 	       && constructor_name_p (id, parser->scope))
@@ -18408,7 +18411,13 @@ cp_parser_namespace_name (cp_parser* parser)
       || TREE_CODE (namespace_decl) != NAMESPACE_DECL)
     {
       if (!cp_parser_uncommitted_to_tentative_parse_p (parser))
-	error_at (token->location, "%qD is not a namespace-name", identifier);
+	{
+	  error_at (token->location, "%qD is not a namespace-name", identifier);
+	  if (namespace_decl == error_mark_node
+	      && parser->scope && TREE_CODE (parser->scope) == NAMESPACE_DECL)
+	    suggest_alternative_in_explicit_scope (token->location, identifier,
+						   parser->scope);
+	}
       cp_parser_error (parser, "expected namespace-name");
       namespace_decl = error_mark_node;
     }

gcc/testsuite/g++.dg/lookup/missing-std-include-4.C

+std::complex<int> c;		// { dg-error "" }
+// { dg-message "#include <complex>" "" { target *-*-* } .-1 }

gcc/testsuite/g++.dg/lookup/missing-std-include-5.C

+using namespace std::complex_literals; // { dg-error "" }
+// { dg-message "#include <complex>" "" { target *-*-* } .-1 }