re PR c++/50732 ([type_traits] is_base_of<Base, Derived> unnecessarily instantiates Base (which shouldn't be instantiated))

/cp
2011-10-15  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/50732
	* semantics.c (finish_trait_expr): Do not try to instantiate the
	the base type of an __is_base_of trait.
	(check_trait_type): Return a tree; use complete_type_or_else.

/testsuite
2011-10-15  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/50732
	* g++.dg/ext/is_base_of_incomplete.C: New.
	* g++.dg/ext/is_base_of_diagnostic.C: Adjust dg-errors.
	* g++.dg/ext/unary_trait_incomplete.C: Likewise.

From-SVN: r180048

6 files changed, 35 insertions, 24 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 09131c5..c2c452d 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2011-10-15  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/50732
+	* semantics.c (finish_trait_expr): Do not try to instantiate the
+	the base type of an __is_base_of trait.
+	(check_trait_type): Return a tree; use complete_type_or_else.
+
 2011-10-14  Jason Merrill  <jason@redhat.com>
 
 	PR c++/50563
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 7d37fa3..1efe579 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -5210,23 +5210,20 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     }
 }
 
-/* Returns true if TYPE is a complete type, an array of unknown bound,
-   or (possibly cv-qualified) void, returns false otherwise.  */
+/* If TYPE is an array of unknown bound, or (possibly cv-qualified)
+   void, or a complete type, returns it, otherwise NULL_TREE.  */
 
-static bool
+static tree
 check_trait_type (tree type)
 {
-  if (COMPLETE_TYPE_P (type))
-    return true;
-
   if (TREE_CODE (type) == ARRAY_TYPE && !TYPE_DOMAIN (type)
       && COMPLETE_TYPE_P (TREE_TYPE (type)))
-    return true;
+    return type;
 
   if (VOID_TYPE_P (type))
-    return true;
+    return type;
 
-  return false;
+  return complete_type_or_else (strip_array_types (type), NULL_TREE);
 }
 
 /* Process a trait expression.  */
@@ -5276,10 +5273,6 @@ finish_trait_expr (cp_trait_kind kind, tree type1, tree type2)
       return trait_expr;
     }
 
-  complete_type (type1);
-  if (type2)
-    complete_type (type2);
-
   switch (kind)
     {
     case CPTK_HAS_NOTHROW_ASSIGN:
@@ -5298,20 +5291,15 @@ finish_trait_expr (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_STD_LAYOUT:
     case CPTK_IS_TRIVIAL:
       if (!check_trait_type (type1))
-	{
-	  error ("incomplete type %qT not allowed", type1);
-	  return error_mark_node;
-	}
+	return error_mark_node;
       break;
 
     case CPTK_IS_BASE_OF:
       if (NON_UNION_CLASS_TYPE_P (type1) && NON_UNION_CLASS_TYPE_P (type2)
 	  && !same_type_ignoring_top_level_qualifiers_p (type1, type2)
-	  && !COMPLETE_TYPE_P (type2))
-	{
-	  error ("incomplete type %qT not allowed", type2);
-	  return error_mark_node;
-	}
+	  && !complete_type_or_else (type2, NULL_TREE))
+	/* We already issued an error.  */
+	return error_mark_node;
       break;
 
     case CPTK_IS_CLASS:
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index cc90250..ce5705e 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2011-10-15  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/50732
+	* g++.dg/ext/is_base_of_incomplete.C: New.
+	* g++.dg/ext/is_base_of_diagnostic.C: Adjust dg-errors.
+	* g++.dg/ext/unary_trait_incomplete.C: Likewise.
+
 2011-10-15  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gcc.target/sparc/combined-1.c: Compile at -O2.
diff --git a/gcc/testsuite/g++.dg/ext/is_base_of_diagnostic.C b/gcc/testsuite/g++.dg/ext/is_base_of_diagnostic.C
index 8cb1ce3..4ccc72b 100644
--- a/gcc/testsuite/g++.dg/ext/is_base_of_diagnostic.C
+++ b/gcc/testsuite/g++.dg/ext/is_base_of_diagnostic.C
@@ -1,7 +1,7 @@
 class A
 { };
 
-class B;
+class B; // { dg-error "forward declaration" }
 
 union C
 { };
diff --git a/gcc/testsuite/g++.dg/ext/is_base_of_incomplete.C b/gcc/testsuite/g++.dg/ext/is_base_of_incomplete.C
new file mode 100644
index 0000000..4704ff5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/is_base_of_incomplete.C
@@ -0,0 +1,9 @@
+// PR c++/50732
+
+template <typename T>
+struct non_instantiable
+{
+  typedef typename T::THIS_TYPE_CANNOT_BE_INSTANTIATED type;
+};
+
+int check[__is_base_of(non_instantiable<int>, void) ? -1 : 1];
diff --git a/gcc/testsuite/g++.dg/ext/unary_trait_incomplete.C b/gcc/testsuite/g++.dg/ext/unary_trait_incomplete.C
index 51cc80c..ecc5ec2 100644
--- a/gcc/testsuite/g++.dg/ext/unary_trait_incomplete.C
+++ b/gcc/testsuite/g++.dg/ext/unary_trait_incomplete.C
@@ -1,6 +1,6 @@
 // PR c++/39475
 
-struct I;
+struct I; // { dg-error "forward declaration" }
 struct C { };
 
 bool nas1 = __has_nothrow_assign(I); // { dg-error "incomplete type" }