Core 975

	Core 975
	* decl.c (cxx_init_decl_processing): Initialize
	dependent_lambda_return_type_node.
	* cp-tree.h (cp_tree_index): Add CPTI_DEPENDENT_LAMBDA_RETURN_TYPE.
	(dependent_lambda_return_type_node): Define.
	(DECLTYPE_FOR_LAMBDA_RETURN): Remove.
	* semantics.c (lambda_return_type): Handle overloaded function.
	Use dependent_lambda_return_type_node instead of
	DECLTYPE_FOR_LAMBDA_RETURN.
	(apply_lambda_return_type): Don't check dependent_type_p.
	* pt.c (tsubst_copy_and_build): Handle lambda return type deduction.
	(instantiate_class_template_1): Likewise.
	(tsubst): Don't use DECLTYPE_FOR_LAMBDA_RETURN.
	* mangle.c (write_type): Likewise.
	* typeck.c (structural_comptypes): Likewise.
	(check_return_expr): Handle dependent_lambda_return_type_node.

From-SVN: r177995

12 files changed, 97 insertions, 58 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 0f60bcb..0f325a8 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,24 @@
 2011-08-23  Jason Merrill  <jason@redhat.com>
 
+	Core 975
+	* decl.c (cxx_init_decl_processing): Initialize
+	dependent_lambda_return_type_node.
+	* cp-tree.h (cp_tree_index): Add CPTI_DEPENDENT_LAMBDA_RETURN_TYPE.
+	(dependent_lambda_return_type_node): Define.
+	(DECLTYPE_FOR_LAMBDA_RETURN): Remove.
+	* semantics.c (lambda_return_type): Handle overloaded function.
+	Use dependent_lambda_return_type_node instead of
+	DECLTYPE_FOR_LAMBDA_RETURN.
+	(apply_lambda_return_type): Don't check dependent_type_p.
+	* pt.c (tsubst_copy_and_build): Handle lambda return type deduction.
+	(instantiate_class_template_1): Likewise.
+	(tsubst): Don't use DECLTYPE_FOR_LAMBDA_RETURN.
+	* mangle.c (write_type): Likewise.
+	* typeck.c (structural_comptypes): Likewise.
+	(check_return_expr): Handle dependent_lambda_return_type_node.
+
+2011-08-23  Jason Merrill  <jason@redhat.com>
+
 	PR c++/50024
 	* semantics.c (maybe_constant_value): Don't try to fold { }.
 	* pt.c (build_non_dependent_expr): Don't wrap { }.
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index ff5509e..8595943 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -83,7 +83,6 @@ c-common.h, not after.
       STMT_IS_FULL_EXPR_P (in _STMT)
       TARGET_EXPR_LIST_INIT_P (in TARGET_EXPR)
       LAMBDA_EXPR_MUTABLE_P (in LAMBDA_EXPR)
-      DECLTYPE_FOR_LAMBDA_RETURN (in DECLTYPE_TYPE)
       DECL_FINAL_P (in FUNCTION_DECL)
       QUALIFIED_NAME_IS_TEMPLATE (in SCOPE_REF)
    2: IDENTIFIER_OPNAME_P (in IDENTIFIER_NODE)
@@ -775,6 +774,7 @@ enum cp_tree_index
     CPTI_CLASS_TYPE,
     CPTI_UNKNOWN_TYPE,
     CPTI_INIT_LIST_TYPE,
+    CPTI_DEPENDENT_LAMBDA_RETURN_TYPE,
     CPTI_VTBL_TYPE,
     CPTI_VTBL_PTR_TYPE,
     CPTI_STD,
@@ -846,6 +846,7 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];
 #define class_type_node			cp_global_trees[CPTI_CLASS_TYPE]
 #define unknown_type_node		cp_global_trees[CPTI_UNKNOWN_TYPE]
 #define init_list_type_node		cp_global_trees[CPTI_INIT_LIST_TYPE]
+#define dependent_lambda_return_type_node cp_global_trees[CPTI_DEPENDENT_LAMBDA_RETURN_TYPE]
 #define vtbl_type_node			cp_global_trees[CPTI_VTBL_TYPE]
 #define vtbl_ptr_type_node		cp_global_trees[CPTI_VTBL_PTR_TYPE]
 #define std_node			cp_global_trees[CPTI_STD]
@@ -3425,12 +3426,10 @@ more_aggr_init_expr_args_p (const aggr_init_expr_arg_iterator *iter)
   (DECLTYPE_TYPE_CHECK (NODE))->type_common.string_flag
 
 /* These flags indicate that we want different semantics from normal
-   decltype: lambda capture just drops references, lambda return also does
-   type decay, lambda proxies look through implicit dereference.  */
+   decltype: lambda capture just drops references, lambda proxies look
+   through implicit dereference.  */
 #define DECLTYPE_FOR_LAMBDA_CAPTURE(NODE) \
   TREE_LANG_FLAG_0 (DECLTYPE_TYPE_CHECK (NODE))
-#define DECLTYPE_FOR_LAMBDA_RETURN(NODE) \
-  TREE_LANG_FLAG_1 (DECLTYPE_TYPE_CHECK (NODE))
 #define DECLTYPE_FOR_LAMBDA_PROXY(NODE) \
   TREE_LANG_FLAG_2 (DECLTYPE_TYPE_CHECK (NODE))
 
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index c125f05..c375cf7 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -3597,6 +3597,10 @@ cxx_init_decl_processing (void)
   init_list_type_node = make_node (LANG_TYPE);
   record_unknown_type (init_list_type_node, "init list");
 
+  dependent_lambda_return_type_node = make_node (LANG_TYPE);
+  record_unknown_type (dependent_lambda_return_type_node,
+		       "undeduced lambda return type");
+
   {
     /* Make sure we get a unique function type, so we can give
        its pointer type a name.  (This wins for gdb.) */
diff --git a/gcc/cp/mangle.c b/gcc/cp/mangle.c
index 53d4bc6..4c7cc79 100644
--- a/gcc/cp/mangle.c
+++ b/gcc/cp/mangle.c
@@ -1953,7 +1953,7 @@ write_type (tree type)
             case DECLTYPE_TYPE:
 	      /* These shouldn't make it into mangling.  */
 	      gcc_assert (!DECLTYPE_FOR_LAMBDA_CAPTURE (type)
-			  && !DECLTYPE_FOR_LAMBDA_RETURN (type));
+			  && !DECLTYPE_FOR_LAMBDA_PROXY (type));
 
 	      /* In ABI <5, we stripped decltype of a plain decl.  */
 	      if (!abi_version_at_least (5)
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 3f9a4c0..6b970f9 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -8887,7 +8887,16 @@ instantiate_class_template_1 (tree type)
     }
 
   if (CLASSTYPE_LAMBDA_EXPR (type))
-    maybe_add_lambda_conv_op (type);
+    {
+      tree lambda = CLASSTYPE_LAMBDA_EXPR (type);
+      if (LAMBDA_EXPR_DEDUCE_RETURN_TYPE_P (lambda))
+	{
+	  apply_lambda_return_type (lambda, void_type_node);
+	  LAMBDA_EXPR_RETURN_TYPE (lambda) = NULL_TREE;
+	}
+      instantiate_decl (lambda_function (type), false, false);
+      maybe_add_lambda_conv_op (type);
+    }
 
   /* Set the file and line number information to whatever is given for
      the class itself.  This puts error messages involving generated
@@ -11420,8 +11429,6 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 
 	if (DECLTYPE_FOR_LAMBDA_CAPTURE (t))
 	  type = lambda_capture_field_type (type);
-	else if (DECLTYPE_FOR_LAMBDA_RETURN (t))
-	  type = lambda_return_type (type);
 	else if (DECLTYPE_FOR_LAMBDA_PROXY (t))
 	  type = lambda_proxy_type (type);
 	else
@@ -13882,10 +13889,17 @@ tsubst_copy_and_build (tree t,
 	LAMBDA_EXPR_MUTABLE_P (r) = LAMBDA_EXPR_MUTABLE_P (t);
 	LAMBDA_EXPR_DISCRIMINATOR (r)
 	  = (LAMBDA_EXPR_DISCRIMINATOR (t));
-	LAMBDA_EXPR_CAPTURE_LIST (r)
-	  = RECUR (LAMBDA_EXPR_CAPTURE_LIST (t));
 	LAMBDA_EXPR_EXTRA_SCOPE (r)
 	  = RECUR (LAMBDA_EXPR_EXTRA_SCOPE (t));
+	if (LAMBDA_EXPR_RETURN_TYPE (t) == dependent_lambda_return_type_node)
+	  {
+	    LAMBDA_EXPR_RETURN_TYPE (r) = dependent_lambda_return_type_node;
+	    LAMBDA_EXPR_DEDUCE_RETURN_TYPE_P (r) = true;
+	  }
+	else
+	  LAMBDA_EXPR_RETURN_TYPE (r)
+	    = tsubst (LAMBDA_EXPR_RETURN_TYPE (t), args, complain, in_decl);
+
 	gcc_assert (LAMBDA_EXPR_THIS_CAPTURE (t) == NULL_TREE
 		    && LAMBDA_EXPR_PENDING_PROXIES (t) == NULL);
 
@@ -13895,9 +13909,10 @@ tsubst_copy_and_build (tree t,
 	   declaration of the op() for later calls to lambda_function.  */
 	complete_type (type);
 
-	type = tsubst (LAMBDA_EXPR_RETURN_TYPE (t), args, complain, in_decl);
-	if (type)
-	  apply_lambda_return_type (r, type);
+	/* The capture list refers to closure members, so this needs to
+	   wait until after we finish instantiating the type.  */
+	LAMBDA_EXPR_CAPTURE_LIST (r)
+	  = RECUR (LAMBDA_EXPR_CAPTURE_LIST (t));
 
 	return build_lambda_object (r);
       }
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 2f62e35..5deb2eb 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -8323,18 +8323,14 @@ tree
 lambda_return_type (tree expr)
 {
   tree type;
-  if (BRACE_ENCLOSED_INITIALIZER_P (expr))
+  if (type_unknown_p (expr)
+      || BRACE_ENCLOSED_INITIALIZER_P (expr))
     {
-      warning (0, "cannot deduce lambda return type from a braced-init-list");
+      cxx_incomplete_type_error (expr, TREE_TYPE (expr));
       return void_type_node;
     }
   if (type_dependent_expression_p (expr))
-    {
-      type = cxx_make_type (DECLTYPE_TYPE);
-      DECLTYPE_TYPE_EXPR (type) = expr;
-      DECLTYPE_FOR_LAMBDA_RETURN (type) = true;
-      SET_TYPE_STRUCTURAL_EQUALITY (type);
-    }
+    type = dependent_lambda_return_type_node;
   else
     type = cv_unqualified (type_decays_to (unlowered_expr_type (expr)));
   return type;
@@ -8394,12 +8390,10 @@ apply_lambda_return_type (tree lambda, tree return_type)
 
   LAMBDA_EXPR_RETURN_TYPE (lambda) = return_type;
 
-  /* If we got a DECLTYPE_TYPE, don't stick it in the function yet,
-     it would interfere with instantiating the closure type.  */
-  if (dependent_type_p (return_type))
-    return;
   if (return_type == error_mark_node)
     return;
+  if (TREE_TYPE (TREE_TYPE (fco)) == return_type)
+    return;
 
   /* TREE_TYPE (FUNCTION_DECL) == METHOD_TYPE
      TREE_TYPE (METHOD_TYPE)   == return-type  */
@@ -8412,6 +8406,7 @@ apply_lambda_return_type (tree lambda, tree return_type)
   /* We already have a DECL_RESULT from start_preparsed_function.
      Now we need to redo the work it and allocate_struct_function
      did to reflect the new type.  */
+  gcc_assert (current_function_decl == fco);
   result = build_decl (input_location, RESULT_DECL, NULL_TREE,
 		       TYPE_MAIN_VARIANT (return_type));
   DECL_ARTIFICIAL (result) = 1;
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 4c130ee..9db0ce3 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -1331,8 +1331,8 @@ structural_comptypes (tree t1, tree t2, int strict)
           != DECLTYPE_TYPE_ID_EXPR_OR_MEMBER_ACCESS_P (t2)
 	  || (DECLTYPE_FOR_LAMBDA_CAPTURE (t1)
 	      != DECLTYPE_FOR_LAMBDA_CAPTURE (t2))
-	  || (DECLTYPE_FOR_LAMBDA_RETURN (t1)
-	      != DECLTYPE_FOR_LAMBDA_RETURN (t2))
+	  || (DECLTYPE_FOR_LAMBDA_PROXY (t1)
+	      != DECLTYPE_FOR_LAMBDA_PROXY (t2))
           || !cp_tree_equal (DECLTYPE_TYPE_EXPR (t1), 
                              DECLTYPE_TYPE_EXPR (t2)))
         return false;
@@ -7657,15 +7657,14 @@ check_return_expr (tree retval, bool *no_warning)
 	  tree type = lambda_return_type (retval);
 	  tree oldtype = LAMBDA_EXPR_RETURN_TYPE (lambda);
 
-	  if (VOID_TYPE_P (type))
-	    { /* Nothing.  */ }
-	  else if (oldtype == NULL_TREE)
-	    {
-	      pedwarn (input_location, OPT_pedantic, "lambda return type "
-		       "can only be deduced when the return statement is "
-		       "the only statement in the function body");
-	      apply_lambda_return_type (lambda, type);
-	    }
+	  if (oldtype == NULL_TREE)
+	    apply_lambda_return_type (lambda, type);
+	  /* If one of the answers is type-dependent, we can't do any
+	     better until instantiation time.  */
+	  else if (oldtype == dependent_lambda_return_type_node)
+	    /* Leave it.  */;
+	  else if (type == dependent_lambda_return_type_node)
+	    apply_lambda_return_type (lambda, type);
 	  else if (!same_type_p (type, oldtype))
 	    error ("inconsistent types %qT and %qT deduced for "
 		   "lambda return type", type, oldtype);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index fe36888..9dfa4d3 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,13 @@
 2011-08-23  Jason Merrill  <jason@redhat.com>
 
+	Core 975
+	* g++.dg/cpp0x/lambda/lambda-deduce-ext-neg2.C: Now accepted.
+	* g++.dg/cpp0x/lambda/lambda-deduce-ext-neg.C: Adjust.
+	* g++.dg/cpp0x/lambda/lambda-deduce2.C: Test returning overload.
+	* g++.dg/cpp0x/lambda/lambda-deduce-neg.C: Remove #include.
+
+2011-08-23  Jason Merrill  <jason@redhat.com>
+
 	PR c++/50024
 	* g++.dg/cpp0x/constexpr-initlist5.C: New.
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce-ext-neg.C b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce-ext-neg.C
index bfe7aca..f93e78a 100644
--- a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce-ext-neg.C
+++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce-ext-neg.C
@@ -1,24 +1,22 @@
-// Testcase for an extension to allow return type deduction when the lambda
-// contains more than just a single return-statement.
+// Testcase for DR 975.
 
 // { dg-options -std=c++0x }
 
 bool b;
-template <class T>
-T f (T t)
-{
-  return [=]
-    {
-      auto i = t+1;
-      if (b)
-	return i+1;
-      else
-	return i+2;		// { dg-error "lambda return type" }
-    }();
+struct A { int fn1(); const int& fn2(); };
+struct B { int fn1(); long fn2(); };
+
+template <class T> int f (T t) {
+  return [](T t){
+    if (b)
+      return t.fn1();
+    else
+      return t.fn2();		// { dg-error "inconsistent types" }
+  }(t);
 }
 
 int main()
 {
-  if (f(1) != 3)
-    return 1;
+  f(A());			// { dg-bogus "" } int and const int& are compatible
+  f(B());			// { dg-message "from here" } int and long are not
 }
diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce-ext-neg2.C b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce-ext-neg2.C
index a236e6d..5c63409 100644
--- a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce-ext-neg2.C
+++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce-ext-neg2.C
@@ -1,6 +1,5 @@
-// Test that in pedantic mode, we warn about the extension to allow return
-// type deduction when the lambda contains more than just a single
-// return-statement.
+// Test that this is accepted even when pedantic now that it's part
+// of the standard.
 
 // { dg-options "-std=c++0x -pedantic" }
 
@@ -11,7 +10,7 @@ T f (T t)
   [=] { return t+1; };		// OK
   return [=] {
     auto i = t+1;
-    return i+1;			// { dg-warning "only statement" }
+    return i+1;
   }();
 }
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce-neg.C b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce-neg.C
index 4abdf59..c932c09 100644
--- a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce-neg.C
+++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce-neg.C
@@ -1,5 +1,4 @@
 // { dg-options "-std=c++0x" }
-#include <cassert>
 
 int main() {
   int i = 0;
diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce2.C b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce2.C
index 718d49c..eeb9814 100644
--- a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce2.C
+++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-deduce2.C
@@ -1,7 +1,11 @@
 // PR c++/43875
 // { dg-options "-std=c++0x" }
 
+void f();
+void f(int);
+
 int main()
 {
-   auto x2 = []{ return { 1, 2 }; }; // { dg-message "return" }
+  auto x1 = []{ return f; };	    // { dg-error "return|overloaded" }
+  auto x2 = []{ return { 1, 2 }; }; // { dg-error "return|list" }
 }