Patchwork Require canonical type comparison for typedefs again.

login
register
mail settings
Submitter Dodji Seketeli
Date Sept. 20, 2010, 10:07 a.m.
Message ID <m3wrqgaftk.fsf@redhat.com>
Download mbox | patch
Permalink /patch/65193/
State New
Headers show

Comments

Dodji Seketeli - Sept. 20, 2010, 10:07 a.m.
Paolo Carlini <paolo.carlini@oracle.com> writes:

> Minor nit...

[...]

> overlong lines?

Oops, correct.

I have addressed that in the patch below and added better comments in
the offending region. Thanks.
H.J. Lu - Sept. 20, 2010, 2:39 p.m.
On Mon, Sep 20, 2010 at 3:07 AM, Dodji Seketeli <dodji@redhat.com> wrote:
> Paolo Carlini <paolo.carlini@oracle.com> writes:
>
>> Minor nit...
>
> [...]
>
>> overlong lines?
>
> Oops, correct.
>
> I have addressed that in the patch below and added better comments in
> the offending region. Thanks.
>
> --
>        Dodji
>
> commit 4e22c88fea32105dbfca1095c457643a1eae56de
> Author: Dodji Seketeli <dodji@redhat.com>
> Date:   Mon Sep 13 12:12:21 2010 +0200
>
>    Restore canonical type comparison for typedefs
>
>    gcc/cp/ChangeLog:
>        * cp-tree.h (TEMPLATE_TYPE_PARM_SIBLING_PARMS): Extend this
>        accessor to make it work on TEMPLATE_TEMPLATE_PARMs too.

Does this patch fix a bug? If yes, please include PR # in ChangeLog entries.

Thanks.

Patch

diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index c594d6a..1537786 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -6673,7 +6673,7 @@  build_self_reference (void)
   DECL_CONTEXT (value) = current_class_type;
   DECL_ARTIFICIAL (value) = 1;
   SET_DECL_SELF_REFERENCE_P (value);
-  cp_set_underlying_type (value);
+  set_underlying_type (value);
 
   if (processing_template_decl)
     value = push_template_decl (value);
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index c78beb7..7216f1a 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -4321,10 +4321,12 @@  enum overload_flags { NO_SPECIAL = 0, DTOR_FLAG, TYPENAME_FLAG };
   (TEMPLATE_PARM_DECL (TEMPLATE_TYPE_PARM_INDEX (NODE)))
 #define TEMPLATE_TYPE_PARAMETER_PACK(NODE) \
   (TEMPLATE_PARM_PARAMETER_PACK (TEMPLATE_TYPE_PARM_INDEX (NODE)))
-/* The list of template parms that a given template parameter of type
-   TEMPLATE_TYPE_PARM belongs to.*/
+/* The list of template parms that a given template type parameter
+   belongs to.  */
 #define TEMPLATE_TYPE_PARM_SIBLING_PARMS(NODE) \
-  (TREE_CHECK ((NODE), TEMPLATE_TYPE_PARM))->type.maxval
+  (TREE_CHECK3 ((NODE), TEMPLATE_TYPE_PARM,    \
+		TEMPLATE_TEMPLATE_PARM,	       \
+		BOUND_TEMPLATE_TEMPLATE_PARM))->type.maxval
 
 /* These constants can used as bit flags in the process of tree formatting.
 
@@ -5005,7 +5007,7 @@  extern void append_type_to_template_for_access_check (tree, tree, tree,
 extern tree splice_late_return_type		(tree, tree);
 extern bool is_auto				(const_tree);
 extern tree process_template_parm		(tree, location_t, tree, 
-						 bool, bool);
+						 bool, bool, unsigned);
 extern tree end_template_parm_list		(tree);
 extern void end_template_decl			(void);
 extern tree maybe_update_decl_type		(tree, tree);
@@ -5341,7 +5343,6 @@  extern bool type_has_nontrivial_copy_init	(const_tree);
 extern bool class_tmpl_impl_spec_p		(const_tree);
 extern int zero_init_p				(const_tree);
 extern tree strip_typedefs			(tree);
-extern void cp_set_underlying_type		(tree);
 extern tree copy_binfo				(tree, tree, tree,
 						 tree *, int);
 extern int member_p				(const_tree);
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index 63197705..1c6bbbe 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -879,7 +879,7 @@  grokfield (const cp_declarator *declarator,
       if (declspecs->specs[(int)ds_typedef]
           && TREE_TYPE (value) != error_mark_node
           && TYPE_NAME (TYPE_MAIN_VARIANT (TREE_TYPE (value))) != value)
-	cp_set_underlying_type (value);
+	set_underlying_type (value);
 
       return value;
     }
diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index 41feb57..a044659 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -872,7 +872,7 @@  pushdecl_maybe_friend (tree x, bool is_friend)
 		     inlining.  */
 		  && (!TYPE_NAME (type)
 		      || TYPE_NAME (type) != DECL_ABSTRACT_ORIGIN (x))))
-	    cp_set_underlying_type (x);
+	    set_underlying_type (x);
 
 	  if (type != error_mark_node
 	      && TYPE_NAME (type)
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 9385344..b8c35b3 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -10997,6 +10997,15 @@  cp_parser_template_parameter_list (cp_parser* parser)
   tree parameter_list = NULL_TREE;
 
   begin_template_parm_list ();
+
+  /* The loop below parses the template parms. Note that dependent
+     types created during this parsing require structural comparison
+     rather than canonical type comparison. This is because we first
+     need to know the total number of template parms to be able to
+     compute canonical types of each dependent type. So after the
+     loop, when we know the total number of template parms,
+     end_template_parm_list computes the proper canonical types and
+     fixes up the dependent types accordingly.  */
   while (true)
     {
       tree parameter;
@@ -11015,11 +11024,11 @@  cp_parser_template_parameter_list (cp_parser* parser)
 						parm_loc,
 						parameter,
 						is_non_type,
-                                                is_parameter_pack);
+						is_parameter_pack,
+						0);
       else
        {
          tree err_parm = build_tree_list (parameter, parameter);
-         TREE_VALUE (err_parm) = error_mark_node;
          parameter_list = chainon (parameter_list, err_parm);
        }
 
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 5a90bdc..636a13b 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -93,10 +93,14 @@  static GTY ((param_is (spec_entry)))
 static GTY ((param_is (spec_entry)))
   htab_t type_specializations;
 
-/* Contains canonical template parameter types. The vector is indexed by
-   the TEMPLATE_TYPE_IDX of the template parameter. Each element is a
-   TREE_LIST, whose TREE_VALUEs contain the canonical template
-   parameters of various types and levels.  */
+/* Contains canonical template parameter types. The vector is indexed
+   by the TEMPLATE_TYPE_IDX of the template parameter. Each element is
+   a TREE_LIST, whose TREE_PURPOSE is a INT_CST tree representing a
+   total size of the template parameter list a given template
+   parameter would belong too, and whose TREE_VALUEs contain the
+   canonical template parameters of various types and levels,
+   belonging to a set of template parameters which size is
+   TREE_PURPOSE.  */
 static GTY(()) VEC(tree,gc) *canonical_template_parms;
 
 #define UNIFY_ALLOW_NONE 0
@@ -190,6 +194,8 @@  static void append_type_to_template_for_access_check_1 (tree, tree, tree,
 static hashval_t iterative_hash_template_arg (tree arg, hashval_t val);
 static tree listify (tree);
 static tree listify_autos (tree, tree);
+static tree current_template_args (void);
+static void fixup_template_parms_canonical_types (void);
 
 /* Make the current scope suitable for access checking when we are
    processing T.  T can be FUNCTION_DECL for instantiated function
@@ -3369,12 +3375,24 @@  build_template_parm_index (int index,
 
 /* Find the canonical type parameter for the given template type
    parameter.  Returns the canonical type parameter, which may be TYPE
-   if no such parameter existed.  */
+   if no such parameter existed. TOTAL_NUM_PARMS is the number of
+   template parameters carried by the considered template.
+
+   If TYPE is the template parameter at position P in a
+   template, this function won't return the same canonical type as for
+   a another TYPE that would be a template parameter at position Q,
+   with Q != P.
+
+   if TOTAL_NUM_PARMS is 0, the function returns NULL_TREE.  */
 static tree
-canonical_type_parameter (tree type)
+canonical_type_parameter (tree type, unsigned total_num_parms)
 {
   tree list;
   int idx = TEMPLATE_TYPE_IDX (type);
+
+  if (total_num_parms == 0)
+    return NULL_TREE;
+
   if (!canonical_template_parms)
     canonical_template_parms = VEC_alloc (tree, gc, idx+1);
 
@@ -3382,15 +3400,20 @@  canonical_type_parameter (tree type)
     VEC_safe_push (tree, gc, canonical_template_parms, NULL_TREE);
 
   list = VEC_index (tree, canonical_template_parms, idx);
-  while (list && !comptypes (type, TREE_VALUE (list), COMPARE_STRUCTURAL))
-    list = TREE_CHAIN (list);
+  while (list)
+    {
+      if (TREE_INT_CST_LOW (TREE_PURPOSE (list)) == total_num_parms
+	  && comptypes (type, TREE_VALUE (list), COMPARE_STRUCTURAL))
+	break;
+      list = TREE_CHAIN (list);
+    }
 
   if (list)
     return TREE_VALUE (list);
   else
     {
       VEC_replace(tree, canonical_template_parms, idx,
-		  tree_cons (NULL_TREE, type, 
+		  tree_cons (size_int (total_num_parms), type, 
 			     VEC_index (tree, canonical_template_parms, idx)));
       return type;
     }
@@ -3438,15 +3461,21 @@  reduce_template_parm_level (tree index, tree type, int levels, tree args,
   return TEMPLATE_PARM_DESCENDANTS (index);
 }
 
-/* Process information from new template parameter PARM and append it to the
-   LIST being built.  This new parameter is a non-type parameter iff
-   IS_NON_TYPE is true. This new parameter is a parameter
-   pack iff IS_PARAMETER_PACK is true.  The location of PARM is in 
-   PARM_LOC.  */
+/* Process information from new template parameter PARM and append it
+   to the LIST being built.  This new parameter is a non-type
+   parameter iff IS_NON_TYPE is true. This new parameter is a
+   parameter pack iff IS_PARAMETER_PACK is true.  The location of PARM
+   is in PARM_LOC. NUM_TEMPLATE_PARMS is the size of the template
+   parameter list PARM belongs to. This is used used to create a
+   proper canonical type for the type of PARM that is to be created,
+   iff PARM is a type.  If the size is not known, this parameter can
+   be set to 0. Setting it to zero would create a template type
+   parameter with no canonical type.  */
 
 tree
-process_template_parm (tree list, location_t parm_loc, tree parm, bool is_non_type, 
-                       bool is_parameter_pack)
+process_template_parm (tree list, location_t parm_loc, tree parm,
+		       bool is_non_type, bool is_parameter_pack,
+		       unsigned num_template_parms)
 {
   tree decl = 0;
   tree defval;
@@ -3556,8 +3585,9 @@  process_template_parm (tree list, location_t parm_loc, tree parm, bool is_non_ty
 				     processing_template_decl,
 				     decl, TREE_TYPE (parm));
       TEMPLATE_TYPE_PARAMETER_PACK (t) = is_parameter_pack;
-      TYPE_CANONICAL (t) = canonical_type_parameter (t);
-    }
+      TYPE_CANONICAL (t) =
+	canonical_type_parameter (t, num_template_parms);
+   }
   DECL_ARTIFICIAL (decl) = 1;
   SET_DECL_TEMPLATE_PARM_P (decl);
   pushdecl (decl);
@@ -3586,16 +3616,94 @@  end_template_parm_list (tree parms)
       next = TREE_CHAIN (parm);
       TREE_VEC_ELT (saved_parmlist, nparms) = parm;
       TREE_CHAIN (parm) = NULL_TREE;
-      if (TREE_CODE (TREE_VALUE (parm)) == TYPE_DECL)
+      if (TREE_CODE (TREE_VALUE (parm)) == TYPE_DECL
+	  || TREE_CODE (TREE_VALUE (parm)) == TEMPLATE_DECL)
 	TEMPLATE_TYPE_PARM_SIBLING_PARMS (TREE_TYPE (TREE_VALUE (parm))) =
 	      current_template_parms;
     }
 
+  fixup_template_parms_canonical_types ();
+
   --processing_template_parmlist;
 
   return saved_parmlist;
 }
 
+/* Walk current the template parms and properly compute the canonical
+   types of the dependent types created during
+   cp_parser_template_parameter_list.  */
+
+static void
+fixup_template_parms_canonical_types (void)
+{
+  tree parm;
+  tree full_template_args;
+  tree parameter_vec;
+  int i, num_parms;
+
+  parameter_vec = INNERMOST_TEMPLATE_PARMS (current_template_parms);
+  if (parameter_vec == NULL_TREE)
+    return;
+
+  num_parms = TREE_VEC_LENGTH (parameter_vec);
+
+  for (i = 0; i < num_parms; ++i)
+    {
+      tree main_type, variant;
+
+      parm = TREE_VALUE (TREE_VEC_ELT (parameter_vec, i));
+      if (TREE_CODE (parm) == TYPE_DECL
+	  || TREE_CODE (parm) == TEMPLATE_DECL)
+	{
+	  /* Compute the canonical type of type template
+	     parameters and their variants.  */
+	  main_type = TYPE_MAIN_VARIANT (TREE_TYPE (parm));
+	  TYPE_CANONICAL (main_type) =
+	    canonical_type_parameter (main_type, num_parms);
+	  for (variant = TYPE_NEXT_VARIANT (main_type);
+	       variant;
+	       variant = TYPE_NEXT_VARIANT (variant))
+	    TYPE_CANONICAL (variant) =
+	      canonical_type_parameter (variant, num_parms);
+	}
+    }
+
+  full_template_args = current_template_args ();
+
+  for (i = 0; i < num_parms; ++i)
+    {
+      tree cur = TREE_VEC_ELT (parameter_vec, i);
+
+      if ((TREE_CODE (TREE_VALUE (cur)) == TYPE_DECL
+	   || TREE_CODE (TREE_VALUE (cur)) == TEMPLATE_DECL)
+	  && TREE_PURPOSE (cur))
+	{
+	  tree default_arg = TREE_PURPOSE (cur);
+
+	  if (TYPE_P (default_arg)
+	      && !dependent_type_p (default_arg))
+	    continue;
+
+	  ++cp_unevaluated_operand;
+	  TREE_PURPOSE (cur) =
+	    tsubst_expr (default_arg, full_template_args,
+			 tf_none, default_arg, false);
+	  --cp_unevaluated_operand;
+	}
+
+      if (TREE_CODE (TREE_VALUE (cur)) == PARM_DECL)
+	{
+	  tree non_type_parm = TREE_VALUE (cur);
+	  ++cp_unevaluated_operand;
+	  TREE_VALUE (cur) =
+	    tsubst_decl (non_type_parm,
+			 full_template_args,
+			 tf_none);
+	  --cp_unevaluated_operand;
+	}
+    }
+}
+
 /* end_template_decl is called after a template declaration is seen.  */
 
 void
@@ -3706,7 +3814,23 @@  current_template_args (void)
       else
 	args = a;
     }
-
+  
+    if (length > 1 && TREE_VEC_ELT (args, 0) == NULL_TREE)
+      /* This can happen for template parms of a template template
+	 parameter, e.g:
+
+	 template<template<class T, class U> class TT> struct S;
+
+	 Consider the level of the parms of TT; T and U both have
+	 level 2; TT has no template parm of level 1. So in this case
+	 the first element of full_template_args is NULL_TREE. If we
+	 leave it like this TMPL_ARG_DEPTH on args returns 1 instead
+	 of 2. This will make tsubst wrongly consider that T and U
+	 have level 1. Instead, let's create a dummy vector as the
+	 first element of full_template_args so that TMPL_ARG_DEPTH
+	 returns the correct depth for args.
+      */
+      TREE_VEC_ELT (args, 0) = make_tree_vec (1);
   return args;
 }
 
@@ -6681,16 +6805,22 @@  lookup_template_class (tree d1,
 	  if (context == current_function_decl)
 	    pushtag (DECL_NAME (gen_tmpl), t, /*tag_scope=*/ts_current);
 
-	  if (comp_template_args (CLASSTYPE_TI_ARGS (template_type), arglist))
+	  if (any_template_arguments_need_structural_equality_p (arglist))
+	    /* Some of the template arguments require structural
+	       equality testing, so this template class requires
+	       structural equality testing. Note that we check this
+	       condition first because for dependent types that are
+	       created /during/ the parsing of template parameter lists,
+	       we must not require canonical type equality because
+	       canonical types of dependent types are actually going
+	       to be properly computed right at /the end/ of the
+	       template parms parsing.  */
+	    SET_TYPE_STRUCTURAL_EQUALITY (t);
+	  else if (comp_template_args (CLASSTYPE_TI_ARGS (template_type), arglist))
 	    /* This instantiation is another name for the primary
 	       template type. Set the TYPE_CANONICAL field
 	       appropriately. */
 	    TYPE_CANONICAL (t) = template_type;
-	  else if (any_template_arguments_need_structural_equality_p (arglist))
-	    /* Some of the template arguments require structural
-	       equality testing, so this template class requires
-	       structural equality testing. */
-	    SET_TYPE_STRUCTURAL_EQUALITY (t);
 	}
 
       /* If we called start_enum or pushtag above, this information
@@ -10291,7 +10421,15 @@  tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 		else if (TYPE_STRUCTURAL_EQUALITY_P (t))
 		  SET_TYPE_STRUCTURAL_EQUALITY (r);
 		else
-		  TYPE_CANONICAL (r) = canonical_type_parameter (r);
+		  {
+		    unsigned num_parms =
+		      (TEMPLATE_TYPE_PARM_SIBLING_PARMS (t))
+		      ? TREE_VEC_LENGTH (INNERMOST_TEMPLATE_PARMS
+					 (TEMPLATE_TYPE_PARM_SIBLING_PARMS (t)))
+		      : 0;
+		    TYPE_CANONICAL (r) =
+		      canonical_type_parameter (r, num_parms);
+		  }
 
 		if (code == BOUND_TEMPLATE_TEMPLATE_PARM)
 		  {
@@ -17786,7 +17924,8 @@  type_dependent_expression_p (tree expression)
   if (!processing_template_decl)
     return false;
 
-  if (expression == error_mark_node)
+  if (expression == error_mark_node
+      || expression == NULL_TREE)
     return false;
 
   /* An unresolved name is always dependent.  */
@@ -18406,7 +18545,7 @@  make_auto (void)
   TEMPLATE_TYPE_PARM_INDEX (au) = build_template_parm_index
     (0, processing_template_decl + 1, processing_template_decl + 1,
      TYPE_NAME (au), NULL_TREE);
-  TYPE_CANONICAL (au) = canonical_type_parameter (au);
+  TYPE_CANONICAL (au) = canonical_type_parameter (au, 0);
   DECL_ARTIFICIAL (TYPE_NAME (au)) = 1;
   SET_DECL_TEMPLATE_PARM_P (TYPE_NAME (au));
 
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index ea01d1f..580ebf3 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -1063,22 +1063,6 @@  strip_typedefs (tree t)
   return cp_build_qualified_type (result, cp_type_quals (t));
 }
 
-/* Setup a TYPE_DECL node as a typedef representation.
-   See comments of set_underlying_type in c-common.c.  */
-
-void
-cp_set_underlying_type (tree t)
-{
-  set_underlying_type (t);
-  /* If T is a template type parm, make it require structural equality.
-     This is useful when comparing two template type parms,
-     because it forces the comparison of the template parameters of their
-     decls.  */
-  if (TREE_CODE (TREE_TYPE (t)) == TEMPLATE_TYPE_PARM)
-    SET_TYPE_STRUCTURAL_EQUALITY (TREE_TYPE (t));
-}
-
-
 /* Makes a copy of BINFO and TYPE, which is to be inherited into a
    graph dominated by T.  If BINFO is NULL, TYPE is a dependent base,
    and we do a shallow copy.  If BINFO is non-NULL, we do a deep copy.
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 0ac95d0..6524b3c 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -1143,114 +1143,13 @@  comp_template_parms_position (tree t1, tree t2)
 		  || TREE_CODE (t1) == TEMPLATE_TEMPLATE_PARM
 		  || TREE_CODE (t1) == TEMPLATE_TYPE_PARM));
 
-      if (TEMPLATE_TYPE_IDX (t1) != TEMPLATE_TYPE_IDX (t2)
-	  || TEMPLATE_TYPE_LEVEL (t1) != TEMPLATE_TYPE_LEVEL (t2)
-          || (TEMPLATE_TYPE_PARAMETER_PACK (t1) 
-              != TEMPLATE_TYPE_PARAMETER_PACK (t2)))
-	return false;
-
-      return true;
-}
-
-/* Subroutine of incompatible_dependent_types_p.
-   Return the template parameter of the dependent type T.
-   If T is a typedef, return the template parameters of
-   the _decl_ of the typedef. T must be a dependent type.  */
-
-static tree
-get_template_parms_of_dependent_type (tree t)
-{
-  tree tinfo = NULL_TREE, tparms = NULL_TREE;
-
-  /* First, try the obvious case of getting the
-     template info from T itself.  */
-  if ((tinfo = get_template_info (t)))
-    ;
-  else if (TREE_CODE (t) == TEMPLATE_TYPE_PARM)
-    return TEMPLATE_TYPE_PARM_SIBLING_PARMS (t);
-  else if (typedef_variant_p (t)
-	   && !NAMESPACE_SCOPE_P (TYPE_NAME (t)))
-    tinfo = get_template_info (DECL_CONTEXT (TYPE_NAME (t)));
-  /* If T is a TYPENAME_TYPE which context is a template type
-     parameter, get the template parameters from that context.  */
-  else if (TYPE_CONTEXT (t)
-	   && TREE_CODE (TYPE_CONTEXT (t)) == TEMPLATE_TYPE_PARM)
-   return TEMPLATE_TYPE_PARM_SIBLING_PARMS (TYPE_CONTEXT (t));
-  else if (TYPE_CONTEXT (t)
-	   && !NAMESPACE_SCOPE_P (t))
-    tinfo = get_template_info (TYPE_CONTEXT (t));
-
-  if (tinfo)
-    tparms = DECL_TEMPLATE_PARMS (TI_TEMPLATE (tinfo));
-
-  return tparms;
-}
-
-/* Subroutine of structural_comptypes.
-   Compare the dependent types T1 and T2.
-   Return TRUE if we are sure they can't be equal, FALSE otherwise.
-   The whole point of this function is to support cases where either T1 or
-   T2 is a typedef. In those cases, we need to compare the template parameters
-   of the _decl_ of the typedef. If those don't match then we know T1
-   and T2 cannot be equal.  */
-
-static bool
-incompatible_dependent_types_p (tree t1, tree t2)
-{
-  tree tparms1 = NULL_TREE, tparms2 = NULL_TREE;
-  bool t1_typedef_variant_p, t2_typedef_variant_p;
-
-  if (!uses_template_parms (t1) || !uses_template_parms (t2))
+  if (TEMPLATE_TYPE_IDX (t1) != TEMPLATE_TYPE_IDX (t2)
+      || TEMPLATE_TYPE_LEVEL (t1) != TEMPLATE_TYPE_LEVEL (t2)
+      || (TEMPLATE_TYPE_PARAMETER_PACK (t1) 
+	  != TEMPLATE_TYPE_PARAMETER_PACK (t2)))
     return false;
 
-  if (TREE_CODE (t1) == TEMPLATE_TYPE_PARM)
-    {
-      /* If T1 and T2 don't have the same relative position in their
-	 template parameters set, they can't be equal.  */
-      if (!comp_template_parms_position (t1, t2))
-	return true;
-    }
-
-  t1_typedef_variant_p = typedef_variant_p (t1);
-  t2_typedef_variant_p = typedef_variant_p (t2);
-
-  /* Either T1 or T2 must be a typedef.  */
-  if (!t1_typedef_variant_p && !t2_typedef_variant_p)
-    return false;
-
-  if (!t1_typedef_variant_p || !t2_typedef_variant_p)
-    /* Either T1 or T2 is not a typedef so we cannot compare the
-       template parms of the typedefs of T1 and T2.
-       At this point, if the main variant type of T1 and T2 are equal
-       it means the two types can't be incompatible, from the perspective
-       of this function.  */
-    if (TYPE_MAIN_VARIANT (t1) == TYPE_MAIN_VARIANT (t2))
-      return false;
-
-  /* So if we reach this point, it means either T1 or T2 is a typedef variant.
-     Let's compare their template parameters.  */
-
-  tparms1 = get_template_parms_of_dependent_type (t1);
-  tparms2 = get_template_parms_of_dependent_type (t2);
-
-  /* If T2 is a template type parm and if we could not get the template
-     parms it belongs to, that means we have not finished parsing the
-     full set of template parameters of the template declaration it
-     belongs to yet. If we could get the template parms T1 belongs to,
-     that mostly means T1 and T2 belongs to templates that are
-     different and incompatible.  */
-  if (TREE_CODE (t1) == TEMPLATE_TYPE_PARM
-      && (tparms1 == NULL_TREE || tparms2 == NULL_TREE)
-      && tparms1 != tparms2)
-    return true;
-
-  if (tparms1 == NULL_TREE
-      || tparms2 == NULL_TREE
-      || tparms1 == tparms2)
-    return false;
-
-  /* And now compare the mighty template parms!  */
-  return !comp_template_parms (tparms1, tparms2);
+  return true;
 }
 
 /* Subroutine in comptypes.  */
@@ -1295,12 +1194,6 @@  structural_comptypes (tree t1, tree t2, int strict)
   if (TYPE_FOR_JAVA (t1) != TYPE_FOR_JAVA (t2))
     return false;
 
-  /* If T1 and T2 are dependent typedefs then check upfront that
-     the template parameters of their typedef DECLs match before
-     going down checking their subtypes.  */
-  if (incompatible_dependent_types_p (t1, t2))
-    return false;
-
   /* Allow for two different type nodes which have essentially the same
      definition.  Note that we already checked for equality of the type
      qualifiers (just above).  */
@@ -1345,6 +1238,30 @@  structural_comptypes (tree t1, tree t2, int strict)
 	  (DECL_TEMPLATE_PARMS (TEMPLATE_TEMPLATE_PARM_TEMPLATE_DECL (t1)),
 	   DECL_TEMPLATE_PARMS (TEMPLATE_TEMPLATE_PARM_TEMPLATE_DECL (t2))))
 	return false;
+
+      /* If T1 belongs to a not-yet fully parsed template parameters
+	 list, let's assume it's different from T2 which belongs to an
+	 already fully parsed template template parameters list.  */
+      if ((TEMPLATE_TYPE_PARM_SIBLING_PARMS
+	   (TYPE_MAIN_VARIANT (t1)) != NULL_TREE)
+	  != (TEMPLATE_TYPE_PARM_SIBLING_PARMS
+	      (TYPE_MAIN_VARIANT (t1)) != NULL_TREE))
+	return false;
+
+      /* If T1 and T2 belong to template parm lists of different
+	 size, then can't be equal.  */
+      if ((TEMPLATE_TYPE_PARM_SIBLING_PARMS
+	   (TYPE_MAIN_VARIANT (t1)) != NULL_TREE)
+	  && (TEMPLATE_TYPE_PARM_SIBLING_PARMS
+	      (TYPE_MAIN_VARIANT (t2)) != NULL_TREE)
+	  && (TREE_VEC_LENGTH (INNERMOST_TEMPLATE_PARMS
+			       (TEMPLATE_TYPE_PARM_SIBLING_PARMS
+				(TYPE_MAIN_VARIANT (t1))))
+	      != TREE_VEC_LENGTH (INNERMOST_TEMPLATE_PARMS
+				  (TEMPLATE_TYPE_PARM_SIBLING_PARMS
+				   (TYPE_MAIN_VARIANT (t2))))))
+	return false;
+
       if (TREE_CODE (t1) == TEMPLATE_TEMPLATE_PARM)
 	break;
       /* Don't check inheritance.  */
@@ -1401,8 +1318,35 @@  structural_comptypes (tree t1, tree t2, int strict)
       break;
 
     case TEMPLATE_TYPE_PARM:
-      /* If incompatible_dependent_types_p called earlier didn't decide
-         T1 and T2 were different, they might be equal.  */
+      {
+	/* If T1 and T2 don't have the same relative position in their
+	   template parameters set, they can't be equal.  */
+	if (!comp_template_parms_position (t1, t2))
+	  return false;
+
+	/* If T1 belongs to a not-yet fully parsed template parameters
+	 list, let's assume it's different from T2 which belongs to an
+	 already fully parsed template template parameters list.  */
+	if ((TEMPLATE_TYPE_PARM_SIBLING_PARMS
+	     (TYPE_MAIN_VARIANT (t1)) != NULL_TREE)
+	    != (TEMPLATE_TYPE_PARM_SIBLING_PARMS
+		(TYPE_MAIN_VARIANT (t1)) != NULL_TREE))
+	  return false;
+	
+	/* If T1 and T2 belong to template parm lists of different
+	   size, then can't be equal either.  */
+	if ((TEMPLATE_TYPE_PARM_SIBLING_PARMS
+	     (TYPE_MAIN_VARIANT (t1)) != NULL_TREE)
+	    && (TEMPLATE_TYPE_PARM_SIBLING_PARMS
+		(TYPE_MAIN_VARIANT (t2)) != NULL_TREE)
+	    && (TREE_VEC_LENGTH (INNERMOST_TEMPLATE_PARMS
+				 (TEMPLATE_TYPE_PARM_SIBLING_PARMS
+				  (TYPE_MAIN_VARIANT (t1))))
+		!= TREE_VEC_LENGTH (INNERMOST_TEMPLATE_PARMS
+				    (TEMPLATE_TYPE_PARM_SIBLING_PARMS
+				     (TYPE_MAIN_VARIANT (t2))))))
+	  return false;
+      }
       break;
 
     case TYPENAME_TYPE:
diff --git a/gcc/testsuite/g++.dg/template/typedef36.C b/gcc/testsuite/g++.dg/template/typedef36.C
new file mode 100644
index 0000000..f6155c1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/typedef36.C
@@ -0,0 +1,23 @@ 
+// Origin: PR c++/45606
+// { dg-do compile }
+
+#include <list>
+
+template<class T>
+class Test
+{
+protected:
+  typedef std::list<T> ListAlias;
+  ListAlias list;
+public:
+  typedef typename ListAlias::const_iterator const_iterator;
+  inline const_iterator begin() const;
+
+};
+
+template<class T>
+inline typename std::list<T>::const_iterator Test<T>::begin() const
+{
+  return list.begin();
+}
+