[COMMITTED] c++: Fix use of local in constexpr if.

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index b8035b4360d..c46d1e92b3b 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -3482,7 +3482,7 @@  struct GTY(()) lang_decl {
    for the alias template (if any).  Otherwise behave as
    TYPE_TEMPLATE_INFO.  */
 #define TYPE_TEMPLATE_INFO_MAYBE_ALIAS(NODE)				\
-  (TYPE_ALIAS_P (NODE)							\
+  (typedef_variant_p (NODE)						\
    ? TYPE_ALIAS_TEMPLATE_INFO (NODE)					\
    : TYPE_TEMPLATE_INFO (NODE))
 
diff --git a/gcc/cp/error.c b/gcc/cp/error.c
index 973b3034e12..ab8638fbaec 100644
--- a/gcc/cp/error.c
+++ b/gcc/cp/error.c
@@ -1526,12 +1526,6 @@  find_typenames_r (tree *tp, int *walk_subtrees, void *data)
   if (mv && (mv == *tp || !d->p_set->add (mv)))
     vec_safe_push (d->typenames, mv);
 
-  /* Search into class template arguments, which cp_walk_subtrees
-     doesn't do.  */
-  if (CLASS_TYPE_P (*tp) && CLASSTYPE_TEMPLATE_INFO (*tp))
-    cp_walk_tree (&CLASSTYPE_TI_ARGS (*tp), find_typenames_r,
-		  data, d->p_set);
-
   return NULL_TREE;
 }
 
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 01bade85cdf..2fb52caa5d4 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -3818,9 +3818,12 @@  find_parameter_packs_r (tree *tp, int *walk_subtrees, void* data)
     (struct find_parameter_pack_data*)data;
   bool parameter_pack_p = false;
 
-  /* Handle type aliases/typedefs.  */
-  if (TYPE_ALIAS_P (t))
+  /* Don't look through typedefs; we are interested in whether a
+     parameter pack is actually written in the expression/type we're
+     looking at, not the target type.  */
+  if (TYPE_P (t) && typedef_variant_p (t))
     {
+      /* But do look at arguments for an alias template.  */
       if (tree tinfo = TYPE_ALIAS_TEMPLATE_INFO (t))
 	cp_walk_tree (&TI_ARGS (tinfo),
 		      &find_parameter_packs_r,
@@ -3903,27 +3906,13 @@  find_parameter_packs_r (tree *tp, int *walk_subtrees, void* data)
 		  &find_parameter_packs_r, ppd, ppd->visited);
 
   /* This switch statement will return immediately if we don't find a
-     parameter pack.  */
+     parameter pack.  ??? Should some of these be in cp_walk_subtrees?  */
   switch (TREE_CODE (t))
     {
-    case TEMPLATE_PARM_INDEX:
-      return NULL_TREE;
-
     case BOUND_TEMPLATE_TEMPLATE_PARM:
       /* Check the template itself.  */
       cp_walk_tree (&TREE_TYPE (TYPE_TI_TEMPLATE (t)),
 		    &find_parameter_packs_r, ppd, ppd->visited);
-      /* Check the template arguments.  */
-      cp_walk_tree (&TYPE_TI_ARGS (t), &find_parameter_packs_r, ppd,
-		    ppd->visited);
-      *walk_subtrees = 0;
-      return NULL_TREE;
-
-    case TEMPLATE_TYPE_PARM:
-    case TEMPLATE_TEMPLATE_PARM:
-      return NULL_TREE;
-
-    case PARM_DECL:
       return NULL_TREE;
 
     case DECL_EXPR:
@@ -3932,20 +3921,6 @@  find_parameter_packs_r (tree *tp, int *walk_subtrees, void* data)
 	*walk_subtrees = 0;
       return NULL_TREE;
 
-    case RECORD_TYPE:
-      if (TYPE_PTRMEMFUNC_P (t))
-	return NULL_TREE;
-      /* Fall through.  */
-
-    case UNION_TYPE:
-    case ENUMERAL_TYPE:
-      if (TYPE_TEMPLATE_INFO (t))
-	cp_walk_tree (&TYPE_TI_ARGS (t),
-		      &find_parameter_packs_r, ppd, ppd->visited);
-
-      *walk_subtrees = 0;
-      return NULL_TREE;
-
     case TEMPLATE_DECL:
       if (!DECL_TEMPLATE_TEMPLATE_PARM_P (t))
 	return NULL_TREE;
@@ -5794,8 +5769,7 @@  push_template_decl_real (tree decl, bool is_friend)
       if (check_for_bare_parameter_packs (TYPE_RAISES_EXCEPTIONS (type)))
 	TYPE_RAISES_EXCEPTIONS (type) = NULL_TREE;
     }
-  else if (check_for_bare_parameter_packs ((TREE_CODE (decl) == TYPE_DECL
-					    && TYPE_DECL_ALIAS_P (decl))
+  else if (check_for_bare_parameter_packs (is_typedef_decl (decl)
 					   ? DECL_ORIGINAL_TYPE (decl)
 					   : TREE_TYPE (decl)))
     {
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 21f733af486..fda630790a2 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -4918,6 +4918,11 @@  cp_walk_subtrees (tree *tp, int *walk_subtrees_p, walk_tree_fn func,
     }							\
   while (0)
 
+  if (TYPE_P (*tp))
+    /* Walk into template args without looking through typedefs.  */
+    if (tree ti = TYPE_TEMPLATE_INFO_MAYBE_ALIAS (*tp))
+      WALK_SUBTREE (TI_ARGS (ti));
+
   /* Not one of the easy cases.  We must explicitly go through the
      children.  */
   result = NULL_TREE;
diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda2.C b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda2.C
new file mode 100644
index 00000000000..fb26ac716d4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda2.C
@@ -0,0 +1,12 @@ 
+// PR c++/92654
+// { dg-do compile { target c++17 } }
+
+template <unsigned long> struct C;
+template <auto I>
+void am() {
+  [](auto an)
+     {
+       if constexpr (C<an>::ap) ; // { dg-error "constant" }
+     }(42);
+}
+void fn() { am<42>(); }