replace custom validation logic in the parse module with a simple DFA validator (closes #26526)

Patch from A. Skrobov.

1 files changed, 93 insertions, 2452 deletions

diff --git a/Modules/parsermodule.c b/Modules/parsermodule.c
index deae049..82770a5 100644
--- a/Modules/parsermodule.c
+++ b/Modules/parsermodule.c
@@ -670,9 +670,75 @@ parser_suite(PyST_Object *self, PyObject *args, PyObject *kw)
 
 
 static node* build_node_tree(PyObject *tuple);
-static int   validate_expr_tree(node *tree);
-static int   validate_file_input(node *tree);
-static int   validate_encoding_decl(node *tree);
+
+static int
+validate_node(node *tree)
+{
+    int type = TYPE(tree);
+    int nch = NCH(tree);
+    dfa *nt_dfa;
+    state *dfa_state;
+    int pos, arc;
+
+    assert(ISNONTERMINAL(type));
+    type -= NT_OFFSET;
+    if (type >= _PyParser_Grammar.g_ndfas) {
+        PyErr_Format(parser_error, "Unrecognized node type %d.", TYPE(tree));
+        return 0;
+    }
+    nt_dfa = &_PyParser_Grammar.g_dfa[type];
+    REQ(tree, nt_dfa->d_type);
+
+    /* Run the DFA for this nonterminal. */
+    dfa_state = &nt_dfa->d_state[nt_dfa->d_initial];
+    for (pos = 0; pos < nch; ++pos) {
+        node *ch = CHILD(tree, pos);
+        int ch_type = TYPE(ch);
+        for (arc = 0; arc < dfa_state->s_narcs; ++arc) {
+            short a_label = dfa_state->s_arc[arc].a_lbl;
+            assert(a_label < _PyParser_Grammar.g_ll.ll_nlabels);
+            if (_PyParser_Grammar.g_ll.ll_label[a_label].lb_type == ch_type) {
+     	        /* The child is acceptable; if non-terminal, validate it recursively. */
+                if (ISNONTERMINAL(ch_type) && !validate_node(ch))
+                    return 0;
+
+                /* Update the state, and move on to the next child. */
+                dfa_state = &nt_dfa->d_state[dfa_state->s_arc[arc].a_arrow];
+                goto arc_found;
+            }
+        }
+        /* What would this state have accepted? */
+        {
+            short a_label = dfa_state->s_arc->a_lbl;
+            int next_type;
+            if (!a_label) /* Wouldn't accept any more children */
+                goto illegal_num_children;
+
+            next_type = _PyParser_Grammar.g_ll.ll_label[a_label].lb_type;
+            if (ISNONTERMINAL(next_type))
+                PyErr_Format(parser_error, "Expected node type %d, got %d.",
+                             next_type, ch_type);
+            else
+                PyErr_Format(parser_error, "Illegal terminal: expected %s.",
+                             _PyParser_TokenNames[next_type]);
+            return 0;
+        }
+
+arc_found:
+        continue;
+    }
+    /* Are we in a final state? If so, return 1 for successful validation. */
+    for (arc = 0; arc < dfa_state->s_narcs; ++arc) {
+        if (!dfa_state->s_arc[arc].a_lbl) {
+            return 1;
+        }
+    }
+
+illegal_num_children:
+    PyErr_Format(parser_error,
+                 "Illegal number of children for %s node.", nt_dfa->d_name);
+    return 0;
+}
 
 /*  PyObject* parser_tuple2st(PyObject* self, PyObject* args)
  *
@@ -681,7 +747,7 @@ static int   validate_encoding_decl(node *tree);
  *  tuple can be validated.  It does this by checking the first code of the
  *  tuple, and, if acceptable, builds the internal representation.  If this
  *  step succeeds, the internal representation is validated as fully as
- *  possible with the various validate_*() routines defined below.
+ *  possible with the recursive validate_node() routine defined above.
  *
  *  This function must be changed if support is to be added for PyST_FRAGMENT
  *  ST objects.
@@ -710,33 +776,35 @@ parser_tuple2st(PyST_Object *self, PyObject *args, PyObject *kw)
      */
     tree = build_node_tree(tuple);
     if (tree != 0) {
-        int start_sym = TYPE(tree);
-        if (start_sym == eval_input) {
+        node *validation_root = tree;
+        int tree_type = 0;
+        switch (TYPE(tree)) {
+        case eval_input:
             /*  Might be an eval form.  */
-            if (validate_expr_tree(tree))
-                st = parser_newstobject(tree, PyST_EXPR);
-            else
-                PyNode_Free(tree);
-        }
-        else if (start_sym == file_input) {
-            /*  This looks like an exec form so far.  */
-            if (validate_file_input(tree))
-                st = parser_newstobject(tree, PyST_SUITE);
-            else
-                PyNode_Free(tree);
-        }
-        else if (start_sym == encoding_decl) {
+            tree_type = PyST_EXPR;
+            break;
+        case encoding_decl:
             /* This looks like an encoding_decl so far. */
-            if (validate_encoding_decl(tree))
-                st = parser_newstobject(tree, PyST_SUITE);
-            else
-                PyNode_Free(tree);
-        }
-        else {
+            if (NCH(tree) != 1)
+                err_string("Error Parsing encoding_decl");
+            validation_root = CHILD(tree, 0);
+            /* Fall through */
+        case file_input:
+            /*  This looks like an exec form so far.  */
+
+            tree_type = PyST_SUITE;
+            break;
+        default:
             /*  This is a fragment, at best. */
             PyNode_Free(tree);
             err_string("parse tree does not use a valid start symbol");
+            return (0);
         }
+
+        if (validate_node(validation_root))
+            st = parser_newstobject(tree, tree_type);
+        else
+            PyNode_Free(tree);
     }
     /*  Make sure we raise an exception on all errors.  We should never
      *  get this, but we'd do well to be sure something is done.
@@ -981,2433 +1049,6 @@ build_node_tree(PyObject *tuple)
 }
 
 
-/*
- *  Validation routines used within the validation section:
- */
-static int validate_terminal(node *terminal, int type, const char *string);
-
-#define validate_ampersand(ch)  validate_terminal(ch,      AMPER, "&")
-#define validate_circumflex(ch) validate_terminal(ch, CIRCUMFLEX, "^")
-#define validate_colon(ch)      validate_terminal(ch,      COLON, ":")
-#define validate_comma(ch)      validate_terminal(ch,      COMMA, ",")
-#define validate_dedent(ch)     validate_terminal(ch,     DEDENT, "")
-#define validate_equal(ch)      validate_terminal(ch,      EQUAL, "=")
-#define validate_indent(ch)     validate_terminal(ch,     INDENT, (char*)NULL)
-#define validate_lparen(ch)     validate_terminal(ch,       LPAR, "(")
-#define validate_newline(ch)    validate_terminal(ch,    NEWLINE, (char*)NULL)
-#define validate_rparen(ch)     validate_terminal(ch,       RPAR, ")")
-#define validate_semi(ch)       validate_terminal(ch,       SEMI, ";")
-#define validate_star(ch)       validate_terminal(ch,       STAR, "*")
-#define validate_vbar(ch)       validate_terminal(ch,       VBAR, "|")
-#define validate_doublestar(ch) validate_terminal(ch, DOUBLESTAR, "**")
-#define validate_dot(ch)        validate_terminal(ch,        DOT, ".")
-#define validate_at(ch)         validate_terminal(ch,         AT, "@")
-#define validate_rarrow(ch)     validate_terminal(ch,     RARROW, "->")
-#define validate_name(ch, str)  validate_terminal(ch,       NAME, str)
-
-#define VALIDATER(n)    static int validate_##n(node *tree)
-
-VALIDATER(node);                VALIDATER(small_stmt);
-VALIDATER(class);               VALIDATER(node);
-VALIDATER(parameters);          VALIDATER(suite);
-VALIDATER(testlist);            VALIDATER(varargslist);
-VALIDATER(vfpdef);
-VALIDATER(stmt);                VALIDATER(simple_stmt);
-VALIDATER(expr_stmt);           VALIDATER(power);
-VALIDATER(del_stmt);
-VALIDATER(return_stmt);         VALIDATER(raise_stmt);
-VALIDATER(import_stmt);         VALIDATER(import_stmt);
-VALIDATER(import_name);         VALIDATER(yield_stmt);
-VALIDATER(global_stmt);         VALIDATER(nonlocal_stmt);
-VALIDATER(assert_stmt);
-VALIDATER(compound_stmt);       VALIDATER(test_or_star_expr);
-VALIDATER(while);               VALIDATER(for);
-VALIDATER(try);                 VALIDATER(except_clause);
-VALIDATER(test);                VALIDATER(and_test);
-VALIDATER(not_test);            VALIDATER(comparison);
-VALIDATER(comp_op);
-VALIDATER(star_expr);           VALIDATER(expr);
-VALIDATER(xor_expr);            VALIDATER(and_expr);
-VALIDATER(shift_expr);          VALIDATER(arith_expr);
-VALIDATER(term);                VALIDATER(factor);
-VALIDATER(atom);                VALIDATER(lambdef);
-VALIDATER(trailer);             VALIDATER(subscript);
-VALIDATER(subscriptlist);       VALIDATER(sliceop);
-VALIDATER(exprlist);            VALIDATER(dictorsetmaker);
-VALIDATER(arglist);             VALIDATER(argument);
-VALIDATER(comp_for);
-VALIDATER(comp_iter);           VALIDATER(comp_if);
-VALIDATER(testlist_comp);       VALIDATER(yield_expr);
-VALIDATER(or_test);
-VALIDATER(test_nocond);         VALIDATER(lambdef_nocond);
-VALIDATER(yield_arg);
-VALIDATER(async_funcdef);       VALIDATER(async_stmt);
-VALIDATER(atom_expr);
-
-#undef VALIDATER
-
-#define is_even(n)      (((n) & 1) == 0)
-#define is_odd(n)       (((n) & 1) == 1)
-
-
-static int
-validate_ntype(node *n, int t)
-{
-    if (TYPE(n) != t) {
-        PyErr_Format(parser_error, "Expected node type %d, got %d.",
-                     t, TYPE(n));
-        return 0;
-    }
-    return 1;
-}
-
-
-/*  Verifies that the number of child nodes is exactly 'num', raising
- *  an exception if it isn't.  The exception message does not indicate
- *  the exact number of nodes, allowing this to be used to raise the
- *  "right" exception when the wrong number of nodes is present in a
- *  specific variant of a statement's syntax.  This is commonly used
- *  in that fashion.
- */
-static int
-validate_numnodes(node *n, int num, const char *const name)
-{
-    if (NCH(n) != num) {
-        PyErr_Format(parser_error,
-                     "Illegal number of children for %s node.", name);
-        return 0;
-    }
-    return 1;
-}
-
-
-static int
-validate_terminal(node *terminal, int type, const char *string)
-{
-    int res = (validate_ntype(terminal, type)
-               && ((string == 0) || (strcmp(string, STR(terminal)) == 0)));
-
-    if (!res && !PyErr_Occurred()) {
-        PyErr_Format(parser_error,
-                     "Illegal terminal: expected \"%s\"", string);
-    }
-    return (res);
-}
-
-/*  X (',' X) [','] */
-static int
-validate_repeating_list_variable(node *tree,
-                                 int list_node_type,
-                                 int (*validate_child_func_inc)(node *, int *),
-                                 int *pos,
-                                 const char *const list_node_type_name)
-{
-    int nch = NCH(tree);
-    int res = (nch && validate_ntype(tree, list_node_type));
-
-    if (!res && !PyErr_Occurred()) {
-        /* Unconditionally raise. */
-        (void) validate_numnodes(tree, 1, list_node_type_name);
-    }
-    else {
-        for ( ; res && *pos < nch; ) {
-            res = validate_child_func_inc(tree, pos);
-            if (!res || *pos >= nch)
-                break;
-            res = validate_comma(CHILD(tree, (*pos)++));
-        }
-    }
-    return res;
-}
-
-/*  X (',' X) [','] */
-static int
-validate_repeating_list(node *tree,
-                        int list_node_type,
-                        int (*validate_child_func)(node *),
-                        const char *const list_node_type_name)
-{
-    int nch = NCH(tree);
-    int res = (nch && validate_ntype(tree, list_node_type));
-    int pos = 0;
-
-    if (!res && !PyErr_Occurred()) {
-        /* Unconditionally raise. */
-        (void) validate_numnodes(tree, 1, list_node_type_name);
-    }
-    else {
-        for ( ; res && pos < nch; ) {
-            res = validate_child_func(CHILD(tree, pos++));
-            if (!res || pos >= nch)
-                break;
-            res = validate_comma(CHILD(tree, pos++));
-        }
-    }
-    return res;
-}
-
-
-/*  validate_class()
- *
- *  classdef:
- *      'class' NAME ['(' testlist ')'] ':' suite
- */
-static int
-validate_class(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, classdef) &&
-                ((nch == 4) || (nch == 6) || (nch == 7)));
-
-    if (res) {
-        res = (validate_name(CHILD(tree, 0), "class")
-               && validate_ntype(CHILD(tree, 1), NAME)
-               && validate_colon(CHILD(tree, nch - 2))
-               && validate_suite(CHILD(tree, nch - 1)));
-    }
-    else {
-        (void) validate_numnodes(tree, 4, "class");
-    }
-
-    if (res) {
-        if (nch == 7) {
-                res = ((validate_lparen(CHILD(tree, 2)) &&
-                        validate_arglist(CHILD(tree, 3)) &&
-                        validate_rparen(CHILD(tree, 4))));
-        }
-        else if (nch == 6) {
-                res = (validate_lparen(CHILD(tree,2)) &&
-                        validate_rparen(CHILD(tree,3)));
-        }
-    }
-    return (res);
-}
-
-
-/*  if_stmt:
- *      'if' test ':' suite ('elif' test ':' suite)* ['else' ':' suite]
- */
-static int
-validate_if(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, if_stmt)
-               && (nch >= 4)
-               && validate_name(CHILD(tree, 0), "if")
-               && validate_test(CHILD(tree, 1))
-               && validate_colon(CHILD(tree, 2))
-               && validate_suite(CHILD(tree, 3)));
-
-    if (res && ((nch % 4) == 3)) {
-        /*  ... 'else' ':' suite  */
-        res = (validate_name(CHILD(tree, nch - 3), "else")
-               && validate_colon(CHILD(tree, nch - 2))
-               && validate_suite(CHILD(tree, nch - 1)));
-        nch -= 3;
-    }
-    else if (!res && !PyErr_Occurred())
-        (void) validate_numnodes(tree, 4, "if");
-    if ((nch % 4) != 0)
-        /* Will catch the case for nch < 4 */
-        res = validate_numnodes(tree, 0, "if");
-    else if (res && (nch > 4)) {
-        /*  ... ('elif' test ':' suite)+ ...  */
-        int j = 4;
-        while ((j < nch) && res) {
-            res = (validate_name(CHILD(tree, j), "elif")
-                   && validate_colon(CHILD(tree, j + 2))
-                   && validate_test(CHILD(tree, j + 1))
-                   && validate_suite(CHILD(tree, j + 3)));
-            j += 4;
-        }
-    }
-    return (res);
-}
-
-
-/*  parameters:
- *      '(' [varargslist] ')'
- *
- */
-static int
-validate_parameters(node *tree)
-{
-    int nch = NCH(tree);
-    int res = validate_ntype(tree, parameters) && ((nch == 2) || (nch == 3));
-
-    if (res) {
-        res = (validate_lparen(CHILD(tree, 0))
-               && validate_rparen(CHILD(tree, nch - 1)));
-        if (res && (nch == 3))
-            res = validate_varargslist(CHILD(tree, 1));
-    }
-    else {
-        (void) validate_numnodes(tree, 2, "parameters");
-    }
-    return (res);
-}
-
-
-/*  validate_suite()
- *
- *  suite:
- *      simple_stmt
- *    | NEWLINE INDENT stmt+ DEDENT
- */
-static int
-validate_suite(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, suite) && ((nch == 1) || (nch >= 4)));
-
-    if (res && (nch == 1))
-        res = validate_simple_stmt(CHILD(tree, 0));
-    else if (res) {
-        /*  NEWLINE INDENT stmt+ DEDENT  */
-        res = (validate_newline(CHILD(tree, 0))
-               && validate_indent(CHILD(tree, 1))
-               && validate_stmt(CHILD(tree, 2))
-               && validate_dedent(CHILD(tree, nch - 1)));
-
-        if (res && (nch > 4)) {
-            int i = 3;
-            --nch;                      /* forget the DEDENT     */
-            for ( ; res && (i < nch); ++i)
-                res = validate_stmt(CHILD(tree, i));
-        }
-        else if (nch < 4)
-            res = validate_numnodes(tree, 4, "suite");
-    }
-    return (res);
-}
-
-
-static int
-validate_testlist(node *tree)
-{
-    return (validate_repeating_list(tree, testlist,
-                                    validate_test, "testlist"));
-}
-
-static int
-validate_testlist_star_expr(node *tl)
-{
-    return (validate_repeating_list(tl, testlist_star_expr, validate_test_or_star_expr,
-                                    "testlist"));
-}
-
-
-/* validate either vfpdef or tfpdef.
- * vfpdef: NAME
- * tfpdef: NAME [':' test]
- */
-static int
-validate_vfpdef(node *tree)
-{
-    int nch = NCH(tree);
-    if (TYPE(tree) == vfpdef) {
-        return nch == 1 && validate_name(CHILD(tree, 0), NULL);
-    }
-    else if (TYPE(tree) == tfpdef) {
-        if (nch == 1) {
-            return validate_name(CHILD(tree, 0), NULL);
-        }
-        else if (nch == 3) {
-            return validate_name(CHILD(tree, 0), NULL) &&
-                   validate_colon(CHILD(tree, 1)) &&
-                   validate_test(CHILD(tree, 2));
-        }
-    }
-    return 0;
-}
-
-/* '*' [vfpdef] (',' vfpdef ['=' test])* [',' '**' vfpdef] | '**' vfpdef
- * ..or tfpdef in place of vfpdef. vfpdef: NAME; tfpdef: NAME [':' test]
- */
-static int
-validate_varargslist_trailer(node *tree, int start)
-{
-    int nch = NCH(tree);
-    int res = 0;
-
-    if (nch <= start) {
-        err_string("expected variable argument trailer for varargslist");
-        return 0;
-    }
-    if (TYPE(CHILD(tree, start)) == STAR) {
-        /*
-         * '*' [vfpdef]
-         */
-        res = validate_star(CHILD(tree, start++));
-        if (res && start < nch && (TYPE(CHILD(tree, start)) == vfpdef ||
-                                   TYPE(CHILD(tree, start)) == tfpdef))
-            res = validate_vfpdef(CHILD(tree, start++));
-        /*
-         * (',' vfpdef ['=' test])*
-         */
-        while (res && start + 1 < nch && (
-                   TYPE(CHILD(tree, start + 1)) == vfpdef ||
-                   TYPE(CHILD(tree, start + 1)) == tfpdef)) {
-            res = (validate_comma(CHILD(tree, start++))
-                   && validate_vfpdef(CHILD(tree, start++)));
-            if (res && start + 1 < nch && TYPE(CHILD(tree, start)) == EQUAL)
-                res = (validate_equal(CHILD(tree, start++))
-                       && validate_test(CHILD(tree, start++)));
-        }
-        /*
-         * [',' '**' vfpdef]
-         */
-        if (res && start + 2 < nch && TYPE(CHILD(tree, start+1)) == DOUBLESTAR)
-            res = (validate_comma(CHILD(tree, start++))
-                   && validate_doublestar(CHILD(tree, start++))
-                   && validate_vfpdef(CHILD(tree, start++)));
-    }
-    else if (TYPE(CHILD(tree, start)) == DOUBLESTAR) {
-        /*
-         * '**' vfpdef
-         */
-        if (start + 1 < nch)
-            res = (validate_doublestar(CHILD(tree, start++))
-                   && validate_vfpdef(CHILD(tree, start++)));
-        else {
-            res = 0;
-            err_string("expected vfpdef after ** in varargslist trailer");
-        }
-    }
-    else {
-        res = 0;
-        err_string("expected * or ** in varargslist trailer");
-    }
-
-    if (res && start != nch) {
-        res = 0;
-        err_string("unexpected extra children in varargslist trailer");
-    }
-    return res;
-}
-
-
-/* validate_varargslist()
- *
- * Validate typedargslist or varargslist.
- *
- * typedargslist: ((tfpdef ['=' test] ',')*
- *                 ('*' [tfpdef] (',' tfpdef ['=' test])* [',' '**' tfpdef] |
- *                  '**' tfpdef)
- *                 | tfpdef ['=' test] (',' tfpdef ['=' test])* [','])
- * tfpdef: NAME [':' test]
- * varargslist: ((vfpdef ['=' test] ',')*
- *               ('*' [vfpdef] (',' vfpdef ['=' test])*  [',' '**' vfpdef] |
- *                '**' vfpdef)
- *               | vfpdef ['=' test] (',' vfpdef ['=' test])* [','])
- * vfpdef: NAME
- *
- */
-static int
-validate_varargslist(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (TYPE(tree) == varargslist ||
-               TYPE(tree) == typedargslist) &&
-              (nch != 0);
-    int sym;
-    node *ch;
-    int i = 0;
-
-    if (!res)
-        return 0;
-    if (nch < 1) {
-        err_string("varargslist missing child nodes");
-        return 0;
-    }
-    while (i < nch) {
-        ch = CHILD(tree, i);
-        sym = TYPE(ch);
-        if (sym == vfpdef || sym == tfpdef) {
-            /* validate (vfpdef ['=' test] ',')+ */
-            res = validate_vfpdef(ch);
-            ++i;
-            if (res && (i+2 <= nch) && TYPE(CHILD(tree, i)) == EQUAL) {
-                res = (validate_equal(CHILD(tree, i))
-                       && validate_test(CHILD(tree, i+1)));
-                if (res)
-                  i += 2;
-            }
-            if (res && i < nch) {
-                res = validate_comma(CHILD(tree, i));
-                ++i;
-            }
-        } else if (sym == DOUBLESTAR || sym == STAR) {
-            res = validate_varargslist_trailer(tree, i);
-            break;
-        } else {
-            res = 0;
-            err_string("illegal formation for varargslist");
-        }
-    }
-    return res;
-}
-
-
-/*  comp_iter:  comp_for | comp_if
- */
-static int
-validate_comp_iter(node *tree)
-{
-    int res = (validate_ntype(tree, comp_iter)
-               && validate_numnodes(tree, 1, "comp_iter"));
-    if (res && TYPE(CHILD(tree, 0)) == comp_for)
-        res = validate_comp_for(CHILD(tree, 0));
-    else
-        res = validate_comp_if(CHILD(tree, 0));
-
-    return res;
-}
-
-/*  comp_for:  'for' exprlist 'in' test [comp_iter]
- */
-static int
-validate_comp_for(node *tree)
-{
-    int nch = NCH(tree);
-    int res;
-
-    if (nch == 5)
-        res = validate_comp_iter(CHILD(tree, 4));
-    else
-        res = validate_numnodes(tree, 4, "comp_for");
-
-    if (res)
-        res = (validate_name(CHILD(tree, 0), "for")
-               && validate_exprlist(CHILD(tree, 1))
-               && validate_name(CHILD(tree, 2), "in")
-               && validate_or_test(CHILD(tree, 3)));
-
-    return res;
-}
-
-/*  comp_if:  'if' test_nocond [comp_iter]
- */
-static int
-validate_comp_if(node *tree)
-{
-    int nch = NCH(tree);
-    int res;
-
-    if (nch == 3)
-        res = validate_comp_iter(CHILD(tree, 2));
-    else
-        res = validate_numnodes(tree, 2, "comp_if");
-
-    if (res)
-        res = (validate_name(CHILD(tree, 0), "if")
-               && validate_test_nocond(CHILD(tree, 1)));
-
-    return res;
-}
-
-
-/*  simple_stmt | compound_stmt
- *
- */
-static int
-validate_stmt(node *tree)
-{
-    int res = (validate_ntype(tree, stmt)
-               && validate_numnodes(tree, 1, "stmt"));
-
-    if (res) {
-        tree = CHILD(tree, 0);
-
-        if (TYPE(tree) == simple_stmt)
-            res = validate_simple_stmt(tree);
-        else
-            res = validate_compound_stmt(tree);
-    }
-    return (res);
-}
-
-
-/*  small_stmt (';' small_stmt)* [';'] NEWLINE
- *
- */
-static int
-validate_simple_stmt(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, simple_stmt)
-               && (nch >= 2)
-               && validate_small_stmt(CHILD(tree, 0))
-               && validate_newline(CHILD(tree, nch - 1)));
-
-    if (nch < 2)
-        res = validate_numnodes(tree, 2, "simple_stmt");
-    --nch;                              /* forget the NEWLINE    */
-    if (res && is_even(nch))
-        res = validate_semi(CHILD(tree, --nch));
-    if (res && (nch > 2)) {
-        int i;
-
-        for (i = 1; res && (i < nch); i += 2)
-            res = (validate_semi(CHILD(tree, i))
-                   && validate_small_stmt(CHILD(tree, i + 1)));
-    }
-    return (res);
-}
-
-
-static int
-validate_small_stmt(node *tree)
-{
-    int nch = NCH(tree);
-    int res = validate_numnodes(tree, 1, "small_stmt");
-
-    if (res) {
-        int ntype = TYPE(CHILD(tree, 0));
-
-        if (  (ntype == expr_stmt)
-              || (ntype == del_stmt)
-              || (ntype == pass_stmt)
-              || (ntype == flow_stmt)
-              || (ntype == import_stmt)
-              || (ntype == global_stmt)
-              || (ntype == nonlocal_stmt)
-              || (ntype == assert_stmt))
-            res = validate_node(CHILD(tree, 0));
-        else {
-            res = 0;
-            err_string("illegal small_stmt child type");
-        }
-    }
-    else if (nch == 1) {
-        res = 0;
-        PyErr_Format(parser_error,
-                     "Unrecognized child node of small_stmt: %d.",
-                     TYPE(CHILD(tree, 0)));
-    }
-    return (res);
-}
-
-
-/*  compound_stmt:
- *      if_stmt | while_stmt | for_stmt | try_stmt | with_stmt | funcdef | classdef | decorated
- */
-static int
-validate_compound_stmt(node *tree)
-{
-    int res = (validate_ntype(tree, compound_stmt)
-               && validate_numnodes(tree, 1, "compound_stmt"));
-    int ntype;
-
-    if (!res)
-        return (0);
-
-    tree = CHILD(tree, 0);
-    ntype = TYPE(tree);
-    if (  (ntype == if_stmt)
-          || (ntype == while_stmt)
-          || (ntype == for_stmt)
-          || (ntype == try_stmt)
-          || (ntype == with_stmt)
-          || (ntype == funcdef)
-          || (ntype == async_stmt)
-          || (ntype == classdef)
-          || (ntype == decorated))
-        res = validate_node(tree);
-    else {
-        res = 0;
-        PyErr_Format(parser_error,
-                     "Illegal compound statement type: %d.", TYPE(tree));
-    }
-    return (res);
-}
-
-static int
-validate_yield_or_testlist(node *tree, int tse)
-{
-    if (TYPE(tree) == yield_expr) {
-        return validate_yield_expr(tree);
-    }
-    else {
-        if (tse)
-            return validate_testlist_star_expr(tree);
-        else
-            return validate_testlist(tree);
-    }
-}
-
-static int
-validate_expr_stmt(node *tree)
-{
-    int j;
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, expr_stmt)
-               && is_odd(nch)
-               && validate_testlist_star_expr(CHILD(tree, 0)));
-
-    if (res && nch == 3
-        && TYPE(CHILD(tree, 1)) == augassign) {
-        res = validate_numnodes(CHILD(tree, 1), 1, "augassign")
-            && validate_yield_or_testlist(CHILD(tree, 2), 0);
-
-        if (res) {
-            char *s = STR(CHILD(CHILD(tree, 1), 0));
-
-            res = (strcmp(s, "+=") == 0
-                   || strcmp(s, "-=") == 0
-                   || strcmp(s, "*=") == 0
-                   || strcmp(s, "/=") == 0
-                   || strcmp(s, "//=") == 0
-                   || strcmp(s, "%=") == 0
-                   || strcmp(s, "&=") == 0
-                   || strcmp(s, "|=") == 0
-                   || strcmp(s, "^=") == 0
-                   || strcmp(s, "<<=") == 0
-                   || strcmp(s, ">>=") == 0
-                   || strcmp(s, "**=") == 0);
-            if (!res)
-                err_string("illegal augmented assignment operator");
-        }
-    }
-    else {
-        for (j = 1; res && (j < nch); j += 2)
-            res = validate_equal(CHILD(tree, j))
-                && validate_yield_or_testlist(CHILD(tree, j + 1), 1);
-    }
-    return (res);
-}
-
-
-static int
-validate_del_stmt(node *tree)
-{
-    return (validate_numnodes(tree, 2, "del_stmt")
-            && validate_name(CHILD(tree, 0), "del")
-            && validate_exprlist(CHILD(tree, 1)));
-}
-
-
-static int
-validate_return_stmt(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, return_stmt)
-               && ((nch == 1) || (nch == 2))
-               && validate_name(CHILD(tree, 0), "return"));
-
-    if (res && (nch == 2))
-        res = validate_testlist(CHILD(tree, 1));
-
-    return (res);
-}
-
-
-/*
- *  raise_stmt:
- *
- *  'raise' [test ['from' test]]
- */
-static int
-validate_raise_stmt(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, raise_stmt)
-               && ((nch == 1) || (nch == 2) || (nch == 4)));
-
-    if (!res && !PyErr_Occurred())
-        (void) validate_numnodes(tree, 2, "raise");
-
-    if (res) {
-        res = validate_name(CHILD(tree, 0), "raise");
-        if (res && (nch >= 2))
-            res = validate_test(CHILD(tree, 1));
-        if (res && (nch == 4)) {
-            res = (validate_name(CHILD(tree, 2), "from")
-                   && validate_test(CHILD(tree, 3)));
-        }
-    }
-    return (res);
-}
-
-
-/* yield_expr: 'yield' [yield_arg]
- */
-static int
-validate_yield_expr(node *tree)
-{
-    int nch = NCH(tree);
-    if (nch < 1 || nch > 2)
-        return 0;
-    if (!validate_ntype(tree, yield_expr))
-        return 0;
-    if (!validate_name(CHILD(tree, 0), "yield"))
-        return 0;
-    if (nch == 2) {
-        if (!validate_yield_arg(CHILD(tree, 1)))
-            return 0;
-    }
-    return 1;
-}
-
-/* yield_arg: 'from' test | testlist
- */
-static int
-validate_yield_arg(node *tree)
-{
-    int nch = NCH(tree);
-    if (!validate_ntype(tree, yield_arg))
-        return 0;
-    switch (nch) {
-      case 1:
-        if (!validate_testlist(CHILD(tree, nch - 1)))
-            return 0;
-        break;
-      case 2:
-        if (!validate_name(CHILD(tree, 0), "from"))
-            return 0;
-        if (!validate_test(CHILD(tree, 1)))
-            return 0;
-        break;
-      default:
-        return 0;
-    }
-    return 1;
-}
-
-/* yield_stmt: yield_expr
- */
-static int
-validate_yield_stmt(node *tree)
-{
-    return (validate_ntype(tree, yield_stmt)
-            && validate_numnodes(tree, 1, "yield_stmt")
-            && validate_yield_expr(CHILD(tree, 0)));
-}
-
-
-static int
-validate_import_as_name(node *tree)
-{
-    int nch = NCH(tree);
-    int ok = validate_ntype(tree, import_as_name);
-
-    if (ok) {
-        if (nch == 1)
-            ok = validate_name(CHILD(tree, 0), NULL);
-        else if (nch == 3)
-            ok = (validate_name(CHILD(tree, 0), NULL)
-                  && validate_name(CHILD(tree, 1), "as")
-                  && validate_name(CHILD(tree, 2), NULL));
-        else
-            ok = validate_numnodes(tree, 3, "import_as_name");
-    }
-    return ok;
-}
-
-
-/* dotted_name:  NAME ("." NAME)*
- */
-static int
-validate_dotted_name(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, dotted_name)
-               && is_odd(nch)
-               && validate_name(CHILD(tree, 0), NULL));
-    int i;
-
-    for (i = 1; res && (i < nch); i += 2) {
-        res = (validate_dot(CHILD(tree, i))
-               && validate_name(CHILD(tree, i+1), NULL));
-    }
-    return res;
-}
-
-
-/* dotted_as_name:  dotted_name [NAME NAME]
- */
-static int
-validate_dotted_as_name(node *tree)
-{
-    int nch = NCH(tree);
-    int res = validate_ntype(tree, dotted_as_name);
-
-    if (res) {
-        if (nch == 1)
-            res = validate_dotted_name(CHILD(tree, 0));
-        else if (nch == 3)
-            res = (validate_dotted_name(CHILD(tree, 0))
-                   && validate_name(CHILD(tree, 1), "as")
-                   && validate_name(CHILD(tree, 2), NULL));
-        else {
-            res = 0;
-            err_string("illegal number of children for dotted_as_name");
-        }
-    }
-    return res;
-}
-
-
-/* dotted_as_name (',' dotted_as_name)* */
-static int
-validate_dotted_as_names(node *tree)
-{
-        int nch = NCH(tree);
-        int res = is_odd(nch) && validate_dotted_as_name(CHILD(tree, 0));
-        int i;
-
-        for (i = 1; res && (i < nch); i += 2)
-            res = (validate_comma(CHILD(tree, i))
-                   && validate_dotted_as_name(CHILD(tree, i + 1)));
-        return (res);
-}
-
-
-/* import_as_name (',' import_as_name)* [','] */
-static int
-validate_import_as_names(node *tree)
-{
-    int nch = NCH(tree);
-    int res = validate_import_as_name(CHILD(tree, 0));
-    int i;
-
-    for (i = 1; res && (i + 1 < nch); i += 2)
-        res = (validate_comma(CHILD(tree, i))
-               && validate_import_as_name(CHILD(tree, i + 1)));
-    return (res);
-}
-
-
-/* 'import' dotted_as_names */
-static int
-validate_import_name(node *tree)
-{
-        return (validate_ntype(tree, import_name)
-                && validate_numnodes(tree, 2, "import_name")
-                && validate_name(CHILD(tree, 0), "import")
-                && validate_dotted_as_names(CHILD(tree, 1)));
-}
-
-/* Helper function to count the number of leading dots (or ellipsis tokens) in
- * 'from ...module import name'
- */
-static int
-count_from_dots(node *tree)
-{
-    int i;
-    for (i = 1; i < NCH(tree); i++)
-        if (TYPE(CHILD(tree, i)) != DOT && TYPE(CHILD(tree, i)) != ELLIPSIS)
-            break;
-    return i - 1;
-}
-
-/* import_from: ('from' ('.'* dotted_name | '.'+)
- *               'import' ('*' | '(' import_as_names ')' | import_as_names))
- */
-static int
-validate_import_from(node *tree)
-{
-        int nch = NCH(tree);
-        int ndots = count_from_dots(tree);
-        int havename = (TYPE(CHILD(tree, ndots + 1)) == dotted_name);
-        int offset = ndots + havename;
-        int res = validate_ntype(tree, import_from)
-                && (offset >= 1)
-                && (nch >= 3 + offset)
-                && validate_name(CHILD(tree, 0), "from")
-                && (!havename || validate_dotted_name(CHILD(tree, ndots + 1)))
-                && validate_name(CHILD(tree, offset + 1), "import");
-
-        if (res && TYPE(CHILD(tree, offset + 2)) == LPAR)
-            res = ((nch == offset + 5)
-                   && validate_lparen(CHILD(tree, offset + 2))
-                   && validate_import_as_names(CHILD(tree, offset + 3))
-                   && validate_rparen(CHILD(tree, offset + 4)));
-        else if (res && TYPE(CHILD(tree, offset + 2)) != STAR)
-            res = validate_import_as_names(CHILD(tree, offset + 2));
-        return (res);
-}
-
-
-/* import_stmt: import_name | import_from */
-static int
-validate_import_stmt(node *tree)
-{
-    int nch = NCH(tree);
-    int res = validate_numnodes(tree, 1, "import_stmt");
-
-    if (res) {
-        int ntype = TYPE(CHILD(tree, 0));
-
-        if (ntype == import_name || ntype == import_from)
-            res = validate_node(CHILD(tree, 0));
-        else {
-            res = 0;
-            err_string("illegal import_stmt child type");
-        }
-    }
-    else if (nch == 1) {
-        res = 0;
-        PyErr_Format(parser_error,
-                     "Unrecognized child node of import_stmt: %d.",
-                     TYPE(CHILD(tree, 0)));
-    }
-    return (res);
-}
-
-
-/*  global_stmt:
- *
- *  'global' NAME (',' NAME)*
- */
-static int
-validate_global_stmt(node *tree)
-{
-    int j;
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, global_stmt)
-               && is_even(nch) && (nch >= 2));
-
-    if (!res && !PyErr_Occurred())
-        err_string("illegal global statement");
-
-    if (res)
-        res = (validate_name(CHILD(tree, 0), "global")
-               && validate_ntype(CHILD(tree, 1), NAME));
-    for (j = 2; res && (j < nch); j += 2)
-        res = (validate_comma(CHILD(tree, j))
-               && validate_ntype(CHILD(tree, j + 1), NAME));
-
-    return (res);
-}
-
-/*  nonlocal_stmt:
- *
- *  'nonlocal' NAME (',' NAME)*
- */
-static int
-validate_nonlocal_stmt(node *tree)
-{
-    int j;
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, nonlocal_stmt)
-               && is_even(nch) && (nch >= 2));
-
-    if (!res && !PyErr_Occurred())
-        err_string("illegal nonlocal statement");
-
-    if (res)
-        res = (validate_name(CHILD(tree, 0), "nonlocal")
-               && validate_ntype(CHILD(tree, 1), NAME));
-    for (j = 2; res && (j < nch); j += 2)
-        res = (validate_comma(CHILD(tree, j))
-               && validate_ntype(CHILD(tree, j + 1), NAME));
-
-    return res;
-}
-
-/*  assert_stmt:
- *
- *  'assert' test [',' test]
- */
-static int
-validate_assert_stmt(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, assert_stmt)
-               && ((nch == 2) || (nch == 4))
-               && (validate_name(CHILD(tree, 0), "assert"))
-               && validate_test(CHILD(tree, 1)));
-
-    if (!res && !PyErr_Occurred())
-        err_string("illegal assert statement");
-    if (res && (nch > 2))
-        res = (validate_comma(CHILD(tree, 2))
-               && validate_test(CHILD(tree, 3)));
-
-    return (res);
-}
-
-
-static int
-validate_while(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, while_stmt)
-               && ((nch == 4) || (nch == 7))
-               && validate_name(CHILD(tree, 0), "while")
-               && validate_test(CHILD(tree, 1))
-               && validate_colon(CHILD(tree, 2))
-               && validate_suite(CHILD(tree, 3)));
-
-    if (res && (nch == 7))
-        res = (validate_name(CHILD(tree, 4), "else")
-               && validate_colon(CHILD(tree, 5))
-               && validate_suite(CHILD(tree, 6)));
-
-    return (res);
-}
-
-
-static int
-validate_for(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, for_stmt)
-               && ((nch == 6) || (nch == 9))
-               && validate_name(CHILD(tree, 0), "for")
-               && validate_exprlist(CHILD(tree, 1))
-               && validate_name(CHILD(tree, 2), "in")
-               && validate_testlist(CHILD(tree, 3))
-               && validate_colon(CHILD(tree, 4))
-               && validate_suite(CHILD(tree, 5)));
-
-    if (res && (nch == 9))
-        res = (validate_name(CHILD(tree, 6), "else")
-               && validate_colon(CHILD(tree, 7))
-               && validate_suite(CHILD(tree, 8)));
-
-    return (res);
-}
-
-
-/*  try_stmt:
- *      'try' ':' suite (except_clause ':' suite)+ ['else' ':' suite]
-                                                   ['finally' ':' suite]
- *    | 'try' ':' suite 'finally' ':' suite
- *
- */
-static int
-validate_try(node *tree)
-{
-    int nch = NCH(tree);
-    int pos = 3;
-    int res = (validate_ntype(tree, try_stmt)
-               && (nch >= 6) && ((nch % 3) == 0));
-
-    if (res)
-        res = (validate_name(CHILD(tree, 0), "try")
-               && validate_colon(CHILD(tree, 1))
-               && validate_suite(CHILD(tree, 2))
-               && validate_colon(CHILD(tree, nch - 2))
-               && validate_suite(CHILD(tree, nch - 1)));
-    else if (!PyErr_Occurred()) {
-        const char* name = "except";
-        if (TYPE(CHILD(tree, nch - 3)) != except_clause)
-            name = STR(CHILD(tree, nch - 3));
-
-        PyErr_Format(parser_error,
-                     "Illegal number of children for try/%s node.", name);
-    }
-    /* Handle try/finally statement */
-    if (res && (TYPE(CHILD(tree, pos)) == NAME) &&
-        (strcmp(STR(CHILD(tree, pos)), "finally") == 0)) {
-        res = (validate_numnodes(tree, 6, "try/finally")
-               && validate_colon(CHILD(tree, 4))
-               && validate_suite(CHILD(tree, 5)));
-        return (res);
-    }
-    /* try/except statement: skip past except_clause sections */
-    while (res && pos < nch && (TYPE(CHILD(tree, pos)) == except_clause)) {
-        res = (validate_except_clause(CHILD(tree, pos))
-               && validate_colon(CHILD(tree, pos + 1))
-               && validate_suite(CHILD(tree, pos + 2)));
-        pos += 3;
-    }
-    /* skip else clause */
-    if (res && pos < nch && (TYPE(CHILD(tree, pos)) == NAME) &&
-        (strcmp(STR(CHILD(tree, pos)), "else") == 0)) {
-        res = (validate_colon(CHILD(tree, pos + 1))
-               && validate_suite(CHILD(tree, pos + 2)));
-        pos += 3;
-    }
-    if (res && pos < nch) {
-        /* last clause must be a finally */
-        res = (validate_name(CHILD(tree, pos), "finally")
-               && validate_numnodes(tree, pos + 3, "try/except/finally")
-               && validate_colon(CHILD(tree, pos + 1))
-               && validate_suite(CHILD(tree, pos + 2)));
-    }
-    return (res);
-}
-
-
-static int
-validate_except_clause(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, except_clause)
-               && ((nch == 1) || (nch == 2) || (nch == 4))
-               && validate_name(CHILD(tree, 0), "except"));
-
-    if (res && (nch > 1))
-        res = validate_test(CHILD(tree, 1));
-    if (res && (nch == 4))
-        res = (validate_name(CHILD(tree, 2), "as")
-               && validate_ntype(CHILD(tree, 3), NAME));
-
-    return (res);
-}
-
-
-static int
-validate_test(node *tree)
-{
-    int nch = NCH(tree);
-    int res = validate_ntype(tree, test) && is_odd(nch);
-
-    if (res && (TYPE(CHILD(tree, 0)) == lambdef))
-        res = ((nch == 1)
-               && validate_lambdef(CHILD(tree, 0)));
-    else if (res) {
-        res = validate_or_test(CHILD(tree, 0));
-        res = (res && (nch == 1 || (nch == 5 &&
-            validate_name(CHILD(tree, 1), "if") &&
-            validate_or_test(CHILD(tree, 2)) &&
-            validate_name(CHILD(tree, 3), "else") &&
-            validate_test(CHILD(tree, 4)))));
-    }
-    return (res);
-}
-
-static int
-validate_test_nocond(node *tree)
-{
-    int nch = NCH(tree);
-    int res = validate_ntype(tree, test_nocond) && (nch == 1);
-
-    if (res && (TYPE(CHILD(tree, 0)) == lambdef_nocond))
-        res = (validate_lambdef_nocond(CHILD(tree, 0)));
-    else if (res) {
-        res = (validate_or_test(CHILD(tree, 0)));
-    }
-    return (res);
-}
-
-static int
-validate_or_test(node *tree)
-{
-    int nch = NCH(tree);
-    int res = validate_ntype(tree, or_test) && is_odd(nch);
-
-    if (res) {
-        int pos;
-        res = validate_and_test(CHILD(tree, 0));
-        for (pos = 1; res && (pos < nch); pos += 2)
-            res = (validate_name(CHILD(tree, pos), "or")
-                   && validate_and_test(CHILD(tree, pos + 1)));
-    }
-    return (res);
-}
-
-
-static int
-validate_and_test(node *tree)
-{
-    int pos;
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, and_test)
-               && is_odd(nch)
-               && validate_not_test(CHILD(tree, 0)));
-
-    for (pos = 1; res && (pos < nch); pos += 2)
-        res = (validate_name(CHILD(tree, pos), "and")
-               && validate_not_test(CHILD(tree, 0)));
-
-    return (res);
-}
-
-
-static int
-validate_not_test(node *tree)
-{
-    int nch = NCH(tree);
-    int res = validate_ntype(tree, not_test) && ((nch == 1) || (nch == 2));
-
-    if (res) {
-        if (nch == 2)
-            res = (validate_name(CHILD(tree, 0), "not")
-                   && validate_not_test(CHILD(tree, 1)));
-        else if (nch == 1)
-            res = validate_comparison(CHILD(tree, 0));
-    }
-    return (res);
-}
-
-
-static int
-validate_comparison(node *tree)
-{
-    int pos;
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, comparison)
-               && is_odd(nch)
-               && validate_expr(CHILD(tree, 0)));
-
-    for (pos = 1; res && (pos < nch); pos += 2)
-        res = (validate_comp_op(CHILD(tree, pos))
-               && validate_expr(CHILD(tree, pos + 1)));
-
-    return (res);
-}
-
-
-static int
-validate_comp_op(node *tree)
-{
-    int res = 0;
-    int nch = NCH(tree);
-
-    if (!validate_ntype(tree, comp_op))
-        return (0);
-    if (nch == 1) {
-        /*
-         *  Only child will be a terminal with a well-defined symbolic name
-         *  or a NAME with a string of either 'is' or 'in'
-         */
-        tree = CHILD(tree, 0);
-        switch (TYPE(tree)) {
-          case LESS:
-          case GREATER:
-          case EQEQUAL:
-          case EQUAL:
-          case LESSEQUAL:
-          case GREATEREQUAL:
-          case NOTEQUAL:
-              res = 1;
-              break;
-          case NAME:
-              res = ((strcmp(STR(tree), "in") == 0)
-                     || (strcmp(STR(tree), "is") == 0));
-              if (!res) {
-                  PyErr_Format(parser_error,
-                               "illegal operator '%s'", STR(tree));
-              }
-              break;
-          default:
-              err_string("illegal comparison operator type");
-              break;
-        }
-    }
-    else if ((res = validate_numnodes(tree, 2, "comp_op")) != 0) {
-        res = (validate_ntype(CHILD(tree, 0), NAME)
-               && validate_ntype(CHILD(tree, 1), NAME)
-               && (((strcmp(STR(CHILD(tree, 0)), "is") == 0)
-                    && (strcmp(STR(CHILD(tree, 1)), "not") == 0))
-                   || ((strcmp(STR(CHILD(tree, 0)), "not") == 0)
-                       && (strcmp(STR(CHILD(tree, 1)), "in") == 0))));
-        if (!res && !PyErr_Occurred())
-            err_string("unknown comparison operator");
-    }
-    return (res);
-}
-
-
-static int
-validate_star_expr(node *tree)
-{
-    int res = validate_ntype(tree, star_expr);
-    if (!res) return res;
-    if (!validate_numnodes(tree, 2, "star_expr"))
-        return 0;
-    return validate_ntype(CHILD(tree, 0), STAR) &&      \
-        validate_expr(CHILD(tree, 1));
-}
-
-
-static int
-validate_expr(node *tree)
-{
-    int j;
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, expr)
-               && is_odd(nch)
-               && validate_xor_expr(CHILD(tree, 0)));
-
-    for (j = 2; res && (j < nch); j += 2)
-        res = (validate_xor_expr(CHILD(tree, j))
-               && validate_vbar(CHILD(tree, j - 1)));
-
-    return (res);
-}
-
-
-static int
-validate_xor_expr(node *tree)
-{
-    int j;
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, xor_expr)
-               && is_odd(nch)
-               && validate_and_expr(CHILD(tree, 0)));
-
-    for (j = 2; res && (j < nch); j += 2)
-        res = (validate_circumflex(CHILD(tree, j - 1))
-               && validate_and_expr(CHILD(tree, j)));
-
-    return (res);
-}
-
-
-static int
-validate_and_expr(node *tree)
-{
-    int pos;
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, and_expr)
-               && is_odd(nch)
-               && validate_shift_expr(CHILD(tree, 0)));
-
-    for (pos = 1; res && (pos < nch); pos += 2)
-        res = (validate_ampersand(CHILD(tree, pos))
-               && validate_shift_expr(CHILD(tree, pos + 1)));
-
-    return (res);
-}
-
-
-static int
-validate_chain_two_ops(node *tree, int (*termvalid)(node *), int op1, int op2)
- {
-    int pos = 1;
-    int nch = NCH(tree);
-    int res = (is_odd(nch)
-               && (*termvalid)(CHILD(tree, 0)));
-
-    for ( ; res && (pos < nch); pos += 2) {
-        if (TYPE(CHILD(tree, pos)) != op1)
-            res = validate_ntype(CHILD(tree, pos), op2);
-        if (res)
-            res = (*termvalid)(CHILD(tree, pos + 1));
-    }
-    return (res);
-}
-
-
-static int
-validate_shift_expr(node *tree)
-{
-    return (validate_ntype(tree, shift_expr)
-            && validate_chain_two_ops(tree, validate_arith_expr,
-                                      LEFTSHIFT, RIGHTSHIFT));
-}
-
-
-static int
-validate_arith_expr(node *tree)
-{
-    return (validate_ntype(tree, arith_expr)
-            && validate_chain_two_ops(tree, validate_term, PLUS, MINUS));
-}
-
-
-static int
-validate_term(node *tree)
-{
-    int pos = 1;
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, term)
-               && is_odd(nch)
-               && validate_factor(CHILD(tree, 0)));
-
-    for ( ; res && (pos < nch); pos += 2)
-        res = (((TYPE(CHILD(tree, pos)) == STAR)
-               || (TYPE(CHILD(tree, pos)) == SLASH)
-               || (TYPE(CHILD(tree, pos)) == DOUBLESLASH)
-               || (TYPE(CHILD(tree, pos)) == PERCENT))
-               && validate_factor(CHILD(tree, pos + 1)));
-
-    return (res);
-}
-
-
-/*  factor:
- *
- *  factor: ('+'|'-'|'~') factor | power
- */
-static int
-validate_factor(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, factor)
-               && (((nch == 2)
-                    && ((TYPE(CHILD(tree, 0)) == PLUS)
-                        || (TYPE(CHILD(tree, 0)) == MINUS)
-                        || (TYPE(CHILD(tree, 0)) == TILDE))
-                    && validate_factor(CHILD(tree, 1)))
-                   || ((nch == 1)
-                       && validate_power(CHILD(tree, 0)))));
-    return (res);
-}
-
-
-/*  power:
- *
- *  power: atom_expr trailer* ['**' factor]
- */
-static int
-validate_power(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, power) && (nch >= 1)
-               && validate_atom_expr(CHILD(tree, 0)));
-
-    if (nch > 1) {
-        if (nch != 3) {
-            err_string("illegal number of nodes for 'power'");
-            return (0);
-        }
-        res = (validate_doublestar(CHILD(tree, 1))
-               && validate_factor(CHILD(tree, 2)));
-    }
-
-    return (res);
-}
-
-
-/*  atom_expr:
- *
- *  atom_expr: [AWAIT] atom trailer*
- */
-static int
-validate_atom_expr(node *tree)
-{
-    int start = 0;
-    int nch = NCH(tree);
-    int res;
-    int pos;
-
-    res = validate_ntype(tree, atom_expr) && (nch >= 1);
-    if (!res) {
-        return (res);
-    }
-
-    if (TYPE(CHILD(tree, 0)) == AWAIT) {
-        start = 1;
-        if (nch < 2) {
-            err_string("illegal number of nodes for 'atom_expr'");
-            return (0);
-        }
-    }
-
-    res = validate_atom(CHILD(tree, start));
-    if (res) {
-        pos = start + 1;
-        while (res && (pos < nch) && (TYPE(CHILD(tree, pos)) == trailer))
-            res = validate_trailer(CHILD(tree, pos++));
-    }
-
-    return (res);
-}
-
-
-static int
-validate_atom(node *tree)
-{
-    int pos;
-    int nch = NCH(tree);
-    int res = validate_ntype(tree, atom);
-
-    if (res && nch < 1)
-        res = validate_numnodes(tree, nch+1, "atom");
-    if (res) {
-        switch (TYPE(CHILD(tree, 0))) {
-          case LPAR:
-            res = ((nch <= 3)
-                   && (validate_rparen(CHILD(tree, nch - 1))));
-
-            if (res && (nch == 3)) {
-                if (TYPE(CHILD(tree, 1))==yield_expr)
-                        res = validate_yield_expr(CHILD(tree, 1));
-                else
-                        res = validate_testlist_comp(CHILD(tree, 1));
-            }
-            break;
-          case LSQB:
-            if (nch == 2)
-                res = validate_ntype(CHILD(tree, 1), RSQB);
-            else if (nch == 3)
-                res = (validate_testlist_comp(CHILD(tree, 1))
-                       && validate_ntype(CHILD(tree, 2), RSQB));
-            else {
-                res = 0;
-                err_string("illegal list display atom");
-            }
-            break;
-          case LBRACE:
-            res = ((nch <= 3)
-                   && validate_ntype(CHILD(tree, nch - 1), RBRACE));
-
-            if (res && (nch == 3))
-                res = validate_dictorsetmaker(CHILD(tree, 1));
-            break;
-          case NAME:
-          case NUMBER:
-          case ELLIPSIS:
-            res = (nch == 1);
-            break;
-          case STRING:
-            for (pos = 1; res && (pos < nch); ++pos)
-                res = validate_ntype(CHILD(tree, pos), STRING);
-            break;
-          default:
-            res = 0;
-            break;
-        }
-    }
-    return (res);
-}
-
-
-/*  testlist_comp:
- *    (test|star_expr) ( comp_for | (',' (test|star_expr))* [','] )
- */
-static int
-validate_testlist_comp(node *tree)
-{
-    int nch = NCH(tree);
-    int ok;
-
-    if (nch == 0) {
-        err_string("missing child nodes of testlist_comp");
-        return 0;
-    }
-
-    if (nch == 2 && TYPE(CHILD(tree, 1)) == comp_for) {
-        ok = (validate_test(CHILD(tree, 0))
-                && validate_comp_for(CHILD(tree, 1)));
-    }
-    else {
-        ok = validate_repeating_list(tree,
-                testlist_comp,
-                validate_test_or_star_expr,
-                "testlist_comp");
-    }
-    return ok;
-}
-
-/*  decorator:
- *    '@' dotted_name [ '(' [arglist] ')' ] NEWLINE
- */
-static int
-validate_decorator(node *tree)
-{
-    int ok;
-    int nch = NCH(tree);
-    ok = (validate_ntype(tree, decorator) &&
-          (nch == 3 || nch == 5 || nch == 6) &&
-          validate_at(CHILD(tree, 0)) &&
-          validate_dotted_name(CHILD(tree, 1)) &&
-          validate_newline(RCHILD(tree, -1)));
-
-    if (ok && nch != 3) {
-        ok = (validate_lparen(CHILD(tree, 2)) &&
-              validate_rparen(RCHILD(tree, -2)));
-
-        if (ok && nch == 6)
-            ok = validate_arglist(CHILD(tree, 3));
-    }
-
-    return ok;
-}
-
-/*  decorators:
- *    decorator+
- */
-static int
-validate_decorators(node *tree)
-{
-    int i, nch, ok;
-    nch = NCH(tree);
-    ok = validate_ntype(tree, decorators) && nch >= 1;
-
-    for (i = 0; ok && i < nch; ++i)
-        ok = validate_decorator(CHILD(tree, i));
-
-    return ok;
-}
-
-/*  with_item:
- *   test ['as' expr]
- */
-static int
-validate_with_item(node *tree)
-{
-    int nch = NCH(tree);
-    int ok = (validate_ntype(tree, with_item)
-              && (nch == 1 || nch == 3)
-              && validate_test(CHILD(tree, 0)));
-    if (ok && nch == 3)
-        ok = (validate_name(CHILD(tree, 1), "as")
-              && validate_expr(CHILD(tree, 2)));
-    return ok;
-}
-
-/*  with_stmt:
- *    0      1          ...             -2   -1
- *   'with' with_item (',' with_item)* ':' suite
- */
-static int
-validate_with_stmt(node *tree)
-{
-    int i;
-    int nch = NCH(tree);
-    int ok = (validate_ntype(tree, with_stmt)
-        && (nch % 2 == 0)
-        && validate_name(CHILD(tree, 0), "with")
-        && validate_colon(RCHILD(tree, -2))
-        && validate_suite(RCHILD(tree, -1)));
-    for (i = 1; ok && i < nch - 2; i += 2)
-        ok = validate_with_item(CHILD(tree, i));
-    return ok;
-}
-
-/* funcdef: 'def' NAME parameters ['->' test] ':' suite */
-
-static int
-validate_funcdef(node *tree)
-{
-    int nch = NCH(tree);
-    int res = validate_ntype(tree, funcdef);
-    if (res) {
-        if (nch == 5) {
-            res = (validate_name(CHILD(tree, 0), "def")
-                   && validate_ntype(CHILD(tree, 1), NAME)
-                   && validate_parameters(CHILD(tree, 2))
-                   && validate_colon(CHILD(tree, 3))
-                   && validate_suite(CHILD(tree, 4)));
-        }
-        else if (nch == 7) {
-            res = (validate_name(CHILD(tree, 0), "def")
-                   && validate_ntype(CHILD(tree, 1), NAME)
-                   && validate_parameters(CHILD(tree, 2))
-                   && validate_rarrow(CHILD(tree, 3))
-                   && validate_test(CHILD(tree, 4))
-                   && validate_colon(CHILD(tree, 5))
-                   && validate_suite(CHILD(tree, 6)));
-        }
-        else {
-            res = 0;
-            err_string("illegal number of children for funcdef");
-        }
-    }
-    return res;
-}
-
-/* async_funcdef: ASYNC funcdef */
-
-static int
-validate_async_funcdef(node *tree)
-{
-    int nch = NCH(tree);
-    int res = validate_ntype(tree, async_funcdef);
-    if (res) {
-        if (nch == 2) {
-            res = (validate_ntype(CHILD(tree, 0), ASYNC)
-                   && validate_funcdef(CHILD(tree, 1)));
-        }
-        else {
-            res = 0;
-            err_string("illegal number of children for async_funcdef");
-        }
-    }
-    return res;
-}
-
-
-/* async_stmt: ASYNC (funcdef | with_stmt | for_stmt) */
-
-static int
-validate_async_stmt(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, async_stmt)
-                && validate_ntype(CHILD(tree, 0), ASYNC));
-
-    if (nch != 2) {
-        res = 0;
-        err_string("illegal number of children for async_stmt");
-    } else {
-        if (TYPE(CHILD(tree, 1)) == funcdef) {
-            res = validate_funcdef(CHILD(tree, 1));
-        }
-        else if (TYPE(CHILD(tree, 1)) == with_stmt) {
-            res = validate_with_stmt(CHILD(tree, 1));
-        }
-        else if (TYPE(CHILD(tree, 1)) == for_stmt) {
-            res = validate_for(CHILD(tree, 1));
-        }
-    }
-
-    return res;
-}
-
-
-
-/* decorated
- *   decorators (classdef | funcdef)
- */
-static int
-validate_decorated(node *tree)
-{
-    int nch = NCH(tree);
-    int ok = (validate_ntype(tree, decorated)
-              && (nch == 2)
-              && validate_decorators(RCHILD(tree, -2)));
-    if (TYPE(RCHILD(tree, -1)) == funcdef)
-        ok = ok && validate_funcdef(RCHILD(tree, -1));
-    else
-        ok = ok && validate_class(RCHILD(tree, -1));
-    return ok;
-}
-
-static int
-validate_lambdef(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, lambdef)
-               && ((nch == 3) || (nch == 4))
-               && validate_name(CHILD(tree, 0), "lambda")
-               && validate_colon(CHILD(tree, nch - 2))
-               && validate_test(CHILD(tree, nch - 1)));
-
-    if (res && (nch == 4))
-        res = validate_varargslist(CHILD(tree, 1));
-    else if (!res && !PyErr_Occurred())
-        (void) validate_numnodes(tree, 3, "lambdef");
-
-    return (res);
-}
-
-
-static int
-validate_lambdef_nocond(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, lambdef_nocond)
-               && ((nch == 3) || (nch == 4))
-               && validate_name(CHILD(tree, 0), "lambda")
-               && validate_colon(CHILD(tree, nch - 2))
-               && validate_test(CHILD(tree, nch - 1)));
-
-    if (res && (nch == 4))
-        res = validate_varargslist(CHILD(tree, 1));
-    else if (!res && !PyErr_Occurred())
-        (void) validate_numnodes(tree, 3, "lambdef_nocond");
-
-    return (res);
-}
-
-
-/*  arglist:
- *
- *  (argument ',')* (argument [','] | '*' test [',' '**' test] | '**' test)
- */
-static int
-validate_arglist(node *tree)
-{
-    int nch = NCH(tree);
-    int i = 0;
-    int ok = 1;
-
-    if (nch <= 0)
-        /* raise the right error from having an invalid number of children */
-        return validate_numnodes(tree, nch + 1, "arglist");
-
-    if (nch > 1) {
-        for (i=0; i<nch; i++) {
-            if (TYPE(CHILD(tree, i)) == argument) {
-                node *ch = CHILD(tree, i);
-                if (NCH(ch) == 2 && TYPE(CHILD(ch, 1)) == comp_for) {
-                    err_string("need '(', ')' for generator expression");
-                    return 0;
-                }
-            }
-        }
-    }
-
-    while (ok && nch-i >= 2) {
-        /* skip leading (argument ',') */
-        ok = (validate_argument(CHILD(tree, i))
-              && validate_comma(CHILD(tree, i+1)));
-        if (ok)
-            i += 2;
-        else
-            PyErr_Clear();
-    }
-    ok = 1;
-    if (nch-i > 0) {
-        int sym = TYPE(CHILD(tree, i));
-
-        if (sym == argument) {
-            ok = validate_argument(CHILD(tree, i));
-            if (ok && i+1 != nch) {
-                err_string("illegal arglist specification"
-                           " (extra stuff on end)");
-                ok = 0;
-            }
-        }
-       else {
-            err_string("illegal arglist specification");
-            ok = 0;
-        }
-    }
-    return (ok);
-}
-
-
-
-/*  argument: ( test [comp_for] |
- *              test '=' test |
- *              '**' test |
- *              '*' test )
- */
-static int
-validate_argument(node *tree)
-{
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, argument)
-               && ((nch == 1) || (nch == 2) || (nch == 3)));
-
-    if (res) {
-        if (TYPE(CHILD(tree, 0)) == DOUBLESTAR) {
-            res = validate_test(CHILD(tree, 1));
-        }
-        else if (TYPE(CHILD(tree, 0)) == STAR) {
-            res = validate_test(CHILD(tree, 1));
-        }
-        else if (nch == 1) {
-            res = validate_test(CHILD(tree, 0));
-        }
-        else if (nch == 2) {
-            res = (validate_test(CHILD(tree, 0))
-                    && validate_comp_for(CHILD(tree, 1)));
-        }
-        else if (res && (nch == 3)) {
-            res = (validate_test(CHILD(tree, 0))
-                    && validate_equal(CHILD(tree, 1))
-                    && validate_test(CHILD(tree, 2)));
-        }
-    }
-    return (res);
-}
-
-
-
-/*  trailer:
- *
- *  '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME
- */
-static int
-validate_trailer(node *tree)
-{
-    int nch = NCH(tree);
-    int res = validate_ntype(tree, trailer) && ((nch == 2) || (nch == 3));
-
-    if (res) {
-        switch (TYPE(CHILD(tree, 0))) {
-          case LPAR:
-            res = validate_rparen(CHILD(tree, nch - 1));
-            if (res && (nch == 3))
-                res = validate_arglist(CHILD(tree, 1));
-            break;
-          case LSQB:
-            res = (validate_numnodes(tree, 3, "trailer")
-                   && validate_subscriptlist(CHILD(tree, 1))
-                   && validate_ntype(CHILD(tree, 2), RSQB));
-            break;
-          case DOT:
-            res = (validate_numnodes(tree, 2, "trailer")
-                   && validate_ntype(CHILD(tree, 1), NAME));
-            break;
-          default:
-            res = 0;
-            break;
-        }
-    }
-    else {
-        (void) validate_numnodes(tree, 2, "trailer");
-    }
-    return (res);
-}
-
-
-/*  subscriptlist:
- *
- *  subscript (',' subscript)* [',']
- */
-static int
-validate_subscriptlist(node *tree)
-{
-    return (validate_repeating_list(tree, subscriptlist,
-                                    validate_subscript, "subscriptlist"));
-}
-
-
-/*  subscript:
- *
- *  '.' '.' '.' | test | [test] ':' [test] [sliceop]
- */
-static int
-validate_subscript(node *tree)
-{
-    int offset = 0;
-    int nch = NCH(tree);
-    int res = validate_ntype(tree, subscript) && (nch >= 1) && (nch <= 4);
-
-    if (!res) {
-        if (!PyErr_Occurred())
-            err_string("invalid number of arguments for subscript node");
-        return (0);
-    }
-    if (TYPE(CHILD(tree, 0)) == DOT)
-        /* take care of ('.' '.' '.') possibility */
-        return (validate_numnodes(tree, 3, "subscript")
-                && validate_dot(CHILD(tree, 0))
-                && validate_dot(CHILD(tree, 1))
-                && validate_dot(CHILD(tree, 2)));
-    if (nch == 1) {
-        if (TYPE(CHILD(tree, 0)) == test)
-            res = validate_test(CHILD(tree, 0));
-        else
-            res = validate_colon(CHILD(tree, 0));
-        return (res);
-    }
-    /*  Must be [test] ':' [test] [sliceop],
-     *  but at least one of the optional components will
-     *  be present, but we don't know which yet.
-     */
-    if ((TYPE(CHILD(tree, 0)) != COLON) || (nch == 4)) {
-        res = validate_test(CHILD(tree, 0));
-        offset = 1;
-    }
-    if (res)
-        res = validate_colon(CHILD(tree, offset));
-    if (res) {
-        int rem = nch - ++offset;
-        if (rem) {
-            if (TYPE(CHILD(tree, offset)) == test) {
-                res = validate_test(CHILD(tree, offset));
-                ++offset;
-                --rem;
-            }
-            if (res && rem)
-                res = validate_sliceop(CHILD(tree, offset));
-        }
-    }
-    return (res);
-}
-
-
-static int
-validate_sliceop(node *tree)
-{
-    int nch = NCH(tree);
-    int res = ((nch == 1) || validate_numnodes(tree, 2, "sliceop"))
-              && validate_ntype(tree, sliceop);
-    if (!res && !PyErr_Occurred()) {
-        res = validate_numnodes(tree, 1, "sliceop");
-    }
-    if (res)
-        res = validate_colon(CHILD(tree, 0));
-    if (res && (nch == 2))
-        res = validate_test(CHILD(tree, 1));
-
-    return (res);
-}
-
-
-static int
-validate_test_or_star_expr(node *n)
-{
-    if (TYPE(n) == test)
-        return validate_test(n);
-    return validate_star_expr(n);
-}
-
-static int
-validate_expr_or_star_expr(node *n)
-{
-    if (TYPE(n) == expr)
-        return validate_expr(n);
-    return validate_star_expr(n);
-}
-
-
-static int
-validate_exprlist(node *tree)
-{
-    return (validate_repeating_list(tree, exprlist,
-                                    validate_expr_or_star_expr, "exprlist"));
-}
-
-/* Incrementing validate functions returns nonzero iff success (like other
- * validate functions, and advance *i by the length of the matched pattern. */
-
-/* test ':' test */
-static int
-validate_test_colon_test_inc(node *tree, int *i)
-{
-    return (validate_test(CHILD(tree, (*i)++))
-            && validate_colon(CHILD(tree, (*i)++))
-            && validate_test(CHILD(tree, (*i)++)));
-}
-
-/* test ':' test | '**' expr */
-static int
-validate_dict_element_inc(node *tree, int *i)
-{
-    int nch = NCH(tree);
-    int res = 0;
-    if (nch - *i >= 2) {
-        if (TYPE(CHILD(tree, *i+1)) == COLON) {
-            /* test ':' test */
-            res = validate_test_colon_test_inc(tree, i);
-        } else {
-            /* '**' expr */
-            res = (validate_doublestar(CHILD(tree, (*i)++))
-                    && validate_expr(CHILD(tree, (*i)++)));
-        }
-    }
-    return res;
-}
-
-/*
- *  dictorsetmaker:
- *
- *   ( ((test ':' test | '**' expr)
- *      (comp_for | (',' (test ':' test | '**' expr))* [','])) |
- *     ((test | '*' test)
- *      (comp_for | (',' (test | '*' test))* [','])) )
- */
-static int
-validate_dictorsetmaker(node *tree)
-{
-    int nch = NCH(tree);
-    int res;
-    int i = 0;
-
-    res = validate_ntype(tree, dictorsetmaker);
-    if (!res)
-        return 0;
-
-    if (nch - i < 1) {
-        /* Unconditionally raise. */
-        (void) validate_numnodes(tree, 1, "dictorsetmaker");
-        return 0;
-    }
-
-    if (nch - i >= 2
-        && ((TYPE(CHILD(tree, i+1)) == COLON) ||
-            (TYPE(CHILD(tree, i)) == DOUBLESTAR))) {
-        /* Dictionary display or dictionary comprehension. */
-        if (nch - i >= 4 && TYPE(CHILD(tree, i+3)) == comp_for) {
-            /* Dictionary comprehension. */
-            res = (validate_test_colon_test_inc(tree, &i)
-                    && validate_comp_for(CHILD(tree, i++)));
-            if (!res)
-                return 0;
-        } else {
-            /* Dictionary display. */
-            return validate_repeating_list_variable(
-                    tree,
-                    dictorsetmaker,
-                    validate_dict_element_inc,
-                    &i,
-                    "dictorsetmaker");
-        }
-    } else {
-        /* Set display or set comprehension. */
-        if (nch - i >= 2 && TYPE(CHILD(tree, i + 1)) == comp_for) {
-            /* Set comprehension. */
-            res = (validate_test(CHILD(tree, i++))
-                   && validate_comp_for(CHILD(tree, i++)));
-            if (!res)
-                return 0;
-        } else {
-            /* Set display. */
-           return validate_repeating_list(tree,
-                                          dictorsetmaker,
-                                          validate_test_or_star_expr,
-                                          "dictorsetmaker");
-        }
-    }
-
-    if (nch - i > 0) {
-        err_string("Illegal trailing nodes for dictorsetmaker.");
-        return 0;
-    }
-
-    return 1;
-}
-
-
-static int
-validate_eval_input(node *tree)
-{
-    int pos;
-    int nch = NCH(tree);
-    int res = (validate_ntype(tree, eval_input)
-               && (nch >= 2)
-               && validate_testlist(CHILD(tree, 0))
-               && validate_ntype(CHILD(tree, nch - 1), ENDMARKER));
-
-    for (pos = 1; res && (pos < (nch - 1)); ++pos)
-        res = validate_ntype(CHILD(tree, pos), NEWLINE);
-
-    return (res);
-}
-
-
-static int
-validate_node(node *tree)
-{
-    int   nch  = 0;                     /* num. children on current node  */
-    int   res  = 1;                     /* result value                   */
-    node* next = 0;                     /* node to process after this one */
-
-    while (res && (tree != 0)) {
-        nch  = NCH(tree);
-        next = 0;
-        switch (TYPE(tree)) {
-            /*
-             *  Definition nodes.
-             */
-          case async_funcdef:
-            res = validate_async_funcdef(tree);
-            break;
-          case async_stmt:
-            res = validate_async_stmt(tree);
-            break;
-          case funcdef:
-            res = validate_funcdef(tree);
-            break;
-          case with_stmt:
-            res = validate_with_stmt(tree);
-            break;
-          case classdef:
-            res = validate_class(tree);
-            break;
-          case decorated:
-            res = validate_decorated(tree);
-            break;
-            /*
-             *  "Trivial" parse tree nodes.
-             *  (Why did I call these trivial?)
-             */
-          case stmt:
-            res = validate_stmt(tree);
-            break;
-          case small_stmt:
-            /*
-             *  expr_stmt | del_stmt | pass_stmt | flow_stmt |
-             *  import_stmt | global_stmt | nonlocal_stmt | assert_stmt
-             */
-            res = validate_small_stmt(tree);
-            break;
-          case flow_stmt:
-            res  = (validate_numnodes(tree, 1, "flow_stmt")
-                    && ((TYPE(CHILD(tree, 0)) == break_stmt)
-                        || (TYPE(CHILD(tree, 0)) == continue_stmt)
-                        || (TYPE(CHILD(tree, 0)) == yield_stmt)
-                        || (TYPE(CHILD(tree, 0)) == return_stmt)
-                        || (TYPE(CHILD(tree, 0)) == raise_stmt)));
-            if (res)
-                next = CHILD(tree, 0);
-            else if (nch == 1)
-                err_string("illegal flow_stmt type");
-            break;
-          case yield_stmt:
-            res = validate_yield_stmt(tree);
-            break;
-            /*
-             *  Compound statements.
-             */
-          case simple_stmt:
-            res = validate_simple_stmt(tree);
-            break;
-          case compound_stmt:
-            res = validate_compound_stmt(tree);
-            break;
-            /*
-             *  Fundamental statements.
-             */
-          case expr_stmt:
-            res = validate_expr_stmt(tree);
-            break;
-          case del_stmt:
-            res = validate_del_stmt(tree);
-            break;
-          case pass_stmt:
-            res = (validate_numnodes(tree, 1, "pass")
-                   && validate_name(CHILD(tree, 0), "pass"));
-            break;
-          case break_stmt:
-            res = (validate_numnodes(tree, 1, "break")
-                   && validate_name(CHILD(tree, 0), "break"));
-            break;
-          case continue_stmt:
-            res = (validate_numnodes(tree, 1, "continue")
-                   && validate_name(CHILD(tree, 0), "continue"));
-            break;
-          case return_stmt:
-            res = validate_return_stmt(tree);
-            break;
-          case raise_stmt:
-            res = validate_raise_stmt(tree);
-            break;
-          case import_stmt:
-            res = validate_import_stmt(tree);
-            break;
-          case import_name:
-            res = validate_import_name(tree);
-            break;
-          case import_from:
-            res = validate_import_from(tree);
-            break;
-          case global_stmt:
-            res = validate_global_stmt(tree);
-            break;
-          case nonlocal_stmt:
-            res = validate_nonlocal_stmt(tree);
-            break;
-          case assert_stmt:
-            res = validate_assert_stmt(tree);
-            break;
-          case if_stmt:
-            res = validate_if(tree);
-            break;
-          case while_stmt:
-            res = validate_while(tree);
-            break;
-          case for_stmt:
-            res = validate_for(tree);
-            break;
-          case try_stmt:
-            res = validate_try(tree);
-            break;
-          case suite:
-            res = validate_suite(tree);
-            break;
-            /*
-             *  Expression nodes.
-             */
-          case testlist:
-            res = validate_testlist(tree);
-            break;
-          case yield_expr:
-            res = validate_yield_expr(tree);
-            break;
-          case test:
-            res = validate_test(tree);
-            break;
-          case and_test:
-            res = validate_and_test(tree);
-            break;
-          case not_test:
-            res = validate_not_test(tree);
-            break;
-          case comparison:
-            res = validate_comparison(tree);
-            break;
-          case exprlist:
-            res = validate_exprlist(tree);
-            break;
-          case comp_op:
-            res = validate_comp_op(tree);
-            break;
-          case expr:
-            res = validate_expr(tree);
-            break;
-          case xor_expr:
-            res = validate_xor_expr(tree);
-            break;
-          case and_expr:
-            res = validate_and_expr(tree);
-            break;
-          case shift_expr:
-            res = validate_shift_expr(tree);
-            break;
-          case arith_expr:
-            res = validate_arith_expr(tree);
-            break;
-          case term:
-            res = validate_term(tree);
-            break;
-          case factor:
-            res = validate_factor(tree);
-            break;
-          case power:
-            res = validate_power(tree);
-            break;
-          case atom:
-            res = validate_atom(tree);
-            break;
-
-          default:
-            /* Hopefully never reached! */
-            err_string("unrecognized node type");
-            res = 0;
-            break;
-        }
-        tree = next;
-    }
-    return (res);
-}
-
-
-static int
-validate_expr_tree(node *tree)
-{
-    int res = validate_eval_input(tree);
-
-    if (!res && !PyErr_Occurred())
-        err_string("could not validate expression tuple");
-
-    return (res);
-}
-
-
-/*  file_input:
- *      (NEWLINE | stmt)* ENDMARKER
- */
-static int
-validate_file_input(node *tree)
-{
-    int j;
-    int nch = NCH(tree) - 1;
-    int res = ((nch >= 0)
-               && validate_ntype(CHILD(tree, nch), ENDMARKER));
-
-    for (j = 0; res && (j < nch); ++j) {
-        if (TYPE(CHILD(tree, j)) == stmt)
-            res = validate_stmt(CHILD(tree, j));
-        else
-            res = validate_newline(CHILD(tree, j));
-    }
-    /*  This stays in to prevent any internal failures from getting to the
-     *  user.  Hopefully, this won't be needed.  If a user reports getting
-     *  this, we have some debugging to do.
-     */
-    if (!res && !PyErr_Occurred())
-        err_string("VALIDATION FAILURE: report this to the maintainer!");
-
-    return (res);
-}
-
-static int
-validate_encoding_decl(node *tree)
-{
-    int nch = NCH(tree);
-    int res = ((nch == 1)
-        && validate_file_input(CHILD(tree, 0)));
-
-    if (!res && !PyErr_Occurred())
-        err_string("Error Parsing encoding_decl");
-
-    return res;
-}
-
 static PyObject*
 pickle_constructor = NULL;