ast.c

/*
 * This file includes functions to transform a concrete syntax tree (CST) to
 * an abstract syntax tree (AST). The main function is PyAST_FromNode().
 *
 */
#include "Python.h"
#include "Python-ast.h"
#include "node.h"
#include "ast.h"
#include "token.h"
#include "pythonrun.h"

#include <assert.h>
#include <stdbool.h>

#define MAXLEVEL 200    /* Max parentheses level */

static int validate_stmts(asdl_seq *);
static int validate_exprs(asdl_seq *, expr_context_ty, int);
static int validate_nonempty_seq(asdl_seq *, const char *, const char *);
static int validate_stmt(stmt_ty);
static int validate_expr(expr_ty, expr_context_ty);

static int
validate_comprehension(asdl_seq *gens)
{
    Py_ssize_t i;
    if (!asdl_seq_LEN(gens)) {
        PyErr_SetString(PyExc_ValueError, "comprehension with no generators");
        return 0;
    }
    for (i = 0; i < asdl_seq_LEN(gens); i++) {
        comprehension_ty comp = asdl_seq_GET(gens, i);
        if (!validate_expr(comp->target, Store) ||
            !validate_expr(comp->iter, Load) ||
            !validate_exprs(comp->ifs, Load, 0))
            return 0;
    }
    return 1;
}

static int
validate_slice(slice_ty slice)
{
    switch (slice->kind) {
    case Slice_kind:
        return (!slice->v.Slice.lower || validate_expr(slice->v.Slice.lower, Load)) &&
            (!slice->v.Slice.upper || validate_expr(slice->v.Slice.upper, Load)) &&
            (!slice->v.Slice.step || validate_expr(slice->v.Slice.step, Load));
    case ExtSlice_kind: {
        Py_ssize_t i;
        if (!validate_nonempty_seq(slice->v.ExtSlice.dims, "dims", "ExtSlice"))
            return 0;
        for (i = 0; i < asdl_seq_LEN(slice->v.ExtSlice.dims); i++)
            if (!validate_slice(asdl_seq_GET(slice->v.ExtSlice.dims, i)))
                return 0;
        return 1;
    }
    case Index_kind:
        return validate_expr(slice->v.Index.value, Load);
    default:
        PyErr_SetString(PyExc_SystemError, "unknown slice node");
        return 0;
    }
}

static int
validate_keywords(asdl_seq *keywords)
{
    Py_ssize_t i;
    for (i = 0; i < asdl_seq_LEN(keywords); i++)
        if (!validate_expr(((keyword_ty)asdl_seq_GET(keywords, i))->value, Load))
            return 0;
    return 1;
}

static int
validate_args(asdl_seq *args)
{
    Py_ssize_t i;
    for (i = 0; i < asdl_seq_LEN(args); i++) {
        arg_ty arg = asdl_seq_GET(args, i);
        if (arg->annotation && !validate_expr(arg->annotation, Load))
            return 0;
    }
    return 1;
}

static const char *
expr_context_name(expr_context_ty ctx)
{
    switch (ctx) {
    case Load:
        return "Load";
    case Store:
        return "Store";
    case Del:
        return "Del";
    case AugLoad:
        return "AugLoad";
    case AugStore:
        return "AugStore";
    case Param:
        return "Param";
    default:
        Py_UNREACHABLE();
    }
}

static int
validate_arguments(arguments_ty args)
{
    if (!validate_args(args->args))
        return 0;
    if (args->vararg && args->vararg->annotation
        && !validate_expr(args->vararg->annotation, Load)) {
            return 0;
    }
    if (!validate_args(args->kwonlyargs))
        return 0;
    if (args->kwarg && args->kwarg->annotation
        && !validate_expr(args->kwarg->annotation, Load)) {
            return 0;
    }
    if (asdl_seq_LEN(args->defaults) > asdl_seq_LEN(args->args)) {
        PyErr_SetString(PyExc_ValueError, "more positional defaults than args on arguments");
        return 0;
    }
    if (asdl_seq_LEN(args->kw_defaults) != asdl_seq_LEN(args->kwonlyargs)) {
        PyErr_SetString(PyExc_ValueError, "length of kwonlyargs is not the same as "
                        "kw_defaults on arguments");
        return 0;
    }
    return validate_exprs(args->defaults, Load, 0) && validate_exprs(args->kw_defaults, Load, 1);
}

static int
validate_constant(PyObject *value)
{
    if (value == Py_None || value == Py_Ellipsis)
        return 1;

    if (PyLong_CheckExact(value)
            || PyFloat_CheckExact(value)
            || PyComplex_CheckExact(value)
            || PyBool_Check(value)
            || PyUnicode_CheckExact(value)
            || PyBytes_CheckExact(value))
        return 1;

    if (PyTuple_CheckExact(value) || PyFrozenSet_CheckExact(value)) {
        PyObject *it;

        it = PyObject_GetIter(value);
        if (it == NULL)
            return 0;

        while (1) {
            PyObject *item = PyIter_Next(it);
            if (item == NULL) {
                if (PyErr_Occurred()) {
                    Py_DECREF(it);
                    return 0;
                }
                break;
            }

            if (!validate_constant(item)) {
                Py_DECREF(it);
                Py_DECREF(item);
                return 0;
            }
            Py_DECREF(item);
        }

        Py_DECREF(it);
        return 1;
    }

    return 0;
}

static int
validate_expr(expr_ty exp, expr_context_ty ctx)
{
    int check_ctx = 1;
    expr_context_ty actual_ctx;

    /* First check expression context. */
    switch (exp->kind) {
    case Attribute_kind:
        actual_ctx = exp->v.Attribute.ctx;
        break;
    case Subscript_kind:
        actual_ctx = exp->v.Subscript.ctx;
        break;
    case Starred_kind:
        actual_ctx = exp->v.Starred.ctx;
        break;
    case Name_kind:
        actual_ctx = exp->v.Name.ctx;
        break;
    case List_kind:
        actual_ctx = exp->v.List.ctx;
        break;
    case Tuple_kind:
        actual_ctx = exp->v.Tuple.ctx;
        break;
    default:
        if (ctx != Load) {
            PyErr_Format(PyExc_ValueError, "expression which can't be "
                         "assigned to in %s context", expr_context_name(ctx));
            return 0;
        }
        check_ctx = 0;
        /* set actual_ctx to prevent gcc warning */
        actual_ctx = 0;
    }
    if (check_ctx && actual_ctx != ctx) {
        PyErr_Format(PyExc_ValueError, "expression must have %s context but has %s instead",
                     expr_context_name(ctx), expr_context_name(actual_ctx));
        return 0;
    }

    /* Now validate expression. */
    switch (exp->kind) {
    case BoolOp_kind:
        if (asdl_seq_LEN(exp->v.BoolOp.values) < 2) {
            PyErr_SetString(PyExc_ValueError, "BoolOp with less than 2 values");
            return 0;
        }
        return validate_exprs(exp->v.BoolOp.values, Load, 0);
    case BinOp_kind:
        return validate_expr(exp->v.BinOp.left, Load) &&
            validate_expr(exp->v.BinOp.right, Load);
    case UnaryOp_kind:
        return validate_expr(exp->v.UnaryOp.operand, Load);
    case Lambda_kind:
        return validate_arguments(exp->v.Lambda.args) &&
            validate_expr(exp->v.Lambda.body, Load);
    case IfExp_kind:
        return validate_expr(exp->v.IfExp.test, Load) &&
            validate_expr(exp->v.IfExp.body, Load) &&
            validate_expr(exp->v.IfExp.orelse, Load);
    case Dict_kind:
        if (asdl_seq_LEN(exp->v.Dict.keys) != asdl_seq_LEN(exp->v.Dict.values)) {
            PyErr_SetString(PyExc_ValueError,
                            "Dict doesn't have the same number of keys as values");
            return 0;
        }
        /* null_ok=1 for keys expressions to allow dict unpacking to work in
           dict literals, i.e. ``{**{a:b}}`` */
        return validate_exprs(exp->v.Dict.keys, Load, /*null_ok=*/ 1) &&
            validate_exprs(exp->v.Dict.values, Load, /*null_ok=*/ 0);
    case Set_kind:
        return validate_exprs(exp->v.Set.elts, Load, 0);
#define COMP(NAME) \
        case NAME ## _kind: \
            return validate_comprehension(exp->v.NAME.generators) && \
                validate_expr(exp->v.NAME.elt, Load);
    COMP(ListComp)
    COMP(SetComp)
    COMP(GeneratorExp)
#undef COMP
    case DictComp_kind:
        return validate_comprehension(exp->v.DictComp.generators) &&
            validate_expr(exp->v.DictComp.key, Load) &&
            validate_expr(exp->v.DictComp.value, Load);
    case Yield_kind:
        return !exp->v.Yield.value || validate_expr(exp->v.Yield.value, Load);
    case YieldFrom_kind:
        return validate_expr(exp->v.YieldFrom.value, Load);
    case Await_kind:
        return validate_expr(exp->v.Await.value, Load);
    case Compare_kind:
        if (!asdl_seq_LEN(exp->v.Compare.comparators)) {
            PyErr_SetString(PyExc_ValueError, "Compare with no comparators");
            return 0;
        }
        if (asdl_seq_LEN(exp->v.Compare.comparators) !=
            asdl_seq_LEN(exp->v.Compare.ops)) {
            PyErr_SetString(PyExc_ValueError, "Compare has a different number "
                            "of comparators and operands");
            return 0;
        }
        return validate_exprs(exp->v.Compare.comparators, Load, 0) &&
            validate_expr(exp->v.Compare.left, Load);
    case Call_kind:
        return validate_expr(exp->v.Call.func, Load) &&
            validate_exprs(exp->v.Call.args, Load, 0) &&
            validate_keywords(exp->v.Call.keywords);
    case Constant_kind:
        if (!validate_constant(exp->v.Constant.value)) {
            PyErr_Format(PyExc_TypeError,
                         "got an invalid type in Constant: %s",
                         Py_TYPE(exp->v.Constant.value)->tp_name);
            return 0;
        }
        return 1;
    case JoinedStr_kind:
        return validate_exprs(exp->v.JoinedStr.values, Load, 0);
    case FormattedValue_kind:
        if (validate_expr(exp->v.FormattedValue.value, Load) == 0)
            return 0;
        if (exp->v.FormattedValue.format_spec)
            return validate_expr(exp->v.FormattedValue.format_spec, Load);
        return 1;
    case Attribute_kind:
        return validate_expr(exp->v.Attribute.value, Load);
    case Subscript_kind:
        return validate_slice(exp->v.Subscript.slice) &&
            validate_expr(exp->v.Subscript.value, Load);
    case Starred_kind:
        return validate_expr(exp->v.Starred.value, ctx);
    case List_kind:
        return validate_exprs(exp->v.List.elts, ctx, 0);
    case Tuple_kind:
        return validate_exprs(exp->v.Tuple.elts, ctx, 0);
    /* This last case doesn't have any checking. */
    case Name_kind:
        return 1;
    default:
        PyErr_SetString(PyExc_SystemError, "unexpected expression");
        return 0;
    }
}

static int
validate_nonempty_seq(asdl_seq *seq, const char *what, const char *owner)
{
    if (asdl_seq_LEN(seq))
        return 1;
    PyErr_Format(PyExc_ValueError, "empty %s on %s", what, owner);
    return 0;
}

static int
validate_assignlist(asdl_seq *targets, expr_context_ty ctx)
{
    return validate_nonempty_seq(targets, "targets", ctx == Del ? "Delete" : "Assign") &&
        validate_exprs(targets, ctx, 0);
}

static int
validate_body(asdl_seq *body, const char *owner)
{
    return validate_nonempty_seq(body, "body", owner) && validate_stmts(body);
}

static int
validate_stmt(stmt_ty stmt)
{
    Py_ssize_t i;
    switch (stmt->kind) {
    case FunctionDef_kind:
        return validate_body(stmt->v.FunctionDef.body, "FunctionDef") &&
            validate_arguments(stmt->v.FunctionDef.args) &&
            validate_exprs(stmt->v.FunctionDef.decorator_list, Load, 0) &&
            (!stmt->v.FunctionDef.returns ||
             validate_expr(stmt->v.FunctionDef.returns, Load));
    case ClassDef_kind:
        return validate_body(stmt->v.ClassDef.body, "ClassDef") &&
            validate_exprs(stmt->v.ClassDef.bases, Load, 0) &&
            validate_keywords(stmt->v.ClassDef.keywords) &&
            validate_exprs(stmt->v.ClassDef.decorator_list, Load, 0);
    case Return_kind:
        return !stmt->v.Return.value || validate_expr(stmt->v.Return.value, Load);
    case Delete_kind:
        return validate_assignlist(stmt->v.Delete.targets, Del);
    case Assign_kind:
        return validate_assignlist(stmt->v.Assign.targets, Store) &&
            validate_expr(stmt->v.Assign.value, Load);
    case AugAssign_kind:
        return validate_expr(stmt->v.AugAssign.target, Store) &&
            validate_expr(stmt->v.AugAssign.value, Load);
    case AnnAssign_kind:
        if (stmt->v.AnnAssign.target->kind != Name_kind &&
            stmt->v.AnnAssign.simple) {
            PyErr_SetString(PyExc_TypeError,
                            "AnnAssign with simple non-Name target");
            return 0;
        }
        return validate_expr(stmt->v.AnnAssign.target, Store) &&
               (!stmt->v.AnnAssign.value ||
                validate_expr(stmt->v.AnnAssign.value, Load)) &&
               validate_expr(stmt->v.AnnAssign.annotation, Load);
    case For_kind:
        return validate_expr(stmt->v.For.target, Store) &&
            validate_expr(stmt->v.For.iter, Load) &&
            validate_body(stmt->v.For.body, "For") &&
            validate_stmts(stmt->v.For.orelse);
    case AsyncFor_kind:
        return validate_expr(stmt->v.AsyncFor.target, Store) &&
            validate_expr(stmt->v.AsyncFor.iter, Load) &&
            validate_body(stmt->v.AsyncFor.body, "AsyncFor") &&
            validate_stmts(stmt->v.AsyncFor.orelse);
    case While_kind:
        return validate_expr(stmt->v.While.test, Load) &&
            validate_body(stmt->v.While.body, "While") &&
            validate_stmts(stmt->v.While.orelse);
    case If_kind:
        return validate_expr(stmt->v.If.test, Load) &&
            validate_body(stmt->v.If.body, "If") &&
            validate_stmts(stmt->v.If.orelse);
    case With_kind:
        if (!validate_nonempty_seq(stmt->v.With.items, "items", "With"))
            return 0;
        for (i = 0; i < asdl_seq_LEN(stmt->v.With.items); i++) {
            withitem_ty item = asdl_seq_GET(stmt->v.With.items, i);
            if (!validate_expr(item->context_expr, Load) ||
                (item->optional_vars && !validate_expr(item->optional_vars, Store)))
                return 0;
        }
        return validate_body(stmt->v.With.body, "With");
    case AsyncWith_kind:
        if (!validate_nonempty_seq(stmt->v.AsyncWith.items, "items", "AsyncWith"))
            return 0;
        for (i = 0; i < asdl_seq_LEN(stmt->v.AsyncWith.items); i++) {
            withitem_ty item = asdl_seq_GET(stmt->v.AsyncWith.items, i);
            if (!validate_expr(item->context_expr, Load) ||
                (item->optional_vars && !validate_expr(item->optional_vars, Store)))
                return 0;
        }
        return validate_body(stmt->v.AsyncWith.body, "AsyncWith");
    case Raise_kind:
        if (stmt->v.Raise.exc) {
            return validate_expr(stmt->v.Raise.exc, Load) &&
                (!stmt->v.Raise.cause || validate_expr(stmt->v.Raise.cause, Load));
        }
        if (stmt->v.Raise.cause) {
            PyErr_SetString(PyExc_ValueError, "Raise with cause but no exception");
            return 0;
        }
        return 1;
    case Try_kind:
        if (!validate_body(stmt->v.Try.body, "Try"))
            return 0;
        if (!asdl_seq_LEN(stmt->v.Try.handlers) &&
            !asdl_seq_LEN(stmt->v.Try.finalbody)) {
            PyErr_SetString(PyExc_ValueError, "Try has neither except handlers nor finalbody");
            return 0;
        }
        if (!asdl_seq_LEN(stmt->v.Try.handlers) &&
            asdl_seq_LEN(stmt->v.Try.orelse)) {
            PyErr_SetString(PyExc_ValueError, "Try has orelse but no except handlers");
            return 0;
        }
        for (i = 0; i < asdl_seq_LEN(stmt->v.Try.handlers); i++) {
            excepthandler_ty handler = asdl_seq_GET(stmt->v.Try.handlers, i);
            if ((handler->v.ExceptHandler.type &&
                 !validate_expr(handler->v.ExceptHandler.type, Load)) ||
                !validate_body(handler->v.ExceptHandler.body, "ExceptHandler"))
                return 0;
        }
        return (!asdl_seq_LEN(stmt->v.Try.finalbody) ||
                validate_stmts(stmt->v.Try.finalbody)) &&
            (!asdl_seq_LEN(stmt->v.Try.orelse) ||
             validate_stmts(stmt->v.Try.orelse));
    case Assert_kind:
        return validate_expr(stmt->v.Assert.test, Load) &&
            (!stmt->v.Assert.msg || validate_expr(stmt->v.Assert.msg, Load));
    case Import_kind:
        return validate_nonempty_seq(stmt->v.Import.names, "names", "Import");
    case ImportFrom_kind:
        if (stmt->v.ImportFrom.level < 0) {
            PyErr_SetString(PyExc_ValueError, "Negative ImportFrom level");
            return 0;
        }
        return validate_nonempty_seq(stmt->v.ImportFrom.names, "names", "ImportFrom");
    case Global_kind:
        return validate_nonempty_seq(stmt->v.Global.names, "names", "Global");
    case Nonlocal_kind:
        return validate_nonempty_seq(stmt->v.Nonlocal.names, "names", "Nonlocal");
    case Expr_kind:
        return validate_expr(stmt->v.Expr.value, Load);
    case AsyncFunctionDef_kind:
        return validate_body(stmt->v.AsyncFunctionDef.body, "AsyncFunctionDef") &&
            validate_arguments(stmt->v.AsyncFunctionDef.args) &&
            validate_exprs(stmt->v.AsyncFunctionDef.decorator_list, Load, 0) &&
            (!stmt->v.AsyncFunctionDef.returns ||
             validate_expr(stmt->v.AsyncFunctionDef.returns, Load));
    case Pass_kind:
    case Break_kind:
    case Continue_kind:
        return 1;
    default:
        PyErr_SetString(PyExc_SystemError, "unexpected statement");
        return 0;
    }
}

static int
validate_stmts(asdl_seq *seq)
{
    Py_ssize_t i;
    for (i = 0; i < asdl_seq_LEN(seq); i++) {
        stmt_ty stmt = asdl_seq_GET(seq, i);
        if (stmt) {
            if (!validate_stmt(stmt))
                return 0;
        }
        else {
            PyErr_SetString(PyExc_ValueError,
                            "None disallowed in statement list");
            return 0;
        }
    }
    return 1;
}

static int
validate_exprs(asdl_seq *exprs, expr_context_ty ctx, int null_ok)
{
    Py_ssize_t i;
    for (i = 0; i < asdl_seq_LEN(exprs); i++) {
        expr_ty expr = asdl_seq_GET(exprs, i);
        if (expr) {
            if (!validate_expr(expr, ctx))
                return 0;
        }
        else if (!null_ok) {
            PyErr_SetString(PyExc_ValueError,
                            "None disallowed in expression list");
            return 0;
        }

    }
    return 1;
}

int
PyAST_Validate(mod_ty mod)
{
    int res = 0;

    switch (mod->kind) {
    case Module_kind:
        res = validate_stmts(mod->v.Module.body);
        break;
    case Interactive_kind:
        res = validate_stmts(mod->v.Interactive.body);
        break;
    case Expression_kind:
        res = validate_expr(mod->v.Expression.body, Load);
        break;
    case Suite_kind:
        PyErr_SetString(PyExc_ValueError, "Suite is not valid in the CPython compiler");
        break;
    default:
        PyErr_SetString(PyExc_SystemError, "impossible module node");
        res = 0;
        break;
    }
    return res;
}

/* This is done here, so defines like "test" don't interfere with AST use above. */
#include "grammar.h"
#include "parsetok.h"
#include "graminit.h"

/* Data structure used internally */
struct compiling {
    PyArena *c_arena; /* Arena for allocating memory. */
    PyObject *c_filename; /* filename */
    PyObject *c_normalize; /* Normalization function from unicodedata. */
};

static asdl_seq *seq_for_testlist(struct compiling *, const node *);
static expr_ty ast_for_expr(struct compiling *, const node *);
static stmt_ty ast_for_stmt(struct compiling *, const node *);
static asdl_seq *ast_for_suite(struct compiling *c, const node *n);
static asdl_seq *ast_for_exprlist(struct compiling *, const node *,
                                  expr_context_ty);
static expr_ty ast_for_testlist(struct compiling *, const node *);
static stmt_ty ast_for_classdef(struct compiling *, const node *, asdl_seq *);

static stmt_ty ast_for_with_stmt(struct compiling *, const node *, bool);
static stmt_ty ast_for_for_stmt(struct compiling *, const node *, bool);

/* Note different signature for ast_for_call */
static expr_ty ast_for_call(struct compiling *, const node *, expr_ty,
                            const node *, const node *);

static PyObject *parsenumber(struct compiling *, const char *);
static expr_ty parsestrplus(struct compiling *, const node *n);
static void get_last_end_pos(asdl_seq *, int *, int *);

#define COMP_GENEXP   0
#define COMP_LISTCOMP 1
#define COMP_SETCOMP  2

static int
init_normalization(struct compiling *c)
{
    PyObject *m = PyImport_ImportModuleNoBlock("unicodedata");
    if (!m)
        return 0;
    c->c_normalize = PyObject_GetAttrString(m, "normalize");
    Py_DECREF(m);
    if (!c->c_normalize)
        return 0;
    return 1;
}

static identifier
new_identifier(const char *n, struct compiling *c)
{
    PyObject *id = PyUnicode_DecodeUTF8(n, strlen(n), NULL);
    if (!id)
        return NULL;
    /* PyUnicode_DecodeUTF8 should always return a ready string. */
    assert(PyUnicode_IS_READY(id));
    /* Check whether there are non-ASCII characters in the
       identifier; if so, normalize to NFKC. */
    if (!PyUnicode_IS_ASCII(id)) {
        PyObject *id2;
        _Py_IDENTIFIER(NFKC);
        if (!c->c_normalize && !init_normalization(c)) {
            Py_DECREF(id);
            return NULL;
        }
        PyObject *form = _PyUnicode_FromId(&PyId_NFKC);
        if (form == NULL) {
            Py_DECREF(id);
            return NULL;
        }
        PyObject *args[2] = {form, id};
        id2 = _PyObject_FastCall(c->c_normalize, args, 2);
        Py_DECREF(id);
        if (!id2)
            return NULL;
        if (!PyUnicode_Check(id2)) {
            PyErr_Format(PyExc_TypeError,
                         "unicodedata.normalize() must return a string, not "
                         "%.200s",
                         Py_TYPE(id2)->tp_name);
            Py_DECREF(id2);
            return NULL;
        }
        id = id2;
    }
    PyUnicode_InternInPlace(&id);
    if (PyArena_AddPyObject(c->c_arena, id) < 0) {
        Py_DECREF(id);
        return NULL;
    }
    return id;
}

#define NEW_IDENTIFIER(n) new_identifier(STR(n), c)

static int
ast_error(struct compiling *c, const node *n, const char *errmsg, ...)
{
    PyObject *value, *errstr, *loc, *tmp;
    va_list va;

    va_start(va, errmsg);
    errstr = PyUnicode_FromFormatV(errmsg, va);
    va_end(va);
    if (!errstr) {
        return 0;
    }
    loc = PyErr_ProgramTextObject(c->c_filename, LINENO(n));
    if (!loc) {
        Py_INCREF(Py_None);
        loc = Py_None;
    }
    tmp = Py_BuildValue("(OiiN)", c->c_filename, LINENO(n), n->n_col_offset + 1, loc);
    if (!tmp) {
        Py_DECREF(errstr);
        return 0;
    }
    value = PyTuple_Pack(2, errstr, tmp);
    Py_DECREF(errstr);
    Py_DECREF(tmp);
    if (value) {
        PyErr_SetObject(PyExc_SyntaxError, value);
        Py_DECREF(value);
    }
    return 0;
}

/* num_stmts() returns number of contained statements.

   Use this routine to determine how big a sequence is needed for
   the statements in a parse tree.  Its raison d'etre is this bit of
   grammar:

   stmt: simple_stmt | compound_stmt
   simple_stmt: small_stmt (';' small_stmt)* [';'] NEWLINE

   A simple_stmt can contain multiple small_stmt elements joined
   by semicolons.  If the arg is a simple_stmt, the number of
   small_stmt elements is returned.
*/

static string
new_type_comment(const char *s, struct compiling *c)
{
    PyObject *res = PyUnicode_DecodeUTF8(s, strlen(s), NULL);
    if (res == NULL)
        return NULL;
    if (PyArena_AddPyObject(c->c_arena, res) < 0) {
        Py_DECREF(res);
        return NULL;
    }
    return res;
}
#define NEW_TYPE_COMMENT(n) new_type_comment(STR(n), c)

static int
num_stmts(const node *n)
{
    int i, l;
    node *ch;

    switch (TYPE(n)) {
        case single_input:
            if (TYPE(CHILD(n, 0)) == NEWLINE)
                return 0;
            else
                return num_stmts(CHILD(n, 0));
        case file_input:
            l = 0;
            for (i = 0; i < NCH(n); i++) {
                ch = CHILD(n, i);
                if (TYPE(ch) == stmt)
                    l += num_stmts(ch);
            }
            return l;
        case stmt:
            return num_stmts(CHILD(n, 0));
        case compound_stmt:
            return 1;
        case simple_stmt:
            return NCH(n) / 2; /* Divide by 2 to remove count of semi-colons */
        case suite:
        case func_body_suite:
            /* func_body_suite: simple_stmt | NEWLINE [TYPE_COMMENT NEWLINE] INDENT stmt+ DEDENT */
            /* suite: simple_stmt | NEWLINE INDENT stmt+ DEDENT */
            if (NCH(n) == 1)
                return num_stmts(CHILD(n, 0));
            else {
                i = 2;
                l = 0;
                if (TYPE(CHILD(n, 1)) == TYPE_COMMENT)
                    i += 2;
                for (; i < (NCH(n) - 1); i++)
                    l += num_stmts(CHILD(n, i));
                return l;
            }
        default: {
            char buf[128];

            sprintf(buf, "Non-statement found: %d %d",
                    TYPE(n), NCH(n));
            Py_FatalError(buf);
        }
    }
    Py_UNREACHABLE();
}

/* Transform the CST rooted at node * to the appropriate AST
*/

mod_ty
PyAST_FromNodeObject(const node *n, PyCompilerFlags *flags,
                     PyObject *filename, PyArena *arena)
{
    int i, j, k, num;
    asdl_seq *stmts = NULL;
    asdl_seq *type_ignores = NULL;
    stmt_ty s;
    node *ch;
    struct compiling c;
    mod_ty res = NULL;
    asdl_seq *argtypes = NULL;
    expr_ty ret, arg;

    c.c_arena = arena;
    /* borrowed reference */
    c.c_filename = filename;
    c.c_normalize = NULL;

    if (TYPE(n) == encoding_decl)
        n = CHILD(n, 0);

    k = 0;
    switch (TYPE(n)) {
        case file_input:
            stmts = _Py_asdl_seq_new(num_stmts(n), arena);
            if (!stmts)
                goto out;
            for (i = 0; i < NCH(n) - 1; i++) {
                ch = CHILD(n, i);
                if (TYPE(ch) == NEWLINE)
                    continue;
                REQ(ch, stmt);
                num = num_stmts(ch);
                if (num == 1) {
                    s = ast_for_stmt(&c, ch);
                    if (!s)
                        goto out;
                    asdl_seq_SET(stmts, k++, s);
                }
                else {
                    ch = CHILD(ch, 0);
                    REQ(ch, simple_stmt);
                    for (j = 0; j < num; j++) {
                        s = ast_for_stmt(&c, CHILD(ch, j * 2));
                        if (!s)
                            goto out;
                        asdl_seq_SET(stmts, k++, s);
                    }
                }
            }

            /* Type ignores are stored under the ENDMARKER in file_input. */
            ch = CHILD(n, NCH(n) - 1);
            REQ(ch, ENDMARKER);
            num = NCH(ch);
            type_ignores = _Py_asdl_seq_new(num, arena);
            if (!type_ignores)
                goto out;

            for (i = 0; i < num; i++) {
                type_ignore_ty ti = TypeIgnore(LINENO(CHILD(ch, i)), arena);
                if (!ti)
                   goto out;
               asdl_seq_SET(type_ignores, i, ti);
            }

            res = Module(stmts, type_ignores, arena);
            break;
        case eval_input: {
            expr_ty testlist_ast;

            /* XXX Why not comp_for here? */
            testlist_ast = ast_for_testlist(&c, CHILD(n, 0));
            if (!testlist_ast)
                goto out;
            res = Expression(testlist_ast, arena);
            break;
        }
        case single_input:
            if (TYPE(CHILD(n, 0)) == NEWLINE) {
                stmts = _Py_asdl_seq_new(1, arena);
                if (!stmts)
                    goto out;
                asdl_seq_SET(stmts, 0, Pass(n->n_lineno, n->n_col_offset,
                                            n->n_end_lineno, n->n_end_col_offset,
                                            arena));
                if (!asdl_seq_GET(stmts, 0))
                    goto out;
                res = Interactive(stmts, arena);
            }
            else {
                n = CHILD(n, 0);
                num = num_stmts(n);
                stmts = _Py_asdl_seq_new(num, arena);
                if (!stmts)
                    goto out;
                if (num == 1) {
                    s = ast_for_stmt(&c, n);
                    if (!s)
                        goto out;
                    asdl_seq_SET(stmts, 0, s);
                }
                else {
                    /* Only a simple_stmt can contain multiple statements. */
                    REQ(n, simple_stmt);
                    for (i = 0; i < NCH(n); i += 2) {
                        if (TYPE(CHILD(n, i)) == NEWLINE)
                            break;
                        s = ast_for_stmt(&c, CHILD(n, i));
                        if (!s)
                            goto out;
                        asdl_seq_SET(stmts, i / 2, s);
                    }
                }

                res = Interactive(stmts, arena);
            }
            break;
        case func_type_input:
            n = CHILD(n, 0);
            REQ(n, func_type);

            if (TYPE(CHILD(n, 1)) == typelist) {
                ch = CHILD(n, 1);
                /* this is overly permissive -- we don't pay any attention to
                 * stars on the args -- just parse them into an ordered list */
                num = 0;
                for (i = 0; i < NCH(ch); i++) {
                    if (TYPE(CHILD(ch, i)) == test) {
                        num++;
                    }
                }

                argtypes = _Py_asdl_seq_new(num, arena);
                if (!argtypes)
                    goto out;

                j = 0;
                for (i = 0; i < NCH(ch); i++) {
                    if (TYPE(CHILD(ch, i)) == test) {
                        arg = ast_for_expr(&c, CHILD(ch, i));
                        if (!arg)
                            goto out;
                        asdl_seq_SET(argtypes, j++, arg);
                    }
                }
            }
            else {
                argtypes = _Py_asdl_seq_new(0, arena);
                if (!argtypes)
                    goto out;
            }

            ret = ast_for_expr(&c, CHILD(n, NCH(n) - 1));
            if (!ret)
                goto out;
            res = FunctionType(argtypes, ret, arena);
            break;
        default:
            PyErr_Format(PyExc_SystemError,
                         "invalid node %d for PyAST_FromNode", TYPE(n));
            goto out;
    }
 out:
    if (c.c_normalize) {
        Py_DECREF(c.c_normalize);
    }
    return res;
}

mod_ty
PyAST_FromNode(const node *n, PyCompilerFlags *flags, const char *filename_str,
               PyArena *arena)
{
    mod_ty mod;
    PyObject *filename;
    filename = PyUnicode_DecodeFSDefault(filename_str);
    if (filename == NULL)
        return NULL;
    mod = PyAST_FromNodeObject(n, flags, filename, arena);
    Py_DECREF(filename);
    return mod;

}

/* Return the AST repr. of the operator represented as syntax (|, ^, etc.)
*/

static operator_ty
get_operator(const node *n)
{
    switch (TYPE(n)) {
        case VBAR:
            return BitOr;
        case CIRCUMFLEX:
            return BitXor;
        case AMPER:
            return BitAnd;
        case LEFTSHIFT:
            return LShift;
        case RIGHTSHIFT:
            return RShift;
        case PLUS:
            return Add;
        case MINUS:
            return Sub;
        case STAR:
            return Mult;
        case AT:
            return MatMult;
        case SLASH:
            return Div;
        case DOUBLESLASH:
            return FloorDiv;
        case PERCENT:
            return Mod;
        default:
            return (operator_ty)0;
    }
}

static const char * const FORBIDDEN[] = {
    "None",
    "True",
    "False",
    "__debug__",
    NULL,
};

static int
forbidden_name(struct compiling *c, identifier name, const node *n,
               int full_checks)