add ydb deps

1 files changed, 946 insertions, 0 deletions

diff --git a/contrib/tools/python3/src/Python/ast_unparse.c b/contrib/tools/python3/src/Python/ast_unparse.c
new file mode 100644
index 0000000000..6565b6b33e
--- /dev/null
+++ b/contrib/tools/python3/src/Python/ast_unparse.c
@@ -0,0 +1,946 @@
+#include "Python.h"
+#include "pycore_ast.h"           // expr_ty
+#include "pycore_runtime.h"       // _Py_ID()
+#include <float.h>                // DBL_MAX_10_EXP
+#include <stdbool.h>
+
+/* This limited unparser is used to convert annotations back to strings
+ * during compilation rather than being a full AST unparser.
+ * See ast.unparse for a full unparser (written in Python)
+ */
+
+_Py_DECLARE_STR(open_br, "{");
+_Py_DECLARE_STR(dbl_open_br, "{{");
+_Py_DECLARE_STR(close_br, "}");
+_Py_DECLARE_STR(dbl_close_br, "}}");
+static PyObject *_str_replace_inf;
+
+/* Forward declarations for recursion via helper functions. */
+static PyObject *
+expr_as_unicode(expr_ty e, int level);
+static int
+append_ast_expr(_PyUnicodeWriter *writer, expr_ty e, int level);
+static int
+append_joinedstr(_PyUnicodeWriter *writer, expr_ty e, bool is_format_spec);
+static int
+append_formattedvalue(_PyUnicodeWriter *writer, expr_ty e);
+static int
+append_ast_slice(_PyUnicodeWriter *writer, expr_ty e);
+
+static int
+append_charp(_PyUnicodeWriter *writer, const char *charp)
+{
+    return _PyUnicodeWriter_WriteASCIIString(writer, charp, -1);
+}
+
+#define APPEND_STR_FINISH(str)  do { \
+        return append_charp(writer, (str)); \
+    } while (0)
+
+#define APPEND_STR(str)  do { \
+        if (-1 == append_charp(writer, (str))) { \
+            return -1; \
+        } \
+    } while (0)
+
+#define APPEND_STR_IF(cond, str)  do { \
+        if ((cond) && -1 == append_charp(writer, (str))) { \
+            return -1; \
+        } \
+    } while (0)
+
+#define APPEND_STR_IF_NOT_FIRST(str)  do { \
+        APPEND_STR_IF(!first, (str)); \
+        first = false; \
+    } while (0)
+
+#define APPEND_EXPR(expr, pr)  do { \
+        if (-1 == append_ast_expr(writer, (expr), (pr))) { \
+            return -1; \
+        } \
+    } while (0)
+
+#define APPEND(type, value)  do { \
+        if (-1 == append_ast_ ## type(writer, (value))) { \
+            return -1; \
+        } \
+    } while (0)
+
+static int
+append_repr(_PyUnicodeWriter *writer, PyObject *obj)
+{
+    PyObject *repr = PyObject_Repr(obj);
+
+    if (!repr) {
+        return -1;
+    }
+
+    if ((PyFloat_CheckExact(obj) && Py_IS_INFINITY(PyFloat_AS_DOUBLE(obj))) ||
+       PyComplex_CheckExact(obj))
+    {
+        PyObject *new_repr = PyUnicode_Replace(
+            repr,
+            &_Py_ID(inf),
+            _str_replace_inf,
+            -1
+        );
+        Py_DECREF(repr);
+        if (!new_repr) {
+            return -1;
+        }
+        repr = new_repr;
+    }
+    int ret = _PyUnicodeWriter_WriteStr(writer, repr);
+    Py_DECREF(repr);
+    return ret;
+}
+
+/* Priority levels */
+
+enum {
+    PR_TUPLE,
+    PR_TEST,            /* 'if'-'else', 'lambda' */
+    PR_OR,              /* 'or' */
+    PR_AND,             /* 'and' */
+    PR_NOT,             /* 'not' */
+    PR_CMP,             /* '<', '>', '==', '>=', '<=', '!=',
+                           'in', 'not in', 'is', 'is not' */
+    PR_EXPR,
+    PR_BOR = PR_EXPR,   /* '|' */
+    PR_BXOR,            /* '^' */
+    PR_BAND,            /* '&' */
+    PR_SHIFT,           /* '<<', '>>' */
+    PR_ARITH,           /* '+', '-' */
+    PR_TERM,            /* '*', '@', '/', '%', '//' */
+    PR_FACTOR,          /* unary '+', '-', '~' */
+    PR_POWER,           /* '**' */
+    PR_AWAIT,           /* 'await' */
+    PR_ATOM,
+};
+
+static int
+append_ast_boolop(_PyUnicodeWriter *writer, expr_ty e, int level)
+{
+    Py_ssize_t i, value_count;
+    asdl_expr_seq *values;
+    const char *op = (e->v.BoolOp.op == And) ? " and " : " or ";
+    int pr = (e->v.BoolOp.op == And) ? PR_AND : PR_OR;
+
+    APPEND_STR_IF(level > pr, "(");
+
+    values = e->v.BoolOp.values;
+    value_count = asdl_seq_LEN(values);
+
+    for (i = 0; i < value_count; ++i) {
+        APPEND_STR_IF(i > 0, op);
+        APPEND_EXPR((expr_ty)asdl_seq_GET(values, i), pr + 1);
+    }
+
+    APPEND_STR_IF(level > pr, ")");
+    return 0;
+}
+
+static int
+append_ast_binop(_PyUnicodeWriter *writer, expr_ty e, int level)
+{
+    const char *op;
+    int pr;
+    bool rassoc = false;  /* is right-associative? */
+
+    switch (e->v.BinOp.op) {
+    case Add: op = " + "; pr = PR_ARITH; break;
+    case Sub: op = " - "; pr = PR_ARITH; break;
+    case Mult: op = " * "; pr = PR_TERM; break;
+    case MatMult: op = " @ "; pr = PR_TERM; break;
+    case Div: op = " / "; pr = PR_TERM; break;
+    case Mod: op = " % "; pr = PR_TERM; break;
+    case LShift: op = " << "; pr = PR_SHIFT; break;
+    case RShift: op = " >> "; pr = PR_SHIFT; break;
+    case BitOr: op = " | "; pr = PR_BOR; break;
+    case BitXor: op = " ^ "; pr = PR_BXOR; break;
+    case BitAnd: op = " & "; pr = PR_BAND; break;
+    case FloorDiv: op = " // "; pr = PR_TERM; break;
+    case Pow: op = " ** "; pr = PR_POWER; rassoc = true; break;
+    default:
+        PyErr_SetString(PyExc_SystemError,
+                        "unknown binary operator");
+        return -1;
+    }
+
+    APPEND_STR_IF(level > pr, "(");
+    APPEND_EXPR(e->v.BinOp.left, pr + rassoc);
+    APPEND_STR(op);
+    APPEND_EXPR(e->v.BinOp.right, pr + !rassoc);
+    APPEND_STR_IF(level > pr, ")");
+    return 0;
+}
+
+static int
+append_ast_unaryop(_PyUnicodeWriter *writer, expr_ty e, int level)
+{
+    const char *op;
+    int pr;
+
+    switch (e->v.UnaryOp.op) {
+    case Invert: op = "~"; pr = PR_FACTOR; break;
+    case Not: op = "not "; pr = PR_NOT; break;
+    case UAdd: op = "+"; pr = PR_FACTOR; break;
+    case USub: op = "-"; pr = PR_FACTOR; break;
+    default:
+        PyErr_SetString(PyExc_SystemError,
+                        "unknown unary operator");
+        return -1;
+    }
+
+    APPEND_STR_IF(level > pr, "(");
+    APPEND_STR(op);
+    APPEND_EXPR(e->v.UnaryOp.operand, pr);
+    APPEND_STR_IF(level > pr, ")");
+    return 0;
+}
+
+static int
+append_ast_arg(_PyUnicodeWriter *writer, arg_ty arg)
+{
+    if (-1 == _PyUnicodeWriter_WriteStr(writer, arg->arg)) {
+        return -1;
+    }
+    if (arg->annotation) {
+        APPEND_STR(": ");
+        APPEND_EXPR(arg->annotation, PR_TEST);
+    }
+    return 0;
+}
+
+static int
+append_ast_args(_PyUnicodeWriter *writer, arguments_ty args)
+{
+    bool first;
+    Py_ssize_t i, di, arg_count, posonlyarg_count, default_count;
+
+    first = true;
+
+    /* positional-only and positional arguments with defaults */
+    posonlyarg_count = asdl_seq_LEN(args->posonlyargs);
+    arg_count = asdl_seq_LEN(args->args);
+    default_count = asdl_seq_LEN(args->defaults);
+    for (i = 0; i < posonlyarg_count + arg_count; i++) {
+        APPEND_STR_IF_NOT_FIRST(", ");
+        if (i < posonlyarg_count){
+            APPEND(arg, (arg_ty)asdl_seq_GET(args->posonlyargs, i));
+        } else {
+            APPEND(arg, (arg_ty)asdl_seq_GET(args->args, i-posonlyarg_count));
+        }
+
+        di = i - posonlyarg_count - arg_count + default_count;
+        if (di >= 0) {
+            APPEND_STR("=");
+            APPEND_EXPR((expr_ty)asdl_seq_GET(args->defaults, di), PR_TEST);
+        }
+        if (posonlyarg_count && i + 1 == posonlyarg_count) {
+            APPEND_STR(", /");
+        }
+    }
+
+    /* vararg, or bare '*' if no varargs but keyword-only arguments present */
+    if (args->vararg || asdl_seq_LEN(args->kwonlyargs)) {
+        APPEND_STR_IF_NOT_FIRST(", ");
+        APPEND_STR("*");
+        if (args->vararg) {
+            APPEND(arg, args->vararg);
+        }
+    }
+
+    /* keyword-only arguments */
+    arg_count = asdl_seq_LEN(args->kwonlyargs);
+    default_count = asdl_seq_LEN(args->kw_defaults);
+    for (i = 0; i < arg_count; i++) {
+        APPEND_STR_IF_NOT_FIRST(", ");
+        APPEND(arg, (arg_ty)asdl_seq_GET(args->kwonlyargs, i));
+
+        di = i - arg_count + default_count;
+        if (di >= 0) {
+            expr_ty default_ = (expr_ty)asdl_seq_GET(args->kw_defaults, di);
+            if (default_) {
+                APPEND_STR("=");
+                APPEND_EXPR(default_, PR_TEST);
+            }
+        }
+    }
+
+    /* **kwargs */
+    if (args->kwarg) {
+        APPEND_STR_IF_NOT_FIRST(", ");
+        APPEND_STR("**");
+        APPEND(arg, args->kwarg);
+    }
+
+    return 0;
+}
+
+static int
+append_ast_lambda(_PyUnicodeWriter *writer, expr_ty e, int level)
+{
+    APPEND_STR_IF(level > PR_TEST, "(");
+    Py_ssize_t n_positional = (asdl_seq_LEN(e->v.Lambda.args->args) +
+                               asdl_seq_LEN(e->v.Lambda.args->posonlyargs));
+    APPEND_STR(n_positional ? "lambda " : "lambda");
+    APPEND(args, e->v.Lambda.args);
+    APPEND_STR(": ");
+    APPEND_EXPR(e->v.Lambda.body, PR_TEST);
+    APPEND_STR_IF(level > PR_TEST, ")");
+    return 0;
+}
+
+static int
+append_ast_ifexp(_PyUnicodeWriter *writer, expr_ty e, int level)
+{
+    APPEND_STR_IF(level > PR_TEST, "(");
+    APPEND_EXPR(e->v.IfExp.body, PR_TEST + 1);
+    APPEND_STR(" if ");
+    APPEND_EXPR(e->v.IfExp.test, PR_TEST + 1);
+    APPEND_STR(" else ");
+    APPEND_EXPR(e->v.IfExp.orelse, PR_TEST);
+    APPEND_STR_IF(level > PR_TEST, ")");
+    return 0;
+}
+
+static int
+append_ast_dict(_PyUnicodeWriter *writer, expr_ty e)
+{
+    Py_ssize_t i, value_count;
+    expr_ty key_node;
+
+    APPEND_STR("{");
+    value_count = asdl_seq_LEN(e->v.Dict.values);
+
+    for (i = 0; i < value_count; i++) {
+        APPEND_STR_IF(i > 0, ", ");
+        key_node = (expr_ty)asdl_seq_GET(e->v.Dict.keys, i);
+        if (key_node != NULL) {
+            APPEND_EXPR(key_node, PR_TEST);
+            APPEND_STR(": ");
+            APPEND_EXPR((expr_ty)asdl_seq_GET(e->v.Dict.values, i), PR_TEST);
+        }
+        else {
+            APPEND_STR("**");
+            APPEND_EXPR((expr_ty)asdl_seq_GET(e->v.Dict.values, i), PR_EXPR);
+        }
+    }
+
+    APPEND_STR_FINISH("}");
+}
+
+static int
+append_ast_set(_PyUnicodeWriter *writer, expr_ty e)
+{
+    Py_ssize_t i, elem_count;
+
+    APPEND_STR("{");
+    elem_count = asdl_seq_LEN(e->v.Set.elts);
+    for (i = 0; i < elem_count; i++) {
+        APPEND_STR_IF(i > 0, ", ");
+        APPEND_EXPR((expr_ty)asdl_seq_GET(e->v.Set.elts, i), PR_TEST);
+    }
+
+    APPEND_STR_FINISH("}");
+}
+
+static int
+append_ast_list(_PyUnicodeWriter *writer, expr_ty e)
+{
+    Py_ssize_t i, elem_count;
+
+    APPEND_STR("[");
+    elem_count = asdl_seq_LEN(e->v.List.elts);
+    for (i = 0; i < elem_count; i++) {
+        APPEND_STR_IF(i > 0, ", ");
+        APPEND_EXPR((expr_ty)asdl_seq_GET(e->v.List.elts, i), PR_TEST);
+    }
+
+    APPEND_STR_FINISH("]");
+}
+
+static int
+append_ast_tuple(_PyUnicodeWriter *writer, expr_ty e, int level)
+{
+    Py_ssize_t i, elem_count;
+
+    elem_count = asdl_seq_LEN(e->v.Tuple.elts);
+
+    if (elem_count == 0) {
+        APPEND_STR_FINISH("()");
+    }
+
+    APPEND_STR_IF(level > PR_TUPLE, "(");
+
+    for (i = 0; i < elem_count; i++) {
+        APPEND_STR_IF(i > 0, ", ");
+        APPEND_EXPR((expr_ty)asdl_seq_GET(e->v.Tuple.elts, i), PR_TEST);
+    }
+
+    APPEND_STR_IF(elem_count == 1, ",");
+    APPEND_STR_IF(level > PR_TUPLE, ")");
+    return 0;
+}
+
+static int
+append_ast_comprehension(_PyUnicodeWriter *writer, comprehension_ty gen)
+{
+    Py_ssize_t i, if_count;
+
+    APPEND_STR(gen->is_async ? " async for " : " for ");
+    APPEND_EXPR(gen->target, PR_TUPLE);
+    APPEND_STR(" in ");
+    APPEND_EXPR(gen->iter, PR_TEST + 1);
+
+    if_count = asdl_seq_LEN(gen->ifs);
+    for (i = 0; i < if_count; i++) {
+        APPEND_STR(" if ");
+        APPEND_EXPR((expr_ty)asdl_seq_GET(gen->ifs, i), PR_TEST + 1);
+    }
+    return 0;
+}
+
+static int
+append_ast_comprehensions(_PyUnicodeWriter *writer, asdl_comprehension_seq *comprehensions)
+{
+    Py_ssize_t i, gen_count;
+    gen_count = asdl_seq_LEN(comprehensions);
+
+    for (i = 0; i < gen_count; i++) {
+        APPEND(comprehension, (comprehension_ty)asdl_seq_GET(comprehensions, i));
+    }
+
+    return 0;
+}
+
+static int
+append_ast_genexp(_PyUnicodeWriter *writer, expr_ty e)
+{
+    APPEND_STR("(");
+    APPEND_EXPR(e->v.GeneratorExp.elt, PR_TEST);
+    APPEND(comprehensions, e->v.GeneratorExp.generators);
+    APPEND_STR_FINISH(")");
+}
+
+static int
+append_ast_listcomp(_PyUnicodeWriter *writer, expr_ty e)
+{
+    APPEND_STR("[");
+    APPEND_EXPR(e->v.ListComp.elt, PR_TEST);
+    APPEND(comprehensions, e->v.ListComp.generators);
+    APPEND_STR_FINISH("]");
+}
+
+static int
+append_ast_setcomp(_PyUnicodeWriter *writer, expr_ty e)
+{
+    APPEND_STR("{");
+    APPEND_EXPR(e->v.SetComp.elt, PR_TEST);
+    APPEND(comprehensions, e->v.SetComp.generators);
+    APPEND_STR_FINISH("}");
+}
+
+static int
+append_ast_dictcomp(_PyUnicodeWriter *writer, expr_ty e)
+{
+    APPEND_STR("{");
+    APPEND_EXPR(e->v.DictComp.key, PR_TEST);
+    APPEND_STR(": ");
+    APPEND_EXPR(e->v.DictComp.value, PR_TEST);
+    APPEND(comprehensions, e->v.DictComp.generators);
+    APPEND_STR_FINISH("}");
+}
+
+static int
+append_ast_compare(_PyUnicodeWriter *writer, expr_ty e, int level)
+{
+    const char *op;
+    Py_ssize_t i, comparator_count;
+    asdl_expr_seq *comparators;
+    asdl_int_seq *ops;
+
+    APPEND_STR_IF(level > PR_CMP, "(");
+
+    comparators = e->v.Compare.comparators;
+    ops = e->v.Compare.ops;
+    comparator_count = asdl_seq_LEN(comparators);
+    assert(comparator_count > 0);
+    assert(comparator_count == asdl_seq_LEN(ops));
+
+    APPEND_EXPR(e->v.Compare.left, PR_CMP + 1);
+
+    for (i = 0; i < comparator_count; i++) {
+        switch ((cmpop_ty)asdl_seq_GET(ops, i)) {
+        case Eq:
+            op = " == ";
+            break;
+        case NotEq:
+            op = " != ";
+            break;
+        case Lt:
+            op = " < ";
+            break;
+        case LtE:
+            op = " <= ";
+            break;
+        case Gt:
+            op = " > ";
+            break;
+        case GtE:
+            op = " >= ";
+            break;
+        case Is:
+            op = " is ";
+            break;
+        case IsNot:
+            op = " is not ";
+            break;
+        case In:
+            op = " in ";
+            break;
+        case NotIn:
+            op = " not in ";
+            break;
+        default:
+            PyErr_SetString(PyExc_SystemError,
+                            "unexpected comparison kind");
+            return -1;
+        }
+
+        APPEND_STR(op);
+        APPEND_EXPR((expr_ty)asdl_seq_GET(comparators, i), PR_CMP + 1);
+    }
+
+    APPEND_STR_IF(level > PR_CMP, ")");
+    return 0;
+}
+
+static int
+append_ast_keyword(_PyUnicodeWriter *writer, keyword_ty kw)
+{
+    if (kw->arg == NULL) {
+        APPEND_STR("**");
+    }
+    else {
+        if (-1 == _PyUnicodeWriter_WriteStr(writer, kw->arg)) {
+            return -1;
+        }
+
+        APPEND_STR("=");
+    }
+
+    APPEND_EXPR(kw->value, PR_TEST);
+    return 0;
+}
+
+static int
+append_ast_call(_PyUnicodeWriter *writer, expr_ty e)
+{
+    bool first;
+    Py_ssize_t i, arg_count, kw_count;
+    expr_ty expr;
+
+    APPEND_EXPR(e->v.Call.func, PR_ATOM);
+
+    arg_count = asdl_seq_LEN(e->v.Call.args);
+    kw_count = asdl_seq_LEN(e->v.Call.keywords);
+    if (arg_count == 1 && kw_count == 0) {
+        expr = (expr_ty)asdl_seq_GET(e->v.Call.args, 0);
+        if (expr->kind == GeneratorExp_kind) {
+            /* Special case: a single generator expression. */
+            return append_ast_genexp(writer, expr);
+        }
+    }
+
+    APPEND_STR("(");
+
+    first = true;
+    for (i = 0; i < arg_count; i++) {
+        APPEND_STR_IF_NOT_FIRST(", ");
+        APPEND_EXPR((expr_ty)asdl_seq_GET(e->v.Call.args, i), PR_TEST);
+    }
+
+    for (i = 0; i < kw_count; i++) {
+        APPEND_STR_IF_NOT_FIRST(", ");
+        APPEND(keyword, (keyword_ty)asdl_seq_GET(e->v.Call.keywords, i));
+    }
+
+    APPEND_STR_FINISH(")");
+}
+
+static PyObject *
+escape_braces(PyObject *orig)
+{
+    PyObject *temp;
+    PyObject *result;
+    temp = PyUnicode_Replace(orig, &_Py_STR(open_br), &_Py_STR(dbl_open_br), -1);
+    if (!temp) {
+        return NULL;
+    }
+    result = PyUnicode_Replace(temp, &_Py_STR(close_br), &_Py_STR(dbl_close_br), -1);
+    Py_DECREF(temp);
+    return result;
+}
+
+static int
+append_fstring_unicode(_PyUnicodeWriter *writer, PyObject *unicode)
+{
+    PyObject *escaped;
+    int result = -1;
+    escaped = escape_braces(unicode);
+    if (escaped) {
+        result = _PyUnicodeWriter_WriteStr(writer, escaped);
+        Py_DECREF(escaped);
+    }
+    return result;
+}
+
+static int
+append_fstring_element(_PyUnicodeWriter *writer, expr_ty e, bool is_format_spec)
+{
+    switch (e->kind) {
+    case Constant_kind:
+        return append_fstring_unicode(writer, e->v.Constant.value);
+    case JoinedStr_kind:
+        return append_joinedstr(writer, e, is_format_spec);
+    case FormattedValue_kind:
+        return append_formattedvalue(writer, e);
+    default:
+        PyErr_SetString(PyExc_SystemError,
+                        "unknown expression kind inside f-string");
+        return -1;
+    }
+}
+
+/* Build body separately to enable wrapping the entire stream of Strs,
+   Constants and FormattedValues in one opening and one closing quote. */
+static PyObject *
+build_fstring_body(asdl_expr_seq *values, bool is_format_spec)
+{
+    Py_ssize_t i, value_count;
+    _PyUnicodeWriter body_writer;
+    _PyUnicodeWriter_Init(&body_writer);
+    body_writer.min_length = 256;
+    body_writer.overallocate = 1;
+
+    value_count = asdl_seq_LEN(values);
+    for (i = 0; i < value_count; ++i) {
+        if (-1 == append_fstring_element(&body_writer,
+                                         (expr_ty)asdl_seq_GET(values, i),
+                                         is_format_spec
+                                         )) {
+            _PyUnicodeWriter_Dealloc(&body_writer);
+            return NULL;
+        }
+    }
+
+    return _PyUnicodeWriter_Finish(&body_writer);
+}
+
+static int
+append_joinedstr(_PyUnicodeWriter *writer, expr_ty e, bool is_format_spec)
+{
+    int result = -1;
+    PyObject *body = build_fstring_body(e->v.JoinedStr.values, is_format_spec);
+    if (!body) {
+        return -1;
+    }
+
+    if (!is_format_spec) {
+        if (-1 != append_charp(writer, "f") &&
+            -1 != append_repr(writer, body))
+        {
+            result = 0;
+        }
+    }
+    else {
+        result = _PyUnicodeWriter_WriteStr(writer, body);
+    }
+    Py_DECREF(body);
+    return result;
+}
+
+static int
+append_formattedvalue(_PyUnicodeWriter *writer, expr_ty e)
+{
+    const char *conversion;
+    const char *outer_brace = "{";
+    /* Grammar allows PR_TUPLE, but use >PR_TEST for adding parenthesis
+       around a lambda with ':' */
+    PyObject *temp_fv_str = expr_as_unicode(e->v.FormattedValue.value, PR_TEST + 1);
+    if (!temp_fv_str) {
+        return -1;
+    }
+    if (PyUnicode_Find(temp_fv_str, &_Py_STR(open_br), 0, 1, 1) == 0) {
+        /* Expression starts with a brace, split it with a space from the outer
+           one. */
+        outer_brace = "{ ";
+    }
+    if (-1 == append_charp(writer, outer_brace)) {
+        Py_DECREF(temp_fv_str);
+        return -1;
+    }
+    if (-1 == _PyUnicodeWriter_WriteStr(writer, temp_fv_str)) {
+        Py_DECREF(temp_fv_str);
+        return -1;
+    }
+    Py_DECREF(temp_fv_str);
+
+    if (e->v.FormattedValue.conversion > 0) {
+        switch (e->v.FormattedValue.conversion) {
+        case 'a':
+            conversion = "!a";
+            break;
+        case 'r':
+            conversion = "!r";
+            break;
+        case 's':
+            conversion = "!s";
+            break;
+        default:
+            PyErr_SetString(PyExc_SystemError,
+                            "unknown f-value conversion kind");
+            return -1;
+        }
+        APPEND_STR(conversion);
+    }
+    if (e->v.FormattedValue.format_spec) {
+        if (-1 == _PyUnicodeWriter_WriteASCIIString(writer, ":", 1) ||
+            -1 == append_fstring_element(writer,
+                                         e->v.FormattedValue.format_spec,
+                                         true
+                                        ))
+        {
+            return -1;
+        }
+    }
+
+    APPEND_STR_FINISH("}");
+}
+
+static int
+append_ast_constant(_PyUnicodeWriter *writer, PyObject *constant)
+{
+    if (PyTuple_CheckExact(constant)) {
+        Py_ssize_t i, elem_count;
+
+        elem_count = PyTuple_GET_SIZE(constant);
+        APPEND_STR("(");
+        for (i = 0; i < elem_count; i++) {
+            APPEND_STR_IF(i > 0, ", ");
+            if (append_ast_constant(writer, PyTuple_GET_ITEM(constant, i)) < 0) {
+                return -1;
+            }
+        }
+
+        APPEND_STR_IF(elem_count == 1, ",");
+        APPEND_STR(")");
+        return 0;
+    }
+    return append_repr(writer, constant);
+}
+
+static int
+append_ast_attribute(_PyUnicodeWriter *writer, expr_ty e)
+{
+    const char *period;
+    expr_ty v = e->v.Attribute.value;
+    APPEND_EXPR(v, PR_ATOM);
+
+    /* Special case: integers require a space for attribute access to be
+       unambiguous. */
+    if (v->kind == Constant_kind && PyLong_CheckExact(v->v.Constant.value)) {
+        period = " .";
+    }
+    else {
+        period = ".";
+    }
+    APPEND_STR(period);
+
+    return _PyUnicodeWriter_WriteStr(writer, e->v.Attribute.attr);
+}
+
+static int
+append_ast_slice(_PyUnicodeWriter *writer, expr_ty e)
+{
+    if (e->v.Slice.lower) {
+        APPEND_EXPR(e->v.Slice.lower, PR_TEST);
+    }
+
+    APPEND_STR(":");
+
+    if (e->v.Slice.upper) {
+        APPEND_EXPR(e->v.Slice.upper, PR_TEST);
+    }
+
+    if (e->v.Slice.step) {
+        APPEND_STR(":");
+        APPEND_EXPR(e->v.Slice.step, PR_TEST);
+    }
+    return 0;
+}
+
+static int
+append_ast_subscript(_PyUnicodeWriter *writer, expr_ty e)
+{
+    APPEND_EXPR(e->v.Subscript.value, PR_ATOM);
+    APPEND_STR("[");
+    APPEND_EXPR(e->v.Subscript.slice, PR_TUPLE);
+    APPEND_STR_FINISH("]");
+}
+
+static int
+append_ast_starred(_PyUnicodeWriter *writer, expr_ty e)
+{
+    APPEND_STR("*");
+    APPEND_EXPR(e->v.Starred.value, PR_EXPR);
+    return 0;
+}
+
+static int
+append_ast_yield(_PyUnicodeWriter *writer, expr_ty e)
+{
+    if (!e->v.Yield.value) {
+        APPEND_STR_FINISH("(yield)");
+    }
+
+    APPEND_STR("(yield ");
+    APPEND_EXPR(e->v.Yield.value, PR_TEST);
+    APPEND_STR_FINISH(")");
+}
+
+static int
+append_ast_yield_from(_PyUnicodeWriter *writer, expr_ty e)
+{
+    APPEND_STR("(yield from ");
+    APPEND_EXPR(e->v.YieldFrom.value, PR_TEST);
+    APPEND_STR_FINISH(")");
+}
+
+static int
+append_ast_await(_PyUnicodeWriter *writer, expr_ty e, int level)
+{
+    APPEND_STR_IF(level > PR_AWAIT, "(");
+    APPEND_STR("await ");
+    APPEND_EXPR(e->v.Await.value, PR_ATOM);
+    APPEND_STR_IF(level > PR_AWAIT, ")");
+    return 0;
+}
+
+static int
+append_named_expr(_PyUnicodeWriter *writer, expr_ty e, int level)
+{
+    APPEND_STR_IF(level > PR_TUPLE, "(");
+    APPEND_EXPR(e->v.NamedExpr.target, PR_ATOM);
+    APPEND_STR(" := ");
+    APPEND_EXPR(e->v.NamedExpr.value, PR_ATOM);
+    APPEND_STR_IF(level > PR_TUPLE, ")");
+    return 0;
+}
+
+static int
+append_ast_expr(_PyUnicodeWriter *writer, expr_ty e, int level)
+{
+    switch (e->kind) {
+    case BoolOp_kind:
+        return append_ast_boolop(writer, e, level);
+    case BinOp_kind:
+        return append_ast_binop(writer, e, level);
+    case UnaryOp_kind:
+        return append_ast_unaryop(writer, e, level);
+    case Lambda_kind:
+        return append_ast_lambda(writer, e, level);
+    case IfExp_kind:
+        return append_ast_ifexp(writer, e, level);
+    case Dict_kind:
+        return append_ast_dict(writer, e);
+    case Set_kind:
+        return append_ast_set(writer, e);
+    case GeneratorExp_kind:
+        return append_ast_genexp(writer, e);
+    case ListComp_kind:
+        return append_ast_listcomp(writer, e);
+    case SetComp_kind:
+        return append_ast_setcomp(writer, e);
+    case DictComp_kind:
+        return append_ast_dictcomp(writer, e);
+    case Yield_kind:
+        return append_ast_yield(writer, e);
+    case YieldFrom_kind:
+        return append_ast_yield_from(writer, e);
+    case Await_kind:
+        return append_ast_await(writer, e, level);
+    case Compare_kind:
+        return append_ast_compare(writer, e, level);
+    case Call_kind:
+        return append_ast_call(writer, e);
+    case Constant_kind:
+        if (e->v.Constant.value == Py_Ellipsis) {
+            APPEND_STR_FINISH("...");
+        }
+        if (e->v.Constant.kind != NULL
+            && -1 == _PyUnicodeWriter_WriteStr(writer, e->v.Constant.kind)) {
+            return -1;
+        }
+        return append_ast_constant(writer, e->v.Constant.value);
+    case JoinedStr_kind:
+        return append_joinedstr(writer, e, false);
+    case FormattedValue_kind:
+        return append_formattedvalue(writer, e);
+    /* The following exprs can be assignment targets. */
+    case Attribute_kind:
+        return append_ast_attribute(writer, e);
+    case Subscript_kind:
+        return append_ast_subscript(writer, e);
+    case Starred_kind:
+        return append_ast_starred(writer, e);
+    case Slice_kind:
+        return append_ast_slice(writer, e);
+    case Name_kind:
+        return _PyUnicodeWriter_WriteStr(writer, e->v.Name.id);
+    case List_kind:
+        return append_ast_list(writer, e);
+    case Tuple_kind:
+        return append_ast_tuple(writer, e, level);
+    case NamedExpr_kind:
+        return append_named_expr(writer, e, level);
+    // No default so compiler emits a warning for unhandled cases
+    }
+    PyErr_SetString(PyExc_SystemError,
+                    "unknown expression kind");
+    return -1;
+}
+
+static int
+maybe_init_static_strings(void)
+{
+    if (!_str_replace_inf &&
+        !(_str_replace_inf = PyUnicode_FromFormat("1e%d", 1 + DBL_MAX_10_EXP))) {
+        return -1;
+    }
+    return 0;
+}
+
+static PyObject *
+expr_as_unicode(expr_ty e, int level)
+{
+    _PyUnicodeWriter writer;
+    _PyUnicodeWriter_Init(&writer);
+    writer.min_length = 256;
+    writer.overallocate = 1;
+    if (-1 == maybe_init_static_strings() ||
+        -1 == append_ast_expr(&writer, e, level))
+    {
+        _PyUnicodeWriter_Dealloc(&writer);
+        return NULL;
+    }
+    return _PyUnicodeWriter_Finish(&writer);
+}
+
+PyObject *
+_PyAST_ExprAsUnicode(expr_ty e)
+{
+    return expr_as_unicode(e, PR_TEST);
+}