1 files changed, 26 insertions, 13 deletions

diff --git a/Python/ast_unparse.c b/Python/ast_unparse.c
index c121ec096ae..557c12cfda6 100644
--- a/Python/ast_unparse.c
+++ b/Python/ast_unparse.c
@@ -702,6 +702,13 @@ append_templatestr(PyUnicodeWriter *writer, expr_ty e)
 
     Py_ssize_t last_idx = 0;
     Py_ssize_t len = asdl_seq_LEN(e->v.TemplateStr.values);
+    if (len == 0) {
+        int result = _write_values_subarray(writer, e->v.TemplateStr.values,
+                0, len - 1, 't', arena);
+        _PyArena_Free(arena);
+        return result;
+    }
+
     for (Py_ssize_t i = 0; i < len; i++) {
         expr_ty value = asdl_seq_GET(e->v.TemplateStr.values, i);
 
@@ -742,6 +749,7 @@ append_templatestr(PyUnicodeWriter *writer, expr_ty e)
             goto error;
         }
     }
+    _PyArena_Free(arena);
 
     return 0;
 
@@ -774,33 +782,38 @@ append_joinedstr(PyUnicodeWriter *writer, expr_ty e, bool is_format_spec)
 }
 
 static int
-append_interpolation_value(PyUnicodeWriter *writer, expr_ty e)
+append_interpolation_str(PyUnicodeWriter *writer, PyObject *str)
 {
     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, PR_TEST + 1);
-    if (!temp_fv_str) {
-        return -1;
-    }
-    if (PyUnicode_Find(temp_fv_str, _Py_LATIN1_CHR('{'), 0, 1, 1) == 0) {
+    if (PyUnicode_Find(str, _Py_LATIN1_CHR('{'), 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);
+    if (-1 == PyUnicodeWriter_WriteStr(writer, str)) {
         return -1;
     }
-    Py_DECREF(temp_fv_str);
     return 0;
 }
 
 static int
+append_interpolation_value(PyUnicodeWriter *writer, expr_ty e)
+{
+    /* Grammar allows PR_TUPLE, but use >PR_TEST for adding parenthesis
+       around a lambda with ':' */
+    PyObject *temp_fv_str = expr_as_unicode(e, PR_TEST + 1);
+    if (!temp_fv_str) {
+        return -1;
+    }
+    int result = append_interpolation_str(writer, temp_fv_str);
+    Py_DECREF(temp_fv_str);
+    return result;
+}
+
+static int
 append_interpolation_conversion(PyUnicodeWriter *writer, int conversion)
 {
     if (conversion < 0) {
@@ -843,7 +856,7 @@ append_interpolation_format_spec(PyUnicodeWriter *writer, expr_ty e)
 static int
 append_interpolation(PyUnicodeWriter *writer, expr_ty e)
 {
-    if (-1 == append_interpolation_value(writer, e->v.Interpolation.value)) {
+    if (-1 == append_interpolation_str(writer, e->v.Interpolation.str)) {
         return -1;
     }