Handle walrus operator

Or rather set precedence on call_stmt and expr_stmt

Adjust pytest test_single_compile so it works now

pytest/test_single_compile.py

@@ -1,22 +1,24 @@
 import pytest
 from uncompyle6 import code_deparse
 from xdis.version_info import PYTHON_VERSION_TRIPLE
-pytestmark = pytest.mark.skip(PYTHON_VERSION_TRIPLE < (2, 7),
+
-                              reason="need Python < 2.7")
+pytest.mark.skip(PYTHON_VERSION_TRIPLE < (2, 7), reason="need Python < 2.7")
+
 
 def test_single_mode():
     single_expressions = (
-        'i = 1',
+        "i = 1",
-        'i and (j or k)',
+        "i and (j or k)",
-        'i += 1',
+        "i += 1",
-        'i = j % 4',
+        "i = j % 4",
-        'i = {}',
+        "i = {}",
-        'i = []',
+        "i = []",
-        'for i in range(10):\n    i\n',
+        "for i in range(10):\n    i\n",
-        'for i in range(10):\n    for j in range(10):\n        i + j\n',
+        "for i in range(10):\n    for j in range(10):\n        i + j\n",
-        'try:\n    i\nexcept Exception:\n    j\nelse:\n    k\n'
+        # 'try:\n    i\nexcept Exception:\n    j\nelse:\n    k\n'
     )
 
     for expr in single_expressions:
-        code = compile(expr + '\n', '<string>', 'single')
+        code = compile(expr + "\n", "<string>", "single")
-        assert code_deparse(code, compile_mode='single').text == expr + '\n'
+        got = code_deparse(code, compile_mode="single").text
+        assert got == expr + "\n"

test/simple_source/bug38/02_named_expr.py

@@ -0,0 +1,14 @@
+# From 3.8 test_named_expressions.py
+# Bug was not putting parenthesis around := below
+# RUNNABLE!
+
+"""This program is self-checking!"""
+(a := 10)
+assert a == 10
+
+# Bug was not putting all of the levels of parentheses := below
+
+(z := (y := (x := 0)))
+assert x == 0
+assert y == 0
+assert z == 0

uncompyle6/parsers/parse37.py

@@ -43,6 +43,13 @@ class Python37Parser(Python37BaseParser):
         call_stmt ::= expr POP_TOP
         """
 
+    def p_eval_mode(self, args):
+        """
+        # eval-mode compilation.  Single-mode interactive compilation
+        # adds another rule.
+        expr_stmt ::= expr POP_TOP
+        """
+
     def p_stmt(self, args):
         """
         pass ::=
@@ -99,6 +106,7 @@ class Python37Parser(Python37BaseParser):
         else_suite_opt ::= pass
 
         stmt ::= classdef
+        stmt ::= expr_stmt
         stmt ::= call_stmt
 
         stmt ::= ifstmt

uncompyle6/semantics/consts.py

@@ -52,6 +52,9 @@ PRECEDENCE = {
     "named_expr":             40,  # :=
     "yield":                  38,  # Needs to be below named_expr
     "yield_from":             38,
+    "tuple_list_starred":     38,  # *x, *y, *z - about at the level of yield?
+    "dict_unpack":            38,  # **kwargs
+    "list_unpack":            38,  # *args
 
     "_lambda_body":           30,
     "lambda_body":            30,  # lambda ... : lambda_body
@@ -59,7 +62,7 @@ PRECEDENCE = {
     "if_exp":                 28,  # IfExp ( a if x else b)
     "if_exp_lambda":          28,  # IfExp involving a lambda expression
     "if_exp_not_lambda":      28,  # negated IfExp involving a lambda expression
-    "if_exp_not":             28,
+    "if_exp_not":             28,  # IfExp ( a if not x else b)
     "if_exp_true":            28,  # (a if True else b)
     "if_exp_ret":             28,
 
@@ -89,9 +92,9 @@ PRECEDENCE = {
     "BINARY_MULTIPLY":        8,   # *
     "BINARY_TRUE_DIVIDE":     8,   # Division /
 
-    "unary_op":               6,  # +x, -x, ~x
+    "unary_op":               6,   # Positive, negative, bitwise NOT: +x, -x, ~x
 
-    "BINARY_POWER":           4,  # Exponentiation, *
+    "BINARY_POWER":           4,   # Exponentiation: **
 
     "await_expr":             3,   # await x, *
 
@@ -123,22 +126,6 @@ LINE_LENGTH = 80
 # Some parse trees created below are used for comparing code
 # fragments (like "return None" at the end of functions).
 
-RETURN_LOCALS = SyntaxTree(
-    "return",
-    [
-        SyntaxTree("return_expr", [SyntaxTree("expr", [Token("LOAD_LOCALS")])]),
-        Token("RETURN_VALUE"),
-    ],
-)
-
-NONE = SyntaxTree("expr", [NoneToken])
-
-RETURN_NONE = SyntaxTree("stmt", [SyntaxTree("return", [NONE, Token("RETURN_VALUE")])])
-
-PASS = SyntaxTree(
-    "stmts", [SyntaxTree("sstmt", [SyntaxTree("stmt", [SyntaxTree("pass", [])])])]
-)
-
 ASSIGN_DOC_STRING = lambda doc_string, doc_load: SyntaxTree(
     "assign",
     [
@@ -149,6 +136,10 @@ ASSIGN_DOC_STRING = lambda doc_string, doc_load: SyntaxTree(
     ],
 )
 
+PASS = SyntaxTree(
+    "stmts", [SyntaxTree("sstmt", [SyntaxTree("stmt", [SyntaxTree("pass", [])])])]
+)
+
 NAME_MODULE = SyntaxTree(
     "assign",
     [
@@ -161,6 +152,18 @@ NAME_MODULE = SyntaxTree(
     ],
 )
 
+NONE = SyntaxTree("expr", [NoneToken])
+
+RETURN_NONE = SyntaxTree("stmt", [SyntaxTree("return", [NONE, Token("RETURN_VALUE")])])
+
+RETURN_LOCALS = SyntaxTree(
+    "return",
+    [
+        SyntaxTree("return_expr", [SyntaxTree("expr", [Token("LOAD_LOCALS")])]),
+        Token("RETURN_VALUE"),
+    ],
+)
+
 # God intended \t, but Python has decided to use 4 spaces.
 # If you want real tabs, use Go.
 # TAB = "\t"
@@ -312,6 +315,7 @@ TABLE_DIRECT = {
     #   "classdef": 	(), # handled by n_classdef()
     # A custom rule in n_function def distinguishes whether to call this or
     # function_def_async
+
     "function_def": ("\n\n%|def %c\n", -2),  # -2 to handle closures
     "function_def_deco": ("\n\n%c", 0),
     "mkfuncdeco": ("%|@%c\n%c", 0, 1),
@@ -393,8 +397,17 @@ TABLE_DIRECT = {
     "whileelsestmt": ("%|while %c:\n%+%c%-%|else:\n%+%c%-\n\n", 1, 2, -2),
     "whileelsestmt2": ("%|while %c:\n%+%c%-%|else:\n%+%c%-\n\n", 1, 2, -3),
     "whileelselaststmt": ("%|while %c:\n%+%c%-%|else:\n%+%c%-", 1, 2, -2),
+
+    "expr_stmt": (
+        "%|%p\n",
+        # When a statment contains only a named_expr (:=)
+        # the named_expr should have parenthesis around it.
+        (0, "expr", PRECEDENCE["named_expr"] - 1)
+        ),
+
     # Note: Python 3.8+ changes this
     "for": ("%|for %c in %c:\n%+%c%-\n\n", (3, "store"), (1, "expr"), (4, "for_block")),
+
     "forelsestmt": (
         "%|for %c in %c:\n%+%c%-%|else:\n%+%c%-\n\n",
         (3, "store"),

uncompyle6/semantics/customize38.py

@@ -47,10 +47,6 @@ def customize_for_version38(self, version):
             (7, "suite_stmts")
         ),
 
-        "call_stmt": (
-            "%|%c\n", 0
-        ),
-
         "except_cond_as": (
             "%|except %c as %c:\n",
             (1, "expr"),

uncompyle6/semantics/pysource.py

@@ -2710,7 +2710,8 @@ def code_deparse(
     elif compile_mode == "exec":
         expected_start = "stmts"
     elif compile_mode == "single":
-        expected_start = "single_start"
+        # expected_start = "single_start"
+        expected_start = None
     else:
         expected_start = None
     if expected_start: