From 296e4dd15e3754fdddf70d33f2d630462d4b3309 Mon Sep 17 00:00:00 2001
From: Dario Gjorgjevski <dario.gjorgjevski@gmail.com>
Date: Wed, 11 Nov 2020 10:49:04 +0100
Subject: [PATCH] Fix font lock of assignments with type hints in Python
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* lisp/progmodes/python.el
(python-font-lock-keywords-maximum-decoration): Fix regular
expressions for font lock of assignments with type hints (bug#44568).

The font lock of assignments with type hints in Python is rather bad.
Consider the following example:

    from typing import Mapping, Tuple, Sequence
    var1: int = 5
    var2: Mapping[int, int] = {10: 1024}
    var3: Mapping[Tuple[int, int], int] = {(2, 5): 32}
    var4: Sequence[Sequence[int]] = [[1], [1, 2], [1, 2, 3]]
    var5: Sequence[Mapping[str, Sequence[str]]] = [
        {
            'red': ['scarlet', 'vermilion', 'ruby'],
            'green': ['emerald green', 'aqua']
        },
        {
            'sword': ['cutlass', 'rapier']
        }
    ]

As things stand right now, only ‘var1’ would be highlighted.  To make
things worse, the ‘Mapping’ type hint of ‘var2’ would also be
highlighted, which is entirely incorrect.

This commit makes all of ‘var1’ through ‘var5’ be highlighted
correctly.
---
 lisp/progmodes/python.el | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index 378ff8cc2c1..eb84b494e35 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -662,10 +662,14 @@ builtins.")
     ;; assignments
     ;; support for a = b = c = 5
     (,(lambda (limit)
-        (let ((re (python-rx (group (+ (any word ?. ?_)))
-                             (? ?\[ (+ (not (any  ?\]))) ?\]) (* space)
+        (let ((re (python-rx (group (+ symbol-name))
+                             (? ?\[ (+ (not ?\])) ?\])
+                             (* space)
                              ;; A type, like " : int ".
-                             (? ?: (* space) (+ (any word ?. ?_)) (* space))
+                             (? ?:
+                                (* space)
+                                (+ not-simple-operator)
+                                (* space))
                              assignment-operator))
               (res nil))
           (while (and (setq res (re-search-forward re limit t))
@@ -675,9 +679,9 @@ builtins.")
      (1 font-lock-variable-name-face nil nil))
     ;; support for a, b, c = (1, 2, 3)
     (,(lambda (limit)
-        (let ((re (python-rx (group (+ (any word ?. ?_))) (* space)
-                             (* ?, (* space) (+ (any word ?. ?_)) (* space))
-                             ?, (* space) (+ (any word ?. ?_)) (* space)
+        (let ((re (python-rx (group (+ symbol-name)) (* space)
+                             (* ?, (* space) (+ symbol-name) (* space))
+                             ?, (* space) (+ symbol-name) (* space)
                              assignment-operator))
               (res nil))
           (while (and (setq res (re-search-forward re limit t))
-- 
2.39.2