Fix font lock of assignments with type hints in Python

* 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.

1 files 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))