Confusing syntax error for missing comma after import-as target

Bug report

Bug description:

Right now we have:

>>> import a as a  b
  File "<python-input-0>", line 1
    import a as a  b
                ^
SyntaxError: cannot use name as import target

>>> from x import a as a  b
  File "<python-input-1>", line 1
    from x import a as a  b
                       ^
SyntaxError: cannot use name as import target

This happens since these cases match these two rules.

One possible fix would be to add NAME to the list of not-matched tokens so that the current rules don't match this case.

However, I have an idea for a slightly nicer error. PR forthcoming.

cc @pablogsal @lysnikolaou @sobolevn

CPython versions tested on:

3.14, 3.15, CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-146493

在 Python REPL 中复现两个 import-as 示例，然后检查 Grammar/python.gram 中 1435 行和 1439 行附近的两个匹配规则。将得到的诊断与 issue 中描述的预期行为进行比较；当缺少逗号的情况能够收到更清晰的语法错误时，即视为完成。已注明一个关联的 PR。