autodoc typehints do not create link for parametrized types

[anntzer]

Describe the bug

autodoc typehints normally generate a link to the hinted type, but do not do so for parametrized types.

To Reproduce
Steps to reproduce the behavior:

$ cat >project.py <<EOF
from typing import Literal

def func(x: Literal["a", "b"], y: int):
    """
    :param x: The x.
    :param y: The y.
    """
EOF
sphinx-apidoc . -o . -F -A me -V 0.0 --extensions sphinx.ext.intersphinx
PYTHONPATH=. make O=-Dautodoc_typehints=description html

and open _build/html/project.html

Expected behavior
Literal (in the parameter description) should link to typing.Literal in CPython's docs, just like int does.

Your project
N/A

Screenshots

Environment info

• OS: linux
• Python version: 3.9.4
• Sphinx version: 4.0.0
• Sphinx extensions: intersphinx, autodoc
• Extra tools: N/A

Additional context
N/A

[tk0miya]

Duplicated with #9195? Closing.

[tk0miya]

Oh, sorry. I understood these are different topic. Reopened now.

[pradyunsg]

The issue seems to be stemming from

sphinx/sphinx/ext/autodoc/typehints.py

Line 33 in 80fbbb8

annotation[param.name] = typing.stringify(param.annotation)

-- since the types coming from typing are "stringified" and not being passed through intersphinx.

[pradyunsg]

I guess the fix here is to pass these through typing.restify instead?