[Lang] Support template arguments for ti.func

[KLozes]

This PR implements support for template arguments in ti.funcs. This just required skipping python AST transform for arguments type-hinted with ti.template(). I also slightly refactored ASTTransformer by removing the is_classfunc argument.

The test I added doesn't work atm. For some reason it runs into a python sytnax error. This syntax error does not occur when the test is run as stand alone script. So I think its related some weird nested function syntax. If you have another idea for the test to get around that please let me know!

Related issue = #1042

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[archibate]

Cool! With function argument templates, we can easily use SNode as arguments (in #824), right? If so, could you also add this usage to test as well?
Setting up type-hint system for functions is also a big step in #602, many thanks!

[KLozes]

No problem! But cant we already pass snodes into funcs without ti.template(), like we did in #824 with ia = draw_rect(qt.parent(r+1), i, j, s, k, 1, 0)?

[archibate]

Yes, we already can, but requires a dirty hack (is it?), see 0139195#r39384288.

[KLozes]

Actually, I just tried commenting out elif isinstance(rhs, ti.SNode): return rhs and quadtree.py ran just fine. What was that hack needed for exactly?

[yuanming-hu]

Thank you! LGTM. I suggest adding a couple of lines of comments in case we forget what's happening here in the future.

The test I added doesn't work atm. For some reason it runs into a python sytnax error. This syntax error does not occur when the test is run as stand alone script. So I think its related some weird nested function syntax. If you have another idea for the test to get around that please let me know!

Is this still an issue? It seems to me that CI tests are passing.

[yuanming-hu]

Suggested change

	if isinstance(self.func.arguments[i], ti.template):
	continue
	# Directly pass in template arguments,
	# such as class instances ("self"), tensors, SNodes, etc.
	if isinstance(self.func.arguments[i], ti.template):
	continue
	# Create a copy for non-template arguments,
	# so that they are passed by value.

[KLozes]

Aliright thanks! Yes, both tests are passing. Although the second one passes even without making x a template. I assume its related to the hack 0139195#r39384288 @archibate was talking about, which I think we can get rid of at some point.