This is a panic in the go2go type checker. The current type checker reports an error (undefined: some). I don't think it's worth updating the go2go type checker to better handle erroneous cases, but leaving for @griesemer .

Well

panic: prog.go2:4:7: unknown expression type *ast.ListExpr [recovered]
	panic: prog.go2:4:7: unknown expression type *ast.ListExp

is quite cryptic for the end user in my opinion, so I think it's definitely worth improving. Note, again, that it works fine with single parameter identifiers.

What's more important is that this seems to also break references to identifiers in different packages.
Locally, the go2go tool panics when instantiating multi-parameter imported types/functions.

I don't see that error on tip. Which version of the program are you testing?

@rvolosatovs This is working as expected on tip (types2, and compiler with -G=3 option). It doesn't produce any error message with go/types at the moment, and that seems like a bug. What you are seeing is likely due to running a version that is not fully up-to-date. The go2go playground will be updated eventually, but currently is a bit behind.

@findleyr This program:

package main

func main() {
	some[int, int]()
}

doesn't seem to produce an error message with go/types at the moment.

Change https://golang.org/cl/311669 mentions this issue: go/types: fix panic when using multiple type arguments

Change https://golang.org/cl/312149 mentions this issue: go/types: add more guards against accidentally checking a ListExpr