[BUG] `List` doesn't work at compile time. about mojo HOT 7 OPEN

I went back in time using the following CLI commands
(Note: modular clean removes the entire install of MAX/serving/mojo)

modular clean

modular install nightly/mojo --install-version

and found that this bug does not exist in 2024.6.2305 but does exist in 2024.6.2505.

Additionally, there is some odd - to me as I am truly a rookie with extra time on his hands - behavior. If someone could shed light on the following, I would greatly appreciate it.

As expected:
In 2024.6.2305 through to today (Note use of var)

fn main():
    var l = List[Int](1, 2, 3)
    print(l[0])  # prints 0

In 2024.6.2305 alias behaves as expected

fn main():
    alias l = List[Int](1, 2, 3)
    print(l[0])  # prints 1

However, in 2024.6.2505

fn main():
    alias l = List[Int](1, 2, 3)
    print(l[0])  # prints 0

from mojo.

There is some history of compile time issues as collections switched to returning references. But there is at least one use of alias List in the stdlib so that problem seems to have been solved or occurs much more narrowly than in previous implementations.

If this is a recent breakage as mentioned above then it is probably this commit. My PR (#2847 ) was merged afterward just for the changes to tests if I understood the comment there correctly.

from mojo.

I think we need way more "compile time tests" because those regressions/bugs are really frequent. Not many structs are currently tested at both compile-time and runtime. This could be a very good "good first issue".

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Is this a dup of #3098?

@ematejska I don't think so. #3098 likely has something to do with Tensor and not List.

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@DWSimmons Thanks for the detailed analysis here. Looks like a regression. Still reproduces in mojo 2024.7.905 (e860c551)

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Possibly related to #2847 ?

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Is this a dup of #3098?

from mojo.