Type Alias with Generics and datatypes causes cgen error

[mike-ward]

Describe the bug

import datatypes

struct Data {
    id string
}

type DataCollection = datatypes.DoublyLinkedList[Data]

fn main() {
    mut data := DataCollection{}
    data.push_back(Data{ id: 'a' })
    for d in data {
        println(d.id)
    }
}

Reproduction Steps

v run the program above

Expected Behavior

Should compile

Current Behavior

cgen error: next method not found

Possible Solution

No response

Additional Information/Context

No response

V version

V 0.4.11 b7b1c2e

Environment details (OS name and version, etc.)

V full version	V 0.4.11 da3112e.b7b1c2e
OS	macos, macOS, 15.5, 24F74
Processor	8 cpus, 64bit, little endian, Apple M2
Memory	0.13GB/8GB
V executable	/Users/mike/Documents/github/v/v
V last modified time	2025-07-12 14:37:24
V home dir	OK, value: /Users/mike/Documents/github/v
VMODULES	OK, value: /Users/mike/.vmodules
VTMP	OK, value: /tmp/v_501
Current working dir	OK, value: /Users/mike/Documents/github/bug
env VFLAGS	"-path @vlib
Git version	git version 2.50.0
V git status	weekly.2025.25-112-gb7b1c2e2
.git/config present	true
cc version	Apple clang version 17.0.0 (clang-1700.0.13.5)
gcc version	Apple clang version 17.0.0 (clang-1700.0.13.5)
clang version	Apple clang version 17.0.0 (clang-1700.0.13.5)
tcc version	tcc version 0.9.28rc 2024-02-05 HEAD@105d70f7 (AArch64 Darwin)
tcc git status	thirdparty-macos-arm64 c8df4e27
emcc version	N/A
glibc version	N/A

Note

You can use the 👍 reaction to increase the issue's priority for developers.

Please note that only the 👍 reaction to the issue itself counts as a vote.
Other reactions and those to comments will not be taken into account.

[huly-for-github]

Connected to Huly®: V_0.6-23320