builder error: struct or union expected

[Eliyaan]

Describe the bug

When compiling the code it outputs a builder error.

Reproduction Steps

struct Parse {
mut:
        stack []&Element
}

struct Balise {}

struct RawText {}

type Element = Balise | RawText

fn (mut p Parse) process_open_tag() {
        mut last := &p.stack[0]
        if mut last is RawText {
        }
}

Expected Behavior

No builder error or an error explaining what is wrong.

Current Behavior

❯ v run main.v
==================
/tmp/v_1000/main.01J1506VYF091BH3R85WEJH7MS.tmp.c:13185: error: struct or union expected
...
==================
(Use `v -cg` to print the entire error message)

builder error

Possible Solution

No response

Additional Information/Context

No response

V version

V 0.4.6 294f7e4.4d2c2da

Environment details (OS name and version, etc.)

OS: linux, Linux version 6.7.11-200.fc39.x86_64 (mockbuild@bdb8d24f206645e2bda44c1cf867612d) (gcc (GCC) 13.2.1 20240316 (Red Hat 13.2.1-7), GNU ld version 2.40-14.fc39) #1 SMP PREEMPT_DYNAMIC Wed Mar 27 16:50:39 UTC 2024

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[JalonSolov]

Compiling with v -g main.v shows the problem to be on line 14... this line:

        if mut last is RawText {