cgen error, when compiling mut r3 := Zip[int,int]{}, for struct Zip[A,B] { a Iterator[A] b Iterator[B] }

[spytheman]

V version: V 0.4.9 6b0c272, press to see full `v doctor` output

V full version	V 0.4.9 bd10e12.6b0c272
OS	linux, Ubuntu 20.04.6 LTS
Processor	4 cpus, 64bit, little endian, Intel(R) Core(TM) i3-3225 CPU @ 3.30GHz
Memory	3.3GB/15.05GB
V executable	/home/delian/code/v/v
V last modified time	2025-01-23 09:58:28
V home dir	OK, value: /home/delian/code/v
VMODULES	OK, value: /home/delian/.vmodules
VTMP	OK, value: /tmp/v_1000
Current working dir	OK, value: /home/delian/code/v
Git version	git version 2.47.1
V git status	weekly.2025.03-25-g6b0c2722
.git/config present	true
cc version	cc (Ubuntu 10.5.0-1ubuntu1~20.04) 10.5.0
gcc version	gcc (Ubuntu 10.5.0-1ubuntu1~20.04) 10.5.0
clang version	clang version 10.0.0-4ubuntu1
tcc version	tcc version 0.9.28rc 2024-07-31 HEAD@1cee0908 (x86_64 Linux)
tcc git status	thirdparty-linux-amd64 0134e9b9
emcc version	N/A
glibc version	ldd (Ubuntu GLIBC 2.31-0ubuntu9.16) 2.31

What did you do?
./v -g -o vdbg cmd/v && ./vdbg /home/delian/r.v && /home/delian/r

pub struct Range[T] {
pub:
	from T
	to T
	inclusive bool
pub mut:	
	step T = T(1)
	i T
mut:	
	started bool
}

pub fn (mut r Range[T]) next[T]() ?T {
	if !r.started {
		r.started = true
		assert r.step > 0
		if r.from > r.to {
			r.step = -r.step
		}
		r.i = r.from
	}
	i := r.i
	next_i := i + r.step
	if r.inclusive {
		if r.step < 0 && i < r.to {
			return none
		}
		if r.step > 0 && i > r.to {
			return none
		}
	} else {
		if r.step < 0 && i <= r.to {
			return none
		}
		if r.step > 0 && i >= r.to {
			return none
		}
	}
	r.i = next_i
	return i
}


pub interface Iterator[T] {
mut:
	next() ?T
}

pub struct Zip[A,B] {
mut:
	a Iterator[A]
	b Iterator[B]
}
pub struct Pair[A,B] {
	a A
	b B
}

pub fn (mut z Zip[A,B]) next[A,B]() ?Pair[A,B] {
	a := z.a.next()?
	b := z.b.next()?
	return Pair[A,B]{a,b}
}

for i in Range{from: 5, to: 10} { println('from 5 to 10, i= ${i}') }
for i in Range{from: 5, to: 10, inclusive: true} { println('from 5 to 10, inclusive, i= ${i}') }
for i in Range{from: 10, to: 5, inclusive: true} { println('from 10 to 5, inclusive, i= ${i}') }
for i in Range{from: 10, to: 5} { println('from 10 to 5, i= ${i}') }

for x in Range{from: 2.0, to: 3.0, step: 0.5} { println('from 2.0 to 3.0, step: 0.5, i= ${x}') }
for x in Range{from: 2.0, to: 3.0, step: 0.5, inclusive: true} { println('from 2.0 to 3.0, step: 0.5, inclusive, i= ${x}') }

mut r1 := Range{from: 5, to: 10}
mut i1 := Iterator[int](r1)
println(i1)
mut r2 := Range{from: 10, to: 5}
mut i2 := Iterator[int](r2)
println(i2)

mut r3 := Zip[int,int]{} // cgen error for main__Iterator_T_int
//r3.a = i1 // checker error: cannot implement interface `Iterator<A>[int]` with a different interface `Iterator[int]`
//r3.b = i2 // checker error: cannot implement interface `Iterator<A>[int]` with a different interface `Iterator[int]`
//dump(r3)
//for x in r3 {
//	println(x)
//}

What did you see?

/home/delian/r.v:80:11: notice: interface field `Zip[int, int].a` must be initialized
   78 | println(i2)
   79 | 
   80 | mut r3 := Zip[int,int]{} // cgen error for main__Iterator_T_int
      |           ~~~~~~~~~~~~~~
   81 | //r3.a = i1 // checker error: cannot implement interface `Iterator<A>[int]` with a different interface `Iterator[int]`
   82 | //r3.b = i2 // checker error: cannot implement interface `Iterator<A>[int]` with a different interface `Iterator[int]`
/home/delian/r.v:80:11: notice: interface field `Zip[int, int].b` must be initialized
   78 | println(i2)
   79 | 
   80 | mut r3 := Zip[int,int]{} // cgen error for main__Iterator_T_int
      |           ~~~~~~~~~~~~~~
   81 | //r3.a = i1 // checker error: cannot implement interface `Iterator<A>[int]` with a different interface `Iterator[int]`
   82 | //r3.b = i2 // checker error: cannot implement interface `Iterator<A>[int]` with a different interface `Iterator[int]`
/home/delian/r.v:80:5: warning: unused variable: `r3`
   78 | println(i2)
   79 | 
   80 | mut r3 := Zip[int,int]{} // cgen error for main__Iterator_T_int
      |     ~~
   81 | //r3.a = i1 // checker error: cannot implement interface `Iterator<A>[int]` with a different interface `Iterator[int]`
   82 | //r3.b = i2 // checker error: cannot implement interface `Iterator<A>[int]` with a different interface `Iterator[int]`
================== C compilation error (from tcc): ==============
cc: /tmp/v_1000/r.01JJ99K99KTPH0SK41R6JFASP5.tmp.c:861: error: struct/union/enum already defined
=================================================================
(You can pass `-cg`, or `-show-c-output` as well, to print all the C error messages).

What did you expect to see?

a compiled program

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