Error: Failed to run custom build command

[Tastaturtaste]

I am currently checking out slint and tried to write a simple lights-out game. The slint GUI code seems to be fine, because the "Show Preview" inline button in vscode opens the window as expected and it also works in SlintPad.

The build.rs was automatically generated by the cargo-generate command and the slint project template. Its contents are:

fn main() {
    slint_build::compile("ui/appwindow.slint").unwrap();
}

The complete error message with RUST_BACKTRACE=1 is as follows:

Error Message

Compiling lights-out v0.1.0 (I:\dev\lights-out)
error: failed to run custom build command for `lights-out v0.1.0 (I:\dev\lights-out)`

Caused by:
  process didn't exit successfully: `I:\dev\lights-out\target\debug\build\lights-out-fca21e9d9512d328\build-script-build` (exit code: 101)
  --- stderr
  thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', C:\Users\joshu\.cargo\registry\src\index.crates.io-6f17d22bba15001f\i-slint-compiler-1.0.2\generator\rust.rs:690:71
  stack backtrace:
     0: std::panicking::begin_panic_handler
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library\std\src\panicking.rs:578
     1: core::panicking::panic_fmt
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library\core\src\panicking.rs:67
     2: core::panicking::panic
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library\core\src\panicking.rs:117
     3: enum2$<core::option::Option<proc_macro2::TokenStream> >::unwrap<proc_macro2::TokenStream>
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca\library\core\src\option.rs:950
     4: i_slint_compiler::generator::rust::generate_sub_component
               at C:\Users\joshu\.cargo\registry\src\index.crates.io-6f17d22bba15001f\i-slint-compiler-1.0.2\generator\rust.rs:690
     5: i_slint_compiler::generator::rust::generate_item_tree
               at C:\Users\joshu\.cargo\registry\src\index.crates.io-6f17d22bba15001f\i-slint-compiler-1.0.2\generator\rust.rs:1242
     6: i_slint_compiler::generator::rust::generate_repeated_component
               at C:\Users\joshu\.cargo\registry\src\index.crates.io-6f17d22bba15001f\i-slint-compiler-1.0.2\generator\rust.rs:1478
     7: i_slint_compiler::generator::rust::generate_sub_component
               at C:\Users\joshu\.cargo\registry\src\index.crates.io-6f17d22bba15001f\i-slint-compiler-1.0.2\generator\rust.rs:743
     8: i_slint_compiler::generator::rust::generate::closure$1
               at C:\Users\joshu\.cargo\registry\src\index.crates.io-6f17d22bba15001f\i-slint-compiler-1.0.2\generator\rust.rs:163
     9: core::iter::adapters::map::map_fold::closure$0<ref$<alloc::rc::Rc<i_slint_compiler::llr::item_tree::SubComponent> >,proc_macro2::TokenStream,tuple$<>,i_slint_compiler::generator::rust::generate::closure_env$1,core::iter::traits::iterator::Iterator::for_ea
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca\library\core\src\iter\adapters\map.rs:84
    10: core::iter::traits::iterator::Iterator::fold<core::slice::iter::Iter<alloc::rc::Rc<i_slint_compiler::llr::item_tree::SubComponent> >,tuple$<>,core::iter::adapters::map::map_fold::closure_env$0<ref$<alloc::rc::Rc<i_slint_compiler::llr::item_tree::SubCompon
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca\library\core\src\iter\traits\iterator.rs:2482
    11: core::iter::adapters::map::impl$2::fold<proc_macro2::TokenStream,core::slice::iter::Iter<alloc::rc::Rc<i_slint_compiler::llr::item_tree::SubComponent> >,i_slint_compiler::generator::rust::generate::closure_env$1,tuple$<>,core::iter::traits::iterator::Iter
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca\library\core\src\iter\adapters\map.rs:124
    12: core::iter::traits::iterator::Iterator::for_each<core::iter::adapters::map::Map<core::slice::iter::Iter<alloc::rc::Rc<i_slint_compiler::llr::item_tree::SubComponent> >,i_slint_compiler::generator::rust::generate::closure_env$1>,alloc::vec::impl$20::extend
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca\library\core\src\iter\traits\iterator.rs:857
    13: alloc::vec::Vec<proc_macro2::TokenStream,alloc::alloc::Global>::extend_trusted<proc_macro2::TokenStream,alloc::alloc::Global,core::iter::adapters::map::Map<core::slice::iter::Iter<alloc::rc::Rc<i_slint_compiler::llr::item_tree::SubComponent> >,i_slint_com
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca\library\alloc\src\vec\mod.rs:2844
    14: alloc::vec::spec_extend::impl$1::spec_extend<proc_macro2::TokenStream,core::iter::adapters::map::Map<core::slice::iter::Iter<alloc::rc::Rc<i_slint_compiler::llr::item_tree::SubComponent> >,i_slint_compiler::generator::rust::generate::closure_env$1>,alloc:
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca\library\alloc\src\vec\spec_extend.rs:26
    15: alloc::vec::spec_from_iter_nested::impl$1::from_iter<proc_macro2::TokenStream,core::iter::adapters::map::Map<core::slice::iter::Iter<alloc::rc::Rc<i_slint_compiler::llr::item_tree::SubComponent> >,i_slint_compiler::generator::rust::generate::closure_env$1
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca\library\alloc\src\vec\spec_from_iter_nested.rs:62
    16: alloc::vec::spec_from_iter::impl$0::from_iter<proc_macro2::TokenStream,core::iter::adapters::map::Map<core::slice::iter::Iter<alloc::rc::Rc<i_slint_compiler::llr::item_tree::SubComponent> >,i_slint_compiler::generator::rust::generate::closure_env$1> >
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca\library\alloc\src\vec\spec_from_iter.rs:33
    17: alloc::vec::impl$15::from_iter<proc_macro2::TokenStream,core::iter::adapters::map::Map<core::slice::iter::Iter<alloc::rc::Rc<i_slint_compiler::llr::item_tree::SubComponent> >,i_slint_compiler::generator::rust::generate::closure_env$1> >
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca\library\alloc\src\vec\mod.rs:2712
    18: core::iter::traits::iterator::Iterator::collect<core::iter::adapters::map::Map<core::slice::iter::Iter<alloc::rc::Rc<i_slint_compiler::llr::item_tree::SubComponent> >,i_slint_compiler::generator::rust::generate::closure_env$1>,alloc::vec::Vec<proc_macro2:
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca\library\core\src\iter\traits\iterator.rs:1896
    19: i_slint_compiler::generator::rust::generate
               at C:\Users\joshu\.cargo\registry\src\index.crates.io-6f17d22bba15001f\i-slint-compiler-1.0.2\generator\rust.rs:160
    20: slint_build::compile_with_config<ref$<str$> >
               at C:\Users\joshu\.cargo\registry\src\index.crates.io-6f17d22bba15001f\slint-build-1.0.2\lib.rs:338
    21: slint_build::compile<ref$<str$> >
               at C:\Users\joshu\.cargo\registry\src\index.crates.io-6f17d22bba15001f\slint-build-1.0.2\lib.rs:272
    22: build_script_build::main
               at .\build.rs:2
    23: core::ops::function::FnOnce::call_once<void (*)(),tuple$<> >
               at /rustc/90c541806f23a127002de5b4038be731ba1458ca\library\core\src\ops\function.rs:250
  note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Any help would be appreciated.

Edit:
I use slint_build 1.0.2 with rust 1.70 on Windows.

[ogoffart]

I think the problem here is this line:

private property <percent> pad_pct: 5%;

The percent type is an internal type that wasn't really meant to be used as a property.
And it doesn't have an equivalent type in tust, hence the abort.
Where did you find out about this type?

We probably should either have a warning, or somehow a better error when converting to rust. Or maybe just support this type.
@tronical : what do you think?

[tronical]

I'd say supporting it makes sense. Stored as float in 0..1 range?

[Tastaturtaste]

Where did you find out about this type?

In the official slint language documentation :D

[Tastaturtaste]

I think the problem here is this line:

private property <percent> pad_pct: 5%;

Sadly that was not the problem. I replaced this line with

private property <float> pad_pct: 0.05;

but get the same error message.

[Tastaturtaste]

I managed to trace the error back to the for loop:

for tile[idx] in (size*size): Tile{
    width: button_width;
    height: button_height;
    x: pad_width + mod(idx, size) * (self.width + pad_width);
    y: pad_height + floor(idx / size) * (self.height + pad_height);
    notify_clicked => { parent.notify_clicked(mod(idx,size), floor(idx / size)) }
}

Changing the expression (size*size) to a precomputed property private property <int> N: size*size; does not panic and works as expected.