slint_build::compile panic

[petiaccja]

crash_repro.zip

Bug Description

slint_build crashes with a panic. I've attached an minimal cargo project to reproduce.

PS PATH\crash_repro> cargo build
   Compiling crash-repro v0.1.0 (PATH\crash_repro)
error: failed to run custom build command for `crash-repro v0.1.0 (PATH

[crash_repro.zip](https://github.com/user-attachments/files/19056701/crash_repro.zip)

\crash_repro)`
note: To improve backtraces for build dependencies, set the CARGO_PROFILE_DEV_BUILD_OVERRIDE_DEBUG=true environment variable to enable debug information generation.

Caused by:
  process didn't exit successfully: `PATH\build-script-build` (exit code: 101)
  --- stderr

  thread 'main' panicked at PATH\i-slint-compiler-1.10.0\llr\lower_expression.rs:43:34:
  called `Option::unwrap()` on a `None` value
  stack backtrace:
     0: std::panicking::begin_panic_handler
               at /rustc/4d91de4e48198da2e33413efdcd9cd2cc0c46688/library\std\src\panicking.rs:692
     1: core::panicking::panic_fmt
               at /rustc/4d91de4e48198da2e33413efdcd9cd2cc0c46688/library\core\src\panicking.rs:75
     2: core::panicking::panic
               at /rustc/4d91de4e48198da2e33413efdcd9cd2cc0c46688/library\core\src\panicking.rs:145
     3: core::option::unwrap_failed
               at /rustc/4d91de4e48198da2e33413efdcd9cd2cc0c46688/library\core\src\option.rs:2015
     4: i_slint_compiler::llr::lower_expression::ExpressionLoweringCtx::map_property_reference
     5: i_slint_compiler::llr::lower_expression::lower_expression
     6: i_slint_compiler::llr::lower_expression::lower_expression
     7: i_slint_compiler::llr::lower_expression::lower_expression
     8: i_slint_compiler::llr::lower_expression::lower_expression
     9: i_slint_compiler::llr::lower_expression::lower_expression::{{closure}}
    10: i_slint_compiler::llr::lower_expression::lower_expression
    11: i_slint_compiler::llr::lower_expression::lower_expression::{{closure}}
    12: core::iter::adapters::map::map_fold::{{closure}}
    13: <core::slice::iter::Iter<T> as core::iter::traits::iterator::Iterator>::fold
    14: <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
    15: core::iter::traits::iterator::Iterator::for_each
    16: alloc::vec::Vec<T,A>::extend_trusted
    17: <alloc::vec::Vec<T,A> as alloc::vec::spec_extend::SpecExtend<T,I>>::spec_extend
    18: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter_nested::SpecFromIterNested<T,I>>::from_iter
    19: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter
    20: <alloc::vec::Vec<T> as core::iter::traits::collect::FromIterator<T>>::from_iter
    21: core::iter::traits::iterator::Iterator::collect
    22: i_slint_compiler::llr::lower_expression::lower_expression
    23: i_slint_compiler::llr::lower_to_item_tree::lower_component_container::{{closure}}
    24: i_slint_compiler::llr::lower_to_item_tree::lower_to_item_tree
    25: i_slint_compiler::generator::rust::generate
    26: slint_build::compile_with_config::{{closure}}
    27: core::num::nonzero::NonZero<T>::new_unchecked::precondition_check
    28: slint_build::compile
    29: <core::slice::iter::Iter<T> as core::iter::traits::iterator::Iterator>::size_hint
    30: core::ops::function::FnOnce::call_once
  note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Reproducible Code (if applicable)

Environment Details

• Slint Version: 1.10.0
• Platform/OS: Windows 11
• Programming Language: Slint (via slint_build)
• Backend/Renderer: -

Product Impact

No response

[ogoffart]

Thanks for your bug report and minimal example.

Here is the code that makes the compiler panic:

global State {
    in property <int> tab-names;
}

export component AppWindow inherits Window {
    private property <int> current-tab;
    in property <int> tab-names <=> State.tab-names;
    changed tab-names => {
        current-tab = tab-names;
    }
}