Function is_nested_frame_parameter

src/diagnostics/unused_variables.rs:488–506

Check whether a write access at `offset` for variable `name` is actually a parameter declaration of a nested closure or arrow function frame. Closure and arrow function parameters are declared at offsets that fall between `parent.start` and `child.start` — the parent frame body contains them, but `is_in_nested_frame` does not catch them because the child frame's body hasn't started yet. We must

(
    name: &str,
    offset: u32,
    parent: &crate::scope_collector::Frame,
    frames: &[crate::scope_collector::Frame],
)

/// because the child frame's body hasn't started yet.  We must not
/// let the parent frame claim these parameter writes as its own.
fn is_nested_frame_parameter(
    name: &str,
    offset: u32,
    parent: &crate::scope_collector::Frame,
    frames: &[crate::scope_collector::Frame],
) -> bool {
    frames.iter().any(|f| {
        // Only consider frames nested within the parent.
        f.start > parent.start
            && f.end < parent.end
            // The parameter declaration is between the parent body start
            // and the child body start (e.g. in the parameter list of a
            // closure or arrow function).
            && offset < f.start
            && offset > parent.start
            // Check that this variable is actually a parameter of this frame.
            && f.parameters.iter().any(|p| p.as_str() == name)
    })
}

#[cfg(test)]
mod tests {