shuck-linter 0.0.43

use std::collections::{HashMap, HashSet};

use compact_str::CompactString;
use shuck_semantic::{
    Binding, BindingAttributes, BindingId, BindingKind, BindingOrigin, ReferenceKind,
};

use crate::{Checker, Diagnostic, Edit, Fix, FixAvailability, Rule, Violation};

type BindingFamilyKey = String;

pub struct UnusedAssignment {
    pub name: CompactString,
}

impl Violation for UnusedAssignment {
    const FIX_AVAILABILITY: FixAvailability = FixAvailability::Always;

    fn rule() -> Rule {
        Rule::UnusedAssignment
    }

    fn message(&self) -> String {
        format!("variable `{}` is assigned but never used", self.name)
    }

    fn fix_title(&self) -> Option<String> {
        Some("rename the unused assignment target to `_`".to_owned())
    }
}

pub fn unused_assignment(checker: &mut Checker) {
    let semantic = checker.semantic();
    if all_reportable_assignment_spans_suppressed(checker, semantic) {
        return;
    }

    let mut unused_bindings = checker
        .semantic_analysis()
        .unused_assignments_with_options(checker.rule_options().c001.semantic_options())
        .to_vec();
    for binding in semantic.bindings() {
        if matches!(binding.kind, BindingKind::ReadTarget)
            && binding.references.is_empty()
            && !binding
                .attributes
                .contains(BindingAttributes::EXTERNALLY_CONSUMED)
            && !semantic.is_runtime_consumed_binding(binding.id)
            && !unused_bindings.contains(&binding.id)
        {
            unused_bindings.push(binding.id);
        }
    }
    let unused_binding_ids = unused_bindings.iter().copied().collect::<HashSet<_>>();
    let mut families_with_used_bindings = HashSet::new();
    let mut suppressed_binding_offsets_by_family = HashMap::<BindingFamilyKey, Vec<usize>>::new();
    let mut unused_bindings_by_family = HashMap::<BindingFamilyKey, Vec<_>>::new();
    let mut last_unused_binding_by_family = HashMap::new();
    let mut family_keys = HashMap::with_capacity(semantic.bindings().len());

    for binding in semantic.bindings() {
        if is_intentionally_unused_binding(binding) {
            continue;
        }

        family_keys.insert(binding.id, binding.name.to_string());
    }

    for reference in semantic.references() {
        if matches!(reference.kind, ReferenceKind::DeclarationName)
            || is_underscore_name(reference.name.as_str())
        {
            continue;
        }

        families_with_used_bindings.insert(reference.name.to_string());
    }

    for binding in semantic.bindings() {
        if is_intentionally_unused_binding(binding) {
            continue;
        }

        if !participates_in_unused_assignment_family(binding.kind, binding.attributes) {
            continue;
        }

        let family = binding_family_key(&family_keys, binding.id);
        let report_span = report_span_for_binding(checker, binding);
        if checker.is_suppressed_at(Rule::UnusedAssignment, report_span) {
            suppressed_binding_offsets_by_family
                .entry(family.clone())
                .or_default()
                .push(report_span.start.offset);
        }

        if binding.attributes.contains(BindingAttributes::EXPORTED) {
            families_with_used_bindings.insert(family);
            continue;
        }

        if binding_counts_as_used_family_member(binding, &unused_binding_ids) {
            families_with_used_bindings.insert(family);
        }
    }

    for binding_id in &unused_bindings {
        let binding = semantic.binding(*binding_id);
        if is_intentionally_unused_binding(binding) {
            continue;
        }

        if !is_reportable_unused_assignment(binding.kind, binding.attributes) {
            continue;
        }

        let family = binding_family_key(&family_keys, binding.id);

        unused_bindings_by_family
            .entry(family.clone())
            .or_default()
            .push(*binding_id);

        last_unused_binding_by_family
            .entry(family)
            .and_modify(|current_binding_id| {
                let current = semantic.binding(*current_binding_id);
                if binding_follows_in_source(
                    current.span.start.offset,
                    current.span.end.offset,
                    binding.span.start.offset,
                    binding.span.end.offset,
                ) {
                    *current_binding_id = *binding_id;
                }
            })
            .or_insert(*binding_id);
    }

    let mut reportable_bindings = Vec::new();
    for family in unused_bindings_by_family.keys() {
        if families_with_used_bindings.contains(family) {
            continue;
        }

        if let Some(binding_id) = last_unused_binding_by_family.get(family).copied() {
            let binding = semantic.binding(binding_id);
            let report_offset = report_span_for_binding(checker, binding).start.offset;
            if suppressed_binding_offsets_by_family
                .get(family)
                .is_some_and(|offsets| offsets.iter().any(|offset| *offset >= report_offset))
            {
                continue;
            }
            reportable_bindings.push(binding_id);
        }
    }
    reportable_bindings
        .sort_unstable_by_key(|binding_id| semantic.binding(*binding_id).span.start.offset);

    for binding_id in reportable_bindings {
        let binding = semantic.binding(binding_id);

        if !is_reportable_unused_assignment(binding.kind, binding.attributes) {
            continue;
        }

        // Exported variables are consumed by child processes.
        if binding.attributes.contains(BindingAttributes::EXPORTED) {
            continue;
        }

        // Namerefs redirect to another variable; the binding itself is not
        // a conventional assignment.
        if matches!(binding.kind, BindingKind::Nameref) {
            continue;
        }

        let name: CompactString = binding.name.as_str().into();
        let report_span = report_span_for_binding(checker, binding);
        let fix_span = binding.span;

        checker.report_diagnostic(
            Diagnostic::new(UnusedAssignment { name }, report_span)
                .with_fix(Fix::unsafe_edit(Edit::replacement("_", fix_span))),
        );
    }
}

fn all_reportable_assignment_spans_suppressed(
    checker: &Checker<'_>,
    semantic: &shuck_semantic::SemanticModel,
) -> bool {
    let mut saw_reportable_binding = false;
    for binding in semantic.bindings() {
        if is_intentionally_unused_binding(binding) {
            continue;
        }

        if !is_reportable_unused_assignment(binding.kind, binding.attributes) {
            continue;
        }

        if binding.attributes.contains(BindingAttributes::EXPORTED)
            || matches!(binding.kind, BindingKind::Nameref)
        {
            continue;
        }

        saw_reportable_binding = true;
        if !checker.is_suppressed_at(
            Rule::UnusedAssignment,
            report_span_for_binding(checker, binding),
        ) {
            return false;
        }
    }

    saw_reportable_binding
}

fn is_intentionally_unused_binding(binding: &Binding) -> bool {
    is_underscore_name(binding.name.as_str()) || is_intentionally_unused_placeholder(binding)
}

fn is_intentionally_unused_placeholder(binding: &Binding) -> bool {
    if !matches!(binding.name.as_str(), "rest" | "REST") {
        return false;
    }

    matches!(binding.kind, BindingKind::ReadTarget)
        || (matches!(binding.kind, BindingKind::Declaration(_))
            && binding.attributes.contains(BindingAttributes::LOCAL)
            && !binding
                .attributes
                .contains(BindingAttributes::DECLARATION_INITIALIZED))
}

fn is_underscore_name(name: &str) -> bool {
    name.starts_with('_')
}

fn is_reportable_unused_assignment(kind: BindingKind, _attributes: BindingAttributes) -> bool {
    match kind {
        BindingKind::Assignment
        | BindingKind::ArrayAssignment
        | BindingKind::LoopVariable
        | BindingKind::ReadTarget
        | BindingKind::MapfileTarget
        | BindingKind::PrintfTarget
        | BindingKind::GetoptsTarget
        | BindingKind::ZparseoptsTarget
        | BindingKind::ArithmeticAssignment => true,
        BindingKind::AppendAssignment | BindingKind::ParameterDefaultAssignment => false,
        BindingKind::Declaration(_) => true,
        BindingKind::FunctionDefinition | BindingKind::Imported | BindingKind::Nameref => false,
    }
}

fn participates_in_unused_assignment_family(
    kind: BindingKind,
    _attributes: BindingAttributes,
) -> bool {
    matches!(
        kind,
        BindingKind::Assignment
            | BindingKind::ArrayAssignment
            | BindingKind::LoopVariable
            | BindingKind::ReadTarget
            | BindingKind::MapfileTarget
            | BindingKind::PrintfTarget
            | BindingKind::GetoptsTarget
            | BindingKind::ArithmeticAssignment
            | BindingKind::AppendAssignment
            | BindingKind::ParameterDefaultAssignment
            | BindingKind::Declaration(_)
    )
}

fn binding_counts_as_used_family_member(
    binding: &Binding,
    unused_binding_ids: &HashSet<BindingId>,
) -> bool {
    if matches!(binding.kind, BindingKind::AppendAssignment) {
        return true;
    }

    if binding
        .attributes
        .contains(BindingAttributes::SELF_REFERENTIAL_READ)
    {
        return true;
    }

    if binding
        .attributes
        .contains(BindingAttributes::EMPTY_INITIALIZER)
    {
        return false;
    }

    if unused_binding_ids.contains(&binding.id) {
        return false;
    }

    if matches!(binding.kind, BindingKind::Declaration(_))
        && !binding
            .attributes
            .contains(BindingAttributes::DECLARATION_INITIALIZED)
    {
        return false;
    }

    true
}

fn report_span_for_binding(checker: &Checker<'_>, binding: &Binding) -> shuck_ast::Span {
    match binding.origin {
        BindingOrigin::LoopVariable {
            definition_span, ..
        } => loop_keyword_report_span(checker, definition_span).unwrap_or(definition_span),
        BindingOrigin::Assignment {
            definition_span, ..
        }
        | BindingOrigin::ParameterDefaultAssignment {
            definition_span, ..
        }
        | BindingOrigin::Imported { definition_span }
        | BindingOrigin::FunctionDefinition { definition_span }
        | BindingOrigin::BuiltinTarget {
            definition_span, ..
        }
        | BindingOrigin::Declaration { definition_span }
        | BindingOrigin::Nameref { definition_span } => definition_span,
        BindingOrigin::ArithmeticAssignment { target_span, .. } => target_span,
    }
}

fn loop_keyword_report_span(
    checker: &Checker<'_>,
    definition_span: shuck_ast::Span,
) -> Option<shuck_ast::Span> {
    if let Some(header) = checker
        .facts()
        .command_facts()
        .for_headers()
        .iter()
        .find(|header| {
            header
                .command()
                .targets
                .iter()
                .any(|target| target.span == definition_span)
        })
    {
        return Some(keyword_span(header.command().span, "for"));
    }

    checker
        .facts()
        .command_facts()
        .select_headers()
        .iter()
        .find(|header| header.command().variable_span == definition_span)
        .map(|header| keyword_span(header.command().span, "select"))
}

fn keyword_span(command_span: shuck_ast::Span, keyword: &str) -> shuck_ast::Span {
    shuck_ast::Span::from_positions(command_span.start, command_span.start.advanced_by(keyword))
}

fn binding_follows_in_source(
    current_start: usize,
    current_end: usize,
    candidate_start: usize,
    candidate_end: usize,
) -> bool {
    candidate_start > current_start
        || (candidate_start == current_start && candidate_end > current_end)
}

fn binding_family_key(
    family_keys: &HashMap<BindingId, BindingFamilyKey>,
    binding_id: BindingId,
) -> BindingFamilyKey {
    family_keys.get(&binding_id).cloned().unwrap_or_default()
}

#[cfg(test)]
mod tests {
    use std::path::Path;

    use crate::test::{
        test_path_with_fix, test_snippet, test_snippet_at_path, test_snippet_with_fix,
    };
    use crate::{Applicability, LinterSettings, Rule, ShellDialect, assert_diagnostics_diff};

    #[test]
    fn anchors_on_variable_name_span_and_attaches_fix_metadata() {
        let source = "#!/bin/sh\nunused=1\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "unused");
        assert_eq!(
            diagnostics[0].fix.as_ref().map(|fix| fix.applicability()),
            Some(Applicability::Unsafe)
        );
        assert_eq!(
            diagnostics[0].fix_title.as_deref(),
            Some("rename the unused assignment target to `_`")
        );
    }

    #[test]
    fn applies_unsafe_fix_to_reported_assignment_targets() {
        let source = "\
#!/bin/bash
unused=1
arr[0]=x
read -r read_target <<< \"value\"
printf -v printf_target '%s' ok
while getopts \"ab\" opt; do
  :
done
((arith = 1))
for item in a b; do
  :
done
";
        let result = test_snippet_with_fix(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment),
            Applicability::Unsafe,
        );

        assert_eq!(result.fixes_applied, 7);
        assert_eq!(
            result.fixed_source,
            "\
#!/bin/bash
_=1
_[0]=x
read -r _ <<< \"value\"
printf -v _ '%s' ok
while getopts \"ab\" _; do
  :
done
((_ = 1))
for _ in a b; do
  :
done
"
        );
        assert!(result.fixed_diagnostics.is_empty());
    }

    #[test]
    fn leaves_existing_underscore_targets_unchanged_when_fixing() {
        let source = "\
#!/bin/bash
_=1
_[0]=x
read -r _ <<< \"value\"
printf -v _ '%s' ok
while getopts \"ab\" _; do
  :
done
((_ = 1))
for _ in a b; do
  :
done
";
        let result = test_snippet_with_fix(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment),
            Applicability::Unsafe,
        );

        assert_eq!(result.fixes_applied, 0);
        assert_eq!(result.fixed_source, source);
        assert!(result.fixed_diagnostics.is_empty());
    }

    #[test]
    fn snapshots_unsafe_fix_output_for_fixture() -> anyhow::Result<()> {
        let result = test_path_with_fix(
            Path::new("correctness").join("C001.sh").as_path(),
            &LinterSettings::for_rule(Rule::UnusedAssignment),
            Applicability::Unsafe,
        )?;

        assert_diagnostics_diff!("C001_fix_C001.sh", result);
        Ok(())
    }

    #[test]
    fn reports_only_the_last_unused_binding_for_a_name() {
        let source = "#!/bin/sh\nfoo=1\nfoo=2\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.start.line, 3);
        assert_eq!(diagnostics[0].span.slice(source), "foo");
    }

    #[test]
    fn reads_before_assignments_suppress_unused_assignment_for_that_name() {
        let source = "#!/bin/bash\necho \"$foo\"\nfoo=1\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn uncalled_function_reads_suppress_unused_assignment_for_that_name() {
        let source = "#!/bin/bash\nfoo=1\nshow_foo() { echo \"$foo\"; }\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn variable_reads_do_not_conflict_with_same_named_functions() {
        let source = "#!/bin/bash\nprogress=\nprogress=1\nprogress() { :; }\n[ \"$progress\" ] && progress ok\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn zsh_associative_key_literals_do_not_count_as_assignment_reads() {
        let source = "\
#!/bin/zsh
ice=1
iterm2_precmd=1
typeset -A ZINIT
ZINIT[ice-list]=x
functions[iterm2_precmd]=x
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        let names = diagnostics
            .iter()
            .map(|diagnostic| diagnostic.span.slice(source))
            .collect::<Vec<_>>();
        assert!(names.contains(&"ice"), "{diagnostics:#?}");
        assert!(names.contains(&"iterm2_precmd"), "{diagnostics:#?}");
    }

    #[test]
    fn zsh_describe_by_name_arrays_count_as_reads() {
        let source = "\
#!/bin/zsh
cmds=(init:Initialize update:Update)
subcmds=(add:Add remove:Remove)
refs=(main:Main)
_describe 'command' cmds
_describe -t commands command subcmds
_describe -V -t git-refs 'Git References' refs -U
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert!(diagnostics.is_empty(), "{diagnostics:#?}");
    }

    #[test]
    fn zsh_describe_reads_up_to_two_static_array_operands_after_the_description() {
        let source = "\
#!/bin/zsh
primary=(init:Initialize update:Update)
secondary=(add:Add remove:Remove)
tertiary=(main:Main)
_describe -- 'command' primary secondary tertiary
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["tertiary"]
        );
    }

    #[test]
    fn zsh_describe_does_not_treat_options_as_reads() {
        let source = "\
#!/bin/zsh
tag=1
display=1
description=1
consumed=(init:Initialize update:Update)
_describe -t tag -T display description consumed -U
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["tag", "display"]
        );
    }

    #[test]
    fn zsh_describe_o_option_does_not_take_a_value() {
        let source = "\
#!/bin/zsh
opt=-o
nosort=1
description=1
consumed=(init:Initialize update:Update)
_describe -o nosort description consumed
_describe $opt nosort description consumed
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["nosort"]
        );
    }

    #[test]
    fn zsh_describe_does_not_treat_trailing_option_operands_as_reads() {
        let source = "\
#!/bin/zsh
cmds=(init:Initialize update:Update)
group=commands
message=Commands
prefix='('
suffix=')'
_describe 'command' cmds -V group -X message -P prefix -S suffix -U
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["group", "message", "prefix", "suffix"]
        );
    }

    #[test]
    fn zsh_describe_ignores_dynamic_array_names() {
        let source = "\
#!/bin/zsh
target=choices
choices=(init:Initialize update:Update)
_describe 'command' $target
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["choices"]
        );
    }

    #[test]
    fn describe_by_name_reads_are_zsh_only() {
        let source = "\
#!/bin/bash
cmds=(init update)
_describe 'command' cmds
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Bash),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["cmds"]
        );
    }

    #[test]
    fn read_rest_names_are_treated_as_intentional_placeholders() {
        let source = "#!/bin/bash\nread -r cron_id rest\nprintf '%s\\n' \"$cron_id\"\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn function_declaration_queries_do_not_create_unused_variable_targets() {
        let source = "\
#!/bin/bash
if ! declare -f -F config_unset >/dev/null; then
  :
fi
eval \"$(declare -f cd)\"
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn plain_rest_names_are_reported() {
        let source = "#!/bin/bash\nrest=1\nREST=2\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 2);
        assert_eq!(diagnostics[0].span.slice(source), "rest");
        assert_eq!(diagnostics[1].span.slice(source), "REST");
    }

    #[test]
    fn shell_runtime_environment_assignments_are_suppressed() {
        let source = "\
#!/bin/bash
HOSTNAME=example
LD_LIBRARY_PATH=/tmp/lib
APP_NAME=demo
declare -Ap ADD=([de]=Deutsch)
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "APP_NAME");
    }

    #[test]
    fn name_only_rest_declarations_are_placeholders() {
        let source = "\
#!/bin/bash
f() {
  local rest
  local REST
}
f
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn uppercase_references_do_not_hide_lowercase_read_targets() {
        let source = "#!/bin/bash\nread -r endpoint\necho \"$ENDPOINT\"\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "endpoint");
    }

    #[test]
    fn runtime_consumed_read_targets_are_not_reintroduced() {
        let source = "\
#!/bin/bash
read -d '' -ra COMPREPLY < <(compgen -W \"one two\" -- \"$cur\")
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn zsh_describe_named_array_operand_counts_as_use() {
        let source = "\
#!/bin/zsh
cmds=(git:'run git')
_describe -t commands 'external command' cmds
unused=(other:'unused')
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "unused");
    }

    #[test]
    fn zsh_describe_consumes_names_after_options_and_separator() {
        let source = "\
#!/bin/zsh
cmds=(git:'run git')
other_cmds=(hg:'run hg')
_describe -O 'external command' cmds
_describe -- 'other command' other_cmds
unused=(other:'unused')
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "unused");
    }

    #[test]
    fn zsh_describe_consumes_optional_second_array_operand() {
        let source = "\
#!/bin/zsh
values=(git)
descriptions=(git:'run git')
_describe 'external command' values descriptions
unused=(other:'unused')
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "unused");
    }

    #[test]
    fn zsh_describe_consumes_array_operand_after_dynamic_description() {
        let source = "\
#!/bin/zsh
desc='external command'
values=(git)
descriptions=(git:'run git')
_describe \"$desc\" values descriptions
unused=(other:'unused')
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "unused");
    }

    #[test]
    fn zsh_describe_does_not_consume_descriptor_after_dynamic_no_value_options() {
        let source = "\
#!/bin/zsh
opts='-o'
desc=(not:target)
values=(git)
_describe \"$opts\" desc values
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "desc");
    }

    #[test]
    fn zsh_describe_consumes_array_operand_after_group_separator() {
        let source = "\
#!/bin/zsh
values=(git)
more_values=(hg)
more_descriptions=(hg:'run hg')
_describe 'external command' values -- more_values more_descriptions
unused=(other:'unused')
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "unused");
    }

    #[test]
    fn zsh_zstyle_named_target_counts_as_assignment() {
        let source = "\
#!/bin/zsh
zstyle -a ':prezto:load' pmodule-dirs user_pmodule_dirs
print -r -- $user_pmodule_dirs
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn unreachable_assignments_are_still_checked() {
        let source = "\
#!/bin/bash
f() {
  return 1
  dead=1
  used=1
  printf '%s\\n' \"$used\"
}
f
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "dead");
    }

    #[test]
    fn read_rest_placeholders_do_not_hide_real_dead_assignments() {
        let source = "\
#!/bin/bash
rest=1
read -r field rest
printf '%s\\n' \"$field\"
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "rest");
        assert_eq!(diagnostics[0].span.start.line, 2);
    }

    #[test]
    fn rest_placeholders_are_ignored_across_branch_shapes() {
        let source = "\
#!/bin/bash
f(){
  if cond; then
    local rest
  else
    read -r _ rest
  fi
}
f
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn unread_read_targets_are_still_reported() {
        let source = "#!/bin/bash\nread -r first second\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 2);
        assert_eq!(diagnostics[0].span.slice(source), "first");
        assert_eq!(diagnostics[1].span.slice(source), "second");
    }

    #[test]
    fn reports_last_dead_binding_when_every_conditional_arm_assigns_the_name() {
        let source = "\
#!/bin/sh
if [ \"$ARCH\" = \"arm\" ]; then
  LIBDIRSUFFIX=\"\"
elif [ \"$ARCH\" = \"x86_64\" ]; then
  LIBDIRSUFFIX=\"64\"
else
  LIBDIRSUFFIX=\"\"
fi
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.start.line, 7);
        assert_eq!(diagnostics[0].span.slice(source), "LIBDIRSUFFIX");
    }

    #[test]
    fn reports_last_dead_binding_when_branch_family_ends_with_empty_clear() {
        let source = "\
#!/bin/sh
if [ \"$ARCH\" = \"arm\" ]; then
  foo=\"x\"
else
  foo=\"\"
fi
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.start.line, 5);
        assert_eq!(diagnostics[0].span.slice(source), "foo");
    }

    #[test]
    fn array_writes_collapse_to_the_last_name_report() {
        let source = "#!/bin/bash\nemoji[grinning]=1\nprintf '%s\\n' \"$OTHER\"\nemoji[smile]=2\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.start.line, 4);
        assert_eq!(diagnostics[0].span.slice(source), "emoji[smile]");
    }

    #[test]
    fn array_element_reads_keep_the_family_live() {
        let source = "\
#!/bin/bash
declare -A map
map[used]=1
printf '%s\\n' \"${map[used]}\"
map[dead]=2
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn arithmetic_indexed_writes_collapse_to_the_last_name_report() {
        let source = "#!/bin/bash\n(( box[1] = 1 ))\n(( box[2] = 2 ))\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.start.line, 3);
    }

    #[test]
    fn local_families_collapse_by_name_inside_subshells() {
        let source = "#!/bin/bash\n(f(){ local foo=1; }\ng(){ local foo=2; }\nf\ng)\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.start.line, 3);
    }

    #[test]
    fn uses_source_order_when_function_bindings_share_a_name() {
        let source = "#!/bin/bash\nf(){ foo=1; }\nfoo=2\nf\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.start.line, 3);
    }

    #[test]
    fn reports_unused_for_loop_counters() {
        let source = "\
#!/bin/bash
unused=1
for i in {0..5}; do
  printf '%s\\n' retry
done
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 2);
        assert_eq!(diagnostics[0].span.start.line, 2);
        assert_eq!(diagnostics[0].span.slice(source), "unused");
        assert_eq!(diagnostics[1].span.start.line, 3);
        assert_eq!(diagnostics[1].span.slice(source), "for");
    }

    #[test]
    fn body_reads_keep_loop_counters_live() {
        let source = "\
#!/bin/bash
for i in {0..5}; do
  printf '%s\\n' \"$i\"
done
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn used_loop_variables_suppress_prior_dead_assignments() {
        let source = "\
#!/bin/bash
foo=1
foo=2
for foo in a b; do
  printf '%s\\n' \"$foo\"
done
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn later_exports_suppress_the_name_family() {
        let source = "#!/bin/sh\nfoo=1\nexport foo=2\nbar=1\nexport bar=\nbar=2\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn local_scopes_collapse_by_name() {
        let source = "#!/bin/bash\nf(){ local foo=1; }\ng(){ local foo=2; }\nf\ng\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.start.line, 3);
    }

    #[test]
    fn later_appends_suppress_the_name_family() {
        let source = "#!/bin/bash\nfoo=1\nfoo+=2\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn command_prefix_assignments_are_treated_as_consumed() {
        let source = "#!/bin/sh\nfoo=1 echo ok\nbar=1 export baz=2\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn eval_arguments_keep_delayed_references_live() {
        let source = "#!/bin/bash\nDEF=default\nVAR=name\neval \"$VAR=\\${$VAR:-$DEF}\"\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn eval_single_quoted_strings_do_not_keep_assignments_live() {
        let source = "#!/bin/sh\nsaved_line1=$LINENO\neval 'test \"$saved_line1\"'\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "saved_line1");
    }

    #[test]
    fn eval_escaped_dollar_payloads_do_not_keep_assignments_live() {
        let source = r#"#!/bin/bash
foo=1
eval "echo \\\$foo"
"#;
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "foo");
    }

    #[test]
    fn eval_comment_payloads_do_not_keep_assignments_live() {
        let source = r#"#!/bin/bash
foo=1
eval "echo ok # \$foo"
"#;
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "foo");
    }

    #[test]
    fn variable_set_array_tests_keep_target_family_live() {
        let source = "\
#!/bin/bash
f() {
  local -A seen
  seen=()
  if [[ ! -v \"seen[${key}]\" ]]; then
    seen[${key}]=1
  fi
}
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn invalid_variable_set_test_operands_do_not_keep_assignments_live() {
        let source = "\
#!/bin/bash
foo=1
[[ -v '$foo' ]]
[[ -v 1foo ]]
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "foo");
    }

    #[test]
    fn quoted_variable_set_test_operands_keep_assignments_live() {
        let source = "\
#!/bin/bash
foo=1
[[ -v 'foo' ]]
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn flags_parent_is_runtime_consumed() {
        let source = "#!/bin/sh\nFLAGS_PARENT=\"git flow\"\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn zsh_config_namespaces_are_external_consumers() {
        let source = "\
POWERLEVEL9K_LEFT_PROMPT_ELEMENTS=(dir vcs)
POWERLEVEL9K_DIR_FOREGROUND=31
ZDOT_MODULE_NAME=prompt
ordinary=1
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/zdot/.zshrc"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_plugin_config_namespaces_are_external_consumers() {
        let source = "\
#!/usr/bin/env zsh
typeset -g ZSH_AUTOSUGGEST_HIGHLIGHT_STYLE='fg=8'
ZSH_AUTOSUGGEST_STRATEGY=(history completion)
ordinary=1
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/zsh/zsh-autosuggestions/src/config.zsh"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_runtime_consumes_wordchars_assignments() {
        let source = "\
#!/usr/bin/env zsh
WORDCHARS=''
ordinary=1
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/zsh/ohmyzsh/lib/completion.zsh"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_test_data_expected_outputs_are_external_consumers() {
        let source = "\
#!/usr/bin/env zsh
expected_region_highlight=('1 4 fg=red')
ordinary=1
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/zsh/zsh-syntax-highlighting/highlighters/main/test-data/example.zsh"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_test_harness_expected_outputs_are_external_consumers() {
        let source = "\
#!/usr/bin/env zsh
run_test_internal() {
  expected_region_highlight=()
  ordinary=1
  true && _zsh_highlight
}
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/zsh/zsh-syntax-highlighting/tests/test-zprof.zsh"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_history_state_assignments_are_external_consumers() {
        let source = "\
#!/usr/bin/env zsh
HISTFILE=~/.zsh_history
HISTSIZE=10000
SAVEHIST=10000
ordinary=1
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/zsh/holman-dotfiles/zsh/config.zsh"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_module_metadata_triplets_are_external_consumers() {
        let source = "\
#!/usr/bin/env zsh
module_name=\"package-manager\"
module_description=\"Install package manager\"
module_main_function=\"run_package_manager_module\"
ordinary=1

run_package_manager_module() {
  :
}
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/project/install/01-package-manager.zsh"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_module_metadata_accepts_next_line_function_body_brace() {
        let source = "\
#!/usr/bin/env zsh
module_name=\"package-manager\"
module_description=\"Install package manager\"
module_main_function=\"run_package_manager_module\"
ordinary=1

function run_package_manager_module
{
  :
}
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/project/install/01-package-manager.zsh"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_module_metadata_requires_exact_main_function_name() {
        let source = "\
#!/usr/bin/env zsh
module_name=\"package-manager\"
module_description=\"Install package manager\"
module_main_function=\"run\"

runner() {
  :
}
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/project/install/01-package-manager.zsh"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["module_name", "module_description", "module_main_function"]
        );
    }

    #[test]
    fn zsh_ambient_output_parameters_are_external_consumers() {
        let source = "\
#!/usr/bin/env zsh
reply=(one two)
REPLY=value
compstate[insert]=menu
ordinary=1
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/zsh/ohmyzsh/plugins/example/example.plugin.zsh"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_hook_arrays_are_external_consumers_in_runtime_paths() {
        let source = "\
#!/usr/bin/env zsh
precmd_functions=(_async_prompt_precmd)
chpwd_functions=(_async_prompt_chpwd)
ordinary=1
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/zsh/ohmyzsh/lib/async_prompt.zsh"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "ordinary");
    }

    #[test]
    fn pathless_zsh_output_parameters_still_report_unused() {
        let source = "\
#!/usr/bin/env zsh
reply=(one two)
ordinary=1
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 2);
        assert_eq!(diagnostics[0].span.slice(source), "reply");
        assert_eq!(diagnostics[1].span.slice(source), "ordinary");
    }

    #[test]
    fn pathless_zsh_hook_arrays_still_report_unused() {
        let source = "\
#!/usr/bin/env zsh
precmd_functions=(_async_prompt_precmd)
ordinary=1
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 2);
        assert_eq!(diagnostics[0].span.slice(source), "precmd_functions");
        assert_eq!(diagnostics[1].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_ambient_output_parameters_do_not_consume_function_locals() {
        let source = "\
#!/usr/bin/env zsh
helper() {
  local reply=(one two)
  local REPLY=value
}
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/zsh/ohmyzsh/plugins/example/example.plugin.zsh"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 2);
        assert_eq!(diagnostics[0].span.slice(source), "reply");
        assert_eq!(diagnostics[1].span.slice(source), "REPLY");
    }

    #[test]
    fn zsh_function_output_parameters_respect_locals_until_unset() {
        let source = "\
#!/usr/bin/env zsh
helper() {
  local REPLY
  REPLY=value
  unset REPLY
}
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "REPLY");
    }

    #[test]
    fn zsh_special_prompt_parameters_are_runtime_consumed() {
        let source = "\
#!/bin/zsh
PROMPT='%n@%m %~ %# '
RPROMPT='%?'
PROMPT2='continue> '
TIMEFMT='%*Es'
ordinary=1
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_function_output_parameters_are_core_external_consumers() {
        let source = "\
#!/usr/bin/env zsh
helper() {
  REPLY=value
  reply=(one two)
}
ordinary=1
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_arguments_targets_are_not_unused_in_registered_completion_functions() {
        let source = "\
#!/bin/zsh
_example() {
  local state line
  typeset -A opt_args
  _arguments '*:: :->subcmds'
  _example_args
  ordinary=1
}
_example_args() {
  _arguments '--help[show help]'
  helper_unused=1
}
compdef _example example
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["ordinary", "helper_unused"]
        );
    }

    #[test]
    fn zsh_arguments_targets_are_not_unused_without_compdef_registration() {
        let source = "\
#!/bin/zsh
function _cab_commands() {
  local state
  _arguments ':subcommand:->subcommand'
  ordinary=1
}
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_arguments_targets_are_not_unused_when_compdef_shares_branch() {
        let source = "\
#!/bin/zsh
if ! is-at-least 5.7; then
  function _composer() {
    typeset -A opt_args
    _arguments '*:: :->subcmds'
    ordinary=1
  }
  compdef _composer composer
fi
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["ordinary"]
        );
    }

    #[test]
    fn zsh_arguments_targets_ignore_branch_words_in_comments_between_registration() {
        let source = "\
#!/bin/zsh
if ! is-at-least 5.7; then
  function _composer() {
    _arguments '*:: :->subcmds'
    ordinary=1
  }
  # else fallback is handled by zsh itself
  compdef _composer composer
fi
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["ordinary"]
        );
    }

    #[test]
    fn zsh_arguments_declarations_stay_unused_without_matching_target() {
        let source = "\
#!/bin/zsh
function _composer() {
  local state=0
  _arguments '--help[show help]'
}
compdef _composer composer
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["state"]
        );
    }

    #[test]
    fn zsh_arguments_targets_stay_unused_across_exclusive_branches() {
        let source = "\
#!/bin/zsh
if is-at-least 5.7; then
  function _composer() {
    _arguments '*:: :->subcmds'
    ordinary=1
  }
else
  compdef _composer composer
fi
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["ordinary"]
        );
    }

    #[test]
    fn zsh_arguments_targets_keep_case_boundaries_after_parameter_hash() {
        let source = "\
#!/bin/zsh
case $service in
  a)
    function _composer() {
      _arguments '*:: :->subcmds'
      ordinary=1
    }
    print -r -- ${value#prefix} ;;
  b)
    compdef _composer composer ;;
esac
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["ordinary"]
        );
    }

    #[test]
    fn zsh_arguments_targets_stay_unused_for_short_circuit_compdef() {
        let source = "\
#!/bin/zsh
function _composer() {
  _arguments '*:: :->subcmds'
  ordinary=1
} || compdef _composer composer
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["ordinary"]
        );
    }

    #[test]
    fn zsh_wanted_named_array_operand_counts_as_use() {
        let source = "\
#!/bin/zsh
_example() {
  local expl
  _wanted tags expl 'tag description' compadd -- one two
  ordinary=1
}
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["ordinary"]
        );
    }

    #[test]
    fn zsh_wanted_skips_core_option_prefixes_before_named_array_operand() {
        let source = "\
#!/bin/zsh
_example() {
  local expl
  _wanted -x -C commands -1V tags expl 'tag description' compadd -- one two
  ordinary=1
}
";
        let diagnostics = test_snippet(
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment).with_shell(ShellDialect::Zsh),
        );

        assert_eq!(
            diagnostics
                .iter()
                .map(|diagnostic| diagnostic.span.slice(source))
                .collect::<Vec<_>>(),
            vec!["ordinary"]
        );
    }

    #[test]
    fn zsh_config_namespace_names_still_report_on_ordinary_paths() {
        let source = "\
#!/usr/bin/env zsh
POWERLEVEL9K_DIR_FOREGROUND=31
ordinary=1
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/project/plugins/prompt.zsh"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment),
        );

        assert_eq!(diagnostics.len(), 2);
        assert_eq!(
            diagnostics[0].span.slice(source),
            "POWERLEVEL9K_DIR_FOREGROUND"
        );
        assert_eq!(diagnostics[1].span.slice(source), "ordinary");
    }

    #[test]
    fn zsh_config_namespace_names_still_report_in_zshrc_named_directories() {
        let source = "\
#!/usr/bin/env zsh
POWERLEVEL9K_DIR_FOREGROUND=31
ordinary=1
";
        let diagnostics = test_snippet_at_path(
            Path::new("/tmp/project/zshrc-theme/prompt.zsh"),
            source,
            &LinterSettings::for_rule(Rule::UnusedAssignment),
        );

        assert_eq!(diagnostics.len(), 2);
        assert_eq!(
            diagnostics[0].span.slice(source),
            "POWERLEVEL9K_DIR_FOREGROUND"
        );
        assert_eq!(diagnostics[1].span.slice(source), "ordinary");
    }

    #[test]
    fn used_uninitialized_local_declarations_suppress_dead_branch_arms() {
        let source = "#!/bin/bash\nf(){\n  if a; then\n    foo=1\n  elif b; then\n    local foo\n    echo \"$foo\"\n  else\n    foo=3\n  fi\n}\nf\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn unused_uninitialized_local_branches_report_the_last_dead_binding() {
        let source =
            "#!/bin/bash\nf(){\n  if a; then\n    foo=1\n  else\n    local foo\n  fi\n}\nf\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.start.line, 6);
        assert_eq!(diagnostics[0].span.slice(source), "foo");
    }

    #[test]
    fn branch_local_uninitialized_declarations_keep_prior_defs_live() {
        let source = "#!/bin/bash\nf(){\n  foo=1\n  if cond; then\n    local foo\n  fi\n  echo \"$foo\"\n}\nf\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn unused_uninitialized_declarations_do_not_split_linear_chains() {
        let source = "#!/bin/bash\nf(){\n  local foo\n  foo=1\n  foo=2\n}\nf\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.start.line, 5);
    }

    #[test]
    fn reports_declaration_only_bindings_by_default() {
        let source = "\
#!/bin/bash
f(){
  local cur
  declare words
}
f
";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 2);
        assert_eq!(diagnostics[0].span.slice(source), "cur");
        assert_eq!(diagnostics[1].span.slice(source), "words");
    }

    #[test]
    fn isolated_execution_scopes_collapse_by_name() {
        let source = "#!/bin/bash\nfoo=1\n(foo=2)\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.start.line, 3);
    }

    #[test]
    fn later_local_reassignments_collapse_across_functions() {
        let source = "#!/bin/bash\nf(){ local foo=; foo=1; }\ng(){ local foo=; foo=2; }\nf\ng\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.start.line, 3);
    }

    #[test]
    fn used_variable_empty_clear_is_suppressed() {
        let source = "#!/bin/bash\nfoo=1\n: \"$foo\"\nfoo=\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn used_variable_quoted_empty_clear_is_suppressed() {
        let source = "#!/bin/bash\nfoo=1\n: \"$foo\"\nfoo=\"\"\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn standalone_empty_initializer_is_still_reported() {
        let source = "#!/bin/bash\nfoo=\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].span.start.line, 2);
        assert_eq!(diagnostics[0].span.slice(source), "foo");
    }

    #[test]
    fn used_variable_suppresses_prior_dead_reassignment_before_empty_clear() {
        let source = "#!/bin/bash\nfoo=1\n: \"$foo\"\nfoo=2\nfoo=\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn pre_use_empty_initializer_in_used_family_is_suppressed() {
        let source = "#!/bin/bash\nfoo=\nfoo=1\n: \"$foo\"\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }

    #[test]
    fn used_non_reportable_bindings_suppress_dead_branch_arms() {
        let source = "#!/bin/bash\nif a; then\n  foo=1\nelif b; then\n  foo+=x\n  echo \"$foo\"\nelse\n  foo=3\nfi\n";
        let diagnostics = test_snippet(source, &LinterSettings::for_rule(Rule::UnusedAssignment));

        assert!(diagnostics.is_empty());
    }
}