Function replace_usages 

fn replace_usages(
    edit: &mut SourceChangeBuilder,
    ctx: &AssistContext<'_, '_>,
    usages: UsageSearchResult,
    target_definition: Definition,
    target_module: &Module,
    delayed_mutations: &mut Vec<(FileId, ImportScope, Path)>,
    make: &SyntaxFactory,
)

Replaces all usages of the target identifier, both when read and written to.