Function check_nested_occurrences 

fn check_nested_occurrences(
    psess: &ParseSess,
    node_id: NodeId,
    tts: &[TokenTree],
    macros: &Stack<'_, MacroState<'_>>,
    binders: &FxHashMap<MacroRulesNormalizedIdent, BinderInfo>,
    ops: &Stack<'_, KleeneToken>,
    guar: &mut Option<ErrorGuaranteed>,
)

Checks tts as part of the RHS of a macro definition, tries to recognize nested macro definitions.

Arguments:

• psess is used to emit diagnostics and lints
• node_id is used to emit lints
• tts is checked as part of a RHS and may contain macro definitions
• macros is the stack of possible outer macros
• binders contains the binders of the associated LHS
• ops is the stack of Kleene operators from the RHS
• guar is set in case of errors