Method format_op

compiler/src/modules/vm/handlers/dunder.rs:360–368

`format(v, spec)` dispatch: instance `__format__(spec)` wins; otherwise the built-in spec engine runs. Empty spec on an instance still goes through `__format__` so user formatting can opt in. */

(&mut self, v: Val, spec: &str, chunk: &SSAChunk, slots: &mut [Val])

    /* `format(v, spec)` dispatch: instance `__format__(spec)` wins; otherwise the built-in spec engine runs. Empty spec on an instance still goes through `__format__` so user formatting can opt in. */
    pub(crate) fn format_op(&mut self, v: Val, spec: &str, chunk: &SSAChunk, slots: &mut [Val]) -> Result<String, VmErr> {
        if v.is_heap() && matches!(self.heap.get(v), HeapObj::Instance(..)) {
            let spec_val = self.heap.alloc(HeapObj::Str(spec.to_string()))?;
            if let Some(r) = self.try_call_dunder(v, "__format__", &[spec_val], chunk, slots)? {
                return self.require_str(r, "__format__");
            }
        }
        super::format::format_value(v, spec, &self.heap).map_err(super::format::fmt_err)
    }

    /* Coerce a `__len__` / `__length_hint__` return value to bool semantics; rejects negatives. */
    fn len_to_bool(&self, v: Val) -> Result<bool, VmErr> {