monty 0.0.19-beta.2

A sandboxed, snapshotable Python interpreter written in Rust.
Documentation 
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//! Implementation of the len() builtin function.

use crate::{
    args::ArgValues,
    bytecode::VM,
    defer_drop,
    exception_private::{ExcType, RunResult, SimpleException},
    resource::ResourceTracker,
    types::PyTrait,
    value::Value,
};

/// Implementation of the len() builtin function.
///
/// Returns the length of an object (number of items in a container).
pub fn builtin_len(vm: &mut VM<'_, impl ResourceTracker>, args: ArgValues) -> RunResult<Value> {
    let value = args.get_one_arg("len", vm.heap)?;
    defer_drop!(value, vm);
    if let Some(len) = value.py_len(vm) {
        Ok(Value::Int(
            i64::try_from(len).map_err(|_| ExcType::overflow_c_ssize_t())?,
        ))
    } else {
        let type_name = value.py_type_name(vm);
        Err(SimpleException::new_msg(ExcType::TypeError, format!("object of type '{type_name}' has no len()")).into())
    }
}