hakorune/src/mir/join_ir/lowering/carrier_info.rs

//! Carrier variable metadata for JoinIR loop lowering
//!
//! This module defines metadata structures for tracking carrier variables
//! in loop lowering. This enables dynamic generation of exit bindings
//! without hardcoded variable names or ValueIds.

use crate::mir::ValueId;

/// Information about a single carrier variable
#[derive(Debug, Clone)]
pub struct CarrierVar {
    /// Variable name (e.g., "sum", "printed")
    pub name: String,
    /// Host ValueId for this variable
    pub host_id: ValueId,
}

/// Complete carrier information for a loop
#[derive(Debug, Clone)]
pub struct CarrierInfo {
    /// Loop control variable name (e.g., "i")
    pub loop_var_name: String,
    /// Loop control variable ValueId in host
    pub loop_var_id: ValueId,
    /// Additional carrier variables (e.g., sum, printed)
    pub carriers: Vec<CarrierVar>,
}

/// Exit metadata returned by lowerers
///
/// This structure captures the mapping from JoinIR exit values to
/// carrier variable names, enabling dynamic binding generation.
#[derive(Debug, Clone)]
pub struct ExitMeta {
    /// Exit value bindings: (carrier_name, join_exit_value_id)
    ///
    /// Example for Pattern 4:
    /// ```
    /// vec![("sum".to_string(), ValueId(15))]
    /// ```
    /// where ValueId(15) is the k_exit parameter in JoinIR-local space.
    pub exit_values: Vec<(String, ValueId)>,
}

impl ExitMeta {
    /// Create new ExitMeta with no exit values
    pub fn empty() -> Self {
        Self {
            exit_values: vec![],
        }
    }

    /// Create ExitMeta with a single exit value
    pub fn single(carrier_name: String, join_value: ValueId) -> Self {
        Self {
            exit_values: vec![(carrier_name, join_value)],
        }
    }

    /// Create ExitMeta with multiple exit values
    pub fn multiple(exit_values: Vec<(String, ValueId)>) -> Self {
        Self { exit_values }
    }
}