Macro err_ctx 

macro_rules! err_ctx {
    ($mast_forest:expr, $node:expr, $host:expr) => { ... };
    ($mast_forest:expr, $node:expr, $host:expr, $op_idx:expr) => { ... };
}

Constructs an error context for the given node in the MAST forest.

When the no_err_ctx feature is disabled, this macro returns a proper error context; otherwise, it returns (). That is, this macro is designed to be zero-cost when the no_err_ctx feature is enabled.

Usage:

• err_ctx!(mast_forest, node, source_manager) - creates basic error context
• err_ctx!(mast_forest, node, source_manager, op_idx) - creates error context with operation index