fn expand_function(
program: &Program,
function: &FunctionDecl,
function_table: &BTreeMap<String, &MetaFunctionDecl>,
builder_env_cursor: Option<&mut BuilderEnvCursor>,
) -> Result<FunctionDecl, MetaEvalError>fn expand_function(
program: &Program,
function: &FunctionDecl,
function_table: &BTreeMap<String, &MetaFunctionDecl>,
builder_env_cursor: Option<&mut BuilderEnvCursor>,
) -> Result<FunctionDecl, MetaEvalError>