Function require_proto_field 

pub fn require_proto_field<T>(
    opt: Option<T>,
    expr_name: &str,
    field: &str,
) -> Result<T>

Available on crate feature proto only.

Unwrap a required non-expression proto field.

Mirrors PhysicalExprDecodeCtx::decode_required_expression for proto fields that aren’t PhysicalExprNodes — e.g. the arrow_type of a PhysicalCastNode or the scalar of a PhysicalLiteralNode. Keeps the “missing required field” message format identical across expressions:

let arrow_type = require_proto_field(
    cast_expr.arrow_type.as_ref(),
    "CastExpr",
    "arrow_type",
)?;