Implement formula evaluation for DATE statement

src/eval/error.rs

@@ -6,6 +6,7 @@ use crate::files::primitives::{Span, Time};
 
 #[derive(Debug)]
 pub enum Error {
+    /// A delta step resulted in an invalid date.
     DeltaInvalidStep {
         span: Span,
         start: NaiveDate,
@@ -13,6 +14,7 @@ pub enum Error {
         prev: NaiveDate,
         prev_time: Option<Time>,
     },
+    /// A time-based delta step was applied to a date without time.
     DeltaNoTime {
         span: Span,
         start: NaiveDate,
@@ -29,6 +31,16 @@ pub enum Error {
     /// A `MOVE a TO b` statement was executed, but there was no entry at the
     /// date `a`.
     MoveWithoutSource { span: Span },
+    /// A division by zero has occurred.
+    DivByZero { span: Span, date: NaiveDate },
+    /// A modulo operation by zero has occurred.
+    ModByZero { span: Span, date: NaiveDate },
+    /// Easter calculation failed.
+    Easter {
+        span: Span,
+        date: NaiveDate,
+        msg: &'static str,
+    },
 }
 
 pub type Result<T> = result::Result<T, Error>;