handle numerical addition/subtraction from datetime

Author: kbrabrand

src/typeEvaluator/typeEvaluate.ts

@@ -616,6 +616,11 @@ function handleOpCallNode(node: OpCallNode, scope: Scope): TypeNode {
                   : undefined,
             }
           }
+          // datetime + number -> datetime (datetimes are represented as strings)
+          // Returns null for non-datetime strings at runtime, so we include null in the union
+          if (left.type === 'string' && right.type === 'number') {
+            return nullUnion({type: 'string'})
+          }
 
           if (left.type === 'number' && right.type === 'number') {
             return {
@@ -647,6 +652,11 @@ function handleOpCallNode(node: OpCallNode, scope: Scope): TypeNode {
           if (left.type === 'unknown' || right.type === 'unknown') {
             return nullUnion({type: 'number'})
           }
+          // datetime - number -> datetime (datetimes are represented as strings)
+          // Returns null for non-datetime strings at runtime, so we include null in the union
+          if (left.type === 'string' && right.type === 'number') {
+            return nullUnion({type: 'string'})
+          }
           if (left.type === 'number' && right.type === 'number') {
             return {
               type: 'number',

test/typeEvaluate.test.ts

@@ -3735,6 +3735,17 @@ t.test('splatting array', (t) => {
   t.end()
 })
 
+t.test('dateTime with numerical operation', (t) => {
+  const query = `(global::dateTime("2025-03-01T00:00:00Z") + 60) > global::dateTime("2024-03-01T00:00:00Z")`
+  const ast = parse(query)
+  const res = typeEvaluate(ast, schemas)
+  t.same(res, {
+    type: 'union',
+    of: [{type: 'boolean', value: undefined}, {type: 'null'}],
+  })
+  t.end()
+})
+
 function findSchemaType(name: string): TypeNode {
   const type = schemas.find((s) => s.name === name)
   if (!type) {