fix: type a DATE plus INTERVAL 'n' DAY as TIMESTAMP_NTZ(9)

crates/sqlquack-rules/src/catalogue/constants.rs

@@ -1441,7 +1441,7 @@ pub const RULES: &[RuleSpec] = &[
     RuleSpec {
         id: INTERVAL_ARITHMETIC,
         constructs: &["node:add", "node:sub", "node:interval"],
-        conditions: "A DATE or TIMESTAMP_NTZ plus or minus an INTERVAL literal of one whole number of days, hours, minutes or seconds, written '<n> <unit>' with the unit singular or plural in any case: DATEADD of n or -n of that unit. A DATE takes only days and stays a DATE; a TIMESTAMP_NTZ of any precision becomes a TIMESTAMP_NTZ(9), relying on timestamp_range. Other intervals and operands stay refused.",
+        conditions: "A DATE or TIMESTAMP_NTZ plus or minus an INTERVAL literal of one whole number of days, hours, minutes or seconds, written '<n> <unit>' with the unit singular or plural in any case: DATEADD of n or -n of that unit. A DATE takes only days: with the unit inside the quotes ('7 days') it stays a DATE, and with the unit after them (INTERVAL '3' DAY) it becomes a TIMESTAMP_NTZ(9) at midnight, as recorded, relying on timestamp_range; a TIMESTAMP_NTZ of any precision becomes a TIMESTAMP_NTZ(9), relying on timestamp_range. Other intervals and operands stay refused.",
         failures: &[],
     },
     RuleSpec {

crates/sqlquack-rules/src/conversion/_helpers/expressions/intervals.rs

@@ -30,7 +30,7 @@ pub(crate) fn adds_interval(payload: &Value) -> bool {
 
 /// `value + INTERVAL 'n unit'` or `value - INTERVAL 'n unit'`, as DATEADD of n or -n units.
 pub(crate) fn interval_arithmetic(
-    kind: &str,
+    (kind, node): (&str, &Value),
     payload: &Value,
     site: Site<'_>,
 ) -> Result<Emitted, Refusal> {
@@ -41,6 +41,23 @@ pub(crate) fn interval_arithmetic(
     let payload = payload_object(payload, &construct)?;
     let value = convert_expression(field(payload, "left", &construct)?, site)?;
     let interval = field(payload, "right", &construct)?;
+    let quoted_value = site
+        .context
+        .locator
+        .source_text(node)
+        .is_some_and(|written| {
+            let lower = written.to_ascii_lowercase();
+            lower.rfind(INTERVAL_KIND).is_some_and(|start| {
+                lower[start + INTERVAL_KIND.len()..]
+                    .trim_start()
+                    .starts_with('\'')
+            })
+        });
+    if !quoted_value {
+        return Err(refuse(
+            "an INTERVAL whose value is not a quoted string, which no recording shows".to_owned(),
+        ));
+    }
     let (amount, unit) =
         interval_literal(interval, site)?.ok_or_else(|| refuse(INTERVAL_REFUSAL.to_owned()))?;
     let accepted = match value.data_type {
@@ -54,8 +71,12 @@ pub(crate) fn interval_arithmetic(
             value.data_type
         )));
     }
+    let unit_outside_quotes = node_kind(interval)
+        .and_then(|(_, payload)| payload.get("unit"))
+        .is_some_and(|unit| !is_inert(unit));
     let result_type = match value.data_type {
-        SnowflakeType::TimestampNtz { .. } => {
+        SnowflakeType::Date if !unit_outside_quotes => SnowflakeType::Date,
+        SnowflakeType::Date | SnowflakeType::TimestampNtz { .. } => {
             diverge(site.context, TIMESTAMP_RANGE, &construct)?;
             SnowflakeType::TimestampNtz {
                 precision: INTERVAL_TIMESTAMP_PRECISION,

crates/sqlquack-rules/src/conversion/_helpers/expressions/scalar.rs

@@ -285,7 +285,7 @@ fn convert_kind(node: &Value, site: Site<'_>) -> Result<Emitted, Refusal> {
         "annotated" => commented(payload, site),
         "neg" => negate(payload, site),
         "subquery" => scalar_subquery(payload, site),
-        "add" | "sub" if adds_interval(payload) => interval_arithmetic(kind, payload, site),
+        "add" | "sub" if adds_interval(payload) => interval_arithmetic((kind, node), payload, site),
         "add" | "sub" | "mul" | "div" => arithmetic(kind, payload, site),
         "mod" => modulo(payload, site),
         "eq" | "neq" | "lt" | "lte" | "gt" | "gte" => comparison_predicate(kind, payload, site),

crates/sqlquack/src/analysis/tests/test_coverage_batch.rs

@@ -321,11 +321,26 @@ fn given_interval_literals_when_converting_then_dates_and_timestamps_move_by_the
             sql: "SELECT ('2024-03-05'::DATE - INTERVAL '7 days')::VARCHAR AS v",
             expected_outcome: Ok("2024-02-27"),
         },
+        FirstValueTestCase {
+            description: "a DATE plus days written after the quotes is a TIMESTAMP_NTZ at midnight",
+            sql: "SELECT ('2026-04-01'::DATE + INTERVAL '3' DAYS)::VARCHAR AS v",
+            expected_outcome: Ok("2026-04-04 00:00:00.000"),
+        },
+        FirstValueTestCase {
+            description: "a DATE minus one day written after the quotes is a TIMESTAMP_NTZ too",
+            sql: "SELECT ('2024-03-01'::DATE - INTERVAL '1' DAY)::VARCHAR AS v",
+            expected_outcome: Ok("2024-02-29 00:00:00.000"),
+        },
         FirstValueTestCase {
             description: "a timestamp plus hours crosses midnight",
             sql: "SELECT ('2024-02-28 23:30:00'::TIMESTAMP_NTZ + INTERVAL '2 hours')::VARCHAR AS v",
             expected_outcome: Ok("2024-02-29 01:30:00.000"),
         },
+        FirstValueTestCase {
+            description: "an interval of an unquoted number is refused",
+            sql: "SELECT '2024-03-05'::DATE + INTERVAL 3 DAY AS v",
+            expected_outcome: Err("not a quoted string"),
+        },
         FirstValueTestCase {
             description: "a DATE plus hours stays refused",
             sql: "SELECT '2024-03-05'::DATE + INTERVAL '2 hours' AS v",