fix(lint): stop panicking on a query that ends in FROM

crates/sqlquack-lint/src/lint/_helpers/terminal_shape.rs

@@ -209,7 +209,7 @@ pub(super) fn collect_terminal_shape_facts(
     let terminal_is_plain = from_position.is_some_and(|position| {
         let projection = &tail[..position];
         let relation = tail.get(position + 1);
-        let remainder = &tail[position.saturating_add(2)..];
+        let remainder = tail.get(position + 2..).unwrap_or_default();
         !projection.is_empty()
             && plain_terminal_projection(tokens, projection)
             && relation.is_some_and(|&index| {

crates/sqlquack-lint/src/lint/tests.rs

@@ -16,6 +16,8 @@ mod long_chains;
 mod sql_lint;
 #[path = "tests/test_types.rs"]
 mod test_types;
+#[path = "tests/test_trailing_from.rs"]
+mod trailing_from;
 #[path = "tests/test_unused_ctes.rs"]
 mod unused_ctes;
 #[path = "tests/test_unused_table_alias.rs"]

crates/sqlquack-lint/src/lint/tests/test_trailing_from.rs

@@ -0,0 +1,64 @@
+use crate::lint::tests::helpers::diagnostics_for_dialect;
+use crate::lint::tests::test_types::TrailingFromTestCase;
+
+/// A query whose final FROM names no relation: the terminal-shape rule reads past that FROM.
+const SQL: &str = "WITH t AS (SELECT 1) SELECT * FROM";
+
+#[test]
+fn given_a_query_ending_in_from_when_linting_then_each_dialect_refuses_or_lints_it() {
+    let test_cases = [
+        TrailingFromTestCase {
+            description: "Snowflake refuses it",
+            dialect: "snowflake",
+            expected_parse_error: true,
+        },
+        TrailingFromTestCase {
+            description: "DuckDB refuses it",
+            dialect: "duckdb",
+            expected_parse_error: true,
+        },
+        TrailingFromTestCase {
+            description: "SQLite refuses it",
+            dialect: "sqlite",
+            expected_parse_error: true,
+        },
+        TrailingFromTestCase {
+            description: "PostgreSQL refuses it",
+            dialect: "postgres",
+            expected_parse_error: true,
+        },
+        TrailingFromTestCase {
+            description: "Generic refuses it",
+            dialect: "generic",
+            expected_parse_error: true,
+        },
+        TrailingFromTestCase {
+            description: "BigQuery refuses it",
+            dialect: "bigquery",
+            expected_parse_error: true,
+        },
+        TrailingFromTestCase {
+            description: "Databricks parses it, so the terminal-shape rule lints it",
+            dialect: "databricks",
+            expected_parse_error: false,
+        },
+    ];
+    for test_case in test_cases {
+        let result = diagnostics_for_dialect(SQL, test_case.dialect, &["SQLCLEAN035"]);
+        assert_eq!(
+            result
+                .as_ref()
+                .err()
+                .is_some_and(|error| error.contains("Parse error")),
+            test_case.expected_parse_error,
+            "{}: {result:?}",
+            test_case.description
+        );
+        assert_eq!(
+            result.is_ok(),
+            !test_case.expected_parse_error,
+            "{}: {result:?}",
+            test_case.description
+        );
+    }
+}

crates/sqlquack-lint/src/lint/tests/test_types.rs

@@ -115,6 +115,12 @@ pub(crate) struct NestingRefusalTestCase {
     pub expected_code: &'static str,
 }
 
+pub(crate) struct TrailingFromTestCase {
+    pub description: &'static str,
+    pub dialect: &'static str,
+    pub expected_parse_error: bool,
+}
+
 pub(crate) struct CrossJoinTestCase {
     pub description: &'static str,
     pub sql: &'static str,