fix(#2407): respect the HaltIfNull opcode when determining nullability

sqlx-sqlite/src/connection/explain.rs

@@ -125,6 +125,7 @@ const OP_CONCAT: &str = "Concat";
 const OP_OFFSET_LIMIT: &str = "OffsetLimit";
 const OP_RESULT_ROW: &str = "ResultRow";
 const OP_HALT: &str = "Halt";
+const OP_HALT_IF_NULL: &str = "HaltIfNull";
 
 const MAX_LOOP_COUNT: u8 = 2;
 
@@ -942,6 +943,16 @@ pub(super) fn explain(
                     state.r.insert(p2, RegDataType::Single(ColumnType::null()));
                 }
 
+                // if there is a value in p3, and the query passes, then
+                // we know that it is not nullable
+                OP_HALT_IF_NULL => {
+                    if let Some(RegDataType::Single(ColumnType::Single { nullable, .. })) =
+                        state.r.get_mut(&p3)
+                    {
+                        *nullable = Some(false);
+                    }
+                }
+
                 OP_FUNCTION => {
                     // r[p1] = func( _ )
                     match from_utf8(p4).map_err(Error::protocol)? {