VTabCursor lifetime should be bound to VTab lifetime

```c
struct sqlite3_vtab_cursor {
  sqlite3_vtab *pVtab;      /* Virtual table of this cursor */
```
It seems that we need to introduce a lifetime on `VTab` trait
to express such constraint:
https://users.rust-lang.org/t/associated-type-with-lifetime-bound/7256
But there may be another/new way to do it.

src/vtab/array.rs

@@ -27,6 +27,7 @@
 //! ```
 
 use std::default::Default;
+use std::marker::PhantomData;
 use std::os::raw::{c_char, c_int, c_void};
 use std::rc::Rc;
 
@@ -72,9 +73,9 @@ struct ArrayTab {
     base: ffi::sqlite3_vtab,
 }
 
-unsafe impl VTab for ArrayTab {
+unsafe impl<'vtab> VTab<'vtab> for ArrayTab {
     type Aux = ();
-    type Cursor = ArrayTabCursor;
+    type Cursor = ArrayTabCursor<'vtab>;
 
     fn connect(
         _: &mut VTabConnection,
@@ -118,28 +119,30 @@ unsafe impl VTab for ArrayTab {
         Ok(())
     }
 
-    fn open(&self) -> Result<ArrayTabCursor> {
+    fn open(&'vtab self) -> Result<ArrayTabCursor<'vtab>> {
         Ok(ArrayTabCursor::new())
     }
 }
 
 /// A cursor for the Array virtual table
 #[repr(C)]
-struct ArrayTabCursor {
+struct ArrayTabCursor<'vtab> {
     /// Base class. Must be first
     base: ffi::sqlite3_vtab_cursor,
     /// The rowid
     row_id: i64,
     /// Pointer to the array of values ("pointer")
     ptr: Option<Array>,
+    phantom: PhantomData<&'vtab ArrayTab>,
 }
 
-impl ArrayTabCursor {
+impl ArrayTabCursor<'_> {
-    fn new() -> ArrayTabCursor {
+    fn new<'vtab>() -> ArrayTabCursor<'vtab> {
         ArrayTabCursor {
             base: ffi::sqlite3_vtab_cursor::default(),
             row_id: 0,
             ptr: None,
+            phantom: PhantomData,
         }
     }
 
@@ -150,7 +153,7 @@ impl ArrayTabCursor {
         }
     }
 }
-unsafe impl VTabCursor for ArrayTabCursor {
+unsafe impl VTabCursor for ArrayTabCursor<'_> {
     fn filter(&mut self, idx_num: c_int, _idx_str: Option<&str>, args: &Values<'_>) -> Result<()> {
         if idx_num > 0 {
             self.ptr = args.get_array(0)?;

src/vtab/csvtab.rs

@@ -22,6 +22,7 @@
 //! }
 //! ```
 use std::fs::File;
+use std::marker::PhantomData;
 use std::os::raw::c_int;
 use std::path::Path;
 use std::str;
@@ -95,9 +96,9 @@ impl CSVTab {
     }
 }
 
-unsafe impl VTab for CSVTab {
+unsafe impl<'vtab> VTab<'vtab> for CSVTab {
     type Aux = ();
-    type Cursor = CSVTabCursor;
+    type Cursor = CSVTabCursor<'vtab>;
 
     fn connect(
         _: &mut VTabConnection,
@@ -258,16 +259,16 @@ unsafe impl VTab for CSVTab {
         Ok(())
     }
 
-    fn open(&self) -> Result<CSVTabCursor> {
+    fn open(&'vtab self) -> Result<CSVTabCursor<'vtab>> {
         Ok(CSVTabCursor::new(self.reader()?))
     }
 }
 
-impl CreateVTab for CSVTab {}
+impl CreateVTab<'_> for CSVTab {}
 
 /// A cursor for the CSV virtual table
 #[repr(C)]
-struct CSVTabCursor {
+struct CSVTabCursor<'vtab> {
     /// Base class. Must be first
     base: ffi::sqlite3_vtab_cursor,
     /// The CSV reader object
@@ -277,16 +278,18 @@ struct CSVTabCursor {
     /// Values of the current row
     cols: csv::StringRecord,
     eof: bool,
+    phantom: PhantomData<&'vtab CSVTab>,
 }
 
-impl CSVTabCursor {
+impl CSVTabCursor<'_> {
-    fn new(reader: csv::Reader<File>) -> CSVTabCursor {
+    fn new<'vtab>(reader: csv::Reader<File>) -> CSVTabCursor<'vtab> {
         CSVTabCursor {
             base: ffi::sqlite3_vtab_cursor::default(),
             reader,
             row_number: 0,
             cols: csv::StringRecord::new(),
             eof: false,
+            phantom: PhantomData,
         }
     }
 
@@ -296,7 +299,7 @@ impl CSVTabCursor {
     }
 }
 
-unsafe impl VTabCursor for CSVTabCursor {
+unsafe impl VTabCursor for CSVTabCursor<'_> {
     // Only a full table scan is supported.  So `filter` simply rewinds to
     // the beginning.
     fn filter(

src/vtab/mod.rs

@@ -61,13 +61,13 @@ use crate::{str_to_cstring, Connection, Error, InnerConnection, Result};
 ///
 /// (See [SQLite doc](https://sqlite.org/c3ref/module.html))
 #[repr(transparent)]
-pub struct Module<T: VTab> {
+pub struct Module<'vtab, T: VTab<'vtab>> {
     base: ffi::sqlite3_module,
-    phantom: PhantomData<T>,
+    phantom: PhantomData<&'vtab T>,
 }
 
-unsafe impl<T: VTab> Send for Module<T> {}
+unsafe impl<'vtab, T: VTab<'vtab>> Send for Module<'vtab, T> {}
-unsafe impl<T: VTab> Sync for Module<T> {}
+unsafe impl<'vtab, T: VTab<'vtab>> Sync for Module<'vtab, T> {}
 
 union ModuleZeroHack {
     bytes: [u8; std::mem::size_of::<ffi::sqlite3_module>()],
@@ -87,7 +87,7 @@ const ZERO_MODULE: ffi::sqlite3_module = unsafe {
 /// `feature = "vtab"` Create a read-only virtual table implementation.
 ///
 /// Step 2 of [Creating New Virtual Table Implementations](https://sqlite.org/vtab.html#creating_new_virtual_table_implementations).
-pub fn read_only_module<T: CreateVTab>() -> &'static Module<T> {
+pub fn read_only_module<'vtab, T: CreateVTab<'vtab>>() -> &'static Module<'vtab, T> {
     // The xConnect and xCreate methods do the same thing, but they must be
     // different so that the virtual table is not an eponymous virtual table.
     &Module {
@@ -118,14 +118,14 @@ pub fn read_only_module<T: CreateVTab>() -> &'static Module<T> {
             xRollbackTo: None,
             ..ZERO_MODULE
         },
-        phantom: PhantomData::<T>,
+        phantom: PhantomData::<&'vtab T>,
     }
 }
 
 /// `feature = "vtab"` Create an eponymous only virtual table implementation.
 ///
 /// Step 2 of [Creating New Virtual Table Implementations](https://sqlite.org/vtab.html#creating_new_virtual_table_implementations).
-pub fn eponymous_only_module<T: VTab>() -> &'static Module<T> {
+pub fn eponymous_only_module<'vtab, T: VTab<'vtab>>() -> &'static Module<'vtab, T> {
     // A virtual table is eponymous if its xCreate method is the exact same function
     // as the xConnect method For eponymous-only virtual tables, the xCreate
     // method is NULL
@@ -157,7 +157,7 @@ pub fn eponymous_only_module<T: VTab>() -> &'static Module<T> {
             xRollbackTo: None,
             ..ZERO_MODULE
         },
-        phantom: PhantomData::<T>,
+        phantom: PhantomData::<&'vtab T>,
     }
 }
 
@@ -204,7 +204,7 @@ impl VTabConnection {
 /// ```
 ///
 /// (See [SQLite doc](https://sqlite.org/c3ref/vtab.html))
-pub unsafe trait VTab: Sized {
+pub unsafe trait VTab<'vtab>: Sized {
     /// Client data passed to `Connection::create_module`.
     type Aux;
     /// Specific cursor implementation
@@ -225,13 +225,13 @@ pub unsafe trait VTab: Sized {
 
     /// Create a new cursor used for accessing a virtual table.
     /// (See [SQLite doc](https://sqlite.org/vtab.html#the_xopen_method))
-    fn open(&self) -> Result<Self::Cursor>;
+    fn open(&'vtab self) -> Result<Self::Cursor>;
 }
 
 /// `feature = "vtab"` Non-eponymous virtual table instance trait.
 ///
 /// (See [SQLite doc](https://sqlite.org/c3ref/vtab.html))
-pub trait CreateVTab: VTab {
+pub trait CreateVTab<'vtab>: VTab<'vtab> {
     /// Create a new instance of a virtual table in response to a CREATE VIRTUAL
     /// TABLE statement. The `db` parameter is a pointer to the SQLite
     /// database connection that is executing the CREATE VIRTUAL TABLE
@@ -607,10 +607,10 @@ impl Connection {
     ///
     /// Step 3 of [Creating New Virtual Table
     /// Implementations](https://sqlite.org/vtab.html#creating_new_virtual_table_implementations).
-    pub fn create_module<T: VTab>(
+    pub fn create_module<'vtab, T: VTab<'vtab>>(
         &self,
         module_name: &str,
-        module: &'static Module<T>,
+        module: &'static Module<'vtab, T>,
         aux: Option<T::Aux>,
     ) -> Result<()> {
         self.db.borrow_mut().create_module(module_name, module, aux)
@@ -618,10 +618,10 @@ impl Connection {
 }
 
 impl InnerConnection {
-    fn create_module<T: VTab>(
+    fn create_module<'vtab, T: VTab<'vtab>>(
         &mut self,
         module_name: &str,
-        module: &'static Module<T>,
+        module: &'static Module<'vtab, T>,
         aux: Option<T::Aux>,
     ) -> Result<()> {
         let c_name = str_to_cstring(module_name)?;
@@ -703,7 +703,7 @@ unsafe extern "C" fn free_boxed_value<T>(p: *mut c_void) {
     let _: Box<T> = Box::from_raw(p as *mut T);
 }
 
-unsafe extern "C" fn rust_create<T>(
+unsafe extern "C" fn rust_create<'vtab, T>(
     db: *mut ffi::sqlite3,
     aux: *mut c_void,
     argc: c_int,
@@ -712,7 +712,7 @@ unsafe extern "C" fn rust_create<T>(
     err_msg: *mut *mut c_char,
 ) -> c_int
 where
-    T: CreateVTab,
+    T: CreateVTab<'vtab>,
 {
     use std::ffi::CStr;
 
@@ -755,7 +755,7 @@ where
     }
 }
 
-unsafe extern "C" fn rust_connect<T>(
+unsafe extern "C" fn rust_connect<'vtab, T>(
     db: *mut ffi::sqlite3,
     aux: *mut c_void,
     argc: c_int,
@@ -764,7 +764,7 @@ unsafe extern "C" fn rust_connect<T>(
     err_msg: *mut *mut c_char,
 ) -> c_int
 where
-    T: VTab,
+    T: VTab<'vtab>,
 {
     use std::ffi::CStr;
 
@@ -807,12 +807,12 @@ where
     }
 }
 
-unsafe extern "C" fn rust_best_index<T>(
+unsafe extern "C" fn rust_best_index<'vtab, T>(
     vtab: *mut ffi::sqlite3_vtab,
     info: *mut ffi::sqlite3_index_info,
 ) -> c_int
 where
-    T: VTab,
+    T: VTab<'vtab>,
 {
     let vt = vtab as *mut T;
     let mut idx_info = IndexInfo(info);
@@ -831,9 +831,9 @@ where
     }
 }
 
-unsafe extern "C" fn rust_disconnect<T>(vtab: *mut ffi::sqlite3_vtab) -> c_int
+unsafe extern "C" fn rust_disconnect<'vtab, T>(vtab: *mut ffi::sqlite3_vtab) -> c_int
 where
-    T: VTab,
+    T: VTab<'vtab>,
 {
     if vtab.is_null() {
         return ffi::SQLITE_OK;
@@ -843,9 +843,9 @@ where
     ffi::SQLITE_OK
 }
 
-unsafe extern "C" fn rust_destroy<T>(vtab: *mut ffi::sqlite3_vtab) -> c_int
+unsafe extern "C" fn rust_destroy<'vtab, T>(vtab: *mut ffi::sqlite3_vtab) -> c_int
 where
-    T: CreateVTab,
+    T: CreateVTab<'vtab>,
 {
     if vtab.is_null() {
         return ffi::SQLITE_OK;
@@ -869,12 +869,12 @@ where
     }
 }
 
-unsafe extern "C" fn rust_open<T>(
+unsafe extern "C" fn rust_open<'vtab, T: 'vtab>(
     vtab: *mut ffi::sqlite3_vtab,
     pp_cursor: *mut *mut ffi::sqlite3_vtab_cursor,
 ) -> c_int
 where
-    T: VTab,
+    T: VTab<'vtab>,
 {
     let vt = vtab as *mut T;
     match (*vt).open() {

src/vtab/series.rs

@@ -4,6 +4,7 @@
 //! "function"](http://www.sqlite.org/cgi/src/finfo?name=ext/misc/series.c):
 //! https://www.sqlite.org/series.html
 use std::default::Default;
+use std::marker::PhantomData;
 use std::os::raw::c_int;
 
 use crate::ffi;
@@ -49,9 +50,9 @@ struct SeriesTab {
     base: ffi::sqlite3_vtab,
 }
 
-unsafe impl VTab for SeriesTab {
+unsafe impl<'vtab> VTab<'vtab> for SeriesTab {
     type Aux = ();
-    type Cursor = SeriesTabCursor;
+    type Cursor = SeriesTabCursor<'vtab>;
 
     fn connect(
         _: &mut VTabConnection,
@@ -151,15 +152,14 @@ unsafe impl VTab for SeriesTab {
         Ok(())
     }
 
-    fn open(&self) -> Result<SeriesTabCursor> {
+    fn open(&'vtab self) -> Result<SeriesTabCursor<'vtab>> {
         Ok(SeriesTabCursor::new())
     }
 }
 
 /// A cursor for the Series virtual table
-#[derive(Default)]
 #[repr(C)]
-struct SeriesTabCursor {
+struct SeriesTabCursor<'vtab> {
     /// Base class. Must be first
     base: ffi::sqlite3_vtab_cursor,
     /// True to count down rather than up
@@ -174,14 +174,24 @@ struct SeriesTabCursor {
     max_value: i64,
     /// Increment ("step")
     step: i64,
+    phantom: PhantomData<&'vtab SeriesTab>,
 }
 
-impl SeriesTabCursor {
+impl SeriesTabCursor<'_> {
-    fn new() -> SeriesTabCursor {
+    fn new<'vtab>() -> SeriesTabCursor<'vtab> {
-        SeriesTabCursor::default()
+        SeriesTabCursor {
+            base: ffi::sqlite3_vtab_cursor::default(),
+            is_desc: false,
+            row_id: 0,
+            value: 0,
+            min_value: 0,
+            max_value: 0,
+            step: 0,
+            phantom: PhantomData,
+        }
     }
 }
-unsafe impl VTabCursor for SeriesTabCursor {
+unsafe impl VTabCursor for SeriesTabCursor<'_> {
     fn filter(&mut self, idx_num: c_int, _idx_str: Option<&str>, args: &Values<'_>) -> Result<()> {
         let idx_num = QueryPlanFlags::from_bits_truncate(idx_num);
         let mut i = 0;

tests/vtab.rs

@@ -9,6 +9,7 @@ fn test_dummy_module() {
         VTabConnection, VTabCursor, Values,
     };
     use rusqlite::{version_number, Connection, Result};
+    use std::marker::PhantomData;
     use std::os::raw::c_int;
 
     let module = eponymous_only_module::<DummyTab>();
@@ -19,9 +20,9 @@ fn test_dummy_module() {
         base: sqlite3_vtab,
     }
 
-    unsafe impl VTab for DummyTab {
+    unsafe impl<'vtab> VTab<'vtab> for DummyTab {
         type Aux = ();
-        type Cursor = DummyTabCursor;
+        type Cursor = DummyTabCursor<'vtab>;
 
         fn connect(
             _: &mut VTabConnection,
@@ -39,21 +40,22 @@ fn test_dummy_module() {
             Ok(())
         }
 
-        fn open(&self) -> Result<DummyTabCursor> {
+        fn open(&'vtab self) -> Result<DummyTabCursor<'vtab>> {
             Ok(DummyTabCursor::default())
         }
     }
 
     #[derive(Default)]
     #[repr(C)]
-    struct DummyTabCursor {
+    struct DummyTabCursor<'vtab> {
         /// Base class. Must be first
         base: sqlite3_vtab_cursor,
         /// The rowid
         row_id: i64,
+        phantom: PhantomData<&'vtab DummyTab>,
     }
 
-    unsafe impl VTabCursor for DummyTabCursor {
+    unsafe impl VTabCursor for DummyTabCursor<'_> {
         fn filter(
             &mut self,
             _idx_num: c_int,