refactor(ops): op2 support for generics (#19636)

Implementation of generics for `#[op2]`, along with some refactoring to
improve the ergonomics of ops with generics parameters:

- The ops have generics on the struct rather than the associated
methods, which allows us to trait-ify ops (impossible when they are on
the methods)
- The decl() method can become a trait-associated const field which
unlocks future optimizations

Callers of ops need to switch from:
`op_net_connect_tcp::call::<TestPermission>(conn_state, ip_addr)` to
`op_net_connect_tcp::<TestPermission>::call(conn_state, ip_addr)`.

3 files changed, 14 insertions, 2 deletions

diff --git a/core/extensions.rs b/core/extensions.rs
index fa6d7851e..e76b4064b 100644
--- a/core/extensions.rs
+++ b/core/extensions.rs
@@ -65,6 +65,12 @@ pub type OpMiddlewareFn = dyn Fn(OpDecl) -> OpDecl;
 pub type OpStateFn = dyn FnOnce(&mut OpState);
 pub type OpEventLoopFn = dyn Fn(Rc<RefCell<OpState>>, &mut Context) -> bool;
 
+/// Trait implemented by all generated ops.
+pub trait Op {
+  const NAME: &'static str;
+  const DECL: OpDecl;
+}
+
 pub struct OpDecl {
   pub name: &'static str,
   pub v8_fn_ptr: OpFnRef,
@@ -239,7 +245,7 @@ macro_rules! extension {
           ext.ops(vec![
             $(
               $( #[ $m ] )*
-              $( $op )::+ :: decl $( :: < $($op_param),* > )? ()
+              $( $op )::+ $( :: < $($op_param),* > )? :: decl ()
             ),+
           ]);
         )?
diff --git a/core/lib.rs b/core/lib.rs
index 250d7dead..30a14f3e4 100644
--- a/core/lib.rs
+++ b/core/lib.rs
@@ -132,6 +132,7 @@ pub fn v8_version() -> &'static str {
 pub mod _ops {
   pub use super::error::throw_type_error;
   pub use super::error_codes::get_error_code;
+  pub use super::extensions::Op;
   pub use super::extensions::OpDecl;
   pub use super::ops::to_op_result;
   pub use super::ops::OpCtx;
diff --git a/core/runtime/ops.rs b/core/runtime/ops.rs
index 1c871cda0..9e37977c8 100644
--- a/core/runtime/ops.rs
+++ b/core/runtime/ops.rs
@@ -218,7 +218,8 @@ mod tests {
       op_test_result_void_ok,
       op_test_result_void_err,
       op_test_result_primitive_ok,
-      op_test_result_primitive_err
+      op_test_result_primitive_err,
+      op_test_generics<String>,
     ]
   );
 
@@ -404,4 +405,8 @@ mod tests {
     )?;
     Ok(())
   }
+
+  // We don't actually test this one -- we just want it to compile
+  #[op2(core, fast)]
+  pub fn op_test_generics<T: Clone>() {}
 }