At first I was considering moving it to a procedural macro
(source-level information should be sufficient),
and started by trying to reproduce the error case
by changing `htmldivelement.rs` to use `Element` instead of `HTMLElement`
as the first field.
The output was:
```rust
error[E0308]: mismatched types
--> /home/simon/servo2/target/debug/build/script-4caa244faca7d10f/out/Bindings/HTMLDivElementBinding.rs:665:31
|
665 | let _: &HTMLElement = self.as_parent();
| ^^^^^^^^^^^^^^^^ expected struct `dom::htmlelement::HTMLElement`, found struct `dom::element::Element`
|
= note: expected type `&dom::htmlelement::HTMLElement`
found type `&dom::element::Element`
```
This line number is inside a generated method called `__assert_parent_type`.
As far as I can tell, any case where this lint would error is already caught
by such methods. The lint is therefore redundant and can safely be removed.
DOM structs embed their parent type as their first field. This
introduces a `.parent()` method to the DOM struct that returns its first
field, and codegens a type assert that ensures that `.parent()` returns
the parent struct.
This generates:
On `#[dom_struct]`:
```rust
impl HasParent for Type {
type Parent = ParentType;
fn as_parent(&self) -> ParentType {
&self.first_field
}
}
```
In the codegen files:
```rust
impl Type {
fn __assert_parent_type(&self) {
let _: &ParentType = self.as_parent();
}
}
````
Servo currently uses `heapsize`, but Stylo/Gecko use `malloc_size_of`.
`malloc_size_of` is better -- it handles various cases that `heapsize` does not
-- so this patch changes Servo to use `malloc_size_of`.
This patch makes the following changes to the `malloc_size_of` crate.
- Adds `MallocSizeOf` trait implementations for numerous types, some built-in
(e.g. `VecDeque`), some external and Servo-only (e.g. `string_cache`).
- Makes `enclosing_size_of_op` optional, because vanilla jemalloc doesn't
support that operation.
- For `HashSet`/`HashMap`, falls back to a computed estimate when
`enclosing_size_of_op` isn't available.
- Adds an extern "C" `malloc_size_of` function that does the actual heap
measurement; this is based on the same functions from the `heapsize` crate.
This patch makes the following changes elsewhere.
- Converts all the uses of `heapsize` to instead use `malloc_size_of`.
- Disables the "heapsize"/"heap_size" feature for the external crates that
provide it.
- Removes the `HeapSizeOf` implementation from `hashglobe`.
- Adds `ignore` annotations to a few `Rc`/`Arc`, because `malloc_size_of`
doesn't derive those types, unlike `heapsize`.
Before:
```
error[E0412]: cannot find type `SourceBuffer` in this scope
--> /Users/nox/src/servo/components/script/dom/mediasource.rs:25:1
|
25 | #[dom_struct]
| ^^^^^^^^^^^^^ did you mean `SourceBufferList`?
```
After:
```
error[E0412]: cannot find type `SourceBuffer` in this scope
--> /Users/nox/src/servo/components/script/dom/mediasource.rs:28:39
|
28 | source_buffers: DOMRefCell<Vec<JS<SourceBuffer>>>,
| ^^^^^^^^^^^^ did you mean `SourceBufferList`?
```
