Fixed methods with self: &Self consuming the object
#4178
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daxpedda
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Oct 12, 2024
daxpedda
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| // The tricky part here is that `r` can have many forms. E.g. `self`, | ||
| // `&self`, `&mut self`, `self: Self`, `self: &Self`, `self: &mut Self`, | ||
| // `self: Box<Self>`, `self: Rc<Self>`, etc. | ||
| // Luckily, syn always populates the `ty` field with the type of `self`, so | ||
| // e.g. `&self` gets the type `&Self`. So we only have check whether the | ||
| // type is a reference or not. |
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fixes #3958
Rust allows type annotations for the
selfparameter, so it can have many forms. E.g.self,&self,&mut self,self: &Self,self: Self,self: Box<Self>, etc. Wasm bindgen needs to know whether a value is consumed (pass by value) or referenced to generate the correct JS shim.Previously, the parser only looked at whether the self parameter had an
&beforeself. This works forself,&mut self, and&self, but not forself: &Self. So it previously interpretedself: &Self(a reference) as justself(pass by value), because it ignored any and all type annotations, which caused #3958.This PR fixes the issue by looking at the type of
selfinstead. Helpfully, syn always gives us a type even for&self. See their docs for more details. So instead of checking whetherselfhas an&, it now checks whether the type ofselfis a reference type. This is the same approach wasm bindgen uses for all other arguments to figure out whether they are passed by referece or by value.