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ed49386d3a
Emit dropck normalization errors in borrowck Borrowck generally assumes that any queries it runs for type checking will succeed, thinking that HIR typeck will have errored first if there was a problem. However as of #98641, dropck isn't run on HIR, so there's no direct guarantee that it doesn't error. While a type being well-formed might be expected to ensure that its fields are well-formed, this is not the case for types containing a type projection: ```rust pub trait AuthUser { type Id; } pub trait AuthnBackend { type User: AuthUser; } pub struct AuthSession<Backend: AuthnBackend> { data: Option<<<Backend as AuthnBackend>::User as AuthUser>::Id>, } pub trait Authz: Sized { type AuthnBackend: AuthnBackend<User = Self>; } pub fn run_query<User: Authz>(auth: AuthSession<User::AuthnBackend>) {} // ^ No User: AuthUser bound is required or inferred. ``` While improvements to trait solving might fix this in the future, for now we go for a pragmatic solution of emitting an error from borrowck (by rerunning dropck outside of a query) and making drop elaboration check if an error has been emitted previously before panicking for a failed normalization. Closes #103899 Closes #135039 r? `@compiler-errors` (feel free to re-assign) |
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