fix ICE for deref coercions with type errors Follow-up to https://github.com/rust-lang/rust/pull/120895, where I made types with errors go through the full coercion code, which is necessary if we want to build MIR for bodies with errors (https://github.com/rust-lang/rust/pull/120550). The code for coercing `&T` to `&U` currently assumes that autoderef for `&T` will succeed for at least two steps (`&T` and `T`): https://github.com/rust-lang/rust/blob/b17491c8f6d555386104dfd82004c01bfef09c95/compiler/rustc_hir_typeck/src/coercion.rs#L339-L464 But for types with errors, we previously only returned the no-op autoderef step (`&{type error}` -> `&{type error}`) and then stopped early. This PR changes autoderef for types with errors to still go through the built-in derefs (e.g. `&&{type error}` -> `&{type error}` -> `{type error}`) and only stop early when it would have to go looking for `Deref` trait impls. fixes https://github.com/rust-lang/rust/issues/120945 r? ``@compiler-errors`` or compiler