bb582c6d0f
Don't require specifying unrelated assoc types when trait alias is in `dyn` type Object types must specify the associated types for all of the principal trait ref's supertraits. However, we weren't doing elaboration properly, so we incorrectly errored with erroneous suggestions to specify associated types that were unrelated to that principal trait ref. To fix this, use proper supertrait elaboration when expanding trait aliases in `conv_object_ty_poly_trait_ref`. **NOTE**: Please use the ignore-whitespace option when reviewing. This only touches a handful of lines. r? oli-obk or please feel free to reassign. Fixes #122118
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.