from iso@lemy.lol to rust@programming.dev on 22 Nov 2023 21:53
https://lemy.lol/post/14885040
Especially the errors related to traits are very difficult to me. Is there a trick? Will I get used to it? Or am I just a failure? :D
Like WTH is this?
the trait bound ‘(diesel::sql_types::Uuid, diesel::sql_types::Text, diesel::sql_types::Nullable, diesel::sql_types::Timestamp, diesel::sql_types::Timestamp): diesel::query_dsl::CompatibleType’ is not satisfied the following other types implement trait ‘diesel::query_dsl::CompatibleType’: (ST0,) (ST0, ST1) (ST0, ST1, ST2) (ST0, ST1, ST2, ST3) (ST0, ST1, ST2, ST3, ST4) (ST0, ST1, ST2, ST3, ST4, ST5) (ST0, ST1, ST2, ST3, ST4, ST5, ST6) (ST0, ST1, ST2, ST3, ST4, ST5, ST6, ST7) and 24 others required for ‘SelectStatement, DefaultSelectClause>, NoDistinctClause, …, …, …>’ to implement ‘diesel_async::methods::LoadQuery<’_, _, models::Artist>
Or this:
the variant or associated item ‘as_select’ exists for enum ‘Option<Image>’, but its trait bounds were not satisfied the following trait bounds were not satisfied: ‘std::option::Option<models::Image>: diesel::Selectable<_>’ which is required by ‘std::option::Option<models::Image>: diesel::SelectableHelper<_>’ ‘&std::option::Option<models::Image>: diesel::Selectable<_>’ which is required by ‘&std::option::Option<models::Image>: diesel::SelectableHelper<_>’ ‘&mut std::option::Option<models::Image>: diesel::Selectable<_>’ which is required by ‘&mut std::option::Option<models::Image>: diesel::SelectableHelper<_>’
or this:
the trait bound ‘schema::image::columns::id: diesel::SelectableExpression<schema::artist::table>’ is not satisfied the following other types implement trait ‘diesel::SelectableExpression<QS>’: <schema::image::columns::id as diesel::SelectableExpression<diesel::query_source::joins::Join<Left, Right, diesel::query_source::joins::Inner>>> <schema::image::columns::id as diesel::SelectableExpression<diesel::query_source::joins::Join<Left, Right, diesel::query_source::joins::LeftOuter>>> <schema::image::columns::id as diesel::SelectableExpression<schema::image::table>> <schema::image::columns::id as diesel::SelectableExpression<diesel::query_builder::SelectStatement<diesel::query_builder::FromClause<From>>>> <schema::image::columns::id as diesel::SelectableExpression<diesel::query_source::joins::JoinOn<Join, On>>> <schema::image::columns::id as diesel::SelectableExpression<diesel::query_builder::Only<schema::image::table>>> required for ‘(id, url, width, height, color, updated_at, created_at)’ to implement ‘diesel::SelectableExpression<schema::artist::table>’ the full type name has been written to ‘./target/debug/deps/server-25bcf4cf7c62d3bf.long-type-2030200755981097212.txt’ 3 redundant requirements hidden required for ‘(diesel::expression::select_by::SelectBy<models::Artist, _>, diesel::expression::select_by::SelectBy<std::option::Option<models::Image>, _>)’ to implement ‘diesel::SelectableExpression<schema::artist::table>’ required for ‘SelectStatement<FromClause<table>, DefaultSelectClause<FromClause<table>>, NoDistinctClause, WhereClause<…>>’ to implement ‘diesel::query_dsl::methods::SelectDsl<(diesel::expression::select_by::SelectBy<models::Artist, _>, diesel::expression::select_by::SelectBy<std::option::Option<models::Image>, _>)>’ the full type name has been written to ‘./target/debug/deps/server-25bcf4cf7c62d3bf.long-type-3023492822805157679.txt’
threaded - newest
C++ has had the same style of obtuse errors for decades. They can be a real pain to figure out even if you are used to seeing them.
These long confusing errors are near universal in languages / libraries that have complex types. You get the same thing in C++ code that uses template metaprogramming e.g. Eigen.
It is quite annoying but I don’t really know of a solution other than using a library that doesn’t express full expressions as types.
Chumsky does something similar but it also has a
.boxed()modifier you can use to type erase the types at strategic points to keep them a manageable size. I believe Xylem is going to do the same with its statically typed widget tree. Maybe Diesel offers something like that?I usually get errors close in size to this but at the moment I had a diesel to send. I kind of figuring out the problems but it takes time and a few hairs :)
Diesel is well-known for having some of the worst errors in the ecosystem. This is far from the rule.
Indeed, and the maintainer opened this RFC (I think because of it)
I’d rather have long errors and a great type system instead of short errors and a shit type system.