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'
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?