https://doc.rust-lang.org/nightly/nightly-rustc/rustc_infer/infer/canonical/ir/lang_items/enum.SolverTraitLangItem.html
SolverTraitLangItem in rustc_infer::infer::canonical::ir::lang_items - Rust
API documentation for the Rust `SolverTraitLangItem` enum in crate `rustc_infer`.
rustcinfercanonicalirlang