mirror of
https://github.com/rust-lang/rust.git
synced 2025-05-14 02:49:40 +00:00
47dd709bed
Split an item bounds and an item's super predicates This is the moral equivalent of #107614, but instead for predicates this applies to **item bounds**. This PR splits out the item bounds (i.e. *all* predicates that are assumed to hold for the alias) from the item *super predicates*, which are the subset of item bounds which share the same self type as the alias. ## Why? Much like #107614, there are places in the compiler where we *only* care about super-predicates, and considering predicates that possibly don't have anything to do with the alias is problematic. This includes things like closure signature inference (which is at its core searching for `Self: Fn(..)` style bounds), but also lints like `#[must_use]`, error reporting for aliases, computing type outlives predicates. Even in cases where considering all of the `item_bounds` doesn't lead to bugs, unnecessarily considering irrelevant bounds does lead to a regression (#121121) due to doing extra work in the solver. ## Example 1 - Trait Aliases This is best explored via an example: ``` type TAIT<T> = impl TraitAlias<T>; trait TraitAlias<T> = A + B where T: C; ``` The item bounds list for `Tait<T>` will include: * `Tait<T>: A` * `Tait<T>: B` * `T: C` While `item_super_predicates` query will include just the first two predicates. Side-note: You may wonder why `T: C` is included in the item bounds for `TAIT`? This is because when we elaborate `TraitAlias<T>`, we will also elaborate all the predicates on the trait. ## Example 2 - Associated Type Bounds ``` type TAIT<T> = impl Iterator<Item: A>; ``` The `item_bounds` list for `TAIT<T>` will include: * `Tait<T>: Iterator` * `<Tait<T> as Iterator>::Item: A` But the `item_super_predicates` will just include the first bound, since that's the only bound that is relevant to the *alias* itself. ## So what This leads to some diagnostics duplication just like #107614, but none of it will be user-facing. We only see it in the UI test suite because we explicitly disable diagnostic deduplication. Regarding naming, I went with `super_predicates` kind of arbitrarily; this can easily be changed, but I'd consider better names as long as we don't block this PR in perpetuity. |
||
|---|---|---|
| .. | ||
| rustc | ||
| rustc_abi | ||
| rustc_arena | ||
| rustc_ast | ||
| rustc_ast_ir | ||
| rustc_ast_lowering | ||
| rustc_ast_passes | ||
| rustc_ast_pretty | ||
| rustc_attr | ||
| rustc_baked_icu_data | ||
| rustc_borrowck | ||
| rustc_builtin_macros | ||
| rustc_codegen_cranelift | ||
| rustc_codegen_gcc | ||
| rustc_codegen_llvm | ||
| rustc_codegen_ssa | ||
| rustc_const_eval | ||
| rustc_data_structures | ||
| rustc_driver | ||
| rustc_driver_impl | ||
| rustc_error_codes | ||
| rustc_error_messages | ||
| rustc_errors | ||
| rustc_expand | ||
| rustc_feature | ||
| rustc_fluent_macro | ||
| rustc_fs_util | ||
| rustc_graphviz | ||
| rustc_hir | ||
| rustc_hir_analysis | ||
| rustc_hir_pretty | ||
| rustc_hir_typeck | ||
| rustc_incremental | ||
| rustc_index | ||
| rustc_index_macros | ||
| rustc_infer | ||
| rustc_interface | ||
| rustc_lexer | ||
| rustc_lint | ||
| rustc_lint_defs | ||
| rustc_llvm | ||
| rustc_log | ||
| rustc_macros | ||
| rustc_metadata | ||
| rustc_middle | ||
| rustc_mir_build | ||
| rustc_mir_dataflow | ||
| rustc_mir_transform | ||
| rustc_monomorphize | ||
| rustc_next_trait_solver | ||
| rustc_parse | ||
| rustc_parse_format | ||
| rustc_passes | ||
| rustc_pattern_analysis | ||
| rustc_privacy | ||
| rustc_query_impl | ||
| rustc_query_system | ||
| rustc_resolve | ||
| rustc_serialize | ||
| rustc_session | ||
| rustc_smir | ||
| rustc_span | ||
| rustc_symbol_mangling | ||
| rustc_target | ||
| rustc_trait_selection | ||
| rustc_traits | ||
| rustc_transmute | ||
| rustc_ty_utils | ||
| rustc_type_ir | ||
| stable_mir | ||