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Auto merge of #88499 - eddyb:layout-off, r=nagisa

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Provide `layout_of` automatically (given tcx + param_env + error handling).

After #88337, there's no longer any uses of `LayoutOf` within `rustc_target` itself, so I realized I could move the trait to `rustc_middle::ty::layout` and redesign it a bit.

This is similar to #88338 (and supersedes it), but at no ergonomic loss, since there's no funky `C: LayoutOf<Ty = Ty>` -> `Ty: TyAbiInterface<C>` generic `impl` chain, and each `LayoutOf` still corresponds to one `impl` (of `LayoutOfHelpers`) for the specific context.

After this PR, this is what's needed to get `trait LayoutOf` (with the `layout_of` method) implemented on some context type:
* `TyCtxt`, via `HasTyCtxt`
* `ParamEnv`, via `HasParamEnv`
* a way to transform `LayoutError`s into the desired error type
  * an error type of `!` can be paired with having `cx.layout_of(...)` return `TyAndLayout` *without* `Result<...>` around it, such as used by codegen
  * this is done through a new `LayoutOfHelpers` trait (and so is specifying the type of `cx.layout_of(...)`)

When going through this path (and not bypassing it with a manual `impl` of `LayoutOf`), the end result is that only the error case can be customized, the query itself and the success paths are guaranteed to be uniform.

(**EDIT**: just noticed that because of the supertrait relationship, you cannot actually implement `LayoutOf` yourself, the blanket `impl` fully covers all possible context types that could ever implement it)

Part of the motivation for this shape of API is that I've been working on querifying `FnAbi::of_*`, and what I want/need to introduce for that looks a lot like the setup in this PR - in particular, it's harder to express the `FnAbi` methods in `rustc_target`, since they're much more tied to `rustc` concepts.

r? `@nagisa` cc `@oli-obk` `@bjorn3`
This commit is contained in:
bors 2021-09-05 16:14:41 +00:00
commit e2750baf53
51 changed files with 253 additions and 218 deletions
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4
compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
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@ -28,7 +28,7 @@ use rustc_hir::def_id::{DefId, LOCAL_CRATE};
use rustc_index::vec::{Idx, IndexVec};
use rustc_middle::ich::NodeIdHashingMode;
use rustc_middle::mir::{self, GeneratorLayout};
use rustc_middle::ty::layout::{self, IntegerExt, PrimitiveExt, TyAndLayout};
use rustc_middle::ty::layout::{self, IntegerExt, LayoutOf, PrimitiveExt, TyAndLayout};
use rustc_middle::ty::subst::GenericArgKind;
use rustc_middle::ty::Instance;
use rustc_middle::ty::{self, AdtKind, GeneratorSubsts, ParamEnv, Ty, TyCtxt};
@ -37,7 +37,7 @@ use rustc_session::config::{self, DebugInfo};
use rustc_span::symbol::{Interner, Symbol};
use rustc_span::FileNameDisplayPreference;
use rustc_span::{self, SourceFile, SourceFileHash, Span};
use rustc_target::abi::{Abi, Align, HasDataLayout, Integer, LayoutOf, TagEncoding};
use rustc_target::abi::{Abi, Align, HasDataLayout, Integer, TagEncoding};
use rustc_target::abi::{Int, Pointer, F32, F64};
use rustc_target::abi::{Primitive, Size, VariantIdx, Variants};
use tracing::debug;