From 1cf64060e37f1cafca05beb61113f82635da08b4 Mon Sep 17 00:00:00 2001 From: blyxyas Date: Sat, 8 Apr 2023 17:08:06 +0200 Subject: [PATCH] Add "`hir::Ty` and `ty::Ty`" section --- book/src/development/type_checking.md | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/book/src/development/type_checking.md b/book/src/development/type_checking.md index ff08cb1e5..5ce434b99 100644 --- a/book/src/development/type_checking.md +++ b/book/src/development/type_checking.md @@ -102,6 +102,21 @@ impl LateLintPass<'_> for MyStructLint { } ``` +## `hir::Ty` and `ty::Ty` + +We've been talking about [`ty::Ty`][middle_ty] this whole time without addressing [`hir::Ty`][hir_ty], but the latter +is also important to understand. + +`hir::Ty` would represent *what* an user wrote, while `ty::Ty` would understand the meaning of it (because it has more +information). + +**Example: `fn foo(x: u32) -> u32 { x }`** + +Here the HIR sees the types without "thinking" about them, it knows that the function takes an `u32` and returns +an `u32`. But at the `ty::Ty` level the compiler understands that they're the same type, in-depth lifetimes, etc... + +you can use the [`hir_ty_to_ty`][hir_ty_to_ty] function to convert from a `hir::Ty` to a `ty::Ty` + ## Useful Links Below are some useful links to further explore the concepts covered @@ -124,3 +139,6 @@ in this chapter: [Ty]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/struct.Ty.html [TyKind]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/enum.TyKind.html [TypeckResults]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/struct.TypeckResults.html +[middle_ty]: https://doc.rust-lang.org/beta/nightly-rustc/rustc_middle/ty/struct.Ty.html +[hir_ty]: https://doc.rust-lang.org/beta/nightly-rustc/rustc_hir/struct.Ty.html +[hir_ty_to_ty]: https://doc.rust-lang.org/beta/nightly-rustc/rustc_hir_analysis/fn.hir_ty_to_ty.html