From 9692e9e9a1044f3465d923ecbc853f430c06e772 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?L=C3=A9o=20Lanteri=20Thauvin?= Date: Tue, 9 Mar 2021 08:23:59 +0100 Subject: [PATCH] Apply suggestions from code review Co-authored-by: Camelid --- src/thir.md | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/src/thir.md b/src/thir.md index 04bf635c..efbc5284 100644 --- a/src/thir.md +++ b/src/thir.md @@ -2,7 +2,7 @@ -The THIR ("Typed High-Level Intermediate Representation"), previously HAIR for +The THIR ("Typed High-Level Intermediate Representation"), previously called HAIR for "High-Level Abstract IR", is another IR used by rustc that is generated after [type checking]. It is (as of March 2021) only used for [MIR construction] and [exhaustiveness checking], but @@ -16,14 +16,17 @@ for the current MIR unsafety checker. As the name might suggest, the THIR is a lowered version of the [HIR] where all the types have been filled in, which is possible after type checking has completed. -But it has some other interesting features that distinguish it from HIR: -- like the MIR, the THIR only represents bodies, i.e. "executable code"; this includes +But it has some other interesting features that distinguish it from the HIR: + +- Like the MIR, the THIR only represents bodies, i.e. "executable code"; this includes function bodies, but also `const` initializers, for example. Consequently, the THIR has no representation for items like `struct`s or `trait`s. -- a body of THIR is only stored temporarily and is dropped as soon as it's no longer + +- Each body of THIR is only stored temporarily and is dropped as soon as it's no longer needed, as opposed to being stored until the end of the compilation process (which is what is done with the HIR). -- besides making the types of all nodes available, the THIR also has additional + +- Besides making the types of all nodes available, the THIR also has additional desugaring compared to the HIR. For example, automatic references and dereferences are made explicit, and method calls and overloaded operators are converted into plain function calls. Destruction scopes are also made explicit. @@ -32,8 +35,8 @@ But it has some other interesting features that distinguish it from HIR: The THIR lives in [`rustc_mir_build::thir`][thir]. To construct a `thir::Expr`, you can use the `build_thir` function, passing in the memory arena where the THIR -will be allocated. Dropping this arena will result in the THIR being destroyed: -this is useful to keep peak memory in check, as having a THIR representation of +will be allocated. Dropping this arena will result in the THIR being destroyed, +which is useful to keep peak memory in check. Having a THIR representation of all bodies of a crate in memory at the same time would be very heavy. [thir]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_mir_build/thir/index.html