mirror
/
rustc-dev-guide
mirror of https://github.com/rust-lang/rustc-dev-guide.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Add some details about `DefId` creation

This commit is contained in:
Oliver Schneider 2018-07-05 09:34:37 +02:00 committed by Who? Me?!
parent e54c0c413f
commit 3166fb9d3e
1 changed files with 13 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
src/lowering.md
View File

@ -33,3 +33,15 @@ sanity checks in `src/librustc/hir/map/hir_id_validator.rs`:
create new ids for them. This is done by calling the `next_id` method,
which produces both a new `NodeId` as well as automatically lowering it
for you so you also get the `HirId`.
If you are creating new `DefId`s, since each `DefId` needs to have a corresponding
`NodeId`, it is adviseable to add these `NodeId`s to the `AST` so you don't have
to generate new ones during lowering. This has the advantage of creating a
way to find the `DefId` of something via its `NodeId`. If lowering needs this
`DefId` in multiple places, you can't generate a new `NodeId` in all those places
because you'd also get a new `DefId` then. With a `NodeId` from the `AST` this is
not an issue.
Having the `NodeId` also allows the `DefCollector` to generate the `DefId`s instead
of lowering having to do it on the fly. Centralizing the `DefId` generation in one
place makes it easier to refactor and reason about.