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 param_env and wording

This commit is contained in:
nils 2023-02-02 09:18:13 +01:00 committed by Tshepang Mbambo
parent 5db974f386
commit 49c93f661f
1 changed files with 3 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
src/ty.md
View File

@ -167,7 +167,8 @@ equal when testing whether they can be assigned to each other (which is a common
diagnostics code). `==` on them will return `false` though, since they are different types. diagnostics code). `==` on them will return `false` though, since they are different types.
The simplest way to compare two types correctly requires an inference context (`infcx`). The simplest way to compare two types correctly requires an inference context (`infcx`).
If you have one, you can use `infcx.can_eq(ty1, ty2)` to check whether the types can be made equal. If you have one, you can use `infcx.can_eq(param_env, ty1, ty2)`
to check whether the types can be made equal.
This is typically what you want to check during diagnostics, which is concerned with questions such This is typically what you want to check during diagnostics, which is concerned with questions such
as whether two types can be assigned to each other, not whether they're represented identically in as whether two types can be assigned to each other, not whether they're represented identically in
the compiler's type-checking layer. the compiler's type-checking layer.
@ -183,7 +184,7 @@ primarily a concern during HIR type checking and with all types from a `TyCtxt`
(for example from `tcx.type_of()`). (for example from `tcx.type_of()`).
When a `FnCtxt` or an `ObligationCtxt` is available during type checking, `.normalize(ty)` When a `FnCtxt` or an `ObligationCtxt` is available during type checking, `.normalize(ty)`
can be used on them to normalize the type. After type checking, diagnostics code can use should be used on them to normalize the type. After type checking, diagnostics code can use
`tcx.normalize_erasing_regions(ty)`. `tcx.normalize_erasing_regions(ty)`.
There are also cases where using `==` on `Ty` is fine. This is for example the case in late lints There are also cases where using `==` on `Ty` is fine. This is for example the case in late lints