document const generics #901
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ehuss
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Its merged in rust-lang/rust#79135 |
Co-authored-by: est31 <[email protected]>
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Maybe I'm confused, but it seems like the grammar for GenericArgs needs to be updated for expressions?
Also, overall I feel like this is missing a lot of content. There seems to be a large amount of information in the stabilization report that would be good to carry over. There are a lot of details that seem to be missing (like const parameters don't have to be used unlike types and lifetimes). I also see a number of things in the RFC that don't seem to be mentioned.
I appreciate the effort for adding this documentation, but I would like to see a bit more detail if possible.
| > | ( _LifetimeParam_ `,` )<sup>\*</sup> _TypeParams_\ | ||
| > | ( _LifetimeParam_ `,` )<sup>\*</sup> ( _TypeParam_ `,` )<sup>\*</sup> _ConstParams_ |
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I believe this grammar is no longer correct (see #785). The order of the parameters doesn't matter syntactically.
You don't have to fix it if you don't want to (although that would be nice), I just wanted to make a note of it.
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won't do this in that PR, as I don't know what it's expected to look like now.
src/items/generics.md
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| Const parameters may only be be used as standalone arguments inside | ||
| of [types] and [repeat expressions]. | ||
| They can be used freely outside of [const contexts]. |
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I find these sentences a little difficult to understand. Can you add more detail, along with some examples?
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extended this a bit, it feels weird to go more in depth here as the explanation for types and lifetimes are also fairly short
Co-authored-by: Eric Huss <[email protected]>
Co-authored-by: Eric Huss <[email protected]>
Co-authored-by: Eric Huss <[email protected]>
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there is still a lot we could add about const generics or generics in general. I am not able to spend a lot of time on rust in the near future so I would prefer merging this without adding too much more |
src/paths.md
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| > _GenericArgsConsts_ :\ | ||
| > [_Expression_] (`,` [_Expression_])<sup>\*</sup> |
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I don't think this is the actual grammar for arguments is it? According to parse_generic_arg I believe it is something like this:
diff --git a/src/paths.md b/src/paths.md
index 9126e5b..47a14ee 100644
--- a/src/paths.md
+++ b/src/paths.md
@@ -70,7 +70,13 @@ mod m {
> [_Type_] (`,` [_Type_])<sup>\*</sup>
>
> _GenericArgsConsts_ :\
-> [_Expression_] (`,` [_Expression_])<sup>\*</sup>
+> _GenericArgsConst_ (`,` _GenericArgsConst_)<sup>\*</sup>
+>
+> _GenericArgsConst_ :\
+> [_BlockExpression_]\
+> | [_LiteralExpression_]\
+> | `-` [_LiteralExpression_]\
+> | [_SimplePathSegment_]
>
> _GenericArgsBindings_ :\
> _GenericArgsBinding_ (`,` _GenericArgsBinding_)<sup>\*</sup>
@@ -375,10 +381,13 @@ mod without { // ::without
# fn main() {}
```
+[_BlockExpression_]: expressions/block-expr.md
+[_Expression_]: expressions.md
[_GenericArgs_]: #paths-in-expressions
[_Lifetime_]: trait-bounds.md
+[_LiteralExpression_]: expressions/literal-expr.md
+[_SimplePathSegment_]: #simple-paths
[_Type_]: types.md#type-expressions
-[_Expression_]: expressions.md
[literal]: expressions/literal-expr.md
[item]: items.md
[variable]: variables.mdIs that correct?
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yeah, that looks right to me
No worries, if you can confirm the comment above about the grammar, I can probably merge this and work on extending it. |
| ``` | ||
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| Const arguments must be surrounded by braces unless they are a | ||
| [literal] or a single segment path. |
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in this case this section might not be needed
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I went ahead and pushed the fix for the grammar. I'll follow up with other PRs.
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min_const_generics.