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Fix the grammar of const param defaults by reusing rule for const args #2270

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Fix the grammar of const param defaults by reusing rule for const args #2270

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4 changes: 1 addition & 3 deletions src/items/generics.md
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Expand Up @@ -11,9 +11,7 @@ LifetimeParam -> Lifetime ( `:` LifetimeBounds )?

TypeParam -> IDENTIFIER ( `:` Bounds? )? ( `=` Type )?

ConstParam ->
`const` IDENTIFIER `:` Type
( `=` ( BlockExpression | IDENTIFIER | `-`?LiteralExpression ) )?
ConstParam -> `const` IDENTIFIER `:` Type ( `=` ConstArg )?
```

r[items.generics.syntax.intro]
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7 changes: 3 additions & 4 deletions src/paths.md
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Expand Up @@ -62,12 +62,11 @@ TypeList ->
( Type `,` )* Type `,`?

GenericArg ->
Lifetime | Type | GenericArgsConst | GenericArgsBinding | GenericArgsBounds
Lifetime | Type | ConstArg | GenericArgsBinding | GenericArgsBounds

GenericArgsConst ->
ConstArg ->
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@fmease fmease May 11, 2026 •
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const arg / constant argument is the term we use in rustc (internally and in diagnostics).

Moreover, in rustc's parser, const arg doesn't just refer to const arguments literally but also to const param defaults (and to the RHS of associated const bindings as in TraitRef<CT = { 1 + 1 }> but that's unstable syntax). So "reusing" ConstArg in rule ConstParam doesn't come out of thin air.

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BlockExpression
| LiteralExpression
| `-` LiteralExpression
| `-`? LiteralExpression
| SimplePathSegment

GenericArgsBinding ->
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