Generic type for Trait functions #1553
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| TraitFunction: TraitFunction<Expression> = { | ||
| <name:Identifier> ":" <params:TypeTermList> "->" <value:TypeTermBox> => TraitFunction { name, ty: Type::Function(FunctionType{params, value}) } | ||
| <name:Identifier> ":" <ty:Type> => TraitFunction { name, ty } |
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Do you know where the parsing ambiguity comes from?
I think we could change this to TypeTerm here and fix it, but then we would need to use parentheses for functions which is not ideal.
Would it be an option to have to lines here, one for an explicit function as before and one for TypeTerm?
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On the other hand, it's not too bad to use ;
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Ah ok I think it's because a: x, y, z -> w would need too much look-ahead to find out the meaning of the , after the x. Although it's really not too much look-ahead, it's just a single token...
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Ah ok I think it's because a: x, y, z -> w would need too much look-ahead to find out the meaning of the , after the x. Although it's really not too much look-ahead, it's just a single token...
Yes, exactly, by using commas at the end of functions, the parser cannot differentiate when it's another type and when it's the end of the function.
Would it be an option to have to lines here, one for an explicit function as before and one for TypeTerm?
Not really, because it would be equivalent to simply "opening" Type in its two possible variants and replacing them.
On the other hand, it's not too bad to use
;
And it's like in Rust 🥇 😝
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I mean rust traits use fn functions.
I would really like traits to be similar to structs, and I think the two alternatives would work: Note that the second is not Type but TypeTerm, so if you want to use that to represent a function type you would have to put it in parentheses. But you could still use
trait X<T> {
some_const: T,
some_fun: T -> T,
}
Generalises the type of the functions of a trait, to allow more than just functions.
To avoid ambiguity in the grammar, the token marking the end of a trait function was changed from
,to;.