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Add reflect Symbol.info and ClassInfo #11664

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Add reflect Symbol.info and ClassInfo #11664

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7f96001
Add reflect Symbol.info and ClassInfo
nicolasstucki Mar 9, 2021
2d52f5f
Add asSeenFrom to reflection
nicolasstucki Mar 12, 2021
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2 changes: 2 additions & 0 deletions compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala
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Expand Up @@ -1695,6 +1695,8 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
dotc.core.Types.decorateTypeApplications(self).appliedTo(targ)
def appliedTo(targs: List[TypeRepr]): TypeRepr =
dotc.core.Types.decorateTypeApplications(self).appliedTo(targs)
def asSeenFrom(pre: TypeRepr, clazz: Symbol): TypeRepr =
self.asSeenFrom(pre, clazz)
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We already expose memberInfo which calls asSeenFrom, in what situation would you need the raw asSeenFrom?

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@liufengyun ?

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If we expose symbol.info, without asSeenFrom, the info cannot be safely used.

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symbol.info is the info of the symbol itself, I don't see what's unsafe about it, and if you want to see the info from some specific prefix you can do prefix.memberType(symbol). Are there situations where you need to use asSeenFrom directly instead?

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symbol.info is the info of the symbol itself, I don't see what's unsafe about it, if you want to see the info from some specific prefix you can do prefix.memberType(symbol). Are there situations where you need to use asSeenFrom directly instead?

The concern is that users use symbol.info without rebasing, resulting in error-prone macros. I see that we already have TypeEpr.memberType, thus we don't need asSeenFrom. However, it is good to add the following doc to Symbol.info:

Warning: Symbol.info may contain parameterized types, such as class type parameter, types that depend on this, etc. The method call prefix.memberType(symbol) can be used to get the concrete type of the symbol relative to a prefix.

end extension
end TypeReprMethods

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13 changes: 13 additions & 0 deletions library/src/scala/quoted/Quotes.scala
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Expand Up @@ -2448,6 +2448,19 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
/** The current type applied to given type arguments: `this[targ0, ..., targN]` */
def appliedTo(targs: List[TypeRepr]): TypeRepr

/** This type as seen from prefix `pre` and class `clazz`. This means:
* Replace all thistypes of `clazz` or one of its subclasses
* by `pre` and instantiate all parameters by arguments of `pre`.
* Proceed analogously for thistypes referring to outer classes.
*
* Example:
* class D[T] { def m: T }
* class C extends p.D[Int]
* T.asSeenFrom(ThisType(C), D) (where D is owner of m)
* = Int
*/
def asSeenFrom(pre: TypeRepr, clazz: Symbol): TypeRepr

end extension
}

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