Fix macro annotations spliceOwner
#16513
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nicolasstucki
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odersky
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Dec 14, 2022
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| quotePickling.println(i"**** unpickled quote\n$tree") | ||
| var tree = unpickler.tree |
| // When a quote is unpickled with a Quotes context that that has a class `spliceOwner` | ||
| // we need to use a dummy owner to unpickle it. Otherwise any definitions defined | ||
| // in the quoted block would be accidentally entered in the class. | ||
| // This owner is replaced with the correct owner when at the splice site. |
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Is that in callMacro? Maybe refer to it explicitly, then it's clearer where the owner gets replaced.
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It is in this same file in quotedExprToTree and quotedTypeToTree. I added a reference in the comment and explained a bit more.
| @@ -31,14 +31,20 @@ trait MacroAnnotation extends StaticAnnotation: | |||
| * def transform(using Quotes)(tree: quotes.reflect.Definition): List[quotes.reflect.Definition] = | |||
| * import quotes.reflect._ | |||
| * tree match | |||
| * case DefDef(name, TermParamClause(param :: Nil) :: Nil, tpt, Some(rhsTree)) => | |||
| * (Ref(param.symbol).asExpr, rhsTree.asExpr) match | |||
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Why are all these macros here and in run-macros changed? Does the old implementation not work anymore?
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In this case, the old implementation still works but is suboptimal and has a bug. It had three issues:
- With quotes getting unpickled in with the wrong owner each splice has the potential to trigger an owner change.
- If users would assemble the expression using reflection they would need extra explicit
changeOwnercalls - To recover the type of the signature we should look at the signature and not the terms. In the previous version, we had an accidental term reference to the parameter of the annotated def that leaked into the new field.
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An alternative way to construct the RHSs will be added in the documentation in #16454.
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To make the context changes simpler, I plan to add a method like inContext.
Something like
val rhs = inQuotes(owner){ '{...} }
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The splice owner of the macro annotation should be the owner of the annotated definition. The issue was that if that owner was a class quotes unpickled with this context accidentally entered definitions in the quotes into the class. Now we unpickle these definitions using a dummy val owner (similar to the LocalDummy).
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Enable modification of classes with `MacroAnnotation`: * Can annotate `class` to transform it * Can annotate `object` to transform the companion class Supported class modifications: * Modify the implementations of `def`, `val`, `var`, `lazy val`, `class`, `object` in the class * Add new `def`, `val`, `var`, `lazy val`, `class`, `object` members to the class * Add a new override for a `def`, `val`, `var`, `lazy val` members in the class Restrictions: * An annotation on a top-level class cannot return a top-level `def`, `val`, `var`, `lazy val`. Related PRs: * Includes #16513 * Follows #16392 * Followed by #16534
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The splice owner of the macro annotation should be the owner of the
annotated definition. The issue was that if that owner was a class
quotes unpickled with this context accidentally entered definitions
in the quotes into the class. Now we unpickle these definitions using
a dummy val owner (similar to the LocalDummy).