使用Scala宏注释为对象添加额外特征 [英] Adding extra trait to object using scala macro annotation

问题描述

我在Scala的2.10.3使用宏天堂.我在那里我想一个特征添加到对象宏注释，e.g:

I'm on Scala 2.10.3 using Macro Paradise. I have a macro annotation where I'm trying to add a trait to on object, e.g:

@MyAnnotation
object Foo extends Bar {}

扩展后，我想要类似的东西

After expansion I want something like:

object Foo extends Bar with Baz {}

Baz是在编译范围内可访问的特征.使用微距天堂，我可以清晰地解构我的目标树:

Where Baz is a trait accessible in the compilation scope. Using macro paradise I can cleanly destructure my target tree:

q"object $obj extends ..$bases { ..$body }" = tree

其中碱持有订货号(newTypeName(酒吧"))

where bases holds the existing extensions in the form List of Ident(newTypeName("Bar"))

我可以在基础上添加一个额外的Baz条目并重建树，问题是目标可能已经"包含了Baz.在这种情况下，我不想添加它.给我的项名称缩短.有没有一种方法可以将它们转换为宏内的实际类型引用?

I could just add an extra Baz entry to bases and reconstruct the tree, the problem is the target might "already" contain Baz. In this case I don't want to add it. The term names given to me are shortened. Is there a way of converting them to actual type references inside the macro?

我试过在宏以下内容:，但我得到了以下错误:

I've tried the following in the macro: c.typeCheck(Ident(newTypeName("Baz"))) but I get the following error:

scala.reflect.macros.TypeCheckException: trait some.Baz is not a value

我已经通过的背景下审视，看看那里有其他任何明显的方法来使用，但没有跳出.

I've looked through context to see if theres any other obvious methods to use, but none jumps out.

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推荐答案

在斯卡拉2.10，c.typeCheck总是将它的参数作为一个术语，你需要去加倍努力，以类型检查，表示类型的树.

In Scala 2.10, c.typeCheck always treats its argument as a term, and you need to go the extra mile to typecheck a tree representing a type.

此答案说明了一种将类型作为类型进行类型检查的解决方法，并概述了特定于宏注释的限制:

This answer explains a workaround to typecheck something as a type and outlines a limitation specific to macro annotations: Can't access Parent's Members while dealing with Macro Annotations.

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