Scala:非宏方式实现内联方法中带类型占位符的动态编译错误?
内联方法/子句中生成动态编译器错误信息
是否可以在内联方法或子句中生成动态的编译器错误信息?
以下是两种现有实现方式:
1. 基于@implicitNotFound注解的声明式自定义
通过方法上下文参数召唤实例时,可借助@implicitNotFound注解声明式自定义错误信息,该注解支持字面量字符串和类型占位符:
import scala.annotation.implicitNotFound inline def singleInhabitantOf[A](using @implicitNotFound("The received type ${A} is not a singleton") voA: ValueOf[A]): A = voA.value singleInhabitantOf[Option[Int]] // 编译错误:The received type Option[Int] is not a singleton
2. 基于summonFrom+error的命令式自定义
如果用summonFrom实现隐式实例召唤,可调用error方法命令式生成错误信息,但该方法仅支持字面量字符串,不支持类型占位符:
import scala.compiletime.{summonFrom, error} inline def singleInhabitantOf2[A]: A = summonFrom { case voA: ValueOf[A] => voA.value case _ => error("The received type ${A} is not a singleton") } singleInhabitantOf2[Option[Int]] // 编译错误:The received type ${A} is not a singleton
疑问
除宏之外,是否存在一种方式,既能像summonFrom那样在方法体内召唤隐式实例,同时支持类型占位符,甚至实现更灵活的动态字符串插值?
内容的提问来源于stack exchange,提问作者Readren
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