Scala Map，元组和函数参数列表之间的歧义 [英] Scala Map, ambiguity between tuple and function argument list

问题描述

val m = scala.collection.mutable.Map[String, Int]()
// this doesn't work
m += ("foo", 2)
// this does work
m += (("foo", 2))
// this works too
val barpair = ("bar", 3)
m += barpair

那么m += ("foo" , 2)不起作用怎么办? Scala给出了类型错误:

So what's the deal with m += ("foo" , 2) not working? Scala gives the type error:

 error: type mismatch;
 found   : java.lang.String("foo")
 required: (String, Int)
       m += ("foo", 2)
             ^

显然，Scala认为我试图使用两个参数而不是一个元组参数来调用+=.为什么?因为我没有使用m.+=吗?

Apparently Scala thinks that I am trying to call += with two arguments, instead of one tuple argument. Why? Isn't it unambiguous, since I am not using m.+= ?

推荐答案

不幸的是，a b (c, d, e, ..)降低了对a.b(c, d, e, ..)的吸引力.因此是错误.

Unfortunately a b (c, d, e, ..) desugars to a.b(c, d, e, ..). Hence the error.

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