Method overloading in scala gives compilation error ambiguous reference

Question

When I compile this code, I get ambiguous reference error for method m1. Can someone tell me why?

object MyClass { trait T { def m1(str: String): Unit = println(str) def m1: Unit = { println("m1") m1("from:m1") } } class C extends T { override def m1(str: String): Unit = println(str+"1") } def main(args: Array[String]): Unit = { val c = new C() c.m1 } }

There are some questions related to this problems, for example here and here. I hope that these questions can you a little bit. — gianluca aguzzi
– gianluca aguzzi, Commented Aug 25, 2021 at 9:59
Since the second method is doing a side-effect the style guide says that it should be defined as def m1(): Unit = { and thus the call site must be c.m1() and that should fix the ambiguity problem. — Luis Miguel Mejía Suárez
– Luis Miguel Mejía Suárez, Commented Aug 25, 2021 at 12:39

Jarrod Baker · Accepted Answer · 2021-08-25 13:34:45Z

When you call C.m1 in main you don't include parentheses. The compiler doesn't know if you are intentionally calling the arity-0 method, or were intending to call the arity-1 method using infix notation, eg c.m1 "hello".

Replacing c.m1 with c.m1() will compile.

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