Inliner doesn't handle methods with both defaults and implicits

[liufengyun]

The following code fails (it compiles if we remove rewrite):

class Test {
  rewrite def foo(x: Int = 5)(implicit y: Int): Int =
    if (x > 0) y * y
    else y + y

  implicit val m: Int = 7

  (new Test).foo()
}

Error message:

-- Error: examples/implicit.scala:8:13 -----------------------------------------
8 |  (new Test).foo()
  |  ^^^^^^^^^^^^^^
  |  method foo is declared as erased, but is in fact used

It's due to the tree generated where Apply.fun is Block:

  class Test() extends Object() {
    rewrite def foo(x: Int)(implicit y: Int): Int =
      if x.>(0) then y.*(y) else y.+(y)
    def foo$default$1: Int = 5
    implicit val m: Int = 7
    {
      val $1$: Test = new Test()
      $1$.foo($1$.foo$default$1)
    }(this.m)
  }

@odersky I'm wondering if it's possible to enforce the invariant that Apply.fun is never a Block.

[allanrenucci]

Another weird thing:

class Test {
  def foo(x: Int = 5): Int = 1
  def test = (new Test).foo()
}

compiles to:

class Test() extends Object() { 
  def foo(x: Int): Int = 1
  def foo$default$1: Int = 5
  def test: Int = new Test().foo(new Test().foo$default$1)
}

A new instance of Test is created to get the default argument. Only happens if Test's constructor is empty though

[allanrenucci]

If we consider the following example:

class Test {
  def foo(x: Int = 5)(implicit y: Int): Int = 1

  implicit val m: Int = 7
  def test = (new Test).foo()
}

Here is what scalac produces for the method test:

def test: Int = {
  <artifact> val qual$1: Test = new Test();
  <artifact> val x$1: Int = qual$1.foo$default$1;
  qual$1.foo(x$1)(Test.this.m)
}

and dotc:

def test: Int =
  {
    val $1$: Test = new Test()
    $1$.foo($1$.foo$default$1)
  }(this.m)