SD-98 don't emit unnecessary mixin forwarders

In most cases when a class inherits a concrete method from a trait we
don't need to generate a forwarder to the default method in the class.

t5148 is moved to pos as it compiles without error now. the error
message ("missing or invalid dependency") is still tested by t6440b.

5 files changed, 48 insertions, 16 deletions

diff --git a/test/files/run/mixin-signatures.check b/test/files/run/mixin-signatures.check
index 77bff79ac8..9961992e2d 100644
--- a/test/files/run/mixin-signatures.check
+++ b/test/files/run/mixin-signatures.check
@@ -1,19 +1,23 @@
 class Test$bar1$ {
-  public java.lang.String Test$bar1$.f(java.lang.Object)
+  public default java.lang.String Foo1.f(java.lang.Object)
+    generic: public default java.lang.String Foo1.f(T)
   public java.lang.Object Test$bar1$.f(java.lang.Object) <bridge> <synthetic>
   public java.lang.String Test$bar1$.g(java.lang.String)
   public java.lang.Object Test$bar1$.g(java.lang.Object) <bridge> <synthetic>
   public java.lang.String Test$bar1$.g(java.lang.Object) <bridge> <synthetic>
-  public java.lang.Object Test$bar1$.h(java.lang.Object)
+  public default java.lang.Object Base.h(java.lang.Object)
+    generic: public default R Base.h(T)
 }
 
 class Test$bar2$ {
-  public java.lang.Object Test$bar2$.f(java.lang.String)
+  public default java.lang.Object Foo2.f(java.lang.String)
+    generic: public default R Foo2.f(java.lang.String)
   public java.lang.Object Test$bar2$.f(java.lang.Object) <bridge> <synthetic>
   public java.lang.String Test$bar2$.g(java.lang.String)
   public java.lang.Object Test$bar2$.g(java.lang.Object) <bridge> <synthetic>
   public java.lang.Object Test$bar2$.g(java.lang.String) <bridge> <synthetic>
-  public java.lang.Object Test$bar2$.h(java.lang.Object)
+  public default java.lang.Object Base.h(java.lang.Object)
+    generic: public default R Base.h(T)
 }
 
 class Test$bar3$ {
@@ -23,7 +27,8 @@ class Test$bar3$ {
   public java.lang.String Test$bar3$.g(java.lang.String)
   public java.lang.Object Test$bar3$.g(java.lang.Object) <bridge> <synthetic>
   public java.lang.String Test$bar3$.g(java.lang.Object) <bridge> <synthetic>
-  public java.lang.Object Foo3.h(java.lang.Object)
+  public default java.lang.Object Base.h(java.lang.Object)
+    generic: public default R Base.h(T)
 }
 
 class Test$bar4$ {
@@ -33,7 +38,8 @@ class Test$bar4$ {
   public java.lang.String Test$bar4$.g(java.lang.String)
   public java.lang.Object Test$bar4$.g(java.lang.Object) <bridge> <synthetic>
   public java.lang.Object Test$bar4$.g(java.lang.String) <bridge> <synthetic>
-  public java.lang.Object Foo4.h(java.lang.Object)
+  public default java.lang.Object Base.h(java.lang.Object)
+    generic: public default R Base.h(T)
 }
 
 class Test$bar5$ {
@@ -45,7 +51,8 @@ class Test$bar5$ {
   public java.lang.Object Test$bar5$.g(java.lang.Object) <bridge> <synthetic>
   public java.lang.Object Test$bar5$.g(java.lang.String) <bridge> <synthetic>
   public java.lang.String Test$bar5$.g(java.lang.Object) <bridge> <synthetic>
-  public java.lang.Object Test$bar5$.h(java.lang.Object)
+  public default java.lang.Object Base.h(java.lang.Object)
+    generic: public default R Base.h(T)
 }
 
 interface Foo1 {
diff --git a/test/files/run/t5652.check b/test/files/run/t5652.check
index 326b22f9dd..a0fb6fe9b4 100644
--- a/test/files/run/t5652.check
+++ b/test/files/run/t5652.check
@@ -4,5 +4,4 @@ public default void T1.$init$()
 public final int A1.A1$$g$2()
 public int A1.f1()
 public final int A2.A2$$g$1()
-public int A2.f0()
 public int A2.f2()
diff --git a/test/files/run/t6554.scala b/test/files/run/t6554.scala
index 5d29d16666..eed139fea6 100644
--- a/test/files/run/t6554.scala
+++ b/test/files/run/t6554.scala
@@ -1,8 +1,14 @@
-trait Foo[A] {
+trait T1[A] {
   def minBy[B](b: B): A = ???
 }
- 
-class Bar extends Foo[Int]
+
+// The second trait is needed to make sure there's a forwarder generated in Bar.
+// otherwise Bar.minBy is just the inherited default method from T1.
+trait T2[A] { self: T1[A] =>
+  override def minBy[B](b: B): A = ???
+}
+
+class Bar extends T1[Int] with T2[Int]
 
 object Test extends App {
    val sigs = classOf[Bar].getDeclaredMethods.map(m => s"${m.toString} / ${m.toGenericString}").sorted
diff --git a/test/files/run/t7932.check b/test/files/run/t7932.check
index 3f0a0c4f62..a2ad84cd46 100644
--- a/test/files/run/t7932.check
+++ b/test/files/run/t7932.check
@@ -1,3 +1,6 @@
-warning: there was one feature warning; re-run with -feature for details
 public Category<?> C.category()
 public Category<scala.Tuple2> C.category1()
+public default Category<java.lang.Object> M1.category()
+public default Category<scala.Tuple2> M1.category1()
+public default Category<java.lang.Object> M2.category()
+public default Category<scala.Tuple2> M2.category1()
diff --git a/test/files/run/t7932.scala b/test/files/run/t7932.scala
index 8743abff88..e6bdbf2417 100644
--- a/test/files/run/t7932.scala
+++ b/test/files/run/t7932.scala
@@ -1,11 +1,28 @@
+import scala.language.higherKinds
+
 class Category[M[_, _]]
-trait M[F] {
+
+trait M1[F] {
   type X[a, b] = F
   def category: Category[X] = null
   def category1: Category[Tuple2] = null
 }
-abstract class C extends M[Float]
+
+// The second trait is needed to make sure there's a forwarder generated in C.
+// otherwise the trait methods are just the inherited default methods from M1.
+trait M2[F] { self: M1[F] =>
+  override def category: Category[X] = null
+  override def category1: Category[Tuple2] = null
+}
+
+abstract class C extends M1[Float] with M2[Float]
+
 object Test extends App {
-  val ms = classOf[C].getMethods.filter(_.getName.startsWith("category"))
-  println(ms.map(_.toGenericString).sorted.mkString("\n"))
+  def t(c: Class[_]) = {
+    val ms = c.getMethods.filter(_.getName.startsWith("category"))
+    println(ms.map(_.toGenericString).sorted.mkString("\n"))
+  }
+  t(classOf[C])
+  t(classOf[M1[_]])
+  t(classOf[M2[_]])
 }