Fix #1146: Fix bug of ExpandSAMs with non-apply SAM methods.

When expanding a SAM, ExpandSAMs always used the name `apply` for
the generated forwarder, instead of the name of the method which
is abstract in the SAM type. This commit fixes this issue.

Author: sjrd

src/dotty/tools/dotc/transform/ExpandSAMs.scala

@@ -42,8 +42,11 @@ class ExpandSAMs extends MiniPhaseTransform { thisTransformer =>
         case tpe @ SAMType(_) if isJvmSam(tpe.classSymbol.asClass) =>
           tree
         case tpe =>
+          val abstractMethods = tpe.abstractTermMembers.filter(!_.symbol.is(SuperAccessor))
+          assert(abstractMethods.size == 1)
+          val samDenot = abstractMethods.head
           cpy.Block(tree)(stats,
-              AnonClass(tpe :: Nil, fn.symbol.asTerm :: Nil, nme.apply :: Nil))
+              AnonClass(tpe :: Nil, fn.symbol.asTerm :: Nil, samDenot.symbol.asTerm.name :: Nil))
       }
     case _ =>
       tree

tests/run/non-jvm-sam-non-apply.check

@@ -0,0 +1 @@
+4

tests/run/non-jvm-sam-non-apply.scala

@@ -0,0 +1,11 @@
+// shouldn't result in an abstract method error when run
+abstract class NonJVMSam {
+  def foo(x: Int): Int
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    val f: NonJVMSam = x => x + 1
+    println(f.foo(3))
+  }
+}