Single Abstract Method support: synthesize SAMs

Under `-Xexperimental`, `typedFunction` invokes `synthesizeSAMFunction`
when the expected type for the function literal (`pt`) is not the built-in
`FunctionN` type of the expected arity, but `pt` does have a SAM
with the expected number of arguments.

PS: We'll require `import language.sam` instead of `-Xexperimental`,
as soon as the SIP is ready and there are more tests.

7 files changed, 32 insertions, 2 deletions

diff --git a/test/files/pos/sammy_poly.flags b/test/files/pos/sammy_poly.flags
new file mode 100644
index 0000000000..48fd867160
--- /dev/null
+++ b/test/files/pos/sammy_poly.flags
@@ -0,0 +1 @@
+-Xexperimental
diff --git a/test/files/pos/sammy_poly.scala b/test/files/pos/sammy_poly.scala
new file mode 100644
index 0000000000..f03be4f8f5
--- /dev/null
+++ b/test/files/pos/sammy_poly.scala
@@ -0,0 +1,6 @@
+// test synthesizeSAMFunction where the sam type is not fully defined
+class T {
+  trait F[T, U] { def apply(x: T): U }
+  def app[T, U](x: T)(f: F[T, U]): U = f(x)
+  app(1)(x => List(x))
+}
\ No newline at end of file
diff --git a/test/files/pos/sammy_scope.flags b/test/files/pos/sammy_scope.flags
new file mode 100644
index 0000000000..48fd867160
--- /dev/null
+++ b/test/files/pos/sammy_scope.flags
@@ -0,0 +1 @@
+-Xexperimental
diff --git a/test/files/pos/sammy_scope.scala b/test/files/pos/sammy_scope.scala
new file mode 100644
index 0000000000..8f1fe7058e
--- /dev/null
+++ b/test/files/pos/sammy_scope.scala
@@ -0,0 +1,8 @@
+// test synthesizeSAMFunction: scope hygiene
+abstract class SamFun[T1, R] { self =>
+  def apply(v1: T1): R
+
+  // this should type check, as the apply ref is equivalent to self.apply
+  // it shouldn't resolve to the sam's apply that's synthesized (that wouldn't type check, hence the pos test)
+  def compose[A](g: SamFun[A, T1]): SamFun[A, R] = { x => apply(g(x)) }
+}
\ No newline at end of file
diff --git a/test/files/pos/sammy_twice.flags b/test/files/pos/sammy_twice.flags
new file mode 100644
index 0000000000..48fd867160
--- /dev/null
+++ b/test/files/pos/sammy_twice.flags
@@ -0,0 +1 @@
+-Xexperimental
diff --git a/test/files/pos/sammy_twice.scala b/test/files/pos/sammy_twice.scala
new file mode 100644
index 0000000000..c91f5b9fd2
--- /dev/null
+++ b/test/files/pos/sammy_twice.scala
@@ -0,0 +1,9 @@
+// test repeated synthesizeSAMFunction where the sam type is not fully defined
+// the naive implementation would enter the same apply$body in the same scope twice
+trait F[T, U] { def apply(x: T): U }
+
+class C {
+  def app[T, U](x: T)(f: F[T, U]): U = f(x)
+  app(1)(x => List(x))
+  app(2)(x => List(x))
+}
\ No newline at end of file
diff --git a/test/files/pos/t6221.scala b/test/files/pos/t6221.scala
index dd7776f596..34f02859f3 100644
--- a/test/files/pos/t6221.scala
+++ b/test/files/pos/t6221.scala
@@ -7,23 +7,27 @@ class MyCollection[A] {
 class OtherFunc[-A, +B] {}
 
 object Test {
-  implicit def functionToMyFunc[A, B](f: A => B): MyFunc[A, B] = new MyFunc
+  implicit def functionToMyFunc[A, B](f: A => B): MyFunc[A, B] = new MyFunc // = new MyFunc[A,Nothing]();
 
-  implicit def otherFuncToMyFunc[A, B](f: OtherFunc[A, B]): MyFunc[A, B] = new MyFunc
+  implicit def otherFuncToMyFunc[A, B](f: OtherFunc[A, B]): MyFunc[A, B] = new MyFunc // = new MyFunc[A,Nothing]();
 
   def main(args: Array[String]) {
     val col = new MyCollection[Int]
 
     // Doesn't compile: error: missing parameter type for expanded function ((x$1) => x$1.toString)
     println(col.map(_.toString))
+    // scala.this.Predef.println(col.map[String](Test.this.functionToMyFunc[Int, String](((x$1: Int) => x$1.toString()))));
 
     // Doesn't compile: error: missing parameter type
     println(col.map(x => x.toString))
+    // scala.this.Predef.println(col.map[String](Test.this.functionToMyFunc[Int, String](((x: Int) => x.toString()))));
 
     // Does compile
     println(col.map((x: Int) => x.toString))
+    // scala.this.Predef.println(col.map[String](Test.this.functionToMyFunc[Int, String](((x: Int) => x.toString()))));
 
     // Does compile (even though type params of OtherFunc not given)
     println(col.map(new OtherFunc))
+    // scala.this.Predef.println(col.map[Nothing](Test.this.otherFuncToMyFunc[Any, Nothing](new OtherFunc[Any,Nothing]())))
   }
 }
\ No newline at end of file