SI-7187 deprecate eta-expansion of zero-arg method values

For backwards compatiblity with 2.11, we already
don't adapt a zero-arg method value to a SAM.
In 2.13, we won't do any eta-expansion for zero-arg method values,
but we should deprecate first.

7 files changed, 24 insertions, 25 deletions

diff --git a/test/files/neg/t7187.check b/test/files/neg/t7187.check
new file mode 100644
index 0000000000..a30803c746
--- /dev/null
+++ b/test/files/neg/t7187.check
@@ -0,0 +1,6 @@
+t7187.scala:3: warning: Eta-expansion of zero-argument method values is deprecated. Did you intend to write EtaExpandZeroArg.this.foo()?
+  val f: () => Any = foo
+                     ^
+error: No warnings can be incurred under -Xfatal-warnings.
+one warning found
+one error found
diff --git a/test/files/neg/t7187.flags b/test/files/neg/t7187.flags
new file mode 100644
index 0000000000..c6bfaf1f64
--- /dev/null
+++ b/test/files/neg/t7187.flags
@@ -0,0 +1 @@
+-deprecation -Xfatal-warnings
diff --git a/test/files/neg/t7187.scala b/test/files/neg/t7187.scala
new file mode 100644
index 0000000000..45d33f06af
--- /dev/null
+++ b/test/files/neg/t7187.scala
@@ -0,0 +1,6 @@
+class EtaExpandZeroArg {
+  def foo(): () => String = () => ""
+  val f: () => Any = foo
+
+  // f() would evaluate to <function0> instead of ""
+}
diff --git a/test/files/pos/t9178.flags b/test/files/pos/t9178.flags
deleted file mode 100644
index 7de3c0f3ee..0000000000
--- a/test/files/pos/t9178.flags
+++ /dev/null
@@ -1 +0,0 @@
--Xfatal-warnings -deprecation
diff --git a/test/files/pos/t9178.scala b/test/files/pos/t9178.scala
deleted file mode 100644
index f2cf20a778..0000000000
--- a/test/files/pos/t9178.scala
+++ /dev/null
@@ -1,13 +0,0 @@
-// eta expansion to Function0 is problematic (as shown here).
-// Perhaps we should we deprecate it? See discussion in the comments of
-// on SI-9178.
-//
-// This test encodes the status quo: no deprecation.
-object Test {
-  def foo(): () => String = () => ""
-  val f: () => Any = foo
-
-  def main(args: Array[String]): Unit = {
-    println(f()) // <function0>
-  }
-}
diff --git a/test/files/run/Course-2002-08.scala b/test/files/run/Course-2002-08.scala
index 5e21edaba3..1d0e02262d 100644
--- a/test/files/run/Course-2002-08.scala
+++ b/test/files/run/Course-2002-08.scala
@@ -205,7 +205,7 @@ object M5 {
         val inputSig = input.getSignal;
         afterDelay(InverterDelay) {() => output.setSignal(!inputSig) };
       }
-      input addAction invertAction
+      input addAction invertAction _
     }
 
     def andGate(a1: Wire, a2: Wire, output: Wire): Unit = {
@@ -214,8 +214,8 @@ object M5 {
         val a2Sig = a2.getSignal;
         afterDelay(AndGateDelay) {() => output.setSignal(a1Sig & a2Sig) };
       }
-      a1 addAction andAction;
-      a2 addAction andAction;
+      a1 addAction andAction _
+      a2 addAction andAction _
     }
 
     def orGate(o1: Wire, o2: Wire, output: Wire): Unit = {
@@ -224,8 +224,8 @@ object M5 {
         val o2Sig = o2.getSignal;
         afterDelay(OrGateDelay) {() => output.setSignal(o1Sig | o2Sig) };
       }
-      o1 addAction orAction;
-      o2 addAction orAction;
+      o1 addAction orAction _
+      o2 addAction orAction _
     }
 
     def probe(name: String, wire: Wire): Unit = {
@@ -479,7 +479,7 @@ abstract class BasicCircuitSimulator() extends Simulator() {
       val inputSig = input.getSignal;
       afterDelay(InverterDelay) {() => output.setSignal(!inputSig) };
     }
-    input addAction invertAction
+    input addAction invertAction _
   }
 
   def andGate(a1: Wire, a2: Wire, output: Wire) = {
@@ -488,8 +488,8 @@ abstract class BasicCircuitSimulator() extends Simulator() {
       val a2Sig = a2.getSignal;
       afterDelay(AndGateDelay) {() => output.setSignal(a1Sig & a2Sig) };
     }
-    a1 addAction andAction;
-    a2 addAction andAction
+    a1 addAction andAction _
+    a2 addAction andAction _
   }
 
   def orGate(a1: Wire, a2: Wire, output: Wire) = {
@@ -498,8 +498,8 @@ abstract class BasicCircuitSimulator() extends Simulator() {
       val a2Sig = a2.getSignal;
       afterDelay(OrGateDelay) {() => output.setSignal(a1Sig | a2Sig) };
     }
-    a1 addAction orAction;
-    a2 addAction orAction
+    a1 addAction orAction _
+    a2 addAction orAction _
   }
 
   def orGate2(a1: Wire, a2: Wire, output: Wire) = {
diff --git a/test/files/run/runtime.scala b/test/files/run/runtime.scala
index 89348b294d..468a80fc0c 100644
--- a/test/files/run/runtime.scala
+++ b/test/files/run/runtime.scala
@@ -73,7 +73,7 @@ object Test1Test {
     // {System.out.print(22); test1.bar}.System.out.println();
     {Console.print(23); test1.bar.System}.out.println();
     {Console.print(24); test1.bar.System.out}.println();
-    {Console.print(25); test1.bar.System.out.println:(() => Unit)} apply ();
+    {Console.print(25); test1.bar.System.out.println _ : (() => Unit)} apply ();
     {Console.print(26); test1.bar.System.out.println()};
   }