Require postfixOps feature setting

This commit turns the feature warning into an error
if `postfixOps` is not enabled.

Popular sentiment has turned against the feature,
and requiring enablement raises the barrier to entry.

In particular, beginners will not stumble across
it accidentally.

src/library/scala/languageFeature.scala

@@ -18,7 +18,7 @@ object languageFeature {
   sealed trait dynamics
   object dynamics extends dynamics
 
-  @meta.languageFeature("postfix operator #", enableRequired = false)
+  @meta.languageFeature("postfix operator #", enableRequired = true)
   sealed trait postfixOps
   object postfixOps extends postfixOps
 

test/files/neg/post-postfix.check

@@ -0,0 +1,9 @@
+post-postfix.scala:5: error: postfix operator head needs to be enabled
+by making the implicit value scala.language.postfixOps visible.
+This can be achieved by adding the import clause 'import scala.language.postfixOps'
+or by setting the compiler option -language:postfixOps.
+See the Scaladoc for value scala.language.postfixOps for a discussion
+why the feature needs to be explicitly enabled.
+  def f(): Int = List(1) head
+                         ^
+one error found

test/files/neg/post-postfix.scala

@@ -0,0 +1,6 @@
+
+//import language.postfixOps
+
+trait T {
+  def f(): Int = List(1) head
+}

test/files/neg/t5675.scala

@@ -1,9 +1,7 @@
 // scalac: -Xfatal-warnings
 //
-class PostFix {
-  val list = List(1, 2, 3)
-  def main(args: Array[String]): Unit = {
-    val a = list filter (2 !=)
-    val b = list filter (2 != _)
-  }
+// without -feature, don't double-count the warning
+//
+class OneWarningOnly {
+  implicit def `this is why we warn`(x: Any): Int = x.toString.toInt
 }

test/files/neg/t6120.check

@@ -1,20 +1,20 @@
-t6120.scala:7: warning: postfix operator bippy should be enabled
-by making the implicit value scala.language.postfixOps visible.
-This can be achieved by adding the import clause 'import scala.language.postfixOps'
-or by setting the compiler option -language:postfixOps.
-See the Scaladoc for value scala.language.postfixOps for a discussion
-why the feature should be explicitly enabled.
-  def f = null == null bippy
-                       ^
-t6120.scala:7: warning: method bippy in class BooleanOps is deprecated (since 2.11.0): bobo
-  def f = null == null bippy
-                       ^
-t6120.scala:7: warning: comparing values of types Null and Null using `==' will always yield true
-  def f = null == null bippy
+t6120.scala:14: warning: method bippy in class BooleanOps is deprecated (since 2.11.0): bobo
+  def f = (null == null).bippy
+                         ^
+t6120.scala:14: warning: method bippy in class BooleanOps has changed semantics in version 2.12.6:
+Used to return 5
+  def f = (null == null).bippy
+                         ^
+t6120.scala:14: warning: comparing values of types Null and Null using `==' will always yield true
+  def f = (null == null).bippy
+                ^
+t6120.scala:15: warning: method bippy in class BooleanOps is deprecated (since 2.11.0): bobo
+  def g = true.bippy
                ^
-t6120.scala:8: warning: method bippy in class BooleanOps is deprecated (since 2.11.0): bobo
+t6120.scala:15: warning: method bippy in class BooleanOps has changed semantics in version 2.12.6:
+Used to return 5
   def g = true.bippy
                ^
 error: No warnings can be incurred under -Xfatal-warnings.
-four warnings found
+5 warnings found
 one error found

test/files/neg/t6120.scala

@@ -1,9 +1,32 @@
-// scalac: -feature -deprecation -Xfatal-warnings
+// scalac: -deprecation -Xmigration:2.10 -Xfatal-warnings
 //
+// showing that multiple warnings at same location are reported
+//
+package scala.test
+import scala.annotation._
+
 class A {
   implicit class BooleanOps(val b: Boolean) {
-    @deprecated("bobo", "2.11.0") def bippy() = 5
+    @deprecated("bobo", since="2.11.0")
+    @migration("Used to return 5", changedIn="2.12.6")
+    def bippy() = 42
   }
-  def f = null == null bippy
+  def f = (null == null).bippy
   def g = true.bippy
 }
+
+/*
+
+$ ~/scala-2.10.4/bin/scalac -d /tmp -Xmigration:2.10 -deprecation test/files/neg/t6120.scala
+test/files/neg/t6120.scala:14: warning: method bippy in class BooleanOps is deprecated: bobo
+  def f = (null == null).bippy
+                         ^
+test/files/neg/t6120.scala:14: warning: comparing values of types Null and Null using `==' will always yield true
+  def f = (null == null).bippy
+                ^
+test/files/neg/t6120.scala:15: warning: method bippy in class BooleanOps is deprecated: bobo
+  def g = true.bippy
+               ^
+three warnings found
+
+ */

test/files/pos/post-postfix.scala

@@ -0,0 +1,7 @@
+
+// required
+import language.postfixOps
+
+trait T {
+  def f(): Int = List(1) head
+}

test/files/pos/t8223.scala

@@ -17,9 +17,9 @@ package object p {
   type EnvAlias[W <: HasA] = ViewEnv[W#A]
   type SubAlias[W <: HasA] = ViewEnv[W#A]#SubView
 
-  def f0[R](xs: R)(implicit tc: Indexable[R]): ViewEnv[tc.A]#SubView     = new ViewEnv[tc.A]() get
-  def f1[R](xs: R)(implicit tc: Indexable[R]): EnvAlias[tc.type]#SubView = new ViewEnv[tc.A]() get
-  def f2[R](xs: R)(implicit tc: Indexable[R]): SubAlias[tc.type]         = new ViewEnv[tc.A]() get
+  def f0[R](xs: R)(implicit tc: Indexable[R]): ViewEnv[tc.A]#SubView     = new ViewEnv[tc.A]().get
+  def f1[R](xs: R)(implicit tc: Indexable[R]): EnvAlias[tc.type]#SubView = new ViewEnv[tc.A]().get
+  def f2[R](xs: R)(implicit tc: Indexable[R]): SubAlias[tc.type]         = new ViewEnv[tc.A]().get
 
   def g0 = f0(Array(1)) has 2                   // ok
   def g1 = f1(Array(1)) has 2                   // ok

test/files/pos/tcpoly_infer_explicit_tuple_wrapper.scala

@@ -9,5 +9,5 @@ object Test {
 
   val t = (List(1, 2, 3), List(6, 5, 4))
 
-  tupleOfIterableWrapper(t) unzip
+  tupleOfIterableWrapper(t).unzip
 }

test/files/pos/tcpoly_infer_implicit_tuple_wrapper.scala

@@ -11,7 +11,7 @@ object Test {
 
   val t = (List(1, 2, 3), List(6, 5, 4))
 
-  tupleOfIterableWrapper(t) unzip
+  tupleOfIterableWrapper(t).unzip
 
-  t unzip
+  t.unzip
 }

test/files/pos/tcpoly_infer_ticket716.scala

@@ -21,6 +21,6 @@ object Functor{
 object GeneralLiftingDemo extends App {
   import Functor._
   val l = List(1,2,3)
-  val res = l fmap( 1+) // TODO: should not need explicit call to lifttoOO
+  val res = l fmap (1 + _) // TODO: should not need explicit call to lifttoOO
   println("OO : " + res )
 }