12 files changed, 62 insertions, 5 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/TreeInfo.scala b/src/compiler/scala/tools/nsc/ast/TreeInfo.scala
index 5b4622a984..13980856ec 100644
--- a/src/compiler/scala/tools/nsc/ast/TreeInfo.scala
+++ b/src/compiler/scala/tools/nsc/ast/TreeInfo.scala
@@ -225,4 +225,19 @@ abstract class TreeInfo {
     case AppliedTypeTree(fn, _) => methPart(fn)
     case _ => tree
   }
+
+  /** Top-level definition sequence contains a leading import of Predef or scala.Predef
+   */
+  def containsLeadingPredefImport(defs: List[Tree]): boolean = defs match {
+    case List(PackageDef(_, defs1)) =>
+      containsLeadingPredefImport(defs1)
+    case Import(Ident(nme.Predef), _) :: _ =>
+      true
+    case Import(Select(Ident(nme.scala_), nme.Predef), _) :: _ =>
+      true
+    case Import(_, _) :: defs1 =>
+      containsLeadingPredefImport(defs1)
+    case _ =>
+      false
+  }
 }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
index 2e4742e94c..a77098a50f 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
@@ -51,7 +51,7 @@ trait Contexts requires Analyzer {
       addImport(JavaLangPackage)
       assert(ScalaPackage ne null, "Scala package is null")
       addImport(ScalaPackage)
-      if (!settings.nopredefs.value/* || unit.source.file.name != "Predef.scala"*/)
+      if (!(settings.nopredefs.value || treeInfo.containsLeadingPredefImport(List(unit.body))))
         addImport(PredefModule)
     }
     val c = sc.make(unit, tree, sc.owner, sc.scope, sc.imports)
diff --git a/src/compiler/scala/tools/nsc/typechecker/Infer.scala b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
index 983e72c75f..589e36b5d3 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Infer.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
@@ -915,6 +915,13 @@ trait Infer requires Analyzer {
       }
     }
 
+    object approximateAbstracts extends TypeMap {
+      def apply(tp: Type): Type = tp match {
+        case TypeRef(pre, sym, _) if sym.isAbstractType => WildcardType
+        case _ => mapOver(tp)
+      }
+    }
+
     /** A traverser to collect type parameters referred to in a type
      */
     object freeTypeParamsOfTerms extends SymCollector {
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 6c5462196a..3b3c02ce5b 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -630,7 +630,8 @@ trait Typers requires Analyzer {
           if ((mode & PATTERNmode) != 0) {
             if ((tree.symbol ne null) && tree.symbol.isModule)
               inferModulePattern(tree, pt)
-            if (isPopulated(tree.tpe, pt)) return tree
+            if (isPopulated(tree.tpe, approximateAbstracts(pt)))
+              return tree
           }
           val tree1 = constfold(tree, pt) // (10) (11)
           if (tree1.tpe <:< pt) adapt(tree1, mode, pt)
diff --git a/src/library/scala/Stream.scala b/src/library/scala/Stream.scala
index e42947512b..6ecc9b768c 100644
--- a/src/library/scala/Stream.scala
+++ b/src/library/scala/Stream.scala
@@ -192,7 +192,7 @@ trait Stream[+a] extends Seq[a] {
    */
   def elements: Iterator[a] = new Iterator[a] {
     var current = Stream.this
-    def hasNext: boolean = !current.isEmpty
+    def hasNext: Boolean = !current.isEmpty
     def next: a = { val result = current.head; current = current.tail; result }
   }
 
diff --git a/test/files/neg/bug900.check b/test/files/neg/bug900.check
new file mode 100644
index 0000000000..531ac5bee4
--- /dev/null
+++ b/test/files/neg/bug900.check
@@ -0,0 +1,10 @@
+bug900.scala:4: error: type mismatch;
+ found   : Foo.this.x.type (with underlying type Foo.this.bar)
+ required: java.lang.Object
+Note that implicit conversions are not applicable because they are ambiguous:
+ both method any2stringadd in object Predef of type (scala.Any)scala.runtime.StringAdd
+ and method any2ArrowAssoc in object Predef of type [a](a)scala.Predef.ArrowAssoc[a]
+ are possible conversion functions from Foo.this.x.type to java.lang.Object
+        def break(): x.type
+                     ^
+one error found
diff --git a/test/files/neg/bug900.scala b/test/files/neg/bug900.scala
new file mode 100644
index 0000000000..2d2c857575
--- /dev/null
+++ b/test/files/neg/bug900.scala
@@ -0,0 +1,5 @@
+trait Foo {
+        type bar
+        val x : bar
+        def break(): x.type
+}
diff --git a/test/files/neg/implicits.check b/test/files/neg/implicits.check
index 9f9f7f1ced..266d92c765 100644
--- a/test/files/neg/implicits.check
+++ b/test/files/neg/implicits.check
@@ -1,4 +1,7 @@
-implicits.scala:21: error: ambiguous implicit value:
+implicits.scala:21: error: type mismatch;
+ found   : Pos
+ required: ?{val +: ?}
+Note that implicit conversions are not applicable because they are ambiguous:
  most specific definition is: method pos2int in object Super of type (Pos)scala.Int
  yet alternative definition   method any2plus in object Sub of type (scala.Any)Sub.Plus
  is defined in a subclass.
diff --git a/test/files/neg/nopredefs.check b/test/files/neg/nopredefs.check
new file mode 100644
index 0000000000..0a0ab34482
--- /dev/null
+++ b/test/files/neg/nopredefs.check
@@ -0,0 +1,4 @@
+nopredefs.scala:5: error: not found: value Set
+  val y = Set(3)
+          ^
+one error found
diff --git a/test/files/neg/nopredefs.scala b/test/files/neg/nopredefs.scala
new file mode 100644
index 0000000000..1128b18934
--- /dev/null
+++ b/test/files/neg/nopredefs.scala
@@ -0,0 +1,6 @@
+import Predef.{Set => _, _}
+
+object Test {
+  val x = Map(1 -> 2)
+  val y = Set(3)
+}
diff --git a/test/files/neg/viewtest.check b/test/files/neg/viewtest.check
index d84d03fe24..2b1b2c4cbc 100644
--- a/test/files/neg/viewtest.check
+++ b/test/files/neg/viewtest.check
@@ -3,7 +3,7 @@ viewtest.scala:43: error: type mismatch;
  required: scala.List[a(in method view3)]
         case y1: List[a] => compareLists(x, y1)
                                             ^
-viewtest.scala:104: error: ambiguous implicit value:
+viewtest.scala:104: error: ambiguous implicit values:
  both method view4 in object O of type [a](a)a
  and method identity in object Predef of type [a](a)a
  match expected type (test.Str) => test.Ordered[test.Str]
diff --git a/test/files/pos/bug911.scala b/test/files/pos/bug911.scala
new file mode 100644
index 0000000000..224b14cda3
--- /dev/null
+++ b/test/files/pos/bug911.scala
@@ -0,0 +1,6 @@
+object Test {
+def foo : Any = {
+  case class Foo {}
+  Foo;
+}
+}