Better errors for Any/AnyRef issues.

When an error occurs because some type does not conform
to AnyRef (and an AnyRef-derived type would have sufficed)
try to say something useful about the situation.

This commit also initializes scope members before printing
error messages because the + version seems more useful than
the - version (taken from one of the checkfile diffs.)

-  def <init>: <?>
-  def methodIntIntInt: <?>
+  def <init>(): X
+  def methodIntIntInt(x: scala.Int,y: scala.Int): scala.Int

6 files changed, 104 insertions, 6 deletions

diff --git a/test/files/neg/any-vs-anyref.check b/test/files/neg/any-vs-anyref.check
new file mode 100644
index 0000000000..63c4853130
--- /dev/null
+++ b/test/files/neg/any-vs-anyref.check
@@ -0,0 +1,64 @@
+any-vs-anyref.scala:6: error: type mismatch;
+ found   : a.type (with underlying type A)
+ required: AnyRef
+Note that A is bounded only by Equals, which means AnyRef is not a known parent.
+Such types can participate in value classes, but instances
+cannot appear in singleton types or in reference comparisons.
+  def foo1[A <: Product](a: A)                                      = { type X = a.type }
+                                                                                 ^
+any-vs-anyref.scala:7: error: type mismatch;
+ found   : a.type (with underlying type A)
+ required: AnyRef
+Note that A is bounded only by Product, Quux, which means AnyRef is not a known parent.
+Such types can participate in value classes, but instances
+cannot appear in singleton types or in reference comparisons.
+  def foo2[A <: Product with Quux](a: A)                            = { type X = a.type }
+                                                                                 ^
+any-vs-anyref.scala:8: error: type mismatch;
+ found   : a.type (with underlying type Product)
+ required: AnyRef
+Note that Product extends Any, not AnyRef.
+Such types can participate in value classes, but instances
+cannot appear in singleton types or in reference comparisons.
+  def foo3(a: Product)                                              = { type X = a.type }
+                                                                                 ^
+any-vs-anyref.scala:9: error: type mismatch;
+ found   : Product with Quux
+ required: AnyRef
+Note that the parents of this type (Product, Quux) extend Any, not AnyRef.
+Such types can participate in value classes, but instances
+cannot appear in singleton types or in reference comparisons.
+  def foo4(a: Product with Quux)                                    = { type X = a.type }
+                                                                                 ^
+any-vs-anyref.scala:10: error: value eq is not a member of Quux with Product
+Note that the parents of this type (Quux, Product) extend Any, not AnyRef.
+Such types can participate in value classes, but instances
+cannot appear in singleton types or in reference comparisons.
+  def foo5(x: Quux with Product)                                    = (x eq "abc") && ("abc" eq x)
+                                                                         ^
+any-vs-anyref.scala:11: error: value eq is not a member of Quux with Product{def f: Int}
+Note that the parents of this type (Quux, Product) extend Any, not AnyRef.
+Such types can participate in value classes, but instances
+cannot appear in singleton types or in reference comparisons.
+  def foo6(x: Quux with Product { def f: Int })                     = (x eq "abc") && ("abc" eq x)
+                                                                         ^
+any-vs-anyref.scala:12: error: type mismatch;
+ found   : Quux with Product{def eq(other: String): Boolean}
+ required: AnyRef
+Note that the parents of this type (Quux, Product) extend Any, not AnyRef.
+Such types can participate in value classes, but instances
+cannot appear in singleton types or in reference comparisons.
+  def foo7(x: Quux with Product { def eq(other: String): Boolean }) = (x eq "abc") && ("abc" eq x)
+                                                                                                ^
+any-vs-anyref.scala:22: error: value eq is not a member of Bippy
+Note that Bippy extends Any, not AnyRef.
+Such types can participate in value classes, but instances
+cannot appear in singleton types or in reference comparisons.
+  def bad1(x: Bippy, y: Bippy) = x eq y
+                                   ^
+any-vs-anyref.scala:27: error: type mismatch;
+ found   : Quux{def g(x: String): String}
+ required: Quux{def g(x: Int): Int}
+  f(new Quux { def g(x: String) = x })
+    ^
+9 errors found
diff --git a/test/files/neg/any-vs-anyref.scala b/test/files/neg/any-vs-anyref.scala
new file mode 100644
index 0000000000..8d237fbaec
--- /dev/null
+++ b/test/files/neg/any-vs-anyref.scala
@@ -0,0 +1,29 @@
+trait Quux extends Any
+trait QuuxRef extends AnyRef
+final class Bippy(val x: Any) extends AnyVal with Quux
+
+object Foo {
+  def foo1[A <: Product](a: A)                                      = { type X = a.type }
+  def foo2[A <: Product with Quux](a: A)                            = { type X = a.type }
+  def foo3(a: Product)                                              = { type X = a.type }
+  def foo4(a: Product with Quux)                                    = { type X = a.type }
+  def foo5(x: Quux with Product)                                    = (x eq "abc") && ("abc" eq x)
+  def foo6(x: Quux with Product { def f: Int })                     = (x eq "abc") && ("abc" eq x)
+  def foo7(x: Quux with Product { def eq(other: String): Boolean }) = (x eq "abc") && ("abc" eq x)
+
+  def ok1[A <: QuuxRef](a: A)                            = { type X = a.type }
+  def ok2[A <: Product with QuuxRef](a: A)               = { type X = a.type }
+  def ok3(a: QuuxRef)                                    = { type X = a.type }
+  def ok4(a: Product with QuuxRef)                       = { type X = a.type }
+  def ok5(x: QuuxRef with Product)                       = (x eq "abc") && ("abc" eq x)
+  def ok6(x: QuuxRef with Product { def f: Int })        = (x eq "abc") && ("abc" eq x)
+  def ok7(x: QuuxRef { def eq(other: String): Boolean }) = (x eq "abc") && ("abc" eq x)
+
+  def bad1(x: Bippy, y: Bippy) = x eq y
+}
+
+object Bar {
+  def f(x: Quux { def g(x: Int): Int }): Int = x g 5
+  f(new Quux { def g(x: String) = x })
+  f(new Quux { def g(x: Int) = x })
+}
diff --git a/test/files/neg/not-possible-cause.check b/test/files/neg/not-possible-cause.check
index 9111cd0d3d..5c09fa1545 100644
--- a/test/files/neg/not-possible-cause.check
+++ b/test/files/neg/not-possible-cause.check
@@ -1,10 +1,9 @@
 not-possible-cause.scala:2: error: type mismatch;
  found   : a.type (with underlying type A)
  required: AnyRef
-Note that implicit conversions are not applicable because they are ambiguous:
- both method any2stringfmt in object Predef of type (x: Any)scala.runtime.StringFormat
- and method any2stringadd in object Predef of type (x: Any)scala.runtime.StringAdd
- are possible conversion functions from a.type to AnyRef
+Note that A is bounded only by Equals, which means AnyRef is not a known parent.
+Such types can participate in value classes, but instances
+cannot appear in singleton types or in reference comparisons.
   def foo[A <: Product](a: A) { type X = a.type }
                                          ^
 one error found
diff --git a/test/files/neg/t3614.check b/test/files/neg/t3614.check
index 5fdb5cbf1f..0f9c83aa0d 100644
--- a/test/files/neg/t3614.check
+++ b/test/files/neg/t3614.check
@@ -1,4 +1,4 @@
-t3614.scala:2: error: class type required but AnyRef{def a: <?>} found
+t3614.scala:2: error: class type required but AnyRef{def a: Int} found
   def v = new ({ def a=0 })
                ^
-one error found
\ No newline at end of file
+one error found
diff --git a/test/files/neg/t6263.check b/test/files/neg/t6263.check
index 1c5834e1ca..9e9c7c615b 100644
--- a/test/files/neg/t6263.check
+++ b/test/files/neg/t6263.check
@@ -1,6 +1,9 @@
 t6263.scala:5: error: type mismatch;
  found   : A.this.c.type (with underlying type C)
  required: AnyRef
+Note that C extends Any, not AnyRef.
+Such types can participate in value classes, but instances
+cannot appear in singleton types or in reference comparisons.
   type t = c.type
            ^
 one error found
diff --git a/test/files/neg/t900.check b/test/files/neg/t900.check
index ff5304a135..6fe26a31ac 100644
--- a/test/files/neg/t900.check
+++ b/test/files/neg/t900.check
@@ -1,6 +1,9 @@
 t900.scala:4: error: type mismatch;
  found   : Foo.this.x.type (with underlying type Foo.this.bar)
  required: AnyRef
+Note that bar is unbounded, which means AnyRef is not a known parent.
+Such types can participate in value classes, but instances
+cannot appear in singleton types or in reference comparisons.
         def break(): x.type
                      ^
 one error found