Merge pull request #3416 from retronym/topic/any-val-implicit

Prohibit views targeting AnyVal

6 files changed, 54 insertions, 31 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
index 91321d4700..847211945c 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
@@ -137,10 +137,6 @@ trait Implicits {
   private val improvesCache = perRunCaches.newMap[(ImplicitInfo, ImplicitInfo), Boolean]()
   private val implicitSearchId = { var id = 1 ; () => try id finally id += 1 }
 
-  private def isInvalidConversionTarget(tpe: Type): Boolean = tpe match {
-    case Function1(_, out) => AnyRefClass.tpe <:< out
-    case _                 => false
-  }
   private def isInvalidConversionSource(tpe: Type): Boolean = tpe match {
     case Function1(in, _) => in <:< NullClass.tpe
     case _                => false
@@ -629,7 +625,8 @@ trait Implicits {
               // for instance, if we have `class C[T]` and `implicit def conv[T: Numeric](c: C[T]) = ???`
               // then Scaladoc will give us something of type `C[T]`, and it would like to know
               // that `conv` is potentially available under such and such conditions
-              case tree if isImplicitMethodType(tree.tpe) && !isScalaDoc => applyImplicitArgs(tree)
+              case tree if isImplicitMethodType(tree.tpe) && !isScalaDoc =>
+                applyImplicitArgs(tree)
               case tree => tree
             }
           case _ => fallback
@@ -1361,11 +1358,17 @@ trait Implicits {
           if (context.ambiguousErrors)
             context.issueAmbiguousError(AmbiguousImplicitTypeError(tree, msg))
         }
-        if (isInvalidConversionTarget(pt)) {
-          maybeInvalidConversionError("the result type of an implicit conversion must be more specific than AnyRef")
-          result = SearchFailure
+        pt match {
+          case Function1(_, out) =>
+            def prohibit(sym: Symbol) = if (sym.tpe <:< out) {
+               maybeInvalidConversionError(s"the result type of an implicit conversion must be more specific than ${sym.name}")
+              result = SearchFailure
+            }
+            prohibit(AnyRefClass)
+            if (settings.isScala211) prohibit(AnyValClass)
+          case _                 => false
         }
-        else if (settings.isScala211 && isInvalidConversionSource(pt)) {
+        if (settings.isScala211 && isInvalidConversionSource(pt)) {
           maybeInvalidConversionError("an expression of type Null is ineligible for implicit conversion")
           result = SearchFailure
         }
diff --git a/test/files/neg/no-implicit-to-anyref-any-val.check b/test/files/neg/no-implicit-to-anyref-any-val.check
new file mode 100644
index 0000000000..5953e1bd6d
--- /dev/null
+++ b/test/files/neg/no-implicit-to-anyref-any-val.check
@@ -0,0 +1,34 @@
+no-implicit-to-anyref-any-val.scala:11: error: the result type of an implicit conversion must be more specific than AnyRef
+    1: AnyRef
+    ^
+no-implicit-to-anyref-any-val.scala:17: error: type mismatch;
+ found   : Any
+ required: AnyRef
+    (null: Any): AnyRef
+         ^
+no-implicit-to-anyref-any-val.scala:21: error: type mismatch;
+ found   : AnyVal
+ required: AnyRef
+    (0: AnyVal): AnyRef
+      ^
+no-implicit-to-anyref-any-val.scala:27: error: type mismatch;
+ found   : Test.AV
+ required: AnyRef
+Note that AV extends Any, not AnyRef.
+Such types can participate in value classes, but instances
+cannot appear in singleton types or in reference comparisons.
+    new AV(0): AnyRef
+    ^
+no-implicit-to-anyref-any-val.scala:30: error: the result type of an implicit conversion must be more specific than AnyVal
+  "": AnyVal
+  ^
+no-implicit-to-anyref-any-val.scala:32: error: type mismatch;
+ found   : Object
+ required: AnyVal
+Note that implicit conversions are not applicable because they are ambiguous:
+ both method ArrowAssoc in object Predef of type [A](self: A)ArrowAssoc[A]
+ and method Ensuring in object Predef of type [A](self: A)Ensuring[A]
+ are possible conversion functions from Object to AnyVal
+  new Object() : AnyVal
+  ^
+6 errors found
diff --git a/test/files/neg/no-implicit-to-anyref.scala b/test/files/neg/no-implicit-to-anyref-any-val.scala
index 3e3d373e38..f5daf541af 100644
--- a/test/files/neg/no-implicit-to-anyref.scala
+++ b/test/files/neg/no-implicit-to-anyref-any-val.scala
@@ -26,4 +26,8 @@ object Test {
   locally {
     new AV(0): AnyRef
   }
+
+  "": AnyVal
+
+  new Object() : AnyVal
 }
diff --git a/test/files/neg/no-implicit-to-anyref.check b/test/files/neg/no-implicit-to-anyref.check
deleted file mode 100644
index fe417ad8b0..0000000000
--- a/test/files/neg/no-implicit-to-anyref.check
+++ /dev/null
@@ -1,22 +0,0 @@
-no-implicit-to-anyref.scala:11: error: the result type of an implicit conversion must be more specific than AnyRef
-    1: AnyRef
-    ^
-no-implicit-to-anyref.scala:17: error: type mismatch;
- found   : Any
- required: AnyRef
-    (null: Any): AnyRef
-         ^
-no-implicit-to-anyref.scala:21: error: type mismatch;
- found   : AnyVal
- required: AnyRef
-    (0: AnyVal): AnyRef
-      ^
-no-implicit-to-anyref.scala:27: error: type mismatch;
- found   : Test.AV
- required: AnyRef
-Note that AV extends Any, not AnyRef.
-Such types can participate in value classes, but instances
-cannot appear in singleton types or in reference comparisons.
-    new AV(0): AnyRef
-    ^
-four errors found
diff --git a/test/files/pos/implicit-anyval-2.10.flags b/test/files/pos/implicit-anyval-2.10.flags
new file mode 100644
index 0000000000..94c8056747
--- /dev/null
+++ b/test/files/pos/implicit-anyval-2.10.flags
@@ -0,0 +1 @@
+-Xsource:2.10
diff --git a/test/files/pos/implicit-anyval-2.10.scala b/test/files/pos/implicit-anyval-2.10.scala
new file mode 100644
index 0000000000..3082af73b8
--- /dev/null
+++ b/test/files/pos/implicit-anyval-2.10.scala
@@ -0,0 +1,3 @@
+object Test {
+  "": AnyVal // newly prohibited in 2.11, allowed under -Xsourse:2.10
+}
\ No newline at end of file