Merge pull request scala#973 from paulp/topic/unchecked-hk

Improve unchecked warnings.

Author: Adriaan Moors

src/compiler/scala/tools/nsc/typechecker/Infer.scala

@@ -1278,8 +1278,10 @@ trait Infer {
             } else {
               for (arg <- args) {
                 if (sym == ArrayClass) check(arg, bound)
-                else if (arg.typeArgs.nonEmpty) ()              // avoid spurious warnings with higher-kinded types
-                else if (sym == NonLocalReturnControlClass) ()  // no way to suppress unchecked warnings on try/catch
+                // avoid spurious warnings with higher-kinded types
+                else if (arg.typeArgs exists (_.typeSymbol.isTypeParameterOrSkolem)) ()
+                // no way to suppress unchecked warnings on try/catch
+                else if (sym == NonLocalReturnControlClass) ()
                 else arg match {
                   case TypeRef(_, sym, _) if isLocalBinding(sym) =>
                     ;
@@ -1423,7 +1425,7 @@ trait Infer {
         )
 
       // Intentionally *not* using `Type#typeSymbol` here, which would normalize `tp`
-      // and collect symbols from the result type of any resulting `PolyType`s, which 
+      // and collect symbols from the result type of any resulting `PolyType`s, which
       // are not free type parameters of `tp`.
       //
       // Contrast with `isFreeTypeParamNoSkolem`.
@@ -1456,7 +1458,7 @@ trait Infer {
     def inferExprAlternative(tree: Tree, pt: Type) = tree.tpe match {
       case OverloadedType(pre, alts) => tryTwice { isSecondTry =>
         val alts0          = alts filter (alt => isWeaklyCompatible(pre.memberType(alt), pt))
-        val noAlternatives = alts0.isEmpty 
+        val noAlternatives = alts0.isEmpty
         val alts1          = if (noAlternatives) alts else alts0
 
         //println("trying "+alts1+(alts1 map (_.tpe))+(alts1 map (_.locationString))+" for "+pt)
@@ -1614,7 +1616,7 @@ trait Infer {
         val saved = context.state
         var fallback = false
         context.setBufferErrors()
-        // We cache the current buffer because it is impossible to 
+        // We cache the current buffer because it is impossible to
         // distinguish errors that occurred before entering tryTwice
         // and our first attempt in 'withImplicitsDisabled'. If the
         // first attempt fails we try with implicits on *and* clean

test/files/neg/unchecked2.check

@@ -0,0 +1,19 @@
+unchecked2.scala:2: error: non variable type-argument Int in type Option[Int] is unchecked since it is eliminated by erasure
+  Some(123).isInstanceOf[Option[Int]]
+                        ^
+unchecked2.scala:3: error: non variable type-argument String in type Option[String] is unchecked since it is eliminated by erasure
+  Some(123).isInstanceOf[Option[String]]
+                        ^
+unchecked2.scala:4: error: non variable type-argument List[String] in type Option[List[String]] is unchecked since it is eliminated by erasure
+  Some(123).isInstanceOf[Option[List[String]]]
+                        ^
+unchecked2.scala:5: error: non variable type-argument List[Int => String] in type Option[List[Int => String]] is unchecked since it is eliminated by erasure
+  Some(123).isInstanceOf[Option[List[Int => String]]]
+                        ^
+unchecked2.scala:6: error: non variable type-argument (String, Double) in type Option[(String, Double)] is unchecked since it is eliminated by erasure
+  Some(123).isInstanceOf[Option[(String, Double)]]
+                        ^
+unchecked2.scala:7: error: non variable type-argument String => Double in type Option[String => Double] is unchecked since it is eliminated by erasure
+  Some(123).isInstanceOf[Option[String => Double]]
+                        ^
+6 errors found

test/files/neg/unchecked2.flags

@@ -0,0 +1 @@
+-unchecked -Xfatal-warnings

test/files/neg/unchecked2.scala

@@ -0,0 +1,8 @@
+object Test {
+  Some(123).isInstanceOf[Option[Int]]
+  Some(123).isInstanceOf[Option[String]]
+  Some(123).isInstanceOf[Option[List[String]]]
+  Some(123).isInstanceOf[Option[List[Int => String]]]
+  Some(123).isInstanceOf[Option[(String, Double)]]
+  Some(123).isInstanceOf[Option[String => Double]]
+}

test/files/pos/t1439.scala

@@ -2,7 +2,7 @@
 class View[C[A]] { }
 
 object Test {
-  null match {
+  (null: Any) match {
     case v: View[_] =>
   }
 }