fixed #2208

don't expand type aliases that take type arguments in
typedTypeConstructor, as that bypasses refchecks have to expand type
alias without type arguments, as AnyRef must disappear (problem with
cycles during bootstrap)

5 files changed, 39 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/nsc/symtab/Types.scala b/src/compiler/scala/tools/nsc/symtab/Types.scala
index 0ebd2018fb..e115446147 100644
--- a/src/compiler/scala/tools/nsc/symtab/Types.scala
+++ b/src/compiler/scala/tools/nsc/symtab/Types.scala
@@ -1559,6 +1559,8 @@ A type's typeSymbol should never be inspected directly.
         PolyType(typeParams, typeRef(pre, sym.initialize, dummyArgs))
       } else if (sym.isRefinementClass) {
         sym.info.normalize // @MO to AM: OK?
+        //@M I think this is okay, but changeset 12414 (which fixed #1241) re-introduced another bug (#2208)
+        // see typedTypeConstructor in Typers
       } else {
         super.normalize
       }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index a552c2ef7c..c3fa5555c4 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -3875,11 +3875,26 @@ trait Typers { self: Analyzer =>
     /** Types a type constructor tree used in a new or supertype */
     def typedTypeConstructor(tree: Tree, mode: Int): Tree = {
       val result = typed(tree, typeMode(mode) | FUNmode, WildcardType)
-      val restpe = result.tpe.normalize
+
+      val restpe = result.tpe.normalize // normalize to get rid of type aliases for the following check (#1241)
       if (!phase.erasedTypes && restpe.isInstanceOf[TypeRef] && !restpe.prefix.isStable) {
         error(tree.pos, restpe.prefix+" is not a legal prefix for a constructor")
       }
-      result setType restpe // @M: normalization is done during erasure
+
+      //@M fix for #2208
+      // if there are no type arguments, normalization does not bypass any checks, so perform it to get rid of AnyRef
+      if(result.tpe.typeArgs.isEmpty) {
+        // minimal check: if(result.tpe.typeSymbolDirect eq AnyRefClass) {
+        // must expand the fake AnyRef type alias, because bootstrapping (init in Definitions) is not
+        // designed to deal with the cycles in the scala package (ScalaObject extends
+        // AnyRef, but the AnyRef type alias is entered after the scala package is
+        // loaded and completed, so that ScalaObject is unpickled while AnyRef is not
+        // yet defined )
+        result setType(restpe)
+      } else { // must not normalize: type application must be (bounds-)checked (during RefChecks), see #2208
+        // during uncurry (after refchecks), all types are normalized
+        result
+      }
     }
 
     def typedTypeConstructor(tree: Tree): Tree = typedTypeConstructor(tree, NOmode)
diff --git a/test/files/neg/t2208.check b/test/files/neg/t2208.check
new file mode 100644
index 0000000000..6f7d60d84e
--- /dev/null
+++ b/test/files/neg/t2208.check
@@ -0,0 +1,4 @@
+ticket2208.scala:7: error: type arguments [Any] do not conform to type Alias's type parameter bounds [X <: Test.A]
+	class C extends Alias[Any]   // not ok, normalisation should check bounds before expanding Alias
+                        ^
+one error found
\ No newline at end of file
diff --git a/test/files/neg/t2208.scala b/test/files/neg/t2208.scala
new file mode 100644
index 0000000000..43bb0adec5
--- /dev/null
+++ b/test/files/neg/t2208.scala
@@ -0,0 +1,8 @@
+object Test  {
+	class A
+
+	class B[X]
+	type Alias[X <: A] = B[X]
+
+	class C extends Alias[Any]   // not ok, normalisation should check bounds before expanding Alias
+}
\ No newline at end of file
diff --git a/test/files/pos/t2208.scala b/test/files/pos/t2208.scala
new file mode 100644
index 0000000000..f1a521b14c
--- /dev/null
+++ b/test/files/pos/t2208.scala
@@ -0,0 +1,8 @@
+object Test  {
+	class A
+
+	class B[X]
+	type Alias[X <: A] = B[X]
+
+	val foo: B[A] = new Alias[A] // check that type aliases can be instantiated
+}
\ No newline at end of file