SI-5361 Avoid cyclic type with malformed refinement

The statement `val x = this` in the refinment type:

    (new {}): {val x = this}

is lazily typechecked, in order to, according to the comment
in `typedRefinment, "avoid cyclic reference errors".

But the approximate type used ends up with:

    Refinment@1(
      parents = [...]
      decls = { val x: Refinement@1 })

This commit eagerly checks that there is no term definitions
in type refinments, rather than delaying this.

This changes the error message for SI-3614.

4 files changed, 16 insertions, 3 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 5714c2c109..e358917aef 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -2710,6 +2710,12 @@ trait Typers extends Modes with Adaptations with Tags {
     def typedRefinement(templ: Template) {
       val stats = templ.body
       namer.enterSyms(stats)
+
+      // This is also checked later in typedStats, but that is too late for SI-5361, so
+      // we eagerly check this here.
+      for (stat <- stats if !treeInfo.isDeclarationOrTypeDef(stat))
+        OnlyDeclarationsError(stat)
+
       // need to delay rest of typedRefinement to avoid cyclic reference errors
       unit.toCheck += { () =>
         val stats1 = typedStats(stats, NoSymbol)
@@ -5068,7 +5074,7 @@ trait Typers extends Modes with Adaptations with Tags {
           val self = refinedType(parents1 map (_.tpe), context.enclClass.owner, decls, templ.pos)
           newTyper(context.make(templ, self.typeSymbol, decls)).typedRefinement(templ)
           templ updateAttachment CompoundTypeTreeOriginalAttachment(parents1, Nil) // stats are set elsewhere
-          tree setType self
+          tree setType (if (templ.exists(_.isErroneous)) ErrorType else self) // Being conservative to avoid SI-5361
         }
       }
 
diff --git a/test/files/neg/t3614.check b/test/files/neg/t3614.check
index 0f9c83aa0d..81628ef37f 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: Int} found
+t3614.scala:2: error: only declarations allowed here
   def v = new ({ def a=0 })
-               ^
+                     ^
 one error found
diff --git a/test/files/neg/t5361.check b/test/files/neg/t5361.check
new file mode 100644
index 0000000000..d7fee87ccd
--- /dev/null
+++ b/test/files/neg/t5361.check
@@ -0,0 +1,4 @@
+t5361.scala:2: error: only declarations allowed here
+  val x : { val self = this } = new { self => }
+                ^
+one error found
diff --git a/test/files/neg/t5361.scala b/test/files/neg/t5361.scala
new file mode 100644
index 0000000000..1705c09df3
--- /dev/null
+++ b/test/files/neg/t5361.scala
@@ -0,0 +1,3 @@
+class A {
+  val x : { val self = this } = new { self => }
+}