From fd44a171340a87359e267aeb63072bc5a8873b10 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Fri, 11 Dec 2015 09:56:40 +0100
Subject: Disallow hk type parameters in lower bounds.

Also: various cleanups to comments.
---
 src/dotty/tools/dotc/core/TypeComparer.scala  |  4 ++--
 src/dotty/tools/dotc/typer/Applications.scala |  6 +-----
 src/dotty/tools/dotc/typer/Checking.scala     | 12 ++++++++++++
 src/dotty/tools/dotc/typer/Namer.scala        |  1 -
 src/dotty/tools/dotc/typer/Typer.scala        |  1 +
 5 files changed, 16 insertions(+), 8 deletions(-)

(limited to 'src')

diff --git a/src/dotty/tools/dotc/core/TypeComparer.scala b/src/dotty/tools/dotc/core/TypeComparer.scala
index 866c01126..bf82bfe09 100644
--- a/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -550,7 +550,7 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
    *
    *   (2) Try to eta expand the constructor of `other`.
    *
-   *   (3a) In mode `TypeVarsMissConetxt` replace the projection's hk constructor parameter
+   *   (3a) In mode `TypevarsMissConetxt` replace the projection's hk constructor parameter
    *        by the eta expansion of step (2) reapplied to the projection's arguments.
    *   (3b) In normal mode, try to unify the projection's hk constructor parameter with
    *        the eta expansion of step(2)
@@ -573,7 +573,7 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
                   else
                     (tryInstantiate(param, EtaExpansion(tycon)), projection)
                 ok &&
-                (if (inOrder) isSubType(projection1, other) else isSubType(other, projection1)) // ### move out?
+                (if (inOrder) isSubType(projection1, other) else isSubType(other, projection1))
               case _ =>
                 false
             }
diff --git a/src/dotty/tools/dotc/typer/Applications.scala b/src/dotty/tools/dotc/typer/Applications.scala
index d119658be..c6053d0fd 100644
--- a/src/dotty/tools/dotc/typer/Applications.scala
+++ b/src/dotty/tools/dotc/typer/Applications.scala
@@ -613,12 +613,8 @@ trait Applications extends Compatibility { self: Typer =>
     assignType(cpy.TypeApply(tree)(typedFn, typedArgs), typedFn, typedArgs)
   }
 
-  def adaptTypeArg(tree: tpd.Tree, bound: Type)(implicit ctx: Context): tpd.Tree = {
-    //val was = tree.tpe.EtaExpandIfHK(bound)
-    //val now = tree.tpe.adaptIfHK(bound) // ###
-    //if (was != now) println(i"diff adapt ${tree.tpe} to $bound, was: $was, now: $now")
+  def adaptTypeArg(tree: tpd.Tree, bound: Type)(implicit ctx: Context): tpd.Tree =
     tree.withType(tree.tpe.adaptIfHK(bound))
-  }
 
   /** Rewrite `new Array[T](....)` trees to calls of newXYZArray methods. */
   def convertNewArray(tree: tpd.Tree)(implicit ctx: Context): tpd.Tree = tree match {
diff --git a/src/dotty/tools/dotc/typer/Checking.scala b/src/dotty/tools/dotc/typer/Checking.scala
index 9dfe46232..57032c4d9 100644
--- a/src/dotty/tools/dotc/typer/Checking.scala
+++ b/src/dotty/tools/dotc/typer/Checking.scala
@@ -401,6 +401,17 @@ trait Checking {
       errorTree(tpt, d"missing type parameter for ${tpt.tpe}")
     }
     else tpt
+
+  def checkLowerNotHK(sym: Symbol, tparams: List[Symbol], pos: Position)(implicit ctx: Context) =
+    if (tparams.nonEmpty)
+      sym.info match {
+        case info: TypeAlias => // ok
+        case TypeBounds(lo, _) =>
+          for (tparam <- tparams)
+            if (tparam.typeRef.occursIn(lo))
+              ctx.error(i"type parameter ${tparam.name} may not occur in lower bound $lo", pos)
+        case _ =>
+      }
 }
 
 trait NoChecking extends Checking {
@@ -414,4 +425,5 @@ trait NoChecking extends Checking {
   override def checkNoDoubleDefs(cls: Symbol)(implicit ctx: Context): Unit = ()
   override def checkParentCall(call: Tree, caller: ClassSymbol)(implicit ctx: Context) = ()
   override def checkSimpleKinded(tpt: Tree)(implicit ctx: Context): Tree = tpt
+  override def checkLowerNotHK(sym: Symbol, tparams: List[Symbol], pos: Position)(implicit ctx: Context) = ()
 }
diff --git a/src/dotty/tools/dotc/typer/Namer.scala b/src/dotty/tools/dotc/typer/Namer.scala
index eecbd1347..fedbc98b8 100644
--- a/src/dotty/tools/dotc/typer/Namer.scala
+++ b/src/dotty/tools/dotc/typer/Namer.scala
@@ -845,7 +845,6 @@ class Namer { typer: Typer =>
    *  of arguments in F-bounds, because the recursive type was initialized with
    *  TypeBounds.empty.
    */
-  // ### Check whether this is still needed!
   def etaExpandArgs(implicit ctx: Context) = new TypeMap {
     def apply(tp: Type): Type = tp match {
       case tp: RefinedType =>
diff --git a/src/dotty/tools/dotc/typer/Typer.scala b/src/dotty/tools/dotc/typer/Typer.scala
index 0d7db4f9a..08ed04286 100644
--- a/src/dotty/tools/dotc/typer/Typer.scala
+++ b/src/dotty/tools/dotc/typer/Typer.scala
@@ -930,6 +930,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
 
   def typedTypeDef(tdef: untpd.TypeDef, sym: Symbol)(implicit ctx: Context): Tree = track("typedTypeDef") {
     val TypeDef(name, rhs) = tdef
+    checkLowerNotHK(sym, tdef.tparams.map(symbolOfTree), tdef.pos)
     completeAnnotations(tdef, sym)
     val _ = typedType(rhs) // unused, typecheck only to remove from typedTree
     assignType(cpy.TypeDef(tdef)(name, TypeTree(sym.info), Nil), sym)
-- 
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