Asserts about Tree qualifiers.

Encoding recent revelations about certain tree invariants
in the form of asserts.

Author: paulp

src/compiler/scala/tools/nsc/ast/Trees.scala

@@ -56,7 +56,7 @@ trait Trees extends scala.reflect.internal.Trees { self: Global =>
    *  The class `C` is stored as a tree attachment.
    */
   case class InjectDerivedValue(arg: Tree)
-       extends SymTree
+       extends SymTree with TermTree
 
   class PostfixSelect(qual: Tree, name: Name) extends Select(qual, name)
 

src/compiler/scala/tools/nsc/ast/parser/Parsers.scala

@@ -1933,7 +1933,7 @@ self =>
               case _ =>
             }
             val typeAppliedTree = in.token match {
-              case LBRACKET   => atPos(start, in.offset)(TypeApply(convertToTypeId(t), typeArgs()))
+              case LBRACKET   => atPos(start, in.offset)(AppliedTypeTree(convertToTypeId(t), typeArgs()))
               case _          => t
             }
             in.token match {

src/reflect/scala/reflect/internal/Trees.scala

@@ -391,6 +391,9 @@ trait Trees extends api.Trees { self: SymbolTable =>
 
   case class TypeApply(fun: Tree, args: List[Tree])
        extends GenericApply with TypeApplyApi {
+
+    assert(fun.isTerm, fun)
+
     override def symbol: Symbol = fun.symbol
     override def symbol_=(sym: Symbol) { fun.symbol = sym }
   }
@@ -426,7 +429,11 @@ trait Trees extends api.Trees { self: SymbolTable =>
   object This extends ThisExtractor
 
   case class Select(qualifier: Tree, name: Name)
-       extends RefTree with SelectApi
+       extends RefTree with SelectApi {
+
+    // !!! assert disabled due to test case pos/annotDepMethType.scala triggering it.
+    // assert(qualifier.isTerm, qualifier)
+  }
   object Select extends SelectExtractor
 
   case class Ident(name: Name) extends RefTree with IdentContextApi {
@@ -458,7 +465,10 @@ trait Trees extends api.Trees { self: SymbolTable =>
   object SingletonTypeTree extends SingletonTypeTreeExtractor
 
   case class SelectFromTypeTree(qualifier: Tree, name: TypeName)
-       extends RefTree with TypTree with SelectFromTypeTreeApi
+       extends RefTree with TypTree with SelectFromTypeTreeApi {
+
+    assert(qualifier.isType, qualifier)
+  }
   object SelectFromTypeTree extends SelectFromTypeTreeExtractor
 
   case class CompoundTypeTree(templ: Template)
@@ -467,6 +477,9 @@ trait Trees extends api.Trees { self: SymbolTable =>
 
   case class AppliedTypeTree(tpt: Tree, args: List[Tree])
        extends TypTree with AppliedTypeTreeApi {
+
+    assert(tpt.isType, tpt)
+
     override def symbol: Symbol = tpt.symbol
     override def symbol_=(sym: Symbol) { tpt.symbol = sym }
   }
@@ -1314,7 +1327,7 @@ trait Trees extends api.Trees { self: SymbolTable =>
 
   class ChangeOwnerTraverser(val oldowner: Symbol, val newowner: Symbol) extends Traverser {
     final def change(sym: Symbol) = {
-      if (sym != NoSymbol && sym.owner == oldowner) 
+      if (sym != NoSymbol && sym.owner == oldowner)
         sym.owner = newowner
     }
     override def traverse(tree: Tree) {

test/files/neg/gadts1.check

@@ -3,9 +3,9 @@ gadts1.scala:15: error: type mismatch;
  required: a
     case NumTerm(n) => c.x = Double(1.0) 
                                    ^
-gadts1.scala:20: error: class Cell of type Test.Cell does not take type parameters.
+gadts1.scala:20: error: Test.Cell[a] does not take parameters
     case Cell[a](x: Int) => c.x = 5
-             ^
+                ^
 gadts1.scala:20: error: type mismatch;
  found   : Int(5)
  required: a