- Changed Tree.Block(Tree[]) to Tree.Block(Tree...

- Changed Tree.Block(Tree[]) to Tree.Block(Tree[],Tree)

34 files changed, 313 insertions, 319 deletions

diff --git a/sources/meta/scalac/ast/Tree.java b/sources/meta/scalac/ast/Tree.java
index 6efdfea707..eb853b7164 100644
--- a/sources/meta/scalac/ast/Tree.java
+++ b/sources/meta/scalac/ast/Tree.java
@@ -225,7 +225,8 @@ public class Tree {
             setDescription("Block of expressions " +
                 "(semicolon separated expressions)").
             setRange(Phase.PARSER, Phase.END).
-            addField(t_Trees, "stats");
+            addField(t_Trees, "stats").
+            addField(t_TermTree, "expr");
 
         n_Sequence.
             setDescription("Sequence of expressions (comma separated expressions)").
diff --git a/sources/scala/tools/scalac/ast/parser/Parser.scala b/sources/scala/tools/scalac/ast/parser/Parser.scala
index fcf48c48a5..97c19417a2 100644
--- a/sources/scala/tools/scalac/ast/parser/Parser.scala
+++ b/sources/scala/tools/scalac/ast/parser/Parser.scala
@@ -9,6 +9,7 @@
 import scalac.ast.parser.PatternNormalizer;
 import scalac.symtab.Modifiers;
 import scalac.ast._;
+import scalac.atree.AConstant;
 import scalac._;
 import scalac.util._;
 import ch.epfl.lamp.util.Position;
@@ -228,11 +229,11 @@ class Parser(unit: Unit) {
         make.Block(
           pos,
           NewArray.Tree(
-            make.ValDef(pos, 0, x, Tree.Empty, left),
+            make.ValDef(pos, 0, x, Tree.Empty, left)),
             make.Apply(
               pos,
               make.Select(pos, right, NameTransformer.encode(op)),
-              NewArray.Tree(make.Ident(left.pos, x)))));
+              NewArray.Tree(make.Ident(left.pos, x))));
       }
     } else {
       make.Apply(
@@ -339,8 +340,8 @@ class Parser(unit: Unit) {
     val rhs = make.If(
       pos,
       cond,
-      make.Block(body.pos, NewArray.Tree(body, continu)),
-      make.Block(pos, Tree.EMPTY_ARRAY));
+      make.Block(body.pos, NewArray.Tree(body), continu),
+      gen.mkUnitLit(pos));
     make.LabelDef(pos, lname, new Array[Tree$Ident](0), rhs);
   }
 
@@ -350,12 +351,12 @@ class Parser(unit: Unit) {
     val rhs = make.Block(
       body.pos,
       NewArray.Tree(
-        body,
+        body),
         make.If(
           cond.pos,
           cond,
           continu,
-          make.Block(pos, Tree.EMPTY_ARRAY))));
+          gen.mkUnitLit(pos)));
     make.LabelDef(pos, lname, new Array[Tree$Ident](0), rhs)
   }
 
@@ -402,7 +403,7 @@ class Parser(unit: Unit) {
       params
     case Tree$Ident(_) | Tree$Typed(Tree$Ident(_), _) =>
       NewArray.ValDef(convertToParam(t));
-    case Tree$Block(stats) if (stats.length == 0) =>
+    case Tree$Literal(AConstant.UNIT) => // !!!
       Tree.ValDef_EMPTY_ARRAY;
     case _ =>
       syntaxError(t.pos, "malformed formal parameter list", false);
@@ -887,7 +888,7 @@ class Parser(unit: Unit) {
       val pos = s.skipToken();
       val e =
         if (isExprIntro()) expr()
-        else make.Block(pos, Tree.EMPTY_ARRAY);
+        else gen.mkUnitLit(pos);
       make.Return(pos, e)
     } else if (s.token == THROW) {
       val pos = s.skipToken();
@@ -994,7 +995,7 @@ class Parser(unit: Unit) {
         val pos = s.skipToken();
         if (s.token == RPAREN) {
           s.nextToken();
-          t = make.Block(pos, Tree.EMPTY_ARRAY);
+          t = gen.mkUnitLit(pos);
         } else {
           t = expr();
           if (s.token == COMMA) {
@@ -1167,9 +1168,20 @@ class Parser(unit: Unit) {
   /** Block ::= BlockStatSeq
   */
   def block(pos: int): Tree = {
-    val stats = blockStatSeq(new myTreeList());
-    if (stats.length == 1 && stats(0).isTerm()) stats(0)
-    else make.Block(pos, stats)
+    block(pos, blockStatSeq(new myTreeList()));
+  }
+  private def block(pos: int, stats: Array[Tree]): Tree = {
+    if (stats.length == 0)
+      gen.mkUnitLit(pos);
+    else if (!stats(stats.length - 1).isTerm())
+      make.Block(pos, stats, gen.mkUnitLit(pos));
+    else if (stats.length == 1)
+      return stats(0);
+    else {
+      val trees: Array[Tree] = new Array[Tree](stats.length - 1);
+      System.arraycopy(stats, 0, trees, 0, trees.length);
+      return make.Block(pos, trees, stats(stats.length - 1));
+    }
   }
 
   /** caseClause : =>= case Pattern [if PostfixExpr] `=>' Block
@@ -1845,7 +1857,7 @@ class Parser(unit: Unit) {
         if (s.token == SEMI) { s.nextToken(); blockStatSeq(statlist) }
         else statlist.toArray();
       accept(RBRACE);
-      make.Block(pos, stats)
+      block(pos, stats)
     } else {
       selfInvocation()
     }
@@ -2100,13 +2112,13 @@ class Parser(unit: Unit) {
         stats.append(defOrDcl(0));
         accept(SEMI);
         if (s.token == RBRACE || s.token == CASE) {
-          stats.append(make.Block(s.pos, Tree.EMPTY_ARRAY));
+          stats.append(gen.mkUnitLit(s.pos));
         }
       } else if (isLocalModifier()) {
         stats.append(clsDef(localClassModifiers()));
         accept(SEMI);
         if (s.token == RBRACE || s.token == CASE) {
-          stats.append(make.Block(s.pos, Tree.EMPTY_ARRAY));
+          stats.append(gen.mkUnitLit(s.pos));
         }
       } else if (s.token == SEMI) {
         s.nextToken();
diff --git a/sources/scala/tools/scalac/ast/printer/TextTreePrinter.scala b/sources/scala/tools/scalac/ast/printer/TextTreePrinter.scala
index 950083dda9..cc7a89a9a7 100644
--- a/sources/scala/tools/scalac/ast/printer/TextTreePrinter.scala
+++ b/sources/scala/tools/scalac/ast/printer/TextTreePrinter.scala
@@ -334,8 +334,13 @@ class TextTreePrinter(writer: PrintWriter) with TreePrinter {
 	printArray(params.asInstanceOf[Array[Tree]], TXT_LEFT_PAREN, TXT_RIGHT_PAREN, TXT_COMMA_SP);
 	print(rhs);
 
-      case Tree$Block(stats) =>
-	printArray(stats, TXT_BLOCK_BEGIN, TXT_BLOCK_END, TXT_BLOCK_SEP);
+      case Tree$Block(stats, value) =>
+	printArray(stats, TXT_BLOCK_BEGIN, TXT_SEMICOLON, TXT_BLOCK_SEP);
+        indent();
+        printNewLine();
+        print(value);
+        undent();
+        print(TXT_BLOCK_END);
 	printType(tree);
 
       case Tree$Sequence(trees) =>
diff --git a/sources/scala/tools/scalac/transformer/TransMatch.scala b/sources/scala/tools/scalac/transformer/TransMatch.scala
index 3167bf242b..ce7f9af50e 100644
--- a/sources/scala/tools/scalac/transformer/TransMatch.scala
+++ b/sources/scala/tools/scalac/transformer/TransMatch.scala
@@ -86,7 +86,7 @@ class TransMatch( global:scalac_Global )
       var nilvars:Set  = TestRegTraverser.getNilVariables();
       if( !nilvars.isEmpty() ) {
         //System.err.println("nilvars present");
-        val newBody = new Array[Tree]( nilvars.size() + 1 );
+        val newBody = new Array[Tree]( nilvars.size() );
         var j=0;
         var it:Iterator = nilvars.iterator();
         while( it.hasNext() ) {
@@ -94,8 +94,7 @@ class TransMatch( global:scalac_Global )
           val n = gen.mkNil(cases(i).pos);
           newBody.update( {j = j + 1; j} , gen.ValDef(v, n));
         }
-        newBody.update( newBody.length - 1, cases(i).body);
-        cases(i).body = gen.mkBlock( newBody );
+        cases(i).body = gen.mkBlock( newBody, cases(i).body );
       }
       i = i+1;
     }
diff --git a/sources/scala/tools/scalac/typechecker/Analyzer.scala b/sources/scala/tools/scalac/typechecker/Analyzer.scala
index b0085163c9..561104267e 100644
--- a/sources/scala/tools/scalac/typechecker/Analyzer.scala
+++ b/sources/scala/tools/scalac/typechecker/Analyzer.scala
@@ -1419,7 +1419,7 @@ class Analyzer(global: scalac_Global, descr: AnalyzerPhase) extends Transformer(
       }
       if ((mode & EXPRmode) != 0) {
 	if (pt.symbol() == definitions.UNIT_CLASS) {
-	  return gen.Block(NewArray.Tree(tree, gen.mkUnitLit(tree.pos)));
+	  return gen.mkUnitBlock(tree);
 	} else if (infer.isCompatible(tree.getType(), pt)) {
 	  val coerceMeth: Symbol = tree.getType().lookup(Names.coerce);
 	  if (coerceMeth != Symbol.NONE) {
@@ -2037,7 +2037,7 @@ class Analyzer(global: scalac_Global, descr: AnalyzerPhase) extends Transformer(
 	    else transform(
 	      rhs,
 	      if (name == Names.CONSTRUCTOR) CONSTRmode else EXPRmode,
-	      tpe1.getType());
+	      if (name == Names.CONSTRUCTOR) definitions.UNIT_TYPE() else tpe1.getType());
 	  popContext();
 	  context.enclClass.owner.flags = context.enclClass.owner.flags & ~INCONSTRUCTOR;
 	  sym.flags = sym.flags | LOCKED;
@@ -2086,36 +2086,29 @@ class Analyzer(global: scalac_Global, descr: AnalyzerPhase) extends Transformer(
 	  context.imports = new ImportList(tree, context.scope, context.imports);
 	  Tree.Empty
 
-	case Tree$Block(stats) =>
+	case Tree$Block(stats, value) =>
 	  pushContext(tree, context.owner, new Scope(context.scope));
 	  val stats1 = desugarize.Statements(stats, true);
 	  enterSyms(stats1);
 	  context.imports = context.outer.imports;
 	  val curmode: int = mode;
+          var start: Int = 0;
+          var valuemode: Int = curmode;
+	  if ((curmode & CONSTRmode) != 0) {
+	    stats1(0) = transform(stats1(0), curmode, pt);
+	    context.enclClass.owner.flags = context.enclClass.owner.flags & ~INCONSTRUCTOR;
+            start = 1;
+            valuemode = (curmode & ~CONSTRmode) | EXPRmode;
+	  }
+	  var i = start; while (i < stats1.length) {
+	    stats1(i) = transform(stats1(i), EXPRmode);
+	    i = i + 1
+	  }
+	  val value1: Tree = transform(value, valuemode & ~FUNmode, pt);
 	  val owntype: Type =
-	    if ((curmode & CONSTRmode) != 0) {
-	      stats1(0) = transform(stats1(0), curmode, pt);
-	      context.enclClass.owner.flags = context.enclClass.owner.flags & ~INCONSTRUCTOR;
-	      var i = 1; while (i < stats1.length) {
-		stats1(i) = transform(stats1(i), EXPRmode);
-		i = i + 1
-	      }
-	      stats1(0).getType()
-	    } else {
-	      var i = 0; while (i < stats1.length - 1) {
-		stats1(i) = transform(stats1(i), EXPRmode);
-		i = i + 1
-	      }
-	      if (stats1.length > 0) {
-		stats1(stats1.length - 1) =
-		  transform(stats1(stats1.length - 1), curmode & ~FUNmode, pt);
-		checkNoEscape(tree.pos, stats1(stats1.length - 1).getType().deconst())
-	      } else {
-		definitions.UNIT_TYPE()
-	      }
-	    }
+	    checkNoEscape(tree.pos, value1.getType().deconst());
 	  popContext();
-	  copy.Block(tree, stats1)
+	  copy.Block(tree, stats1, value1)
 	    .setType(owntype);
 
         case Tree$Sequence(trees) =>
@@ -2220,8 +2213,7 @@ class Analyzer(global: scalac_Global, descr: AnalyzerPhase) extends Transformer(
 	  var elsep1: Tree = _;
 	  if (elsep == Tree.Empty) {
 	    thenp1 = transform(thenp, EXPRmode, definitions.UNIT_TYPE());
-	    elsep1 = make.Block(tree.pos, Tree.EMPTY_ARRAY)
-	      .setType(definitions.UNIT_TYPE());
+	    elsep1 = gen.mkUnitLit(tree.pos);
 	  } else {
 	    thenp1 = transform(thenp, EXPRmode, pt);
 	    elsep1 = transform(elsep, EXPRmode, pt);
@@ -2307,7 +2299,7 @@ class Analyzer(global: scalac_Global, descr: AnalyzerPhase) extends Transformer(
 			Tree.EMPTY_ARRAY))
 		    .setType(owntype);
 		  popContext();
-		  make.Block(tree.pos, NewArray.Tree(cd1, alloc))
+		  make.Block(tree.pos, NewArray.Tree(cd1), alloc)
 		    .setType(owntype);
 		}
 	      }
diff --git a/sources/scala/tools/scalac/typechecker/Context.scala b/sources/scala/tools/scalac/typechecker/Context.scala
index 81089e0b26..56e3852a18 100644
--- a/sources/scala/tools/scalac/typechecker/Context.scala
+++ b/sources/scala/tools/scalac/typechecker/Context.scala
@@ -51,7 +51,7 @@ class Context {
   }
 
   def isTopLevel(): boolean = tree match {
-    case Tree$Block(_) =>
+    case Tree$Block(_,_) =>
       false
     case Tree$Template(_, _) =>
       outer.tree.isInstanceOf[Tree$PackageDef]
diff --git a/sources/scala/tools/scalac/typechecker/DeSugarize.scala b/sources/scala/tools/scalac/typechecker/DeSugarize.scala
index 37ba3cef27..a74a2ba790 100644
--- a/sources/scala/tools/scalac/typechecker/DeSugarize.scala
+++ b/sources/scala/tools/scalac/typechecker/DeSugarize.scala
@@ -99,7 +99,7 @@ class DeSugarize(make: TreeFactory, copy: TreeCopier, gen: TreeGen, infer: scala
 
   def mkTuple(pos: int, trees: Array[Tree]): Tree =
     if (trees.length == 0)
-      make.Block(pos, trees);
+      gen.mkUnitLit(pos);
     else
       make.Apply(
 	pos,
@@ -353,7 +353,7 @@ class DeSugarize(make: TreeFactory, copy: TreeCopier, gen: TreeGen, infer: scala
 	    pos, mods, vars(i), Tree.Empty,
 	    make.Select(pos, make.Ident(pos, vble), tupleSelectorName(i + 1)));
 	}
-	print(pat, "patdef", new Tree$Block(res));//debug
+	print(pat, "patdef", new Tree$Block(res, gen.mkUnitLit(pos)));//debug
 	shareComment(res, tree);
       }
   }
@@ -416,8 +416,7 @@ class DeSugarize(make: TreeFactory, copy: TreeCopier, gen: TreeGen, infer: scala
     val defs: TreeList = new TreeList();
     val lambda: Tree =
       toFunction(toApply(liftoutPrefix(tree, defs), tpe), tpe);
-    defs.append(lambda);
-    val result: Tree = make.Block(tree.pos, defs.toArray());
+    val result: Tree = make.Block(tree.pos, defs.toArray(), lambda);
     print(tree, "eta", result);//debug
     result
   }
diff --git a/sources/scala/tools/scalai/ExpressionCompiler.java b/sources/scala/tools/scalai/ExpressionCompiler.java
index bb4e3ad9cb..3f88b6d128 100644
--- a/sources/scala/tools/scalai/ExpressionCompiler.java
+++ b/sources/scala/tools/scalai/ExpressionCompiler.java
@@ -116,16 +116,14 @@ public class ExpressionCompiler {
             context.insertLabel(symbol);
             return Code.Label(symbol, vars, compute(body));
 
-        case Block(Tree[] stats):
-            if (stats.length == 0) return Code.Literal(constants.literal());
-            // !!! assert stats.length > 0;
+        case Block(Tree[] stats, Tree value):
+            if (stats.length == 0) return compute(value);
             CodeBuffer buffer = new CodeBuffer();
             int stacksize = context.stacksize();
-            for (int i = 0; i < stats.length - 1; i++)
-                declare(stats[i], buffer);
-            Code value = compute(stats[stats.length - 1]);
+            for (int i = 0; i < stats.length; i++) declare(stats[i], buffer);
+            Code result = compute(value);
             context.stacksize(stacksize);
-            return buffer.code(value);
+            return buffer.code(result);
 
         case Assign(Tree lhs, Tree rhs):
             return store(lhs, lhs.symbol(), compute(rhs));
diff --git a/sources/scalac/ast/Transformer.java.tmpl b/sources/scalac/ast/Transformer.java.tmpl
index 69aef7dfca..1af073fc86 100644
--- a/sources/scalac/ast/Transformer.java.tmpl
+++ b/sources/scalac/ast/Transformer.java.tmpl
@@ -206,8 +206,8 @@ public class GenTransformer {
             Symbol symbol = getSymbolFor(tree);
             return gen.LabelDef(symbol, transform(params), transform(rhs));
 
-        case Block(Tree[] stats):
-            return gen.Block(tree.pos, transform(stats));
+        case Block(Tree[] stats, Tree value):
+            return gen.Block(tree.pos, transform(stats), transform(value));
 
         // case Sequence(Tree[] trees):
         // case Alternative(Tree[] trees):
diff --git a/sources/scalac/ast/TreeGen.java b/sources/scalac/ast/TreeGen.java
index 1ebcaf7c53..27b168abd8 100644
--- a/sources/scalac/ast/TreeGen.java
+++ b/sources/scalac/ast/TreeGen.java
@@ -468,7 +468,7 @@ public class TreeGen implements Kinds, Modifiers, TypeTags {
     // Public Methods - Building expressions - Simple nodes
 
     /** Flattens the given tree array by inlining Block nodes. */
-    public Tree[] flatten(Tree[] trees) {
+    public Tree[] flatten_(Tree[] trees) {
         boolean copy = false;
         int length = 0;
         for (int i = 0; i < trees.length; i++) {
@@ -477,10 +477,9 @@ public class TreeGen implements Kinds, Modifiers, TypeTags {
                 copy = true;
                 length -= 1;
                 continue;
-            case Block(Tree[] stats):
-                if (stats.length == 0) break; // preserve unit literals
+            case Block(Tree[] stats, Tree value):
                 copy = true;
-                length += stats.length;
+                length += stats.length + 1;
                 continue;
             }
             length += 1;
@@ -491,9 +490,9 @@ public class TreeGen implements Kinds, Modifiers, TypeTags {
             switch (trees[i]) {
             case Empty:
                 continue;
-            case Block(Tree[] stats):
-                if (stats.length == 0) break; // preserve unit literals
+            case Block(Tree[] stats, Tree value):
                 for (int j = 0; j < stats.length; j++) clone[o++] = stats[j];
+                clone[o++] = value;
                 continue;
             }
             clone[o++] = trees[i];
@@ -530,16 +529,43 @@ public class TreeGen implements Kinds, Modifiers, TypeTags {
         return mkAsInstanceOf(value.pos, value, type);
     }
 
-    /** Builds an expression with given non-empty tree array. */
-    public Tree mkBlock(int pos, Tree[] trees) {
-        assert trees.length != 0;
-        Tree[] flatten = flatten(trees);
-        assert flatten.length != 0: Debug.show(trees);
-        return Block(pos, flatten);
+    /** Builds an expression of type Unit with given statements. */
+    public Tree mkUnitBlock(int pos, Tree[] stats) {
+        return mkBlock(pos, stats, mkUnitLit(pos));
     }
-    public Tree mkBlock(Tree[] trees) {
-        assert trees.length != 0;
-        return mkBlock(trees[0].pos, trees);
+
+    /** Builds an expression of type Unit with given statement. */
+    public Tree mkUnitBlock(int pos, Tree stat) {
+        return mkUnitBlock(pos, new Tree[]{stat});
+    }
+    public Tree mkUnitBlock(Tree stat) {
+        return mkUnitBlock(stat.pos, stat);
+    }
+
+    /** Builds an expression with given statements and value. */
+    public Tree mkBlock(int pos, Tree[] stats, Tree value) {
+        if (stats.length == 0) return value;
+        return Block(pos, stats, value); // !!! add flatten?
+    }
+    public Tree mkBlock(Tree[] stats, Tree value) {
+        return mkBlock((stats.length!=0 ? stats[0] : value).pos, stats, value);
+    }
+
+    /** Builds an expression with given statement and value. */
+    public Tree mkBlock(int pos, Tree stat, Tree value) {
+        switch (stat) {
+        case Empty:
+            return value;
+        case Block(Tree[] block_stats, Tree block_value):
+            Tree[] stats = Tree.cloneArray(block_stats, 1);
+            stats[block_stats.length] = block_value;
+            return Block(stat.pos, stats, value);
+        default:
+            return Block(pos, new Tree[]{stat}, value);
+        }
+    }
+    public Tree mkBlock(Tree stat, Tree value) {
+        return mkBlock(stat.pos, stat, value);
     }
 
     /** Builds an Import node with given qualifier and names. */
@@ -562,20 +588,29 @@ public class TreeGen implements Kinds, Modifiers, TypeTags {
         return tree;
     }
 
-    /** Builds a Block node with given statements. */
-    public Tree Block(int pos, Tree[] stats) {
-        Block tree = make.Block(pos, stats);
-        global.nextPhase();
-        tree.setType(stats.length == 0
-            ? definitions.UNIT_TYPE()
-            : stats[stats.length - 1].type);
-        global.prevPhase();
+    /** Builds a Block node with given statements and value. */
+    public Block Block(int pos, Tree[] stats, Tree value) {
+        inline:
+        switch (value) {
+        case Block(Tree[] value_stats, Tree value_value):
+            int count = 0;
+            for (int i = 0; i < value_stats.length; i++) {
+                if (value_stats[i].definesSymbol()) break inline;
+                if (value_stats[i] != Tree.Empty) count++;
+            }
+            Tree[] array = Tree.cloneArray(stats, count);
+            for (int i = 0, j = stats.length; i < value_stats.length; i++) {
+                if (value_stats[i] != Tree.Empty) array[j++] = value_stats[i];
+            }
+            stats = array;
+            value = value_value;
+        }
+        Block tree = make.Block(pos, stats, value);
+        tree.setType(value.type());
 	return tree;
     }
-
-    /** Builds a Block node with given non-empty statements list. */
-    public Tree Block(Tree[] stats) {
-	return Block(stats[0].pos, stats);
+    public Block Block(Tree[] stats, Tree value) {
+        return Block((stats.length != 0 ? stats[0] : value).pos, stats, value);
     }
 
     /** Builds an Assign node corresponding to "<lhs> = <rhs>". */
@@ -762,14 +797,13 @@ public class TreeGen implements Kinds, Modifiers, TypeTags {
      */
     public Tree mkNewArray(int pos, Type element, Tree[] values, Symbol owner){
         if (values.length == 0) return mkNewArray(pos, element, 0);
-        Tree[] trees = new Tree[1 + values.length + 1];
+        Tree[] trees = new Tree[1 + values.length];
         Symbol array =
             newLocal(pos, Names.array, owner, definitions.ARRAY_TYPE(element));
         trees[0] = ValDef(array, mkNewArray(pos, element, values.length));
         for (int i = 0; i < values.length; i++)
             trees[1 + i] = mkArraySet(Ident(pos, array), i, values[i]);
-        trees[values.length + 1] = Ident(pos, array);
-        return Block(pos, trees);
+        return Block(pos, trees, Ident(pos, array));
     }
 
     /** Builds an array length operation. */
@@ -1101,7 +1135,7 @@ public class TreeGen implements Kinds, Modifiers, TypeTags {
         Tree classDef = ClassDef(clazz, memberTrees);
 	Tree alloc = New(mkApply__(mkPrimaryConstructorLocalRef(pos, clazz)))
             .setType(parentTypes[1]); // !!!
-	return Block(new Tree[]{classDef, alloc});
+	return mkBlock(classDef, alloc);
     }
 
 
@@ -1123,7 +1157,7 @@ public class TreeGen implements Kinds, Modifiers, TypeTags {
         Tree classDef = ClassDef(clazz, memberTrees);
 	Tree alloc = New(mkApply__(mkPrimaryConstructorLocalRef(pos, clazz)))
 	    .setType(parentTypes[1]); // !!!
-	return Block(new Tree[]{classDef, alloc});
+	return mkBlock(classDef, alloc);
     }
     //where
 	private Tree makeVisitorMethod(int pos, Name name, Tree visitor,
@@ -1172,7 +1206,7 @@ public class TreeGen implements Kinds, Modifiers, TypeTags {
 		.setInfo(obj.type);
 	    Tree tmpdef = ValDef(tmp, obj);
 	    Tree expr = postfixApply(Ident(obj.pos, tmp), fn, owner);
-	    return Block(new Tree[]{tmpdef, expr});
+	    return mkBlock(tmpdef, expr);
 	}
     }
 
diff --git a/sources/scalac/ast/parser/Parser.java b/sources/scalac/ast/parser/Parser.java
index 12226aa922..6cbf3e342a 100644
--- a/sources/scalac/ast/parser/Parser.java
+++ b/sources/scalac/ast/parser/Parser.java
@@ -15,6 +15,7 @@ import scalac.*;
 import scalac.util.*;
 import scalac.symtab.Modifiers;
 import scalac.ast.*;
+import scalac.atree.AConstant;
 import Tree.*;
 
 /** A recursive descent parser for the programming language Scala.
@@ -243,10 +244,10 @@ public class Parser implements Tokens {
                 Name x = fresh();
                 return make.Block(pos,
                     new Tree[]{
-                        make.ValDef(pos, 0, x, Tree.Empty, left),
+                        make.ValDef(pos, 0, x, Tree.Empty, left)},
                         make.Apply(pos,
                             make.Select(pos, right, NameTransformer.encode(op)),
-                            new Tree[]{make.Ident(left.pos, x)})});
+                            new Tree[]{make.Ident(left.pos, x)}));
             }
         } else {
             return make.Apply(pos,
@@ -370,8 +371,8 @@ public class Parser implements Tokens {
         Tree rhs = make.If(
             pos,
             cond,
-            make.Block(body.pos, new Tree[]{body, continu}),
-            make.Block(pos, Tree.EMPTY_ARRAY));
+            make.Block(body.pos, new Tree[]{body}, continu),
+            gen.mkUnitLit(pos));
         return make.LabelDef(pos, lname, new Ident[0], rhs);
     }
 
@@ -381,12 +382,12 @@ public class Parser implements Tokens {
         Tree rhs = make.Block(
             body.pos,
             new Tree[]{
-                body,
+                body},
                 make.If(
                     cond.pos,
                     cond,
                     continu,
-                    make.Block(pos, Tree.EMPTY_ARRAY))});
+                    gen.mkUnitLit(pos)));
         return make.LabelDef(pos, lname, new Ident[0], rhs);
     }
 
@@ -399,8 +400,8 @@ public class Parser implements Tokens {
         case Ident(_):
         case Typed(Ident(_), _):
             return new ValDef[]{convertToParam(t)};
-        case Block(Tree[] stats):
-            if (stats.length == 0) return Tree.ValDef_EMPTY_ARRAY;
+        case Literal(AConstant.UNIT):
+            return Tree.ValDef_EMPTY_ARRAY; // !!!
         }
         syntaxError(t.pos, "malformed formal parameter list", false);
         return Tree.ValDef_EMPTY_ARRAY;
@@ -912,7 +913,7 @@ public class Parser implements Tokens {
 	} else if (s.token == RETURN) {
             int pos = s.skipToken();
             Tree e = (isExprIntro()) ? expr()
-                : make.Block(pos, Tree.EMPTY_ARRAY);
+                : gen.mkUnitLit(pos);
             return make.Return(pos, e);
         } else if (s.token == THROW) {
             int pos = s.skipToken();
@@ -1031,7 +1032,7 @@ public class Parser implements Tokens {
             int pos = s.skipToken();
             if (s.token == RPAREN) {
                 s.nextToken();
-                t = make.Block(pos, Tree.EMPTY_ARRAY);
+                t = gen.mkUnitLit(pos);
             } else {
                 t = expr();
                 if (s.token == COMMA) {
@@ -1126,9 +1127,20 @@ public class Parser implements Tokens {
     /** Block ::= BlockStatSeq
      */
     Tree block(int pos) {
-        Tree[] stats = blockStatSeq(new TreeList());
-        if (stats.length == 1 && stats[0].isTerm()) return stats[0];
-        else return make.Block(pos, stats);
+        return block(pos, blockStatSeq(new TreeList()));
+    }
+    private Tree block(int pos, Tree[] stats) {
+        if (stats.length == 0)
+            return gen.mkUnitLit(pos);
+        else if (!stats[stats.length - 1].isTerm())
+            return make.Block(pos, stats, gen.mkUnitLit(pos));
+        else if (stats.length == 1)
+            return stats[0];
+        else {
+            Tree[] trees = new Tree[stats.length - 1];
+            System.arraycopy(stats, 0, trees, 0, trees.length);
+            return make.Block(pos, trees, stats[stats.length - 1]);
+        }
     }
 
     /** CaseClause ::= case Pattern [if PostfixExpr] `=>' Block
@@ -1832,7 +1844,7 @@ public class Parser implements Tokens {
                 stats = statlist.toArray();
             }
             accept(RBRACE);
-            return make.Block(pos, stats);
+            return block(pos, stats);
         } else {
             return selfInvocation();
         }
@@ -2070,13 +2082,13 @@ public class Parser implements Tokens {
                 stats.append(defOrDcl(0));
                 accept(SEMI);
                 if (s.token == RBRACE || s.token == CASE) {
-                    stats.append(make.Block(s.pos, Tree.EMPTY_ARRAY));
+                    stats.append(gen.mkUnitLit(s.pos));
                 }
             } else if (isLocalModifier()) {
                 stats.append(clsDef(localClassModifiers()));
                 accept(SEMI);
                 if (s.token == RBRACE || s.token == CASE) {
-                    stats.append(make.Block(s.pos, Tree.EMPTY_ARRAY));
+                    stats.append(gen.mkUnitLit(s.pos));
                 }
             } else if (s.token == SEMI) {
                 s.nextToken();
diff --git a/sources/scalac/ast/printer/TextTreePrinter.java b/sources/scalac/ast/printer/TextTreePrinter.java
index 9cefa783d8..6a8be8f696 100644
--- a/sources/scalac/ast/printer/TextTreePrinter.java
+++ b/sources/scalac/ast/printer/TextTreePrinter.java
@@ -391,8 +391,13 @@ public class TextTreePrinter implements TreePrinter {
             print(rhs);
             break;
 
-        case Block(Tree[] stats):
-            printArray(stats, TXT_BLOCK_BEGIN, TXT_BLOCK_END, TXT_BLOCK_SEP);
+        case Block(Tree[] stats, Tree value):
+            printArray(stats, TXT_BLOCK_BEGIN, TXT_SEMICOLON, TXT_BLOCK_SEP);
+            indent();
+            printNewLine();
+            print(value);
+            undent();
+            print(TXT_BLOCK_END);
             printType(tree);
             break;
 
diff --git a/sources/scalac/atree/ATreeFromSTree.java b/sources/scalac/atree/ATreeFromSTree.java
index cf62f951fa..e5eccc8fe8 100644
--- a/sources/scalac/atree/ATreeFromSTree.java
+++ b/sources/scalac/atree/ATreeFromSTree.java
@@ -149,9 +149,9 @@ public class ATreeFromSTree {
     // Private Methods - Translating statements
 
      /** Translates the statements. */
-    private ACode[] statement(List locals, Tree[] trees, int start, int count){
+    private ACode[] statement(List locals, Tree[] trees) {
         List codes = new ArrayList();
-        for (int i = start; i < start + count; i++) {
+        for (int i = 0; i < trees.length; i++) {
             ACode code = statement(locals, trees[i]);
             if (code != ACode.Void) codes.add(code);
         }
@@ -194,16 +194,14 @@ public class ATreeFromSTree {
             Symbol[] locals = Tree.symbolOf(idents);
             return make.Label(tree, tree.symbol(), locals, expression(rhs));
 
-        case Block(Tree[] statements):
-            if (statements.length == 0) return make.Void;
-            int statement_count = statements.length - 1;
+        case Block(Tree[] stats, Tree value):
             List locals = new ArrayList();
-            ACode[] codes = statement(locals,statements,0, statement_count);
-            ACode value = expression(statements[statement_count]);
-            if (locals.size() == 0 && codes.length == 0) return value;
+            ACode[] codes = statement(locals, stats);
+            ACode code = expression(value);
+            if (locals.size() == 0 && codes.length == 0) return code;
             Symbol[] symbols =
                 (Symbol[])locals.toArray(new Symbol[locals.size()]);
-            return make.Block(tree, symbols, codes, value);
+            return make.Block(tree, symbols, codes, code);
 
         case Assign(Tree lhs, Tree rhs):
             return make.Block(tree, Symbol.EMPTY_ARRAY, new ACode[] {
diff --git a/sources/scalac/backend/jvm/GenJVM.java b/sources/scalac/backend/jvm/GenJVM.java
index a4a134654e..d808131b36 100644
--- a/sources/scalac/backend/jvm/GenJVM.java
+++ b/sources/scalac/backend/jvm/GenJVM.java
@@ -234,14 +234,11 @@ class GenJVM {
             ctx.labels.remove(sym);
         } break;
 
-        case Block(Tree[] stats): {
+        case Block(Tree[] stats, Tree value): {
             int statsNum = stats.length;
-            for (int i = 0; i < statsNum - 1; ++i)
+            for (int i = 0; i < stats.length; ++i)
                 gen(ctx, stats[i]);
-            if (statsNum == 0)
-                maybeGenLoadUnit(ctx, expectedType);
-            else
-                genLoad(ctx, stats[stats.length - 1], expectedType);
+            genLoad(ctx, value, expectedType);
             generatedType = expectedType;
         } break;
 
@@ -1276,12 +1273,6 @@ class GenJVM {
                 return args[0];
             } else
                 return tree;
-        case Block(Tree[] stats):
-            if (stats.length == 2
-                && prims.getPrimitive(stats[1].symbol()) == Primitive.BOX) {
-                return stats[0];
-            } else
-                return tree;
         default:
             return tree;
         }
diff --git a/sources/scalac/backend/msil/GenMSIL.java b/sources/scalac/backend/msil/GenMSIL.java
index c12cfea8ea..417c4e2592 100644
--- a/sources/scalac/backend/msil/GenMSIL.java
+++ b/sources/scalac/backend/msil/GenMSIL.java
@@ -326,7 +326,7 @@ public final class GenMSIL {
 
 		// emit the call to the superconstructor
 		switch (rhs) {
-		case Block(Tree[] stats):
+		case Block(Tree[] stats, _):
 		    // this is the call to the super constructor
 		    drop(gen(stats[0], MSILType.VOID));
 		    break;
@@ -346,11 +346,12 @@ public final class GenMSIL {
 		code.Emit(OpCodes.Newobj, ctor);
 		code.Emit(OpCodes.Stsfld, moduleField);
 		switch (rhs) {
-		case Block(Tree[] stats):
+		case Block(Tree[] stats, Tree value):
 		    int n = stats.length;
 		    assert n > 0;
 		    for (int i = 1; i < n; i++)
 			drop(gen(stats[i], MSILType.VOID));
+                    drop(gen(value, MSILType.VOID));
 		    break;
 		}
 		code.Emit(OpCodes.Ret);
@@ -396,21 +397,6 @@ public final class GenMSIL {
     }
 
 
-    /** Generate code for array of trees
-     */
-    Item gen(Tree[] trees) {
-	int n = trees.length;
-	if (n == 0)
-	    return items.VoidItem();
-	boolean tmpLastStatement = lastStatement; lastStatement = false;
-	for (int i = 0; i < n-1; i++) {
-	    drop(gen(trees[i], MSILType.VOID));
-	}
-	lastStatement = tmpLastStatement;
-	return gen(trees[n-1], type2MSILType(trees[n-1].type));
-    }
-
-
     Item gen(Tree tree) {
 	return gen(tree, type2MSILType(tree.type));
     }
@@ -452,8 +438,13 @@ public final class GenMSIL {
 	case Empty:
 	    return items.VoidItem();
 
-	case Block(Tree[] stats):
-	    return gen(stats);
+	case Block(Tree[] stats, Tree value):
+            boolean tmpLastStatement = lastStatement; lastStatement = false;
+            for (int i = 0; i < stats.length; i++) {
+                drop(gen(stats[i], MSILType.VOID));
+            }
+            lastStatement = tmpLastStatement;
+            return gen(value, type2MSILType(value.type));
 
 	case ValDef(_, Name name, Tree tpe, Tree rhs):
 	    LocalBuilder local = code.DeclareLocal(tc.getType(sym));
diff --git a/sources/scalac/checkers/TreeChecker.java b/sources/scalac/checkers/TreeChecker.java
index c6d2af5052..9351110558 100644
--- a/sources/scalac/checkers/TreeChecker.java
+++ b/sources/scalac/checkers/TreeChecker.java
@@ -227,12 +227,11 @@ public class TreeChecker {
             scopeRemoveLabel(symbol);
             return true;
 
-        case Block(Tree[] statements):
+        case Block(Tree[] statements, Tree value):
             Set locals = new HashSet();
-            for (int i = 0; i < statements.length - 1; i++)
+            for (int i = 0; i < statements.length; i++)
                 statement(locals, statements[i]);
-            if (statements.length > 0)
-                expression(statements[statements.length - 1], expected);
+            expression(value, expected);
             for (Iterator i = locals.iterator(); i.hasNext(); )
                 scopeRemoveVVariable((Symbol)i.next());
             return true;
diff --git a/sources/scalac/symtab/Type.java b/sources/scalac/symtab/Type.java
index f0041be728..430718607e 100644
--- a/sources/scalac/symtab/Type.java
+++ b/sources/scalac/symtab/Type.java
@@ -3166,10 +3166,10 @@ public class Type implements Modifiers, Kinds, TypeTags, EntryTags {
      * the "void" type.
      */
     public Type fullErasure() {
-        if (Global.instance.definitions.UNIT_CLASS == symbol())
-            return unbox();
-        else
-            return erasure();
+        Type erasure = erasure();
+        if (Global.instance.definitions.UNIT_CLASS == erasure.symbol())
+            erasure = erasure.unbox();
+        return erasure;
     }
 
 // Object Interface -----------------------------------------------------------------
diff --git a/sources/scalac/transformer/AddConstructors.java b/sources/scalac/transformer/AddConstructors.java
index 5ef1e1c406..d08581aa7c 100644
--- a/sources/scalac/transformer/AddConstructors.java
+++ b/sources/scalac/transformer/AddConstructors.java
@@ -179,10 +179,9 @@ public class AddConstructors extends GenTransformer {
 	    // add valdefs and class-level expression to the constructorr body
 	    constrBody.addAll(constrBody2);
 
-            Tree constrTree = constrBody.size() > 1 ?
-                gen.Block((Tree[])constrBody.
-			  toArray(new Tree[constrBody.size()])):
-                (Tree) constrBody.get(0);
+            Tree constrTree = gen.mkUnitBlock(
+                clasz.primaryConstructor().pos,
+                (Tree[])constrBody.toArray(new Tree[constrBody.size()]));
 
 	    classBody.add(gen.DefDef(clasz.primaryConstructor(),constrTree));
 
@@ -210,7 +209,7 @@ public class AddConstructors extends GenTransformer {
             subst.removeSymbol(constructor.valueParams());
             subst.removeSymbol(constructor.typeParams());
             // add consistent result expression
-            rhs = gen.mkBlock(new Tree[] { rhs, gen.mkUnitLit(rhs.pos) });
+            rhs = gen.mkUnitBlock(rhs);
             return gen.DefDef(initializer, rhs);
 
         case ValDef(_, _, _, _):
diff --git a/sources/scalac/transformer/Erasure.java b/sources/scalac/transformer/Erasure.java
index e6a5fdd795..5da45dd2c5 100644
--- a/sources/scalac/transformer/Erasure.java
+++ b/sources/scalac/transformer/Erasure.java
@@ -220,7 +220,7 @@ public class Erasure extends GenTransformer implements Modifiers {
         case Literal(AConstant.ZERO):
 	    return gen.mkNullLit(tree.pos);
 
-        case Block(_):
+        case Block(_, _):
 	case If(_, _, _):
         case Switch(_, _, _, _):
             return transform(tree, tree.getType().fullErasure());
@@ -251,13 +251,8 @@ public class Erasure extends GenTransformer implements Modifiers {
     private Tree transform(Tree tree, Type pt) {
         switch (tree) {
 
-        case Block(Tree[] stats):
-            if (stats.length == 0) return transformUnit(tree.pos, pt);
-            stats = Tree.cloneArray(stats);
-            for (int i = 0; i < stats.length - 1; i++)
-                stats[i] = transform(stats[i]);
-            stats[stats.length - 1] = transform(stats[stats.length - 1], pt);
-            return gen.Block(tree.pos, stats);
+        case Block(Tree[] stats, Tree value):
+            return gen.Block(tree.pos, transform(stats), transform(value, pt));
 
 	case If(Tree cond, Tree thenp, Tree elsep):
 	    cond = transform(cond, UNBOXED_BOOLEAN);
@@ -272,8 +267,9 @@ public class Erasure extends GenTransformer implements Modifiers {
             return gen.Switch(tree.pos, test, tags, bodies, otherwise, pt);
 
         case Return(_):
+            // !!! why do we build a block here?
             Tree value = transform(gen.mkDefaultValue(tree.pos, pt), pt);
-            return gen.mkBlock(new Tree[] {transform(tree), value});
+            return gen.mkBlock(transform(tree), value);
 
         case LabelDef(_, _, _):
 	case Assign(_, _):
@@ -354,7 +350,7 @@ public class Erasure extends GenTransformer implements Modifiers {
         Symbol symbol = primitives.getBoxValueSymbol(tree.getType());
 	Tree boxtree = gen.mkGlobalRef(tree.pos, symbol);
         return tree.getType().equals(UNBOXED_UNIT)
-            ? gen.Block(new Tree[]{tree, gen.mkApply__(boxtree)})
+            ? gen.mkBlock(tree, gen.mkApply__(boxtree))
             : gen.mkApply_V(boxtree, new Tree[]{tree});
     }
 
diff --git a/sources/scalac/transformer/LambdaLift.java b/sources/scalac/transformer/LambdaLift.java
index 7129d5bdab..b580812ecb 100644
--- a/sources/scalac/transformer/LambdaLift.java
+++ b/sources/scalac/transformer/LambdaLift.java
@@ -350,10 +350,10 @@ public class LambdaLift extends OwnerTransformer
 	tree.type = descr.transform(tree.type, currentOwner);
 	//System.out.println(tree.type);//DEBUG
         switch (tree) {
-	case Block(Tree[] stats):
+	case Block(Tree[] stats, Tree value):
 	    for (int i = 0; i < stats.length; i++)
 		liftSymbol(stats[i]);
-	    return copy.Block(tree, transform(stats));
+	    return copy.Block(tree, transform(stats), transform(value));
 
 	case ClassDef(int mods, _, AbsTypeDef[] tparams, ValDef[][] vparams, Tree tpe, Template impl):
 	    Symbol sym = tree.symbol();
@@ -461,9 +461,7 @@ public class LambdaLift extends OwnerTransformer
                         // fn2 may be like "{ println("hello"); Predef}.Array"
                         switch (fn2) {
                         case Select(Tree qualifier, _):
-                            return gen.Block(
-                                args[0].pos,
-                                new Tree[] {qualifier, array});
+                            return gen.mkBlock(args[0].pos, qualifier, array);
                         default:
                             throw Debug.abort("illegal case", fn2);
                         }
diff --git a/sources/scalac/transformer/TailCallPhase.java b/sources/scalac/transformer/TailCallPhase.java
index 60574ad00c..a170671880 100644
--- a/sources/scalac/transformer/TailCallPhase.java
+++ b/sources/scalac/transformer/TailCallPhase.java
@@ -109,13 +109,8 @@ public class TailCallPhase extends Phase {
                 method = null;
                 return tree;
 
-            case Block(Tree[] stats):
-                if (stats.length == 0) return tree;
-                Tree expr = transform(stats[stats.length - 1]);
-                if (expr == stats[stats.length - 1]) return tree;
-                stats = Tree.cloneArray(stats);
-                stats[stats.length - 1] = expr;
-                return gen.Block(tree.pos, stats);
+            case Block(Tree[] stats, Tree value):
+                return gen.Block(tree.pos, stats, transform(value));
 
             case If(Tree cond, Tree thenp, Tree elsep):
                 Type type = tree.type();
diff --git a/sources/scalac/transformer/TransMatch.java b/sources/scalac/transformer/TransMatch.java
index 19d1fc0eb8..e64191f385 100644
--- a/sources/scalac/transformer/TransMatch.java
+++ b/sources/scalac/transformer/TransMatch.java
@@ -94,14 +94,13 @@ public class TransMatch extends OwnerTransformer {
             Set nilvars = TestRegTraverser.getNilVariables();
             if(!nilvars.isEmpty()) {
                 //System.err.println("nilvars present");
-                Tree[] newBody = new Tree[ nilvars.size() + 1 ];
+                Tree[] newBody = new Tree[ nilvars.size() ];
                 int j=0;
                 for( Iterator it = nilvars.iterator(); it.hasNext(); ) {
                     Symbol v = (Symbol) it.next();
                     newBody[ j++ ] = gen.ValDef(v, gen.mkNil(cases[i].pos));
                 }
-                newBody[ newBody.length - 1 ] = cases[i].body;
-                cases[i].body = gen.mkBlock( newBody );
+                cases[i].body = gen.mkBlock( newBody, cases[i].body );
             }
             i++;
         }
diff --git a/sources/scalac/transformer/matching/AlgebraicMatcher.java b/sources/scalac/transformer/matching/AlgebraicMatcher.java
index 6b96072bae..fc70741cd4 100644
--- a/sources/scalac/transformer/matching/AlgebraicMatcher.java
+++ b/sources/scalac/transformer/matching/AlgebraicMatcher.java
@@ -79,13 +79,13 @@ public class AlgebraicMatcher extends PatternMatcher {
 //////////// generator methods
 
     public Tree toTree() {
-        TreeList ts = new TreeList();
-        ts.append( gen.ValDef(root.symbol(), _m.selector ));
-        ts.append( gen.ValDef(resultVar,
-                              gen.mkDefaultValue(_m.pos, resultVar.info()) ));
-        ts.append( gen.If( toTree(root.and),
+        Tree[] ts = {
+            gen.ValDef(root.symbol(), _m.selector ),
+            gen.ValDef(resultVar,
+                       gen.mkDefaultValue(_m.pos, resultVar.info()) )};
+        Tree res = gen.If( toTree(root.and),
                            gen.Ident( _m.pos, resultVar ),
-                           cf.ThrowMatchError( _m.pos, _m.resultType )));
+                           cf.ThrowMatchError( _m.pos, _m.resultType ));
         /*
             gen.If(
                 _m.pos,
@@ -93,7 +93,7 @@ public class AlgebraicMatcher extends PatternMatcher {
                 gen.Ident( _m.pos, resultVar ),
                 cf.ThrowMatchError( _m.resultType ));
         */
-        return gen.mkBlock(_m.pos, ts.toArray());
+        return gen.mkBlock(_m.pos, ts, res);
     }
 
     protected Tree toTree(PatternNode node, Tree selector) {
diff --git a/sources/scalac/transformer/matching/Autom2Scala.java b/sources/scalac/transformer/matching/Autom2Scala.java
index 6f99a699cf..102353c8d4 100644
--- a/sources/scalac/transformer/matching/Autom2Scala.java
+++ b/sources/scalac/transformer/matching/Autom2Scala.java
@@ -92,9 +92,9 @@ public class Autom2Scala  {
             cf.gen.ValDef( this.curSym,
                            gen.If( gen.Ident( pos, hasnSym ),
                                    cf._next( _iter() ),
-                                   gen.mkDefaultValue(cf.pos,curSym.type()))),
+                                   gen.mkDefaultValue(cf.pos,curSym.type())))},
 
-            body });
+            body );
     }
 
     /** bug ?? */
@@ -189,10 +189,10 @@ public class Autom2Scala  {
     /** some error happened which is due to bug in translation/automaton
      */
     final Tree code_error() {
-        return gen.Block( new Tree[] {
+        return gen.mkBlock(
             gen.Console_print( pos, "System error during pattern matching. Please file bug report\n"),
             cf.ThrowMatchError( pos, funRetType() )
-        });
+        );
     }
 
     Tree code_fail() {
diff --git a/sources/scalac/transformer/matching/LeftTracerInScala.java b/sources/scalac/transformer/matching/LeftTracerInScala.java
index 4c02ce28dc..875b1dd89b 100644
--- a/sources/scalac/transformer/matching/LeftTracerInScala.java
+++ b/sources/scalac/transformer/matching/LeftTracerInScala.java
@@ -208,7 +208,8 @@ public class LeftTracerInScala extends TracerInScala {
                                       new Ident[] {
                                           gen.Ident( pos, stateSym ),
                                           gen.Ident( pos, accumSym )
-                                      }, code_body() /* code_body_new ? */ ))});
+                                      }, code_body() /* code_body_new ? */ ))},
+            gen.Ident( cf.pos, resultSym ));
     }
 
     // calling the AlgebraicMatcher here
diff --git a/sources/scalac/transformer/matching/PatternMatcher.java b/sources/scalac/transformer/matching/PatternMatcher.java
index b2c45278ef..eeebe6321d 100644
--- a/sources/scalac/transformer/matching/PatternMatcher.java
+++ b/sources/scalac/transformer/matching/PatternMatcher.java
@@ -766,16 +766,15 @@ public class PatternMatcher extends PatternTool {
     }
 
     public Tree generalSwitchToTree() {
-        TreeList ts = new TreeList();
-        ts.append(gen.ValDef(root.symbol(), selector));
-        ts.append(gen.ValDef(resultVar, gen.mkDefaultValue(selector.pos, resultVar.getType())));
-        ts.append(
-                  gen.If(
-                         selector.pos,
-                         toTree(root.and),
-                         gen.Ident(selector.pos, resultVar),
-                         cf.ThrowMatchError(selector.pos, resultVar.getType())));
-        return gen.mkBlock(selector.pos, ts.toArray());
+        Tree[] ts = {
+            gen.ValDef(root.symbol(), selector),
+            gen.ValDef(resultVar, gen.mkDefaultValue(selector.pos, resultVar.getType()))};
+        Tree res = gen.If(
+                          selector.pos,
+                          toTree(root.and),
+                          gen.Ident(selector.pos, resultVar),
+                          cf.ThrowMatchError(selector.pos, resultVar.getType()));
+        return gen.mkBlock(selector.pos, ts, res);
     }
 
     protected Tree toTree(PatternNode node) {
@@ -799,18 +798,15 @@ public class PatternMatcher extends PatternTool {
                 } else if (!doBinding)
                     bound = new ValDef[][]{new ValDef[]{}};
                 for (int i = guard.length - 1; i >= 0; i--) {
-                    Tree[] ts = new Tree[bound[i].length + 1];
-                    System.arraycopy(bound[i], 0, ts, 0, bound[i].length);
-                    ts[bound[i].length] = gen.mkBlock(
-                                                      new Tree[]{
-                                                          gen.Assign(
-                                                                     gen.Ident(body[i].pos, resultVar),
-                                                                     body[i]),
-                                                          gen.mkBooleanLit(body[i].pos, true)
-                                                      });
+                    Tree[] ts = bound[i];
+                    Tree res0 = gen.mkBlock(
+                                            gen.Assign(
+                                                       gen.Ident(body[i].pos, resultVar),
+                                                       body[i]),
+                                            gen.mkBooleanLit(body[i].pos, true));
                     if (guard[i] != Tree.Empty)
-                        ts[bound[i].length] = cf.And(guard[i], ts[bound[i].length]);
-                    res = cf.Or(gen.mkBlock(body[i].pos, ts), res);
+                        res0 = cf.And(guard[i], res0);
+                    res = cf.Or(gen.mkBlock(body[i].pos, ts, res0), res);
                 }
                 return res;
             default:
@@ -922,10 +918,9 @@ public class PatternMatcher extends PatternTool {
             return gen.If(
                           gen.mkIsInstanceOf(selector.duplicate(), node.type),
                           gen.mkBlock(
-                                      new Tree[]{
-                                          gen.ValDef(casted,
-                                                     gen.mkAsInstanceOf(selector.duplicate(), node.type)),
-                                          toTree(node.and)}),
+                                      gen.ValDef(casted,
+                                                 gen.mkAsInstanceOf(selector.duplicate(), node.type)),
+                                      toTree(node.and)),
                           toTree(node.or, selector.duplicate()));
         case SequencePat(Symbol casted, int len):
             return gen.If(
@@ -939,10 +934,9 @@ public class PatternMatcher extends PatternTool {
                                                                     defs.SEQ_LENGTH())),
                                            gen.mkIntLit(selector.pos, len))),
                           gen.mkBlock(
-                                      new Tree[]{
-                                          gen.ValDef(casted,
-                                                     gen.mkAsInstanceOf(selector.duplicate(), node.type)),
-                                          toTree(node.and)}),
+                                      gen.ValDef(casted,
+                                                 gen.mkAsInstanceOf(selector.duplicate(), node.type)),
+                                      toTree(node.and)),
                           toTree(node.or, selector.duplicate()));
         case ConstantPat(AConstant value):
             return gen.If(
diff --git a/sources/scalac/transformer/matching/RightTracerInScala.java b/sources/scalac/transformer/matching/RightTracerInScala.java
index e7ef7ae029..e6fc1378ae 100644
--- a/sources/scalac/transformer/matching/RightTracerInScala.java
+++ b/sources/scalac/transformer/matching/RightTracerInScala.java
@@ -32,7 +32,7 @@ public class RightTracerInScala extends TracerInScala  {
 
     HashMap helpMap;
     HashMap helpMap2 ;
-    Vector  helpVarDefs;
+    TreeList helpVarDefs;
 
 
     /** translate right tracer to code
@@ -60,7 +60,7 @@ public class RightTracerInScala extends TracerInScala  {
         this.helpMap = new HashMap();
 
         helpMap2 = new HashMap();
-        helpVarDefs = new Vector();
+        helpVarDefs = new TreeList();
 
         for( Iterator it = seqVars.iterator(); it.hasNext(); ) {
             makeHelpVar( (Symbol) it.next() );
@@ -110,7 +110,7 @@ public class RightTracerInScala extends TracerInScala  {
         helpVar.flags |= Modifiers.MUTABLE;
         Tree varDef = gen.ValDef( helpVar, rhs );
         //((ValDef) varDef).kind = Kinds.VAR;
-        helpVarDefs.add( varDef );
+        helpVarDefs.append( varDef );
 
     }
 
@@ -174,16 +174,16 @@ public class RightTracerInScala extends TracerInScala  {
 
     // load current elem and trace
     Tree loadCurrentElem( Tree body ) {
-        return gen.mkBlock( new Tree[] {
+        return
             gen.If( cf.isEmpty( _iter() ),
                     run_finished( 0 ),            // we are done
                     gen.mkBlock( new Tree[] {
                         gen.ValDef( this.targetSym,
                                     cf.SeqTrace_headState( gen.Ident( pos, iterSym))),
                         gen.ValDef( this.curSym,
-                                    cf.SeqTrace_headElem( gen.Ident( pos, iterSym ))),
-                        body })
-                    )});
+                                    cf.SeqTrace_headElem( gen.Ident( pos, iterSym )))},
+                        body )
+                    );
     }
 
     /** see code_state0_NEW
@@ -354,7 +354,7 @@ System.out.println("RightTracerInScala - the seqVars"+seqVars);
         //             case _     => false
 
 
-        Tree res[] = new Tree[ helpMap3.keySet().size() + 1 ];
+        Tree ts[] = new Tree[ helpMap3.keySet().size() ];
         int j = 0;
         for( Iterator it = helpMap3.keySet().iterator(); it.hasNext(); ) {
             Symbol vsym = (Symbol) it.next();
@@ -362,12 +362,12 @@ System.out.println("RightTracerInScala - the seqVars"+seqVars);
             //hv.setType( defs.LIST_TYPE( elementType ) ) ; DEBUG ALARM ?
             Tree refv   = gen.Ident(cf.pos, vsym);
             Tree refhv  = gen.Ident(cf.pos, hv);
-            res[ j++ ] = gen.Assign( refhv, refv );
+            ts[ j++ ] = gen.Assign( refhv, refv );
             // System.out.println( "the assign" + res[ j - 1 ] );
         }
 
-        res[ j ] = gen.mkBooleanLit( cf.pos, true ); // just `true'
-        Tree theBody =  gen.mkBlock(res);
+        Tree res = gen.mkBooleanLit( cf.pos, true ); // just `true'
+        Tree theBody =  gen.mkBlock(ts, res);
 
         am.construct( m, new CaseDef[] {
 
@@ -417,8 +417,7 @@ System.out.println("RightTracerInScala - the seqVars"+seqVars);
         assert vars != null;
 
         Tree stms[] = new Tree[ vars.size()
-                                + ((algMatchTree != null )? 1 : 0 )
-                                + 1 ];
+                                + ((algMatchTree != null )? 1 : 0 ) ];
         int j = 0;
         for( Iterator it = vars.iterator(); it.hasNext(); ) {
             Symbol var = (Symbol) it.next();
@@ -431,10 +430,10 @@ System.out.println("RightTracerInScala - the seqVars"+seqVars);
         if( algMatchTree != null )
             stms[ j++ ] = algMatchTree ;
 
-        stms[ j ] = callFun( new Tree[] { cf.SeqTrace_tail( _iter() ),
-                                          gen.mkIntLit( cf.pos, ntarget.intValue() ) } );
+        Tree value = callFun( new Tree[] { cf.SeqTrace_tail( _iter() ),
+                                           gen.mkIntLit( cf.pos, ntarget.intValue() ) } );
 
-        return gen.mkBlock( pos, stms );
+        return gen.mkBlock( pos, stms, value );
     }
 
     Tree stateWrap(int i) {
@@ -445,23 +444,23 @@ System.out.println("RightTracerInScala - the seqVars"+seqVars);
 
     /* returns statements that do the work of the right-transducer
      */
-    Tree[] getStms( Tree trace, Unit unit, Tree body ) {
+    Tree getStms( Tree trace, Unit unit, Tree body ) {
 
-        Vector v = new Vector();
+        TreeList stms = new TreeList();
         Tree loopbody = code_body_NEW();
 
-        v.add( gen.ValDef( iterSym, trace ) );
-        v.add( gen.ValDef( stateSym, gen.mkIntLit( cf.pos, 0 ) ) );
-        v.addAll( helpVarDefs );
-        v.add( gen.LabelDef( this.funSym,
-                             new Ident[] {
-                                 gen.Ident( pos, iterSym ),
-                                 gen.Ident( pos, stateSym )
-                             }, loopbody ));
+        stms.append( gen.ValDef( iterSym, trace ) );
+        stms.append( gen.ValDef( stateSym, gen.mkIntLit( cf.pos, 0 ) ) );
+        stms.append( helpVarDefs );
+        stms.append( gen.LabelDef( this.funSym,
+                                   new Ident[] {
+                                       gen.Ident( pos, iterSym ),
+                                       gen.Ident( pos, stateSym )
+                                   }, loopbody ));
 
         // bind variables handled by this righttracer
         for( Iterator it = seqVars.iterator(); it.hasNext(); ) {
-            v.add( bindVar( (Symbol) it.next() ) );
+            stms.append( bindVar( (Symbol) it.next() ) );
         }
 
         Transformer treeCloner = new Transformer(unit.global) {
@@ -475,15 +474,7 @@ System.out.println("RightTracerInScala - the seqVars"+seqVars);
                 }
             };
 
-        v.add( treeCloner.transform( body ) );
-
-        Tree result[] = new Tree[ v.size() ];
-        int j = 0;
-        for( Iterator it = v.iterator(); it.hasNext(); ) {
-            result[ j++ ] = (Tree) it.next();
-        }
-
-        return result;
+        return gen.mkBlock(stms.toArray(), treeCloner.transform( body ));
     }
 
 
@@ -492,7 +483,7 @@ System.out.println("RightTracerInScala - the seqVars"+seqVars);
      *  todo: move tree generation of Unit somewhere else
      */
     Tree run_finished( int state ) {
-        return gen.Block(Position.FIRSTPOS, Tree.EMPTY_ARRAY);
+        return gen.mkUnitLit(Position.FIRSTPOS);
     }
 
     Tree current() {   return gen.Ident( pos, targetSym );}
diff --git a/sources/scalac/transformer/matching/SequenceMatcher.java b/sources/scalac/transformer/matching/SequenceMatcher.java
index 68d698986c..78334e5c10 100644
--- a/sources/scalac/transformer/matching/SequenceMatcher.java
+++ b/sources/scalac/transformer/matching/SequenceMatcher.java
@@ -55,8 +55,6 @@ public class SequenceMatcher extends PatternTool {
 
         Tree trace = ltis.getTrace();
 
-        Tree theTrace = gen.Ident( cf.pos, ltis.resultSym );
-
         //  (c) determinize + translate R
 
         DetWordAutom dRight = new DetWordAutom( right, left, dLeft );
@@ -67,16 +65,10 @@ public class SequenceMatcher extends PatternTool {
             new RightTracerInScala( dRight, seqVars, _m.owner,
                                     cf, pat, elementType );
 
-        Tree stms2[] = rtis.getStms( theTrace, unit, body );
-
-        // paste statements together
-
-        Tree items[] = new Tree[ 1 + stms2.length ];
-
-        items[ 0 ] = trace;
-        System.arraycopy( stms2, 0, items, 1, stms2.length );
-
-        return gen.mkBlock( body.pos, items );
+        // !!! Tree stms2 = rtis.getStms( theTrace, unit, body );
+        // !!! gen.mkBlock_( body.pos, trace, stms2 );
+        Tree stms2 = rtis.getStms( trace, unit, body );
+        return stms2;
     }
 
     private NondetWordAutom[] buildNfas( Tree[] pat ) {
diff --git a/sources/scalac/transformer/matching/WordAutomInScala.java b/sources/scalac/transformer/matching/WordAutomInScala.java
index bb05f6f63b..c84291b9ae 100644
--- a/sources/scalac/transformer/matching/WordAutomInScala.java
+++ b/sources/scalac/transformer/matching/WordAutomInScala.java
@@ -60,8 +60,8 @@ public class WordAutomInScala extends Autom2Scala {
         result = cf.gen.mkBlock( cf.pos, new Tree[] {
             gen.ValDef( iterSym, cf.newIterator( selector )),
             gen.ValDef( stateSym, gen.mkIntLit( cf.pos, 0) ),
-            gen.ValDef( resultSym, theDefDef ),
-            result } );
+            gen.ValDef( resultSym, theDefDef )},
+            result );
         //unit.global.debugPrinter.print( result );
         return result;
     }
diff --git a/sources/scalac/typechecker/Analyzer.java b/sources/scalac/typechecker/Analyzer.java
index 9953f1dde7..7d889f4aef 100644
--- a/sources/scalac/typechecker/Analyzer.java
+++ b/sources/scalac/typechecker/Analyzer.java
@@ -1402,7 +1402,7 @@ public class Analyzer extends Transformer implements Modifiers, Kinds {
 	    }
 	    if ((mode & EXPRmode) != 0) {
 		if (pt.symbol() == definitions.UNIT_CLASS) {
-		    return gen.Block(new Tree[]{tree, gen.mkUnitLit(tree.pos)});
+		    return gen.mkUnitBlock(tree);
 		} else {
 		    Symbol coerceMeth = tree.type.lookup(Names.coerce);
 		    if (coerceMeth != Symbol.NONE) {
@@ -1939,7 +1939,7 @@ public class Analyzer extends Transformer implements Modifiers, Kinds {
 		    rhs1 = transform(
 			rhs,
 			(name == Names.CONSTRUCTOR) ? CONSTRmode : EXPRmode,
-			tpe1.type);
+			(name == Names.CONSTRUCTOR) ? definitions.UNIT_TYPE() : tpe1.type);
 		}
 		popContext();
 		context.enclClass.owner.flags &= ~INCONSTRUCTOR;
@@ -1988,33 +1988,27 @@ public class Analyzer extends Transformer implements Modifiers, Kinds {
 		context.imports = new ImportList(tree, context.scope, context.imports);
 		return Tree.Empty;
 
-	    case Block(Tree[] stats):
+	    case Block(Tree[] stats, Tree value):
 		pushContext(tree, context.owner, new Scope(context.scope));
 		Tree[] stats1 = desugarize.Statements(stats, true);
 		enterSyms(stats1);
 		context.imports = context.outer.imports;
-		Type owntype;
 		int curmode = mode;
+                int start = 0;
+                int valuemode = curmode;
 		if ((curmode & CONSTRmode) != 0) {
 		    stats1[0] = transform(stats1[0], curmode, pt);
 		    context.enclClass.owner.flags &= ~INCONSTRUCTOR;
-		    for (int i = 1; i < stats1.length; i++)
-			stats1[i] = transform(stats1[i], EXPRmode);
-		    owntype = stats1[0].type;
-		} else {
-		    for (int i = 0; i < stats1.length - 1; i++)
-			stats1[i] = transform(stats1[i], EXPRmode);
-		    if (stats1.length > 0) {
-			stats1[stats1.length - 1] =
-			    transform(stats1[stats1.length - 1], curmode & ~FUNmode, pt);
-			owntype = checkNoEscape(tree.pos, stats1[stats1.length - 1].type);
-		    } else {
-			owntype = definitions.UNIT_TYPE();
-		    }
-		}
+                    start = 1;
+                    valuemode = (curmode & ~CONSTRmode) | EXPRmode;
+                }
+                for (int i = start; i < stats1.length; i++)
+                    stats1[i] = transform(stats1[i], EXPRmode);
+                Tree value1 = transform(value, valuemode & ~FUNmode, pt);
+		Type owntype = checkNoEscape(tree.pos, value1.type);
 		popContext();
-		return copy.Block(tree, stats1)
-		    .setType(owntype);
+		return copy.Block(tree, stats1, value1)
+                    .setType(owntype);
 
             case Sequence( Tree[] trees ):
                 for( int i = 0; i < trees.length; i++ ) {
@@ -2115,8 +2109,7 @@ public class Analyzer extends Transformer implements Modifiers, Kinds {
 		Tree thenp1, elsep1;
 		if (elsep == Tree.Empty) {
 		    thenp1 = transform(thenp, EXPRmode, definitions.UNIT_TYPE());
-		    elsep1 = make.Block(tree.pos, Tree.EMPTY_ARRAY)
-			.setType(definitions.UNIT_TYPE());
+		    elsep1 = gen.mkUnitLit(tree.pos);
 		} else {
 		    thenp1 = transform(thenp, EXPRmode, pt);
 		    elsep1 = transform(elsep, EXPRmode, pt);
@@ -2202,7 +2195,7 @@ public class Analyzer extends Transformer implements Modifiers, Kinds {
 				Tree.EMPTY_ARRAY))
 			    .setType(owntype);
 			popContext();
-			return make.Block(tree.pos, new Tree[]{cd, alloc})
+			return make.Block(tree.pos, new Tree[]{cd}, alloc)
 			  .setType(owntype);
 		    }
 		default:
diff --git a/sources/scalac/typechecker/Context.java b/sources/scalac/typechecker/Context.java
index 61bf0a8299..347e6d565d 100644
--- a/sources/scalac/typechecker/Context.java
+++ b/sources/scalac/typechecker/Context.java
@@ -51,7 +51,7 @@ public class Context {
 
     boolean isTopLevel() {
 	switch (tree) {
-	case Block(_):
+	case Block(_, _):
 	    return false;
 	case Template(_, _):
 	    return outer.tree instanceof Tree.PackageDef;
diff --git a/sources/scalac/typechecker/DeSugarize.java b/sources/scalac/typechecker/DeSugarize.java
index 5cb654a636..a996ae9fa4 100644
--- a/sources/scalac/typechecker/DeSugarize.java
+++ b/sources/scalac/typechecker/DeSugarize.java
@@ -143,7 +143,7 @@ public class DeSugarize implements Kinds, Modifiers {
 
     public Tree mkTuple(int pos, Tree[] trees) {
 	if (trees.length == 0)
-	    return make.Block(pos, trees);
+	    return gen.mkUnitLit(pos);
 	else
 	    return make.Apply(pos,
 		make.Select(pos,
@@ -420,7 +420,7 @@ public class DeSugarize implements Kinds, Modifiers {
 			pos, mods, vars[i], Tree.Empty,
 			make.Select(pos, make.Ident(pos, var), tupleSelectorName(i + 1)));
 		}
-		print(pat, "patdef", new Block(res));//debug
+		print(pat, "patdef", new Block(res, gen.mkUnitLit(pos)));//debug
 		return shareComment(res, tree);
 	    }
 	default:
@@ -484,8 +484,7 @@ public class DeSugarize implements Kinds, Modifiers {
 	TreeList defs = new TreeList();
 	Tree lambda =
 	    toFunction(toApply(liftoutPrefix(tree, defs), type), type);
-	defs.append(lambda);
-	Tree result = make.Block(tree.pos, defs.toArray());
+	Tree result = make.Block(tree.pos, defs.toArray(), lambda);
 	print(tree, "eta", result);//debug
 	return result;
     }
diff --git a/sources/scalac/typechecker/RefCheck.java b/sources/scalac/typechecker/RefCheck.java
index ac84a1dbac..3ffe63cf40 100644
--- a/sources/scalac/typechecker/RefCheck.java
+++ b/sources/scalac/typechecker/RefCheck.java
@@ -538,14 +538,14 @@ public class RefCheck extends Transformer implements Modifiers, Kinds {
 	    // { if (null == m$) m$ = new m$class; m$ }
 	    Symbol eqMethod = getUnaryMemberMethod(
 		sym.type(), Names.EQEQ, defs.ANY_TYPE());
-	    Tree body = gen.Block(new Tree[]{
+	    Tree body = gen.mkBlock(
 		gen.If(
 		    gen.Apply(
 			gen.Select(gen.mkNullLit(tree.pos), eqMethod),
 			new Tree[]{gen.mkLocalRef(tree.pos, mvar)}),
 		    gen.Assign(gen.mkLocalRef(tree.pos, mvar), alloc),
-		    gen.Block(tree.pos, Tree.EMPTY_ARRAY)),
-		gen.mkLocalRef(tree.pos, mvar)});
+		    gen.mkUnitLit(tree.pos)),
+		gen.mkLocalRef(tree.pos, mvar));
 
 	    // def m: T = { if (m$ == null[T]) m$ = new m$class; m$ }
 	    sym.flags |= STABLE;
@@ -704,7 +704,7 @@ public class RefCheck extends Transformer implements Modifiers, Kinds {
 			    qualCaseField(clazz,
 				gen.mkLocalRef(clazz.pos, that1sym), i))});
 	    }
-	    thenpart = gen.Block(new Tree[]{that1def, cmp});
+	    thenpart = gen.mkBlock(that1def, cmp);
 	}
 	Tree body = gen.If(cond, thenpart, gen.mkBooleanLit(clazz.pos, false));
 	return gen.DefDef(equalsSym, body);
@@ -970,9 +970,10 @@ public class RefCheck extends Transformer implements Modifiers, Kinds {
 	    }
 	    return copy.Template(tree, bases1, body1);
 
-	case Block(Tree[] stats):
+	case Block(Tree[] stats, Tree value):
 	    Tree[] stats1 = transformStats(stats);
-	    return copy.Block(tree, stats1);
+            Tree value1 = transform(value);
+	    return copy.Block(tree, stats1, value1);
 
 	case This(_):
 	    return tree;
diff --git a/test/files/shl/basic.check b/test/files/shl/basic.check
index 9439e81b3b..1cac379455 100644
--- a/test/files/shl/basic.check
+++ b/test/files/shl/basic.check
@@ -1,4 +1,4 @@
-> > > > > > (): scala.Unit
+> > > > > > (): scala.Unit(())
 > false: scala.Boolean(false)
 > 1: scala.Char('1')
 > 2: scala.Int(2)