Parsing and desugaring fixes for blocks.

Previously, { () }
was expanded to { (); EmptyTree }, because the empty tuple is not a term tree. Now EmptyTree is inserted only after a definition.

Furthermore, blocks ending in EmptyTree are now replaced by blocks that end in a unit literal.

3 files changed, 13 insertions, 4 deletions

diff --git a/src/dotty/tools/dotc/ast/Desugar.scala b/src/dotty/tools/dotc/ast/Desugar.scala
index 31154b2ef..fb80509fd 100644
--- a/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/src/dotty/tools/dotc/ast/Desugar.scala
@@ -255,6 +255,14 @@ object desugar {
     case tree: PatDef => patDef(tree)
   }
 
+  def block(tree: Block)(implicit ctx: Context): Block = tree.expr match {
+    case EmptyTree =>
+      cpy.Block(tree, tree.stats,
+        unitLiteral withPos (if (tree.stats.isEmpty) tree.pos else tree.pos.endPos))
+    case _ =>
+      tree
+  }
+
   /** In case there is exactly one variable x_1 in pattern
    *   val/var p = e  ==>  val/var x_1 = (e: @unchecked) match (case p => (x_1))
    *
diff --git a/src/dotty/tools/dotc/parsing/Parsers.scala b/src/dotty/tools/dotc/parsing/Parsers.scala
index 57356f305..500ea4810 100644
--- a/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -1130,7 +1130,7 @@ object Parsers {
      */
     def block(): Tree = {
       val stats = blockStatSeq()
-      if (stats.nonEmpty && stats.last.isTerm) Block(stats.init, stats.last)
+      if (stats.nonEmpty && !stats.last.isDef) Block(stats.init, stats.last)
       else Block(stats, EmptyTree)
     }
 
diff --git a/src/dotty/tools/dotc/typer/Typer.scala b/src/dotty/tools/dotc/typer/Typer.scala
index 5b79c62f3..bb3e1052a 100644
--- a/src/dotty/tools/dotc/typer/Typer.scala
+++ b/src/dotty/tools/dotc/typer/Typer.scala
@@ -461,8 +461,9 @@ class Typer extends Namer with Applications with Implicits {
     else if (forceFullyDefined(pt)) {
       val expr2 = typed(untpd.Typed(untpd.TypedSplice(expr1), untpd.TypeTree(pt)))
       untpd.Block(stats1, expr2) withType expr2.tpe
-    } else errorTree(result,
-      i"local definition of ${leaks.head.name} escapes as part of block's type ${result.tpe}")
+    } else
+      errorTree(result,
+          i"local definition of ${leaks.head.name} escapes as part of block's type ${result.tpe}")
   }
 
   def typedIf(tree: untpd.If, pt: Type)(implicit ctx: Context) = track("typedIf") {
@@ -825,7 +826,7 @@ class Typer extends Namer with Applications with Implicits {
           case tree: untpd.Typed => typedTyped(tree, pt)
           case tree: untpd.NamedArg => typedNamedArg(tree, pt)
           case tree: untpd.Assign => typedAssign(tree, pt)
-          case tree: untpd.Block => typedBlock(tree, pt)
+          case tree: untpd.Block => typedBlock(desugar.block(tree), pt)
           case tree: untpd.If => typedIf(tree, pt)
           case tree: untpd.Function => typedFunction(tree, pt)
           case tree: untpd.Closure => typedClosure(tree, pt)