Tree-check the Labeled blocks and their Returns.

Author: sjrd

compiler/src/dotty/tools/dotc/transform/TreeChecker.scala

@@ -191,7 +191,7 @@ class TreeChecker extends Phase with SymTransformer {
     def assertDefined(tree: untpd.Tree)(implicit ctx: Context) =
       if (
         tree.symbol.maybeOwner.isTerm &&
-        !(tree.symbol.is(Label) && !tree.symbol.owner.isClass && ctx.phase.labelsReordered) // labeldefs breaks scoping
+        !(tree.symbol.is(Label | Method) && !tree.symbol.owner.isClass && ctx.phase.labelsReordered) // labeldefs breaks scoping
       )
         assert(nowDefinedSyms contains tree.symbol, i"undefined symbol ${tree.symbol} at line " + tree.pos.line)
 
@@ -446,6 +446,22 @@ class TreeChecker extends Phase with SymTransformer {
       super.typedStats(trees, exprOwner)
     }
 
+    override def typedLabeled(tree: untpd.Labeled)(implicit ctx: Context): Labeled = {
+      checkOwner(tree.bind)
+      withDefinedSyms(tree.bind :: Nil) { super.typedLabeled(tree) }
+    }
+
+    override def typedReturn(tree: untpd.Return)(implicit ctx: Context): Return = {
+      val tree1 = super.typedReturn(tree)
+      val from = tree1.from
+      val fromSym = from.symbol
+      if (fromSym.is(Label)) {
+        assert(!fromSym.is(Method), i"return from a label-def $fromSym at $tree")
+        assertDefined(from)
+      }
+      tree1
+    }
+
     override def ensureNoLocalRefs(tree: Tree, pt: Type, localSyms: => List[Symbol])(implicit ctx: Context): Tree =
       tree
 

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -1069,7 +1069,7 @@ class Typer extends Namer
     caseRest(pat1)(gadtCtx.fresh.setNewScope)
   }
 
-  def typedLabeled(tree: untpd.Labeled, pt: Type)(implicit ctx: Context): Tree = track("typedLabeled") {
+  def typedLabeled(tree: untpd.Labeled)(implicit ctx: Context): Labeled = track("typedLabeled") {
     val bind1 = typedBind(tree.bind, WildcardType).asInstanceOf[Bind]
     val expr1 = typed(tree.expr, bind1.symbol.info)
     assignType(cpy.Labeled(tree)(bind1, expr1))
@@ -1815,7 +1815,7 @@ class Typer extends Namer
                 typedClassDef(tree, sym.asClass)(ctx.localContext(tree, sym).setMode(ctx.mode &~ Mode.InSuperCall))
               else
                 typedTypeDef(tree, sym)(ctx.localContext(tree, sym).setNewScope)
-            case tree: untpd.Labeled => typedLabeled(tree, pt)
+            case tree: untpd.Labeled => typedLabeled(tree)
             case _ => typedUnadapted(desugar(tree), pt, locked)
           }
         }