Support break and labeled statements.

frog/leg/typechecker.dart

Index: frog/leg/typechecker.dart
diff --git a/frog/leg/typechecker.dart b/frog/leg/typechecker.dart
index db4df503ea0f19cd4eb389d2dac58664ff90be25..732880a44c1462f235ec749f585e4237297419a4 100644
--- a/frog/leg/typechecker.dart
+++ b/frog/leg/typechecker.dart
@@ -587,7 +587,7 @@ class TypeCheckerVisitor implements Visitor<Type> {
   }
 
   visitBreakStatement(BreakStatement node) {
-    compiler.unimplemented('visitBreakStatement', node: node);
+    return StatementType.NOT_RETURNING;
   }
 
   visitContinueStatement(ContinueStatement node) {
@@ -595,11 +595,13 @@ class TypeCheckerVisitor implements Visitor<Type> {
   }
 
   visitForInStatement(ForInStatement node) {
-    node.visitChildren(this);
+    analyze(node.expression);
+    StatementType bodyType = analyze(node.body);
+    return bodyType.join(StatementType.NOT_RETURNING);
   }
 
   visitLabelledStatement(LabelledStatement node) {
-    compiler.unimplemented('visitLabelledStatement', node: node);
+    return node.statement.accept(this);
   }
 
   visitLiteralMap(LiteralMap node) {