Issue 4460. Mark inferred type variable in for-in loop as inferred

compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java

Index: compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
diff --git a/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java b/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
index 05e70ddfc9a948b2d07a9b01c53ced37df283910..c8185f1675e0f95fa4756cb04110eedc844268c4 100644
--- a/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
+++ b/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
@@ -682,6 +682,7 @@ public class TypeAnalyzer implements DartCompilationPhase {
             // if we fell back to Dynamic, keep it
           } else {
             Type unionType = getUnionType(currentType, inferredType);
+            unionType = Types.makeInferred(unionType);
             Elements.setType(element, unionType);
           }
         }
@@ -705,7 +706,7 @@ public class TypeAnalyzer implements DartCompilationPhase {
           return b;
         }
         // TODO(scheglov) return union of types, but this is not easy
-        return Types.makeInferred(dynamicType);
+        return dynamicType;
       }
 
       void restore() {