[gwt-contrib] Prevent non-null null types from appearing. (issue1028801)

[scottb]

Reviewers: conroy,

Description:
Contradiction in terms, and makes the compiler blow up.

Please review this at http://gwt-code-reviews.appspot.com/1028801/show

Affected files:
  M dev/core/src/com/google/gwt/dev/jjs/ast/JNonNullType.java
  M dev/core/src/com/google/gwt/dev/jjs/ast/JProgram.java


Index: dev/core/src/com/google/gwt/dev/jjs/ast/JNonNullType.java
diff --git a/dev/core/src/com/google/gwt/dev/jjs/ast/JNonNullType.java  
b/dev/core/src/com/google/gwt/dev/jjs/ast/JNonNullType.java
index  
81e97704225ab44b3d0fd9c976a6b2ee4d338cd0..05edfed239b396c360b207d36a61e5410452ffe2  
100644
--- a/dev/core/src/com/google/gwt/dev/jjs/ast/JNonNullType.java
+++ b/dev/core/src/com/google/gwt/dev/jjs/ast/JNonNullType.java
@@ -25,7 +25,7 @@ public class JNonNullType extends JReferenceType {

   JNonNullType(JReferenceType ref) {
     super(ref.getSourceInfo(), ref.getName());
-    assert ref.canBeNull();
+    assert !(ref instanceof JNullType);
     this.ref = ref;
   }

Index: dev/core/src/com/google/gwt/dev/jjs/ast/JProgram.java
diff --git a/dev/core/src/com/google/gwt/dev/jjs/ast/JProgram.java  
b/dev/core/src/com/google/gwt/dev/jjs/ast/JProgram.java
index  
049958bc270245937e33fb7d0e343b489d51e51f..a5eac08d1bb2181b69bdc090131dd20bdaab6022  
100644
--- a/dev/core/src/com/google/gwt/dev/jjs/ast/JProgram.java
+++ b/dev/core/src/com/google/gwt/dev/jjs/ast/JProgram.java
@@ -765,21 +765,18 @@ public class JProgram extends JNode {
   }

   public JsonObject getCastableTypeMap(JReferenceType referenceType) {
-
     // ensure jsonCastableTypeMaps has been initialized
     // it might not have been if the CastNormalizer has not been run
     if (castableTypeMaps == null) {
       initTypeInfo(null);
     }
-
     JsonObject returnMap = castableTypeMaps.get(referenceType);
     if (returnMap == null) {
       // add a new empty map
       returnMap = new JsonObject(createSourceInfoSynthetic(JProgram.class,
-                                        "empty map"),  
getJavaScriptObject());
+          "empty map"), getJavaScriptObject());
       castableTypeMaps.put(referenceType, returnMap);
     }
-
     return returnMap;
   }

@@ -1158,12 +1155,10 @@ public class JProgram extends JNode {
   public JPrimitiveType getTypeVoid() {
     return JPrimitiveType.VOID;
   }
-
+
   public void initTypeInfo(
-      IdentityHashMap<JReferenceType,JsonObject>  
instantiatedTypeCastableTypeMaps) {
-
+      IdentityHashMap<JReferenceType, JsonObject>  
instantiatedTypeCastableTypeMaps) {
     castableTypeMaps = instantiatedTypeCastableTypeMaps;
-
     if (castableTypeMaps == null || castableTypeMaps.size() == 0) {
       castableTypeMaps = new IdentityHashMap<JReferenceType, JsonObject>();
     }
@@ -1241,6 +1236,10 @@ public class JProgram extends JNode {
       return type1;
     }

+    if (type1 instanceof JNullType || type2 instanceof JNullType) {
+      return JNullType.INSTANCE;
+    }
+
     if (type1 instanceof JNonNullType != type2 instanceof JNonNullType) {
       // If either is non-nullable, the result should be non-nullable.
       return strongerType(getNonNullType(type1), getNonNullType(type2));


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