Do not use thisValue when it is the NullType (#636)

checker/src/main/java/org/checkerframework/checker/initialization/InitializationStore.java

@@ -158,7 +158,9 @@ protected boolean isDeclaredInitialized(FieldAccess fieldAccess) {
         InitializationParentAnnotatedTypeFactory atypeFactory =
                 (InitializationParentAnnotatedTypeFactory) analysis.getTypeFactory();
         AnnotatedTypeMirror receiverType;
-        if (thisValue != null && thisValue.getUnderlyingType().getKind() != TypeKind.ERROR) {
+        if (thisValue != null
+                && thisValue.getUnderlyingType().getKind() != TypeKind.ERROR
+                && thisValue.getUnderlyingType().getKind() != TypeKind.NULL) {
             receiverType =
                     AnnotatedTypeMirror.createType(
                             thisValue.getUnderlyingType(), atypeFactory, false);

checker/tests/nullness-initialization/EisopIssue635.java

@@ -0,0 +1,22 @@
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+class EisopIssue635 {
+
+    private @Nullable Runnable r;
+
+    private void f() {
+        // No crash without this assignment first.
+        r = null;
+        r =
+                new Runnable() {
+                    @Override
+                    public void run() {
+                        if (r != this) {
+                            return;
+                        }
+                        // No crash without this call.
+                        f();
+                    }
+                };
+    }
+}

docs/CHANGELOG.md

@@ -7,6 +7,8 @@ Version 3.40.0-eisop3 (November ??, 2023)
 
 **Closed issues:**
 
+eisop#635.
+
 
 Version 3.40.0-eisop2 (November 24, 2023)
 -----------------------------------------