fix error message printing

Author: msridhar

nullaway/src/main/java/com/uber/nullaway/generics/GenericTypePrettyPrintingVisitor.java

@@ -89,6 +89,13 @@ public String visitArrayType(Type.ArrayType t, @Nullable Void unused) {
     return sb.append(" []").toString();
   }
 
+  @Override
+  public String visitErrorType(Type.ErrorType t, @Nullable Void unused) {
+    // this arises for our synthetic @Nullable and @NonNull annotations; we just return the simple
+    // name
+    return t.tsym.getSimpleName().toString();
+  }
+
   @Override
   public String visitType(Type t, @Nullable Void s) {
     return t.toString();

nullaway/src/test/java/com/uber/nullaway/jspecify/GenericMethodTests.java

@@ -425,7 +425,7 @@ abstract class TestCase {
                 static class Bar<T extends @Nullable Object> {}
                 abstract <U> Bar<U> make(Bar<U> other);
                 void test(Bar<Bar<String>> other) {
-                    // BUG: Diagnostic contains: incompatible types: Bar<Bar<String>> cannot be converted to Bar<Bar<@Nullable String>>
+                    // BUG: Diagnostic contains: incompatible types: Bar<@NonNull Bar<String>> cannot be converted to Bar<Bar<@Nullable String>>
                     Bar<Bar<@Nullable String>> unused = make(other);
                 }
             }