Fix an NPE when adding a ToPrettyString annotation to an `@AutoValu…

…e` with a generic property

RELNOTES=n/a
PiperOrigin-RevId: 655236646

value/src/main/java/com/google/auto/value/extension/toprettystring/processor/ToPrettyStringExtension.java

@@ -506,6 +506,7 @@ static class KindVisitor extends SimpleTypeVisitor8<PrettyPrintableKind, Void> {
       private final Types types;
 
       KindVisitor(Types types, Elements elements) {
+        super(REGULAR_OBJECT); // default value, covers generic types
         this.types = types;
         this.elements = elements;
       }

value/src/test/java/com/google/auto/value/extension/toprettystring/ToPrettyStringTest.java

@@ -958,4 +958,24 @@ public void javaBeans() {
     assertThat(valueType.toString())
         .isEqualTo("JavaBeans{int=4, boolean=false, notAJavaIdentifier=not}");
   }
+
+  @AutoValue
+  abstract static class Generic<T> {
+    abstract T get();
+
+    @ToPrettyString
+    abstract String toPrettyString();
+  }
+
+  @Test
+  public void generic() {
+    Generic<String> valueType = new AutoValue_ToPrettyStringTest_Generic<>("hello");
+
+    assertThat(valueType.toPrettyString()).isEqualTo("Generic {\n  get = hello,\n}");
+
+    // Check to make sure that we use the same property names that AutoValue does. This is mostly
+    // defensive, since in some scenarios AutoValue considers the property names of a java bean as
+    // having the prefix removed.
+    assertThat(valueType.toString()).isEqualTo("Generic{get=hello}");
+  }
 }