Report a warning for setters with boxed primitive types for primitive properties

RELNOTES=Report a diagnostic for setters with boxed primitive types for primitive properties
PiperOrigin-RevId: 659352853

Author: cushon

value/src/it/functional/src/test/java/com/google/auto/value/AutoValueTest.java

@@ -1626,7 +1626,7 @@ public static Builder builder() {
 
     @AutoValue.Builder
     public interface Builder {
-      Builder setAnInt(Integer x);
+      Builder setAnInt(int x);
 
       Builder setANullableInteger(int x);
 
@@ -1646,12 +1646,6 @@ public void testPrimitiveAndBoxed() {
 
     PrimitiveAndBoxed instance2 = instance1.toBuilder().setANullableInteger(5).build();
     assertThat(instance2.aNullableInteger()).isEqualTo(5);
-
-    try {
-      instance1.toBuilder().setAnInt(null);
-      fail();
-    } catch (NullPointerException expected) {
-    }
   }
 
   @AutoValue

value/src/main/java/com/google/auto/value/processor/BuilderMethodClassifier.java

@@ -485,6 +485,16 @@ private Optional<Copier> getSetterFunction(E propertyElement, ExecutableElement
           return Optional.empty();
         }
       }
+      if (!parameterElement.asType().getKind().isPrimitive()
+          && originalPropertyType(propertyElement).getKind().isPrimitive()) {
+        errorReporter
+            .reportWarning(
+            setter,
+            "[%sUnnecessaryBoxing] %s is primitive but parameter of setter method is not",
+            autoWhat(),
+            propertyString(propertyElement));
+        return Optional.empty();
+      }
       return Optional.of(Copier.IDENTITY);
     }
 

value/src/test/java/com/google/auto/value/processor/AutoValueCompilationTest.java

@@ -4008,6 +4008,36 @@ public void kotlinMetadataAnnotationsAreImplicitlyExcludedFromCopying() {
         .doesNotContain("kotlin.Metadata");
   }
 
+  @Test
+  public void autoValueBuilderNullableSetterPrimitiveGetter() {
+    JavaFileObject javaFileObject =
+        JavaFileObjects.forSourceLines(
+            "foo.bar.Baz",
+            "package foo.bar;",
+            "",
+            "import com.google.auto.value.AutoValue;",
+            "",
+            "@AutoValue",
+            "public abstract class Baz {",
+            "  abstract int blam();",
+            "",
+            "  @AutoValue.Builder",
+            "  public interface Builder {",
+            "    Builder blam(Integer x);",
+            "    Baz build();",
+            "  }",
+            "}");
+    Compilation compilation =
+        javac()
+            .withProcessors(new AutoValueProcessor(), new AutoValueBuilderProcessor())
+            .compile(javaFileObject);
+    assertThat(compilation)
+        .hadWarningContaining(
+            "property method foo.bar.Baz.blam() is primitive but parameter of setter method is not")
+        .inFile(javaFileObject)
+        .onLineContaining("Builder blam(Integer x)");
+  }
+
   private static String sorted(String... imports) {
     return stream(imports).sorted().collect(joining("\n"));
   }