[J2KT] Add readable to cover another case of nullability inference pr…

…oblem, which we don't want to regress.

PiperOrigin-RevId: 728639938

transpiler/javatests/com/google/j2cl/readable/java/j2kt/NullabilityInferenceProblem6.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2025 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package j2kt;
+
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+@NullMarked
+public class NullabilityInferenceProblem6 {
+  interface Consumer<V extends @Nullable Object> {
+    void accept(V v);
+  }
+
+  interface Container<V extends @Nullable Object> {
+    void forEach(Consumer<V> consumer);
+
+    void add(V v);
+  }
+
+  interface Foo {}
+
+  interface FooConsumer<V extends @Nullable Foo> {
+    void accept(V v);
+  }
+
+  interface FooContainer<V extends @Nullable Foo> {
+    void forEach(Consumer<V> consumer);
+
+    void add(V v);
+  }
+
+  static void testLambda(Container<?> from, Container<? super @Nullable Object> to) {
+    // The type of "it" parameter is incorrectly inferred as capture of non-null Object in the AST.
+    from.forEach(it -> to.add(it));
+  }
+
+  static void testMethodReference(Container<?> from, Container<? super @Nullable Object> to) {
+    // The type of "it" parameter is incorrectly inferred as capture of non-null Object in the AST.
+    from.forEach(to::add);
+  }
+
+  static void testLambda(FooContainer<?> from, FooContainer<? super @Nullable Foo> to) {
+    // The type of "it" parameter is correctly inferred as capture of nullable Foo in the AST.
+    from.forEach(it -> to.add(it));
+  }
+
+  static void testMethodReference(FooContainer<?> from, FooContainer<? super @Nullable Foo> to) {
+    // The type of "it" parameter is correctly inferred as capture of nullable Foo in the AST.
+    from.forEach(to::add);
+  }
+}

transpiler/javatests/com/google/j2cl/readable/java/j2kt/output_kt/NullabilityInferenceProblem6+J2ObjCCompat.h.txt

@@ -0,0 +1,14 @@
+// Generated by J2KT from "j2kt/NullabilityInferenceProblem6.java"
+
+#import <Foundation/NSObjCRuntime.h>
+
+@class J2ktJ2ktNullabilityInferenceProblem6;
+@class J2ktJ2ktNullabilityInferenceProblem6Companion;
+
+NS_ASSUME_NONNULL_BEGIN
+
+@compatibility_alias J2ktNullabilityInferenceProblem6 J2ktJ2ktNullabilityInferenceProblem6;
+
+@compatibility_alias J2ktNullabilityInferenceProblem6Companion J2ktJ2ktNullabilityInferenceProblem6Companion;
+
+NS_ASSUME_NONNULL_END

transpiler/javatests/com/google/j2cl/readable/java/j2kt/output_kt/NullabilityInferenceProblem6.kt.txt

@@ -0,0 +1,114 @@
+// Generated from "j2kt/NullabilityInferenceProblem6.java"
+@file:OptIn(ExperimentalObjCName::class)
+@file:Suppress(
+ "ALWAYS_NULL",
+ "PARAMETER_NAME_CHANGED_ON_OVERRIDE",
+ "SENSELESS_COMPARISON",
+ "UNCHECKED_CAST",
+ "UNNECESSARY_LATEINIT",
+ "UNNECESSARY_NOT_NULL_ASSERTION",
+ "UNREACHABLE_CODE",
+ "UNUSED_ANONYMOUS_PARAMETER",
+ "UNUSED_PARAMETER",
+ "UNUSED_VARIABLE",
+ "USELESS_CAST",
+ "VARIABLE_IN_SINGLETON_WITHOUT_THREAD_LOCAL",
+ "VARIABLE_WITH_REDUNDANT_INITIALIZER",
+ "REDUNDANT_ELSE_IN_WHEN")
+
+package j2kt
+
+import javaemul.lang.*
+import kotlin.Any
+import kotlin.OptIn
+import kotlin.Suppress
+import kotlin.experimental.ExperimentalObjCName
+import kotlin.jvm.JvmStatic
+import kotlin.native.ObjCName
+
+@ObjCName("J2ktJ2ktNullabilityInferenceProblem6", exact = true)
+open class NullabilityInferenceProblem6 {
+ @ObjCName("J2ktJ2ktNullabilityInferenceProblem6Companion", exact = true)
+ companion object {
+  @JvmStatic
+  internal fun testLambda_pp_j2kt(from: NullabilityInferenceProblem6.Container<*>, to: NullabilityInferenceProblem6.Container<in Any?>) {
+   (from as NullabilityInferenceProblem6.Container<Any?>).forEach(
+    NullabilityInferenceProblem6.Consumer/* <capture#1-of out Any> */ { it /* capture#1-of out Any */ ->
+     to.add(it)
+    },
+   )
+  }
+
+  @JvmStatic
+  internal fun testMethodReference_pp_j2kt(from: NullabilityInferenceProblem6.Container<*>, to: NullabilityInferenceProblem6.Container<in Any?>) {
+   (from as NullabilityInferenceProblem6.Container<Any?>).forEach(
+    NullabilityInferenceProblem6.Consumer/* <capture#2-of out Any> */ { arg0 /* capture#2-of out Any */ ->
+     to.add(arg0)
+    },
+   )
+  }
+
+  @JvmStatic
+  internal fun testLambda_pp_j2kt(from: NullabilityInferenceProblem6.FooContainer<*>, to: NullabilityInferenceProblem6.FooContainer<in NullabilityInferenceProblem6.Foo?>) {
+   (from as NullabilityInferenceProblem6.FooContainer<NullabilityInferenceProblem6.Foo?>).forEach(
+    NullabilityInferenceProblem6.Consumer/* <capture#3-of out NullabilityInferenceProblem6.Foo?> */ { it /* capture#3-of out NullabilityInferenceProblem6.Foo? */ ->
+     to.add(it)
+    },
+   )
+  }
+
+  @JvmStatic
+  internal fun testMethodReference_pp_j2kt(from: NullabilityInferenceProblem6.FooContainer<*>, to: NullabilityInferenceProblem6.FooContainer<in NullabilityInferenceProblem6.Foo?>) {
+   (from as NullabilityInferenceProblem6.FooContainer<NullabilityInferenceProblem6.Foo?>).forEach(
+    NullabilityInferenceProblem6.Consumer/* <capture#4-of out NullabilityInferenceProblem6.Foo?> */ { arg0 /* capture#4-of out NullabilityInferenceProblem6.Foo? */ ->
+     to.add(arg0)
+    },
+   )
+  }
+ }
+
+ @ObjCName("J2ktJ2ktNullabilityInferenceProblem6_Consumer", exact = true)
+ fun interface Consumer<V> {
+  @ObjCName("accept")
+  fun accept(
+   @ObjCName("withId") v: V
+  )
+ }
+
+ @ObjCName("J2ktJ2ktNullabilityInferenceProblem6_Container", exact = true)
+ interface Container<V> {
+  @ObjCName("forEach")
+  fun forEach(
+   @ObjCName("withJ2ktNullabilityInferenceProblem6_Consumer") consumer: NullabilityInferenceProblem6.Consumer<V>
+  )
+
+  @ObjCName("add")
+  fun add(
+   @ObjCName("withId") v: V
+  )
+ }
+
+ @ObjCName("J2ktJ2ktNullabilityInferenceProblem6_Foo", exact = true)
+ interface Foo
+
+ @ObjCName("J2ktJ2ktNullabilityInferenceProblem6_FooConsumer", exact = true)
+ fun interface FooConsumer<V: NullabilityInferenceProblem6.Foo?> {
+  @ObjCName("accept")
+  fun accept(
+   @ObjCName("withJ2ktNullabilityInferenceProblem6_Foo") v: V
+  )
+ }
+
+ @ObjCName("J2ktJ2ktNullabilityInferenceProblem6_FooContainer", exact = true)
+ interface FooContainer<V: NullabilityInferenceProblem6.Foo?> {
+  @ObjCName("forEach")
+  fun forEach(
+   @ObjCName("withJ2ktNullabilityInferenceProblem6_Consumer") consumer: NullabilityInferenceProblem6.Consumer<V>
+  )
+
+  @ObjCName("add")
+  fun add(
+   @ObjCName("withJ2ktNullabilityInferenceProblem6_Foo") v: V
+  )
+ }
+}