[J2KT] Add LambdaParameterTypeInference readable to prevent regress…

…ion in case unnecessary projection casts are inserted around lambdas.

PiperOrigin-RevId: 702685974

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

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2024 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.Nullable;
+
+@Nullable
+public class LambdaParameterTypeInference {
+  public interface Supplier<T extends @Nullable Object> {
+    T get();
+  }
+
+  public interface Consumer<T extends @Nullable Object> {
+    void accept(T t);
+  }
+
+  public static <T extends @Nullable Object> Consumer<T> wrap(Consumer<T> consumer) {
+    throw new RuntimeException();
+  }
+
+  public static <T extends @Nullable Object> void add(
+      Supplier<T> supplier, Consumer<? super T> consumer) {
+    throw new RuntimeException();
+  }
+
+  // J2KT inserts nullability- and generic- related casts in case of type mismatch, using
+  // projections if necessary, which can potentially affect type inference in lambdas. This test
+  // covers a case which would cause [CANNOT_INFER_PARAMETER_TYPE] compilation error in Kotlin if
+  // unnecessary cast was inserted for "wrap()" call.
+  public static <T extends @Nullable Object> void test(Supplier<? extends T> supplier) {
+    add(supplier, wrap(x -> {}));
+  }
+}

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

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+// Generated by J2KT from "j2kt/LambdaParameterTypeInference.java"
+
+#import <Foundation/NSObjCRuntime.h>
+
+@class J2ktJ2ktLambdaParameterTypeInference;
+@class J2ktJ2ktLambdaParameterTypeInferenceCompanion;
+
+@protocol J2ktJ2ktLambdaParameterTypeInference_Consumer;
+@protocol J2ktJ2ktLambdaParameterTypeInference_Supplier;
+
+NS_ASSUME_NONNULL_BEGIN
+
+@compatibility_alias J2ktLambdaParameterTypeInference J2ktJ2ktLambdaParameterTypeInference;
+
+@compatibility_alias J2ktLambdaParameterTypeInferenceCompanion J2ktJ2ktLambdaParameterTypeInferenceCompanion;
+
+NS_INLINE id<J2ktJ2ktLambdaParameterTypeInference_Consumer> _Nullable J2ktLambdaParameterTypeInference_wrapWithJ2ktLambdaParameterTypeInference_Consumer_(id<J2ktJ2ktLambdaParameterTypeInference_Consumer> _Nullable consumer) {
+ return [J2ktJ2ktLambdaParameterTypeInferenceCompanion.shared wrapWithJ2ktLambdaParameterTypeInference_Consumer:consumer];
+}
+
+NS_INLINE void J2ktLambdaParameterTypeInference_addWithJ2ktLambdaParameterTypeInference_Supplier_withJ2ktLambdaParameterTypeInference_Consumer_(id<J2ktJ2ktLambdaParameterTypeInference_Supplier> _Nullable supplier, id<J2ktJ2ktLambdaParameterTypeInference_Consumer> _Nullable consumer) {
+ [J2ktJ2ktLambdaParameterTypeInferenceCompanion.shared addWithJ2ktLambdaParameterTypeInference_Supplier:supplier withJ2ktLambdaParameterTypeInference_Consumer:consumer];
+}
+
+NS_INLINE void J2ktLambdaParameterTypeInference_testWithJ2ktLambdaParameterTypeInference_Supplier_(id<J2ktJ2ktLambdaParameterTypeInference_Supplier> _Nullable supplier) {
+ [J2ktJ2ktLambdaParameterTypeInferenceCompanion.shared testWithJ2ktLambdaParameterTypeInference_Supplier:supplier];
+}
+
+#define J2ktLambdaParameterTypeInference_Supplier J2ktJ2ktLambdaParameterTypeInference_Supplier
+
+#define J2ktLambdaParameterTypeInference_Consumer J2ktJ2ktLambdaParameterTypeInference_Consumer
+
+NS_ASSUME_NONNULL_END

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

@@ -0,0 +1,73 @@
+// Generated from "j2kt/LambdaParameterTypeInference.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 java.lang.RuntimeException
+import kotlin.OptIn
+import kotlin.Suppress
+import kotlin.experimental.ExperimentalObjCName
+import kotlin.jvm.JvmStatic
+import kotlin.native.ObjCName
+
+@ObjCName("J2ktJ2ktLambdaParameterTypeInference", exact = true)
+open class LambdaParameterTypeInference {
+ @ObjCName("J2ktJ2ktLambdaParameterTypeInferenceCompanion", exact = true)
+ companion object {
+  @JvmStatic
+  @ObjCName("wrap")
+  fun <T> wrap(
+   @ObjCName("withJ2ktLambdaParameterTypeInference_Consumer") consumer: LambdaParameterTypeInference.Consumer<T>?
+  ): LambdaParameterTypeInference.Consumer<T>? {
+   throw RuntimeException()
+  }
+
+  @JvmStatic
+  @ObjCName("add")
+  fun <T> add(
+   @ObjCName("withJ2ktLambdaParameterTypeInference_Supplier") supplier: LambdaParameterTypeInference.Supplier<T>?,
+   @ObjCName("withJ2ktLambdaParameterTypeInference_Consumer") consumer: LambdaParameterTypeInference.Consumer<in T>?
+  ) {
+   throw RuntimeException()
+  }
+
+  @JvmStatic
+  @ObjCName("test")
+  fun <T> test(
+   @ObjCName("withJ2ktLambdaParameterTypeInference_Supplier") supplier: LambdaParameterTypeInference.Supplier<out T>?
+  ) {
+   LambdaParameterTypeInference.add(supplier, LambdaParameterTypeInference.wrap(LambdaParameterTypeInference.Consumer { x /* capture#1-of out T */ ->
+   }))
+  }
+ }
+
+ @ObjCName("J2ktJ2ktLambdaParameterTypeInference_Supplier", exact = true)
+ fun interface Supplier<T> {
+  @ObjCName("get")
+  fun get(): T
+ }
+
+ @ObjCName("J2ktJ2ktLambdaParameterTypeInference_Consumer", exact = true)
+ fun interface Consumer<T> {
+  @ObjCName("accept")
+  fun accept(
+   @ObjCName("withId") t: T
+  )
+ }
+}