Support void placeholder expressions in Refaster

PiperOrigin-RevId: 450510643

core/src/main/java/com/google/errorprone/refaster/Template.java

@@ -37,6 +37,7 @@
 import com.sun.tools.javac.code.Type;
 import com.sun.tools.javac.code.Type.ForAll;
 import com.sun.tools.javac.code.Type.MethodType;
+import com.sun.tools.javac.code.TypeTag;
 import com.sun.tools.javac.code.Types;
 import com.sun.tools.javac.comp.Attr;
 import com.sun.tools.javac.comp.AttrContext;
@@ -139,7 +140,14 @@ protected List<Type> expectedTypes(Inliner inliner) throws CouldNotResolveImport
         Ordering.natural()
             .immutableSortedCopy(
                 Iterables.filter(inliner.bindings.keySet(), PlaceholderExpressionKey.class))) {
-      result.add(key.method.returnType().inline(inliner));
+      Type type = key.method.returnType().inline(inliner);
+      // Skip void placeholder expressions, because
+      // a) if the expected type is void, any actual type is acceptable
+      // b) these types are used as the argument types in a synthetic MethodType, and method
+      //    argument types cannot be void
+      if (!type.getTag().equals(TypeTag.VOID)) {
+        result.add(type);
+      }
     }
     return List.from(result);
   }
@@ -149,7 +157,7 @@ protected List<Type> expectedTypes(Inliner inliner) throws CouldNotResolveImport
    * bound to the @BeforeTemplate method parameters, concatenated with the types of the expressions
    * bound to expression placeholders, sorted by the name of the placeholder method.
    */
-  protected List<Type> actualTypes(Inliner inliner) {
+  protected List<Type> actualTypes(Inliner inliner) throws CouldNotResolveImportException {
     ArrayList<Type> result = new ArrayList<>();
     ImmutableList<String> argNames = expressionArgumentTypes().keySet().asList();
     for (int i = 0; i < expressionArgumentTypes().size(); i++) {
@@ -177,7 +185,11 @@ protected List<Type> actualTypes(Inliner inliner) {
         Ordering.natural()
             .immutableSortedCopy(
                 Iterables.filter(inliner.bindings.keySet(), PlaceholderExpressionKey.class))) {
-      result.add(inliner.getBinding(key).type);
+      Type keyType = key.method.returnType().inline(inliner);
+      // See comment in `expectedTypes` for why we skip void placeholder keys.
+      if (!keyType.getTag().equals(TypeTag.VOID)) {
+        result.add(inliner.getBinding(key).type);
+      }
     }
     return List.from(result);
   }

core/src/main/java/com/google/errorprone/refaster/UPlaceholderExpression.java

@@ -147,7 +147,7 @@ public boolean reverify(Unifier unifier) {
   @Override
   protected Choice<Unifier> defaultAction(Tree node, Unifier unifier) {
     // for now we only match JCExpressions
-    if (placeholder().returnType().equals(UPrimitiveType.VOID) || !(node instanceof JCExpression)) {
+    if (!(node instanceof JCExpression)) {
       return Choice.none();
     }
     JCExpression expr = (JCExpression) node;

core/src/test/java/com/google/errorprone/refaster/TemplateIntegrationTest.java

@@ -234,6 +234,11 @@ public void expressionPlaceholderAllowsIdentity() throws IOException {
     runTest("PlaceholderAllowsIdentityTemplate");
   }
 
+  @Test
+  public void voidExpressionPlaceholder() throws IOException {
+    runTest("VoidExpressionPlaceholderTemplate");
+  }
+
   @Test
   public void blockPlaceholder() throws IOException {
     runTest("BlockPlaceholderTemplate");

core/src/test/java/com/google/errorprone/refaster/testdata/input/VoidExpressionPlaceholderTemplateExample.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2022 The Error Prone Authors.
+ *
+ * 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
+ *
+ *   http://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 com.google.errorprone.refaster.testdata;
+
+import java.util.List;
+
+/** Test data for {@code VoidExpressionPlaceholderTemplate}. */
+public class VoidExpressionPlaceholderTemplateExample {
+  public static void foo(String s) {
+    s.length();
+  }
+
+  public void positiveExample(List<String> list) {
+    list.stream().forEach(x -> foo(x));
+  }
+}

core/src/test/java/com/google/errorprone/refaster/testdata/output/VoidExpressionPlaceholderTemplateExample.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2022 The Error Prone Authors.
+ *
+ * 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
+ *
+ *   http://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 com.google.errorprone.refaster.testdata;
+
+import java.util.List;
+
+/** Test data for {@code VoidExpressionPlaceholderTemplate}. */
+public class VoidExpressionPlaceholderTemplateExample {
+  public static void foo(String s) {
+    s.length();
+  }
+
+  public void positiveExample(List<String> list) {
+    list.forEach(x->foo(x));
+  }
+}

core/src/test/java/com/google/errorprone/refaster/testdata/template/VoidExpressionPlaceholderTemplate.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2022 The Error Prone Authors.
+ *
+ * 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
+ *
+ *   http://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 com.google.errorprone.refaster.testdata.template;
+
+import com.google.errorprone.refaster.annotation.AfterTemplate;
+import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import com.google.errorprone.refaster.annotation.Placeholder;
+import java.util.Collection;
+
+/** Test case with a void placeholder method that is used as an expression. */
+public abstract class VoidExpressionPlaceholderTemplate<T> {
+  @Placeholder
+  abstract void consume(T t);
+
+  @BeforeTemplate
+  void before(Collection<T> collection) {
+    collection.stream().forEach(x -> consume(x));
+  }
+
+  @AfterTemplate
+  void after(Collection<T> collection) {
+    collection.forEach(x -> consume(x));
+  }
+}