From 3d9aab7c5b9776929da49b32d41cdd9400dd1df1 Mon Sep 17 00:00:00 2001
From: Mohamed Sameh <110535847+mohamedsamehsalah@users.noreply.github.com>
Date: Sun, 11 Aug 2024 15:01:53 +0200
Subject: [PATCH] Introduce `Class{Literal,Reference}Cast` Refaster rules
 (#1269)

---
 .../errorprone/refasterrules/ClassRules.java  | 49 ++++++++++++++++++-
 .../refasterrules/ClassRulesTestInput.java    | 18 +++++--
 .../refasterrules/ClassRulesTestOutput.java   | 18 +++++--
 3 files changed, 73 insertions(+), 12 deletions(-)

diff --git a/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ClassRules.java b/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ClassRules.java
index 2890dd1b9f..496b1f1fcb 100644
--- a/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ClassRules.java
+++ b/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ClassRules.java
@@ -3,6 +3,7 @@
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import java.util.function.Function;
 import java.util.function.Predicate;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
@@ -37,7 +38,12 @@ boolean after(S object) {
     }
   }
 
-  /** Prefer {@link Class#isInstance(Object)} method references over more verbose alternatives. */
+  /**
+   * Prefer {@link Class#isInstance(Object)} method references over lambda expressions that require
+   * naming a variable.
+   */
+  // XXX: Once the `ClassReferenceIsInstancePredicate` rule is dropped, rename this rule to just
+  // `ClassIsInstancePredicate`.
   static final class ClassLiteralIsInstancePredicate<T, S> {
     @BeforeTemplate
     Predicate<S> before() {
@@ -50,7 +56,11 @@ Predicate<S> after() {
     }
   }
 
-  /** Prefer {@link Class#isInstance(Object)} method references over more verbose alternatives. */
+  /**
+   * Prefer {@link Class#isInstance(Object)} method references over lambda expressions that require
+   * naming a variable.
+   */
+  // XXX: Drop this rule once the `MethodReferenceUsage` rule is enabled by default.
   static final class ClassReferenceIsInstancePredicate<T, S> {
     @BeforeTemplate
     Predicate<S> before(Class<T> clazz) {
@@ -62,4 +72,39 @@ Predicate<S> after(Class<T> clazz) {
       return clazz::isInstance;
     }
   }
+
+  /**
+   * Prefer {@link Class#cast(Object)} method references over lambda expressions that require naming
+   * a variable.
+   */
+  // XXX: Once the `ClassReferenceCast` rule is dropped, rename this rule to just `ClassCast`.
+  static final class ClassLiteralCast<T, S> {
+    @BeforeTemplate
+    @SuppressWarnings("unchecked")
+    Function<T, S> before() {
+      return t -> (S) t;
+    }
+
+    @AfterTemplate
+    Function<T, S> after() {
+      return Refaster.<S>clazz()::cast;
+    }
+  }
+
+  /**
+   * Prefer {@link Class#cast(Object)} method references over lambda expressions that require naming
+   * a variable.
+   */
+  // XXX: Drop this rule once the `MethodReferenceUsage` rule is enabled by default.
+  static final class ClassReferenceCast<T, S> {
+    @BeforeTemplate
+    Function<T, S> before(Class<? extends S> clazz) {
+      return o -> clazz.cast(o);
+    }
+
+    @AfterTemplate
+    Function<T, S> after(Class<? extends S> clazz) {
+      return clazz::cast;
+    }
+  }
 }
diff --git a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ClassRulesTestInput.java b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ClassRulesTestInput.java
index 2e94c24213..94f6db36f9 100644
--- a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ClassRulesTestInput.java
+++ b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ClassRulesTestInput.java
@@ -1,26 +1,34 @@
 package tech.picnic.errorprone.refasterrules;
 
 import com.google.common.collect.ImmutableSet;
-import java.io.IOException;
+import java.util.function.Function;
 import java.util.function.Predicate;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
 final class ClassRulesTest implements RefasterRuleCollectionTestCase {
-  boolean testClassIsInstance() throws IOException {
+  boolean testClassIsInstance() {
     return CharSequence.class.isAssignableFrom("foo".getClass());
   }
 
-  ImmutableSet<Boolean> testInstanceof() throws IOException {
+  ImmutableSet<Boolean> testInstanceof() {
     Class<?> clazz = CharSequence.class;
     return ImmutableSet.of(CharSequence.class.isInstance("foo"), clazz.isInstance("bar"));
   }
 
-  Predicate<String> testClassLiteralIsInstancePredicate() throws IOException {
+  Predicate<String> testClassLiteralIsInstancePredicate() {
     return s -> s instanceof CharSequence;
   }
 
-  Predicate<String> testClassReferenceIsInstancePredicate() throws IOException {
+  Predicate<String> testClassReferenceIsInstancePredicate() {
     Class<?> clazz = CharSequence.class;
     return s -> clazz.isInstance(s);
   }
+
+  Function<Number, Integer> testClassLiteralCast() {
+    return i -> (Integer) i;
+  }
+
+  Function<Number, Integer> testClassReferenceCast() {
+    return i -> Integer.class.cast(i);
+  }
 }
diff --git a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ClassRulesTestOutput.java b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ClassRulesTestOutput.java
index 39c08a5068..2c4314157a 100644
--- a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ClassRulesTestOutput.java
+++ b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ClassRulesTestOutput.java
@@ -1,26 +1,34 @@
 package tech.picnic.errorprone.refasterrules;
 
 import com.google.common.collect.ImmutableSet;
-import java.io.IOException;
+import java.util.function.Function;
 import java.util.function.Predicate;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
 final class ClassRulesTest implements RefasterRuleCollectionTestCase {
-  boolean testClassIsInstance() throws IOException {
+  boolean testClassIsInstance() {
     return CharSequence.class.isInstance("foo");
   }
 
-  ImmutableSet<Boolean> testInstanceof() throws IOException {
+  ImmutableSet<Boolean> testInstanceof() {
     Class<?> clazz = CharSequence.class;
     return ImmutableSet.of("foo" instanceof CharSequence, clazz.isInstance("bar"));
   }
 
-  Predicate<String> testClassLiteralIsInstancePredicate() throws IOException {
+  Predicate<String> testClassLiteralIsInstancePredicate() {
     return CharSequence.class::isInstance;
   }
 
-  Predicate<String> testClassReferenceIsInstancePredicate() throws IOException {
+  Predicate<String> testClassReferenceIsInstancePredicate() {
     Class<?> clazz = CharSequence.class;
     return clazz::isInstance;
   }
+
+  Function<Number, Integer> testClassLiteralCast() {
+    return Integer.class::cast;
+  }
+
+  Function<Number, Integer> testClassReferenceCast() {
+    return Integer.class::cast;
+  }
 }