@ImmutableTypeParameter is really a subset of @ThreadSafeTypeParameter, much as @Immutable is a subset of @ThreadSafe.

PiperOrigin-RevId: 797282844

Author: graememorgan

core/src/main/java/com/google/errorprone/bugpatterns/threadsafety/ThreadSafety.java

@@ -32,6 +32,7 @@
 import com.google.errorprone.VisitorState;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.errorprone.annotations.Immutable;
+import com.google.errorprone.annotations.ImmutableTypeParameter;
 import com.google.errorprone.annotations.ThreadSafe;
 import com.google.errorprone.annotations.ThreadSafeTypeParameter;
 import com.google.errorprone.bugpatterns.CanBeStaticAnalyzer;
@@ -94,7 +95,10 @@ public static ThreadSafety.Builder threadSafeBuilder(
             .knownTypes(wellKnownThreadSafety)
             .markerAnnotations(ImmutableSet.of(ThreadSafe.class.getName()))
             .acceptedAnnotations(ImmutableSet.of(Immutable.class.getName()))
-            .typeParameterAnnotation(ImmutableSet.of(ThreadSafeTypeParameter.class.getName()));
+            .typeParameterAnnotation(
+                ImmutableSet.of(
+                    ThreadSafeTypeParameter.class.getName(),
+                    ImmutableTypeParameter.class.getName()));
     return builder;
   }
 

core/src/test/java/com/google/errorprone/bugpatterns/threadsafety/ThreadSafeCheckerTest.java

@@ -1353,6 +1353,23 @@ class Test<@ThreadSafeTypeParameter T> {
         .doTest();
   }
 
+  @Test
+  public void immutableTypeParam_alsoThreadSafe() {
+    compilationHelper
+        .addSourceLines(
+            "Test.java",
+            """
+            import com.google.errorprone.annotations.ThreadSafe;
+            import com.google.errorprone.annotations.ImmutableTypeParameter;
+
+            @ThreadSafe
+            class Test<@ImmutableTypeParameter T> {
+              final T t = null;
+            }
+            """)
+        .doTest();
+  }
+
   @Test
   public void threadSafeTypeParameterInstantiation() {
     compilationHelper