Require types to be the same in PatternMatchingInstanceOf

Accepting subtypes can result in e.g. different overloads being selected.

Fixes #4921

PiperOrigin-RevId: 741195433

Author: cushon

core/src/main/java/com/google/errorprone/bugpatterns/PatternMatchingInstanceof.java

@@ -142,9 +142,11 @@ public Description matchInstanceOf(InstanceOfTree instanceOfTree, VisitorState s
     if (!variableTree.getInitializer().equals(treePath.getLeaf())) {
       return null;
     }
+    // Check that the type is exactly the same (not a subtypes), since refactoring cases where the
+    // instanceof type is a supertype of the cast type could affect overload resolution.
     if (!state
         .getTypes()
-        .isSubtype(getType(instanceOfTree.getType()), getType(variableTree.getType()))) {
+        .isSameType(getType(instanceOfTree.getType()), getType(variableTree.getType()))) {
       return null;
     }
     return variableTree;
@@ -243,7 +245,7 @@ private static ImmutableSet<TreePath> findAllCasts(
           public Void visitTypeCast(TypeCastTree node, Void unused) {
             if (getSymbol(node.getExpression()) instanceof VarSymbol v) {
               if (v.equals(symbol)
-                  && state.getTypes().isSubtype(targetType, getType(node.getType()))) {
+                  && state.getTypes().isSameType(getType(node.getType()), targetType)) {
                 usages.add(getUsage(getCurrentPath()));
               }
             }

core/src/test/java/com/google/errorprone/bugpatterns/PatternMatchingInstanceofTest.java

@@ -719,20 +719,7 @@ public Class stringify(Object o) {
               }
             }
             """)
-        .addOutputLines(
-            "Test.java",
-            """
-            class Test<T> {
-              private String val;
-
-              public Class stringify(Object o) {
-                if (o instanceof Class<?> c) {
-                  return c;
-                }
-                return null;
-              }
-            }
-            """)
+        .expectUnchanged()
         .doTest(BugCheckerRefactoringTestHelper.TestMode.TEXT_MATCH);
   }
 
@@ -830,4 +817,76 @@ boolean test_if() {
             """)
         .doTest(BugCheckerRefactoringTestHelper.TestMode.TEXT_MATCH);
   }
+
+  // https://github.com/google/error-prone/issues/4921
+  @Test
+  public void castToSupertypeOfInstanceofCheck_noFinding() {
+    assume().that(Runtime.version().feature()).isAtLeast(21);
+    helper
+        .addInputLines(
+            "Test.java",
+            """
+            import java.nio.file.Path;
+            import java.util.ArrayList;
+
+            public class Test {
+              void superinterface() {
+                Object o = Path.of(".");
+                if (o instanceof Path) {
+                  f((Iterable<?>) o);
+                }
+              }
+
+              void f(Comparable<?> c) {}
+
+              void f(Iterable<?> c) {}
+
+              void f(Path p) {}
+
+              void rawtypes() {
+                Object o = new ArrayList<Integer>();
+                if (o instanceof ArrayList<?>) {
+                  @SuppressWarnings("rawtypes")
+                  ArrayList list = (ArrayList) o;
+                  rawTypeNecessary(list);
+                }
+              }
+
+              void rawTypeNecessary(ArrayList<Integer> l) {}
+            }
+            """)
+        .addOutputLines(
+            "Test.java",
+            """
+            import java.nio.file.Path;
+            import java.util.ArrayList;
+
+            public class Test {
+              void superinterface() {
+                Object o = Path.of(".");
+                if (o instanceof Path) {
+                  f((Iterable<?>) o);
+                }
+              }
+
+              void f(Comparable<?> c) {}
+
+              void f(Iterable<?> c) {}
+
+              void f(Path p) {}
+
+              void rawtypes() {
+                Object o = new ArrayList<Integer>();
+                if (o instanceof ArrayList<?>) {
+                  @SuppressWarnings("rawtypes")
+                  ArrayList list = (ArrayList) o;
+                  rawTypeNecessary(list);
+                }
+              }
+
+              void rawTypeNecessary(ArrayList<Integer> l) {}
+            }
+            """)
+        .doTest(BugCheckerRefactoringTestHelper.TestMode.TEXT_MATCH);
+  }
 }