Revert "Resolve regression for type annotations directly on inner typ…

…es. (uber#706)"

This reverts commit c5e1a79.

nullaway/src/main/java/com/uber/nullaway/NullabilityUtil.java

@@ -22,9 +22,6 @@
 
 package com.uber.nullaway;
 
-import static com.sun.tools.javac.code.TypeAnnotationPosition.TypePathEntryKind.ARRAY;
-import static com.sun.tools.javac.code.TypeAnnotationPosition.TypePathEntryKind.INNER_TYPE;
-
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableSet;
 import com.google.errorprone.VisitorState;
@@ -44,7 +41,6 @@
 import com.sun.tools.javac.code.Symbol;
 import com.sun.tools.javac.code.TargetType;
 import com.sun.tools.javac.code.Type;
-import com.sun.tools.javac.code.TypeAnnotationPosition.TypePathEntry;
 import com.sun.tools.javac.code.Types;
 import com.sun.tools.javac.tree.JCTree;
 import com.sun.tools.javac.util.JCDiagnostic;
@@ -296,35 +292,7 @@ private static boolean isDirectTypeUseAnnotation(Attribute.TypeCompound t) {
     // location is a list of TypePathEntry objects, indicating whether the annotation is
     // on an array, inner type, wildcard, or type argument. If it's empty, then the
     // annotation is directly on the type.
-    // We care about both annotations directly on the outer type and also those directly
-    // on an inner type or array dimension, but wish to discard annotations on wildcards,
-    // or type arguments.
-    // For arrays, we treat annotations on the outer type and on any dimension of the array
-    // as applying to the nullability of the array itself, not the elements.
-    // We don't allow mixing of inner types and array dimensions in the same location
-    // (i.e. `Foo.@Nullable Bar []` is meaningless).
-    // These aren't correct semantics for type use annotations, but a series of hacky
-    // compromises to keep some semblance of backwards compatibility until we can do a
-    // proper deprecation of the incorrect behaviors for type use annotations when their
-    // semantics don't match those of a declaration annotation in the same position.
-    // See https://github.com/uber/NullAway/issues/708
-    boolean locationHasInnerTypes = false;
-    boolean locationHasArray = false;
-    for (TypePathEntry entry : t.position.location) {
-      switch (entry.tag) {
-        case INNER_TYPE:
-          locationHasInnerTypes = true;
-          break;
-        case ARRAY:
-          locationHasArray = true;
-          break;
-        default:
-          // Wildcard or type argument!
-          return false;
-      }
-    }
-    // Make sure it's not a mix of inner types and arrays for this annotation's location
-    return !(locationHasInnerTypes && locationHasArray);
+    return t.position.location.isEmpty();
   }
 
   /**

nullaway/src/test/java/com/uber/nullaway/NullAwayCoreTests.java

@@ -960,4 +960,34 @@ public void primitiveCastsRememberNullChecks() {
             "}")
         .doTest();
   }
+
+  @Test
+  public void annotationAppliedToTypeParameter() {
+    defaultCompilationHelper
+        .addSourceLines(
+            "Test.java",
+            "package com.uber;",
+            "import java.util.List;",
+            "import java.util.ArrayList;",
+            "import org.checkerframework.checker.nullness.qual.Nullable;",
+            "class TypeArgumentAnnotation {",
+            "  List<@Nullable String> fSafe = new ArrayList<>();",
+            "  @Nullable List<String> fUnsafe = new ArrayList<>();",
+            "  void useParamSafe(List<@Nullable String> list) {",
+            "    list.hashCode();",
+            "  }",
+            "  void useParamUnsafe(@Nullable List<String> list) {",
+            "    // BUG: Diagnostic contains: dereferenced",
+            "    list.hashCode();",
+            "  }",
+            "  void useFieldSafe() {",
+            "    fSafe.hashCode();",
+            "  }",
+            "  void useFieldUnsafe() {",
+            "    // BUG: Diagnostic contains: dereferenced",
+            "    fUnsafe.hashCode();",
+            "  }",
+            "}")
+        .doTest();
+  }
 }