Introduce a NullSpecTypeValidator to ensure unspecified type variables are ok

src/main/java/com/google/jspecify/nullness/NullSpecAnnotatedTypeFactory.java

@@ -145,6 +145,7 @@ final class NullSpecAnnotatedTypeFactory
       new TypeUseLocation[] {
         TypeUseLocation.CONSTRUCTOR_RESULT,
         TypeUseLocation.EXCEPTION_PARAMETER,
+        TypeUseLocation.IMPLICIT_LOWER_BOUND,
         TypeUseLocation.RECEIVER,
       };
 
@@ -157,10 +158,6 @@ final class NullSpecAnnotatedTypeFactory
 
   private static final TypeUseLocation[] defaultLocationsUnspecified =
       new TypeUseLocation[] {
-        // Lower bounds could be MinusNull, but all uses in unmarked code would become unspecified
-        // anyways.
-        // Revisit once https://github.com/eisop/checker-framework/issues/741 is fixed.
-        TypeUseLocation.IMPLICIT_LOWER_BOUND,
         TypeUseLocation.IMPLICIT_WILDCARD_UPPER_BOUND_NO_SUPER,
         TypeUseLocation.TYPE_VARIABLE_USE,
         TypeUseLocation.OTHERWISE

src/main/java/com/google/jspecify/nullness/NullSpecTypeValidator.java

@@ -0,0 +1,45 @@
+// Copyright 2020 The JSpecify 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.jspecify.nullness;
+
+import javax.lang.model.element.AnnotationMirror;
+import org.checkerframework.common.basetype.BaseTypeChecker;
+import org.checkerframework.common.basetype.BaseTypeValidator;
+import org.checkerframework.framework.type.AnnotatedTypeMirror;
+
+final class NullSpecTypeValidator extends BaseTypeValidator {
+  private final AnnotationMirror nullnessOperatorUnspecified;
+
+  /** Constructor. */
+  NullSpecTypeValidator(
+      BaseTypeChecker checker,
+      NullSpecVisitor visitor,
+      NullSpecAnnotatedTypeFactory atypeFactory,
+      Util util) {
+    super(checker, visitor, atypeFactory);
+
+    nullnessOperatorUnspecified = util.nullnessOperatorUnspecified;
+  }
+
+  @Override
+  public boolean areBoundsValid(AnnotatedTypeMirror upperBound, AnnotatedTypeMirror lowerBound) {
+    if (upperBound.hasAnnotation(nullnessOperatorUnspecified)
+        || lowerBound.hasAnnotation(nullnessOperatorUnspecified)) {
+      return true;
+    } else {
+      return super.areBoundsValid(upperBound, lowerBound);
+    }
+  }
+}

src/main/java/com/google/jspecify/nullness/NullSpecVisitor.java

@@ -71,6 +71,7 @@
 import javax.lang.model.type.DeclaredType;
 import javax.lang.model.type.TypeMirror;
 import org.checkerframework.common.basetype.BaseTypeVisitor;
+import org.checkerframework.common.basetype.TypeValidator;
 import org.checkerframework.framework.type.AnnotatedTypeMirror;
 import org.checkerframework.framework.type.AnnotatedTypeMirror.AnnotatedDeclaredType;
 import org.checkerframework.framework.type.AnnotatedTypeMirror.AnnotatedExecutableType;
@@ -637,4 +638,9 @@ protected NullSpecAnnotatedTypeFactory createTypeFactory() {
     // Reading util this way is ugly but necessary. See discussion in NullSpecChecker.
     return new NullSpecAnnotatedTypeFactory(checker, ((NullSpecChecker) checker).util);
   }
+
+  @Override
+  protected TypeValidator createTypeValidator() {
+    return new NullSpecTypeValidator(checker, this, atypeFactory, ((NullSpecChecker) checker).util);
+  }
 }

src/test/java/tests/NullSpecTest.java

@@ -54,6 +54,18 @@ public static String[] getTestDirs() {
     }
   }
 
+  /** A small set of strict regression tests. */
+  public static class RegressionStrict extends NullSpecTest {
+    public RegressionStrict(List<File> testFiles) {
+      super(testFiles, true);
+    }
+
+    @Parameters
+    public static String[] getTestDirs() {
+      return new String[] {"regression-strict"};
+    }
+  }
+
   /** A test that ignores cases where there is limited nullness information. */
   public static class Lenient extends NullSpecTest {
     public Lenient(List<File> testFiles) {

tests/ConformanceTest-report.txt

@@ -1,4 +1,4 @@
-# 90 pass; 24 fail; 114 total; 78.9% score
+# 93 pass; 24 fail; 117 total; 79.5% score
 PASS: Basic.java:28:test:expression-type:Object?:nullable
 PASS: Basic.java:28:test:sink-type:Object!:return
 PASS: Basic.java:28:test:cannot-convert:Object? to Object!
@@ -44,6 +44,7 @@ PASS: irrelevantannotations/notnullmarked/Other.java:Nullable local variable arr
 PASS: irrelevantannotations/notnullmarked/Other.java:NonNull local variable array:test:irrelevant-annotation:NonNull
 PASS: irrelevantannotations/notnullmarked/Other.java:Nullable exception parameter:test:irrelevant-annotation:Nullable
 PASS: irrelevantannotations/notnullmarked/Other.java:NonNull exception parameter:test:irrelevant-annotation:NonNull
+PASS: irrelevantannotations/notnullmarked/Other.java:Intrinsically NonNull exception parameter cannot be assigned null:test:cannot-convert:null? to RuntimeException!
 PASS: irrelevantannotations/notnullmarked/Other.java:Nullable try-with-resources:test:irrelevant-annotation:Nullable
 FAIL: irrelevantannotations/notnullmarked/Other.java:NonNull try-with-resources:test:irrelevant-annotation:NonNull
 FAIL: irrelevantannotations/notnullmarked/Other.java:Nullable exception type:test:irrelevant-annotation:Nullable
@@ -75,6 +76,7 @@ PASS: irrelevantannotations/nullmarked/Other.java:Nullable local variable array:
 PASS: irrelevantannotations/nullmarked/Other.java:NonNull local variable array:test:irrelevant-annotation:NonNull
 PASS: irrelevantannotations/nullmarked/Other.java:Nullable exception parameter:test:irrelevant-annotation:Nullable
 PASS: irrelevantannotations/nullmarked/Other.java:NonNull exception parameter:test:irrelevant-annotation:NonNull
+PASS: irrelevantannotations/nullmarked/Other.java:Intrinsically NonNull exception parameter cannot be assigned null:test:cannot-convert:null? to RuntimeException!
 PASS: irrelevantannotations/nullmarked/Other.java:Nullable try-with-resources:test:irrelevant-annotation:Nullable
 FAIL: irrelevantannotations/nullmarked/Other.java:NonNull try-with-resources:test:irrelevant-annotation:NonNull
 FAIL: irrelevantannotations/nullmarked/Other.java:Nullable exception type:test:irrelevant-annotation:Nullable
@@ -107,6 +109,7 @@ PASS: irrelevantannotations/nullunmarked/Other.java:Nullable local variable arra
 PASS: irrelevantannotations/nullunmarked/Other.java:NonNull local variable array:test:irrelevant-annotation:NonNull
 PASS: irrelevantannotations/nullunmarked/Other.java:Nullable exception parameter:test:irrelevant-annotation:Nullable
 PASS: irrelevantannotations/nullunmarked/Other.java:NonNull exception parameter:test:irrelevant-annotation:NonNull
+PASS: irrelevantannotations/nullunmarked/Other.java:Intrinsically NonNull exception parameter cannot be assigned null:test:cannot-convert:null? to RuntimeException!
 PASS: irrelevantannotations/nullunmarked/Other.java:Nullable try-with-resources:test:irrelevant-annotation:Nullable
 FAIL: irrelevantannotations/nullunmarked/Other.java:NonNull try-with-resources:test:irrelevant-annotation:NonNull
 FAIL: irrelevantannotations/nullunmarked/Other.java:Nullable exception type:test:irrelevant-annotation:Nullable

tests/regression-strict/Issue177.java

@@ -0,0 +1,18 @@
+// Copyright 2024 The JSpecify 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.
+
+// Test case for Issue 177:
+// https://github.com/jspecify/jspecify-reference-checker/issues/177
+
+class Issue177<T> {}

tests/regression/Issue172.java

@@ -21,6 +21,10 @@ class Issue172<E> {
   E e() {
     return null;
   }
+
+  void p(E p) {
+    p = null;
+  }
 }
 
 class Issue172UnmarkedUse {