Recognize Checker Framework declaration annotations.

We are migrating Guava to use these annotations rather than jsr305's
@Nullable. We can't use the Checker Framework's _@Nullable_ yet because
we promise compatibility with Java 7, which doesn't support type
annotations. This is related to but distinct from
https://youtrack.jetbrains.com/issue/KT-21408, which is about a
different jsr305 annotation we use, @ParametersAreNonnullByDefault.

I've also updated some docs to mention Kotlin's existing support for the
Checker Framework _@NonNull_.

compiler/testData/foreignAnnotations/tests/checkerFramework.kt

@@ -0,0 +1,33 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE -UNUSED_PARAMETER
+// FILE: A.java
+
+import org.checkerframework.checker.nullness.compatqual.*;
+
+public class A {
+    @NullableDecl public String field = null;
+
+    @NullableDecl
+    public String foo(@NonNullDecl String x, @NullableDecl CharSequence y) {
+        return "";
+    }
+
+    @NonNullDecl
+    public String bar() {
+        return "";
+    }
+
+}
+
+// FILE: main.kt
+
+fun main(a: A) {
+    a.foo("", null)?.length
+    a.foo("", null)<!UNSAFE_CALL!>.<!>length
+    a.foo(<!NULL_FOR_NONNULL_TYPE!>null<!>, "")<!UNSAFE_CALL!>.<!>length
+
+    a.bar().length
+    a.bar()<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>.length
+
+    a.field?.length
+    a.field<!UNSAFE_CALL!>.<!>length
+}

compiler/testData/foreignAnnotations/tests/checkerFramework.txt

@@ -0,0 +1,13 @@
+package
+
+public fun main(/*0*/ a: A): kotlin.Unit
+
+public open class A {
+    public constructor A()
+    @org.checkerframework.checker.nullness.compatqual.NullableDecl public final var field: kotlin.String?
+    @org.checkerframework.checker.nullness.compatqual.NonNullDecl public open fun bar(): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    @org.checkerframework.checker.nullness.compatqual.NullableDecl public open fun foo(/*0*/ @org.checkerframework.checker.nullness.compatqual.NonNullDecl x: kotlin.String, /*1*/ @org.checkerframework.checker.nullness.compatqual.NullableDecl y: kotlin.CharSequence?): kotlin.String?
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/tests/org/jetbrains/kotlin/checkers/ForeignAnnotationsNoAnnotationInClasspathTestGenerated.java

@@ -48,6 +48,12 @@ public class ForeignAnnotationsNoAnnotationInClasspathTestGenerated extends Abst
         doTest(fileName);
     }
 
+    @TestMetadata("checkerFramework.kt")
+    public void testCheckerFramework() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/foreignAnnotations/tests/checkerFramework.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("eclipse.kt")
     public void testEclipse() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/foreignAnnotations/tests/eclipse.kt");

compiler/tests/org/jetbrains/kotlin/checkers/ForeignAnnotationsNoAnnotationInClasspathWithFastClassReadingTestGenerated.java

@@ -48,6 +48,12 @@ public class ForeignAnnotationsNoAnnotationInClasspathWithFastClassReadingTestGe
         doTest(fileName);
     }
 
+    @TestMetadata("checkerFramework.kt")
+    public void testCheckerFramework() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/foreignAnnotations/tests/checkerFramework.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("eclipse.kt")
     public void testEclipse() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/foreignAnnotations/tests/eclipse.kt");

compiler/tests/org/jetbrains/kotlin/checkers/ForeignAnnotationsTestGenerated.java

@@ -48,6 +48,12 @@ public class ForeignAnnotationsTestGenerated extends AbstractForeignAnnotationsT
         doTest(fileName);
     }
 
+    @TestMetadata("checkerFramework.kt")
+    public void testCheckerFramework() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/foreignAnnotations/tests/checkerFramework.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("eclipse.kt")
     public void testEclipse() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/foreignAnnotations/tests/eclipse.kt");

compiler/tests/org/jetbrains/kotlin/checkers/javac/JavacForeignAnnotationsTestGenerated.java

@@ -48,6 +48,12 @@ public class JavacForeignAnnotationsTestGenerated extends AbstractJavacForeignAn
         doTest(fileName);
     }
 
+    @TestMetadata("checkerFramework.kt")
+    public void testCheckerFramework() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/foreignAnnotations/tests/checkerFramework.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("eclipse.kt")
     public void testEclipse() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/foreignAnnotations/tests/eclipse.kt");

core/descriptors.jvm/src/org/jetbrains/kotlin/load/java/JvmAnnotationNames.kt

@@ -24,6 +24,7 @@ val NULLABLE_ANNOTATIONS = listOf(
         FqName("com.android.annotations.Nullable"),
         FqName("org.eclipse.jdt.annotation.Nullable"),
         FqName("org.checkerframework.checker.nullness.qual.Nullable"),
+        FqName("org.checkerframework.checker.nullness.compatqual.NullableDecl"),
         FqName("javax.annotation.Nullable"),
         FqName("javax.annotation.CheckForNull"),
         FqName("edu.umd.cs.findbugs.annotations.CheckForNull"),
@@ -42,6 +43,7 @@ val NOT_NULL_ANNOTATIONS = listOf(
         FqName("com.android.annotations.NonNull"),
         FqName("org.eclipse.jdt.annotation.NonNull"),
         FqName("org.checkerframework.checker.nullness.qual.NonNull"),
+        FqName("org.checkerframework.checker.nullness.compatqual.NonNullDecl"),
         FqName("lombok.NonNull"),
         FqName("io.reactivex.annotations.NonNull")
 )

spec-docs/flexible-java-types.md

@@ -498,4 +498,8 @@ We can also support the following annotations out-of-the-box:
  * `NotNull` and `NotNull.List`
 * [Project Lombok](http://projectlombok.org/features/NonNull.html)
 * [`org.eclipse.jdt.annotation`](https://wiki.eclipse.org/JDT_Core/Null_Analysis)
-* [`org.checkerframework.checker.nullness.qual`](http://types.cs.washington.edu/checker-framework/current/checker-framework-manual.html#nullness-checker)
+* [`org.checkerframework.checker.nullness`](https://checkerframework.org/manual/#nullness-checker)
+ * [`*.qual.Nullable`](https://checkerframework.org/api/org/checkerframework/checker/nullness/qual/Nullable.html)
+ * [`*.qual.NonNull`](https://checkerframework.org/api/org/checkerframework/checker/nullness/qual/NonNull.html)
+ * [`*.compatqual.NullableDecl`](https://checkerframework.org/api/org/checkerframework/checker/nullness/compatqual/NullableDecl.html)
+ * [`*.compatqual.NonNullDecl`](https://checkerframework.org/api/org/checkerframework/checker/nullness/compatqual/NonNullDecl.html)

third-party/annotations/org/checkerframework/checker/nullness/compatqual/NonNullDecl.java

@@ -0,0 +1,15 @@
+package org.checkerframework.checker.nullness.compatqual;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/**
+ * Java 7 compatibility annotation without dependency on Java 8 classes.
+ *
+ * @see org.checkerframework.checker.nullness.qual.NonNull
+ * @checker_framework.manual #nullness-checker Nullness Checker
+ */
+@Documented
+@Retention(RetentionPolicy.RUNTIME)
+public @interface NonNullDecl {}

third-party/annotations/org/checkerframework/checker/nullness/compatqual/NullableDecl.java

@@ -0,0 +1,15 @@
+package org.checkerframework.checker.nullness.compatqual;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/**
+ * Java 7 compatibility annotation without dependency on Java 8 classes.
+ *
+ * @see org.checkerframework.checker.nullness.qual.Nullable
+ * @checker_framework.manual #nullness-checker Nullness Checker
+ */
+@Documented
+@Retention(RetentionPolicy.RUNTIME)
+public @interface NullableDecl {}