Make ReturnsNullCollection and ProvidesNull use hasDefinitelyNullBranch.

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

@@ -17,15 +17,16 @@
 package com.google.errorprone.bugpatterns;
 
 import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
+import static com.google.errorprone.bugpatterns.nullness.NullnessUtils.hasDefinitelyNullBranch;
 import static com.google.errorprone.matchers.Description.NO_MATCH;
 import static com.google.errorprone.matchers.Matchers.allOf;
 import static com.google.errorprone.matchers.Matchers.anyOf;
 import static com.google.errorprone.matchers.Matchers.isSubtypeOf;
 import static com.google.errorprone.matchers.Matchers.methodReturns;
 import static com.google.errorprone.util.ASTHelpers.findEnclosingMethod;
 import static com.google.errorprone.util.ASTHelpers.getSymbol;
-import static com.sun.source.tree.Tree.Kind.NULL_LITERAL;
 
+import com.google.common.collect.ImmutableSet;
 import com.google.errorprone.BugPattern;
 import com.google.errorprone.VisitorState;
 import com.google.errorprone.bugpatterns.BugChecker.ReturnTreeMatcher;
@@ -62,7 +63,12 @@ private static boolean methodWithoutNullable(MethodTree tree, VisitorState state
 
   @Override
   public final Description matchReturn(ReturnTree tree, VisitorState state) {
-    if (tree.getExpression() == null || tree.getExpression().getKind() != NULL_LITERAL) {
+    if (tree.getExpression() == null
+        || !hasDefinitelyNullBranch(
+            tree.getExpression(),
+            /* definitelyNullVars= */ ImmutableSet.of(),
+            /* varsProvenNullByParentIf= */ ImmutableSet.of(),
+            state)) {
       return NO_MATCH;
     }
     MethodTree methodTree = findEnclosingMethod(state);

core/src/main/java/com/google/errorprone/bugpatterns/inject/dagger/ProvidesNull.java

@@ -17,8 +17,10 @@
 package com.google.errorprone.bugpatterns.inject.dagger;
 
 import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
+import static com.google.errorprone.bugpatterns.nullness.NullnessUtils.hasDefinitelyNullBranch;
 import static com.google.errorprone.util.ASTHelpers.findEnclosingMethod;
 
+import com.google.common.collect.ImmutableSet;
 import com.google.errorprone.BugPattern;
 import com.google.errorprone.VisitorState;
 import com.google.errorprone.bugpatterns.BugChecker;
@@ -31,7 +33,6 @@
 import com.sun.source.tree.ExpressionTree;
 import com.sun.source.tree.MethodTree;
 import com.sun.source.tree.ReturnTree;
-import com.sun.source.tree.Tree.Kind;
 import com.sun.tools.javac.code.Symbol.MethodSymbol;
 
 /**
@@ -53,7 +54,12 @@ public class ProvidesNull extends BugChecker implements ReturnTreeMatcher {
   @Override
   public Description matchReturn(ReturnTree returnTree, VisitorState state) {
     ExpressionTree returnExpression = returnTree.getExpression();
-    if (returnExpression == null || returnExpression.getKind() != Kind.NULL_LITERAL) {
+    if (returnExpression == null
+        || !hasDefinitelyNullBranch(
+            returnExpression,
+            /* definitelyNullVars= */ ImmutableSet.of(),
+            /* varsProvenNullByParentIf= */ ImmutableSet.of(),
+            state)) {
       return Description.NO_MATCH;
     }
 

core/src/main/java/com/google/errorprone/bugpatterns/nullness/NullnessUtils.java

@@ -82,7 +82,7 @@
  *
  * @author awturner@google.com (Andy Turner)
  */
-final class NullnessUtils {
+public final class NullnessUtils {
   private NullnessUtils() {}
 
   private static final Matcher<ExpressionTree> OPTIONAL_OR_NULL =
@@ -472,7 +472,7 @@ enum Polarity {
     }
   }
 
-  static boolean hasDefinitelyNullBranch(
+  public static boolean hasDefinitelyNullBranch(
       ExpressionTree tree,
       Set<VarSymbol> definitelyNullVars,
       /*

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

@@ -135,12 +135,12 @@ public void ternary_b536946282_shouldBeFlagged() {
 
             class Test {
               List<String> methodReturnsNullTernary(boolean foo, List<String> bar) {
-                // TODO(b/536946282): should be flagged by ReturnsNullCollection
+                // BUG: Diagnostic contains: ReturnsNullCollection
                 return foo ? bar : null;
               }
 
               List<String> methodReturnsNullTernaryReversed(boolean foo, List<String> bar) {
-                // TODO(b/536946282): should be flagged by ReturnsNullCollection
+                // BUG: Diagnostic contains: ReturnsNullCollection
                 return foo ? null : bar;
               }
             }

core/src/test/java/com/google/errorprone/bugpatterns/inject/dagger/ProvidesNullTest.java

@@ -253,13 +253,13 @@ public void ternary_b536946282_shouldBeFlagged() {
             public class Test {
               @Provides
               public Object providesObject(boolean foo, Object bar) {
-                // TODO(b/536946282): should be flagged by ProvidesNull
+                // BUG: Diagnostic contains: Did you mean '@Nullable' or 'throw new RuntimeException();'
                 return foo ? bar : null;
               }
 
               @Provides
               public Object providesObjectReversed(boolean foo, Object bar) {
-                // TODO(b/536946282): should be flagged by ProvidesNull
+                // BUG: Diagnostic contains: Did you mean '@Nullable' or 'throw new RuntimeException();'
                 return foo ? null : bar;
               }
             }