Bug fixes for array subtyping at returns / parameter passing

nullaway/src/main/java/com/uber/nullaway/generics/GenericsChecks.java

@@ -1,6 +1,7 @@
 package com.uber.nullaway.generics;
 
 import static com.google.common.base.Verify.verify;
+import static com.uber.nullaway.NullabilityUtil.castToNonNull;
 
 import com.google.errorprone.VisitorState;
 import com.google.errorprone.suppliers.Supplier;
@@ -11,6 +12,7 @@
 import com.sun.source.tree.AssignmentTree;
 import com.sun.source.tree.ConditionalExpressionTree;
 import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.IdentifierTree;
 import com.sun.source.tree.MemberSelectTree;
 import com.sun.source.tree.MethodInvocationTree;
 import com.sun.source.tree.MethodTree;
@@ -270,11 +272,10 @@ private static Type getTreeType(Tree tree, VisitorState state) {
       return typeWithPreservedAnnotations(tree, state);
     } else {
       Type result;
-      if (tree instanceof VariableTree) {
+      if (tree instanceof VariableTree || tree instanceof IdentifierTree) {
         // type on the tree itself can be missing nested annotations for arrays; get the type from
-        // the symbol for the declared variable instead
-        VariableTree varTree = (VariableTree) tree;
-        result = ASTHelpers.getSymbol(varTree).type;
+        // the symbol for the variable instead
+        result = castToNonNull(ASTHelpers.getSymbol(tree)).type;
       } else if (tree instanceof AssignmentTree) {
         // type on the tree itself can be missing nested annotations for arrays; get the type from
         // the symbol for the assigned location instead, if available
@@ -355,10 +356,6 @@ public static void checkTypeParameterNullnessForFunctionReturnType(
     }
 
     Type formalReturnType = methodSymbol.getReturnType();
-    // check nullability of parameters only for generics
-    if (formalReturnType.getTypeArguments().isEmpty()) {
-      return;
-    }
     Type returnExpressionType = getTreeType(retExpr, state);
     if (formalReturnType != null && returnExpressionType != null) {
       boolean isReturnTypeValid =
@@ -514,28 +511,24 @@ public static void compareGenericTypeParameterNullabilityForCall(
     }
     for (int i = 0; i < n; i++) {
       Type formalParameter = formalParams.get(i).type;
-      if (!formalParameter.getTypeArguments().isEmpty()) {
-        Type actualParameter = getTreeType(actualParams.get(i), state);
-        if (actualParameter != null) {
-          if (!subtypeParameterNullability(formalParameter, actualParameter, state)) {
-            reportInvalidParametersNullabilityError(
-                formalParameter, actualParameter, actualParams.get(i), state, analysis);
-          }
+      Type actualParameter = getTreeType(actualParams.get(i), state);
+      if (actualParameter != null) {
+        if (!subtypeParameterNullability(formalParameter, actualParameter, state)) {
+          reportInvalidParametersNullabilityError(
+              formalParameter, actualParameter, actualParams.get(i), state, analysis);
         }
       }
     }
     if (isVarArgs && !formalParams.isEmpty()) {
       Type.ArrayType varargsArrayType =
           (Type.ArrayType) formalParams.get(formalParams.size() - 1).type;
       Type varargsElementType = varargsArrayType.elemtype;
-      if (!varargsElementType.getTypeArguments().isEmpty()) {
-        for (int i = formalParams.size() - 1; i < actualParams.size(); i++) {
-          Type actualParameter = getTreeType(actualParams.get(i), state);
-          if (actualParameter != null) {
-            if (!subtypeParameterNullability(varargsElementType, actualParameter, state)) {
-              reportInvalidParametersNullabilityError(
-                  varargsElementType, actualParameter, actualParams.get(i), state, analysis);
-            }
+      for (int i = formalParams.size() - 1; i < actualParams.size(); i++) {
+        Type actualParameter = getTreeType(actualParams.get(i), state);
+        if (actualParameter != null) {
+          if (!subtypeParameterNullability(varargsElementType, actualParameter, state)) {
+            reportInvalidParametersNullabilityError(
+                varargsElementType, actualParameter, actualParams.get(i), state, analysis);
           }
         }
       }

nullaway/src/test/java/com/uber/nullaway/jspecify/ArrayTests.java

@@ -278,6 +278,56 @@ public void arraysAndGenerics() {
         .doTest();
   }
 
+  @Test
+  public void genericArraysReturnedAndPassed() {
+    makeHelper()
+        .addSourceLines(
+            "Test.java",
+            "package com.uber;",
+            "import org.jspecify.annotations.Nullable;",
+            "class Test {",
+            "  static class Foo<T> {}",
+            "  static class Bar<T> {",
+            "    Foo<T>[] getFoosPositive() {",
+            "      @Nullable Foo<T>[] result = new Foo[0];",
+            "      // BUG: Diagnostic contains: Cannot return expression of type @Nullable Foo<T>[] from method",
+            "      return result;",
+            "    }",
+            "    Foo<T>[] getFoosNegative() {",
+            "      Foo<T>[] result = new Foo[0];",
+            "      return result;",
+            "    }",
+            "    void takeFoos(Foo<T>[] foos) {}",
+            "    void callTakeFoosPositive(@Nullable Foo<T>[] p) {",
+            "      // BUG: Diagnostic contains: Cannot pass parameter of type @Nullable Foo<T>[]",
+            "      takeFoos(p);",
+            "    }",
+            "    void callTakeFoosNegative(Foo<T>[] p) {",
+            "      takeFoos(p);",
+            "    }",
+            "    void takeFoosVarargs(Foo<T>[]... foos) {}",
+            "    void callTakeFoosVarargsPositive(@Nullable Foo<T>[] p, Foo<T>[] p2) {",
+            "      // Under the hood, a @Nullable Foo<T>[][] is passed, which is not a subtype",
+            "      // of the formal parameter type Foo<T>[][]",
+            "      // BUG: Diagnostic contains: Cannot pass parameter of type @Nullable Foo<T>[]",
+            "      takeFoosVarargs(p);",
+            "      // BUG: Diagnostic contains: Cannot pass parameter of type @Nullable Foo<T>[]",
+            "      takeFoosVarargs(p2, p);",
+            "    }",
+            "    void callTakeFoosVarargsNegative(Foo<T>[] p) {",
+            "      takeFoosVarargs(p);",
+            "    }",
+            "    void takeNullableFoosVarargs(@Nullable Foo<T>[]... foos) {}",
+            "    void callTakeNullableFoosVarargsNegative(@Nullable Foo<T>[] p1, Foo<T>[] p2) {",
+            "      takeNullableFoosVarargs(p1);",
+            "      takeNullableFoosVarargs(p2);",
+            "      takeNullableFoosVarargs(p1, p2);",
+            "    }",
+            "  }",
+            "}")
+        .doTest();
+  }
+
   @Test
   public void overridesReturnType() {
     makeHelper()