JSpecify: view type as super in generic method inference (#1177)

Author: msridhar

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

@@ -454,7 +454,7 @@ public void checkTypeParameterNullnessForAssignability(
         // generic method call with no explicit generic arguments
         // update inferred type arguments based on the assignment context
         InferSubstitutionViaAssignmentContextVisitor inferVisitor =
-            new InferSubstitutionViaAssignmentContextVisitor(config);
+            new InferSubstitutionViaAssignmentContextVisitor(state, config);
         Type returnType = methodSymbol.getReturnType();
         returnType.accept(inferVisitor, lhsType);
 

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

@@ -1,5 +1,7 @@
 package com.uber.nullaway.generics;
 
+import com.google.common.base.Verify;
+import com.google.errorprone.VisitorState;
 import com.sun.tools.javac.code.Type;
 import com.sun.tools.javac.code.Types;
 import com.uber.nullaway.Config;
@@ -15,24 +17,29 @@
 public class InferSubstitutionViaAssignmentContextVisitor
     extends Types.DefaultTypeVisitor<Void, Type> {
 
+  private final VisitorState state;
   private final Config config;
   private final Map<TypeVariable, Type> inferredSubstitution = new LinkedHashMap<>();
 
-  InferSubstitutionViaAssignmentContextVisitor(Config config) {
+  InferSubstitutionViaAssignmentContextVisitor(VisitorState state, Config config) {
+    this.state = state;
     this.config = config;
   }
 
   @Override
   public Void visitClassType(Type.ClassType rhsType, Type lhsType) {
-    com.sun.tools.javac.util.List<Type> rhsTypeArguments = rhsType.getTypeArguments();
+    Type rhsTypeAsSuper = state.getTypes().asSuper(rhsType, lhsType.tsym);
+    if (rhsTypeAsSuper == null || rhsTypeAsSuper.isRaw() || lhsType.isRaw()) {
+      return null;
+    }
+    com.sun.tools.javac.util.List<Type> rhsTypeArguments = rhsTypeAsSuper.getTypeArguments();
     com.sun.tools.javac.util.List<Type> lhsTypeArguments = lhsType.getTypeArguments();
-    // recursively visit the type arguments
-    if (!rhsTypeArguments.isEmpty() && !lhsTypeArguments.isEmpty()) {
-      for (int i = 0; i < rhsTypeArguments.size(); i++) {
-        Type rhsTypeArg = rhsTypeArguments.get(i);
-        Type lhsTypeArg = lhsTypeArguments.get(i);
-        rhsTypeArg.accept(this, lhsTypeArg);
-      }
+    int numTypeArgs = rhsTypeArguments.size();
+    Verify.verify(numTypeArgs == lhsTypeArguments.size());
+    for (int i = 0; i < numTypeArgs; i++) {
+      Type rhsTypeArg = rhsTypeArguments.get(i);
+      Type lhsTypeArg = lhsTypeArguments.get(i);
+      rhsTypeArg.accept(this, lhsTypeArg);
     }
     return null;
   }

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

@@ -488,6 +488,24 @@ public void nullableAnnotOnMethodTypeVarUse() {
         .doTest();
   }
 
+  @Test
+  public void issue1176() {
+    makeHelper()
+        .addSourceLines(
+            "Foo.java",
+            "package com.uber;",
+            "import java.util.Set;",
+            "import java.util.concurrent.CompletableFuture;",
+            "import java.util.concurrent.ConcurrentHashMap;",
+            "class Foo {",
+            "    final Set<CompletableFuture<?>> f;",
+            "    public Foo() {",
+            "        f = ConcurrentHashMap.newKeySet();",
+            "    }",
+            "}")
+        .doTest();
+  }
+
   private CompilationTestHelper makeHelper() {
     return makeTestHelperWithArgs(
         Arrays.asList(