Add ResultUsePolicy.UNSPECIFIED.

For now this doesn't change anything for checking since the check just cares whether the policy is `EXPECTED` or not.

PiperOrigin-RevId: 480151888

Author: cgdecker

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

@@ -29,6 +29,7 @@
 import static com.google.errorprone.bugpatterns.checkreturnvalue.ProtoRules.protoBuilders;
 import static com.google.errorprone.bugpatterns.checkreturnvalue.ResultUsePolicy.EXPECTED;
 import static com.google.errorprone.bugpatterns.checkreturnvalue.ResultUsePolicy.OPTIONAL;
+import static com.google.errorprone.bugpatterns.checkreturnvalue.ResultUsePolicy.UNSPECIFIED;
 import static com.google.errorprone.bugpatterns.checkreturnvalue.Rules.globalDefault;
 import static com.google.errorprone.bugpatterns.checkreturnvalue.Rules.mapAnnotationSimpleName;
 import static com.google.errorprone.fixes.SuggestedFix.emptyFix;
@@ -149,11 +150,7 @@ private static Optional<ResultUsePolicy> defaultPolicy(ErrorProneFlags flags, St
    */
   @Override
   public Matcher<ExpressionTree> specializedMatcher() {
-    return (tree, state) ->
-        methodToInspect(tree)
-            .map(method -> evaluator.evaluate(method, state))
-            .orElse(OPTIONAL)
-            .equals(EXPECTED);
+    return (tree, state) -> getMethodPolicy(tree, state).equals(EXPECTED);
   }
 
   private static Optional<MethodSymbol> methodToInspect(ExpressionTree tree) {
@@ -190,6 +187,13 @@ private static Optional<MethodSymbol> methodSymbol(ExpressionTree tree) {
     return sym instanceof MethodSymbol ? Optional.of((MethodSymbol) sym) : Optional.empty();
   }
 
+  /** Returns the {@link ResultUsePolicy} for the method used in the given {@code expression}. */
+  public ResultUsePolicy getMethodPolicy(ExpressionTree expression, VisitorState state) {
+    return methodToInspect(expression)
+        .map(method -> evaluator.evaluate(method, state))
+        .orElse(UNSPECIFIED);
+  }
+
   @Override
   public boolean isCovered(ExpressionTree tree, VisitorState state) {
     return methodToInspect(tree).stream()

core/src/main/java/com/google/errorprone/bugpatterns/checkreturnvalue/ExternalCanIgnoreReturnValue.java

@@ -80,7 +80,7 @@ public String id() {
   @Override
   public Optional<ResultUsePolicy> evaluateMethod(MethodSymbol method, VisitorState state) {
     return EXTERNAL_RULE_EVALUATOR.get(state).methodMatches(method, state)
-        ? Optional.of(ResultUsePolicy.OPTIONAL)
+        ? Optional.of(ResultUsePolicy.UNSPECIFIED)
         : Optional.empty();
   }
 

core/src/main/java/com/google/errorprone/bugpatterns/checkreturnvalue/ResultUsePolicy.java

@@ -27,4 +27,6 @@ public enum ResultUsePolicy {
   EXPECTED,
   /** Use of the result is optional. */
   OPTIONAL,
+  /** It is unspecified whether the result should be used or not. */
+  UNSPECIFIED,
 }

core/src/main/java/com/google/errorprone/bugpatterns/checkreturnvalue/ResultUsePolicyEvaluator.java

@@ -17,7 +17,7 @@
 package com.google.errorprone.bugpatterns.checkreturnvalue;
 
 import static com.google.common.collect.ImmutableListMultimap.toImmutableListMultimap;
-import static com.google.errorprone.bugpatterns.checkreturnvalue.ResultUsePolicy.OPTIONAL;
+import static com.google.errorprone.bugpatterns.checkreturnvalue.ResultUsePolicy.UNSPECIFIED;
 import static com.google.errorprone.bugpatterns.checkreturnvalue.ResultUseRule.RuleScope.ENCLOSING_ELEMENTS;
 import static com.google.errorprone.bugpatterns.checkreturnvalue.ResultUseRule.RuleScope.GLOBAL;
 import static com.google.errorprone.bugpatterns.checkreturnvalue.ResultUseRule.RuleScope.METHOD;
@@ -82,7 +82,7 @@ private ResultUsePolicyEvaluator(Builder builder) {
    * apply to it.
    */
   public ResultUsePolicy evaluate(MethodSymbol method, VisitorState state) {
-    return policies(method, state).findFirst().orElse(OPTIONAL);
+    return policies(method, state).findFirst().orElse(UNSPECIFIED);
   }
 
   private Stream<ResultUsePolicy> policies(MethodSymbol method, VisitorState state) {