TruthConstantAsserts: treat static identifiers as constants.

Sorry, I managed to submit b063711 before amending some more changes. No idea how, there's meant to be a warning.

PiperOrigin-RevId: 828871382

Author: graememorgan

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

@@ -20,6 +20,7 @@
 import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
 import static com.google.errorprone.matchers.method.MethodMatchers.instanceMethod;
 import static com.google.errorprone.matchers.method.MethodMatchers.staticMethod;
+import static com.google.errorprone.util.ASTHelpers.isStatic;
 
 import com.google.errorprone.BugPattern;
 import com.google.errorprone.BugPattern.StandardTags;
@@ -110,7 +111,7 @@ private boolean constantIsh(ExpressionTree tree, VisitorState state) {
         new ConstantExpressionVisitor() {
           @Override
           public void visitIdentifier(Symbol identifier) {
-            if (!(identifier instanceof MethodSymbol)) {
+            if (!(identifier instanceof MethodSymbol) && !isStatic(identifier)) {
               involvesIdentifiers.set(true);
             }
           }

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

@@ -129,4 +129,27 @@ public void test(Object a) {
             """)
         .doTest();
   }
+
+  @Test
+  public void positiveWithEnumOnLeftHandSide() {
+    compilationHelper
+        .addSourceLines(
+            "Test.java",
+            """
+            import static com.google.common.truth.Truth.assertThat;
+
+            public class Test {
+              enum TestEnum {
+                A,
+                B
+              }
+
+              public void test(Object a) {
+                // BUG: Diagnostic contains:
+                assertThat(TestEnum.A).isEqualTo(a);
+              }
+            }
+            """)
+        .doTest();
+  }
 }