Fix a crash in UnnecessaryAsync

PiperOrigin-RevId: 567041651

Author: cushon

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

@@ -142,7 +142,7 @@ private SuggestedFix attemptFix(VariableTree tree, VisitorState state) {
             getPrimitiveType(symbol.type, state.getTypes()),
             symbol.getSimpleName(),
             constructor.getArguments().isEmpty()
-                ? getDefaultInitializer(symbol)
+                ? getDefaultInitializer(symbol, state.getTypes())
                 : state.getSourceForNode(constructor.getArguments().get(0))));
 
     new TreePathScanner<Void, Void>() {
@@ -217,7 +217,8 @@ private boolean isVariableDeclarationItself(Tree parentTree) {
   }
 
   private static String getPrimitiveType(Type type, Types types) {
-    switch (types.erasure(type).toString()) {
+    String name = types.erasure(type).toString();
+    switch (name) {
       case "java.util.concurrent.atomic.AtomicBoolean":
         return "boolean";
       case "java.util.concurrent.atomic.AtomicReference":
@@ -228,22 +229,23 @@ private static String getPrimitiveType(Type type, Types types) {
         return "int";
       case "java.util.concurrent.atomic.AtomicLong":
         return "long";
-      default: // fall out
+      default:
+        throw new AssertionError(name);
     }
-    throw new AssertionError();
   }
 
-  private static String getDefaultInitializer(VarSymbol symbol) {
-    switch (symbol.type.toString()) {
+  private static String getDefaultInitializer(VarSymbol symbol, Types types) {
+    String name = types.erasure(symbol.type).toString();
+    switch (name) {
       case "java.util.concurrent.atomic.AtomicBoolean":
         return "false";
       case "java.util.concurrent.atomic.AtomicReference":
         return "null";
       case "java.util.concurrent.atomic.AtomicInteger":
       case "java.util.concurrent.atomic.AtomicLong":
         return "0";
-      default: // fall out
+      default:
+        throw new AssertionError(name);
     }
-    throw new AssertionError();
   }
 }

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

@@ -205,4 +205,19 @@ public void negative_capturedByLambda() {
             "}")
         .doTest();
   }
+
+  @Test
+  public void atomicReference_unfixable() {
+    helper
+        .addSourceLines(
+            "Test.java",
+            "import java.util.concurrent.atomic.AtomicReference;",
+            "class Test {",
+            "  void f() {",
+            "    // BUG: Diagnostic contains: String result = null;",
+            "    AtomicReference<String> result = new AtomicReference<>();",
+            "  }",
+            "}")
+        .doTest();
+  }
 }