Preserve parentheses around unary plus and minus in non-primitive casts

PiperOrigin-RevId: 749108147

Author: cushon

check_api/src/main/java/com/google/errorprone/util/ASTHelpers.java

@@ -81,6 +81,7 @@
 import com.sun.source.tree.Tree;
 import com.sun.source.tree.Tree.Kind;
 import com.sun.source.tree.TryTree;
+import com.sun.source.tree.TypeCastTree;
 import com.sun.source.tree.TypeParameterTree;
 import com.sun.source.tree.UnaryTree;
 import com.sun.source.tree.VariableTree;
@@ -395,8 +396,19 @@ public static boolean requiresParentheses(ExpressionTree expression, VisitorStat
       return state.getOffsetTokensForNode(expression).stream()
           .anyMatch(t -> t.kind() == TokenKind.PLUS);
     }
-    if (expression instanceof UnaryTree) {
+    if (expression instanceof UnaryTree unaryTree) {
       Tree parent = state.getPath().getParentPath().getLeaf();
+      if (parent instanceof TypeCastTree castTree
+          && !castTree.getType().getKind().equals(Kind.PRIMITIVE_TYPE)) {
+        // unary plus and minus require parens when used with non-primitive casts
+        // see https://docs.oracle.com/javase/specs/jls/se21/html/jls-15.html#jls-15.16
+        switch (unaryTree.getKind()) {
+          case UNARY_PLUS, UNARY_MINUS -> {
+            return true;
+          }
+          default -> {}
+        }
+      }
       if (!(parent instanceof MemberSelectTree memberSelectTree)) {
         return false;
       }

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

@@ -295,4 +295,30 @@ public boolean match(String value) {
         .expectNoDiagnostics()
         .doTest();
   }
+
+  @Test
+  public void unaryMinus() {
+    testHelper
+        .addInputLines(
+            "Test.java",
+            """
+            class Test {
+              public void f() {
+                Double d = (Double) (-1.0);
+                d = (double) (-1.0);
+              }
+            }
+            """)
+        .addOutputLines(
+            "Test.java",
+            """
+            class Test {
+              public void f() {
+                Double d = (Double) (-1.0);
+                d = (double) -1.0;
+              }
+            }
+            """)
+        .doTest();
+  }
 }