Update PeepholeFoldConstants to fold unary operators with bigint literal operands

PiperOrigin-RevId: 325365271

Author: JohnLuck77

src/com/google/javascript/jscomp/PeepholeFoldConstants.java

@@ -24,6 +24,7 @@
 import com.google.javascript.rhino.Node;
 import com.google.javascript.rhino.Token;
 import com.google.javascript.rhino.jstype.TernaryValue;
+import java.math.BigInteger;
 
 /**
  * Peephole optimization to fold constants (e.g. x + 1 + 7 --> x + 8).
@@ -411,6 +412,12 @@ private Node tryFoldUnaryOperator(Node n) {
             report(FRACTIONAL_BITWISE_OPERAND, left);
             return n;
           }
+        } else if (left.isBigInt()) {
+          BigInteger val = left.getBigInt();
+          Node notValNode = IR.bigint(val.not());
+          parent.replaceChild(n, notValNode);
+          reportChangeToEnclosingScope(parent);
+          return notValNode;
         } else {
           return n;
         }

test/com/google/javascript/jscomp/PeepholeFoldConstantsTest.java

@@ -522,6 +522,14 @@ public void testUnaryOps() {
     testSame("a=~.5", PeepholeFoldConstants.FRACTIONAL_BITWISE_OPERAND);
   }
 
+  @Test
+  public void testUnaryOpsWithBigInt() {
+    fold("-(1n)", "-1n");
+    fold("- -1n", "1n");
+    fold("!1n", "false");
+    fold("~0n", "-1n");
+  }
+
   @Test
   public void testUnaryOpsStringCompare() {
     foldSame("a = -1");