Support exponentiation operator in const enums (#20424)

Author: Andy

src/compiler/checker.ts

@@ -22915,6 +22915,7 @@ namespace ts {
                                 case SyntaxKind.PlusToken: return left + right;
                                 case SyntaxKind.MinusToken: return left - right;
                                 case SyntaxKind.PercentToken: return left % right;
+                                case SyntaxKind.AsteriskAsteriskToken: return left ** right;
                             }
                         }
                         break;

tests/baselines/reference/constEnums.js

@@ -21,6 +21,7 @@ const enum Enum1 {
     N = E << 1,
     O = E >> B,
     P = E >> 1,
+    PQ = E ** 2,
     Q = -D,
     R = C & 5,
     S = 5 & C,
@@ -128,6 +129,7 @@ function foo(x: Enum1) {
         case Enum1.N:
         case Enum1.O:
         case Enum1.P:
+        case Enum1.PQ:
         case Enum1.Q:
         case Enum1.R:
         case Enum1.S:
@@ -200,6 +202,7 @@ function foo(x) {
         case 2 /* N */:
         case 0 /* O */:
         case 0 /* P */:
+        case 1 /* PQ */:
         case -1 /* Q */:
         case 0 /* R */:
         case 0 /* S */: