Prefer using enum literal's own base type rather than enum's base type in comparison

Author: jakebailey

src/compiler/checker.ts

@@ -22978,6 +22978,18 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             type;
     }
 
+    // This is the same as getBaseTypeOfLiteralType, but checks EnumLiteral last so we get
+    // a specific literal's base type rather than the enum's base type.
+    function getBaseTypeOfLiteralTypeForComparison(type: Type): Type {
+        return type.flags & (TypeFlags.StringLiteral | TypeFlags.TemplateLiteral | TypeFlags.StringMapping) ? stringType :
+            type.flags & TypeFlags.NumberLiteral ? numberType :
+            type.flags & TypeFlags.BigIntLiteral ? bigintType :
+            type.flags & TypeFlags.BooleanLiteral ? booleanType :
+            type.flags & TypeFlags.EnumLiteral ? getBaseTypeOfEnumLiteralType(type as LiteralType) :
+            type.flags & TypeFlags.Union ? getBaseTypeOfLiteralTypeUnion(type as UnionType) :
+            type;
+    }
+
     function getBaseTypeOfLiteralTypeUnion(type: UnionType) {
         const key = `B${getTypeId(type)}`;
         return getCachedType(key) ?? setCachedType(key, mapType(type, getBaseTypeOfLiteralType));
@@ -36423,8 +36435,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             case SyntaxKind.LessThanEqualsToken:
             case SyntaxKind.GreaterThanEqualsToken:
                 if (checkForDisallowedESSymbolOperand(operator)) {
-                    leftType = getBaseTypeOfLiteralType(checkNonNullType(leftType, left));
-                    rightType = getBaseTypeOfLiteralType(checkNonNullType(rightType, right));
+                    leftType = getBaseTypeOfLiteralTypeForComparison(checkNonNullType(leftType, left));
+                    rightType = getBaseTypeOfLiteralTypeForComparison(checkNonNullType(rightType, right));
                     reportOperatorErrorUnless((left, right) => {
                         if (isTypeAny(left) || isTypeAny(right)) {
                             return true;