Avoid unnecessary type casts

Author: fvictorio

src/slang-nodes/ArgumentsDeclaration.ts

@@ -1,9 +1,9 @@
+import * as ast from '@nomicfoundation/slang/ast';
 import { NonterminalKind } from '@nomicfoundation/slang/cst';
 import { SlangNode } from './SlangNode.js';
 import { PositionalArgumentsDeclaration } from './PositionalArgumentsDeclaration.js';
 import { NamedArgumentsDeclaration } from './NamedArgumentsDeclaration.js';
 
-import type * as ast from '@nomicfoundation/slang/ast';
 import type { AstPath, Doc, ParserOptions } from 'prettier';
 import type { AstNode } from './types.d.ts';
 import type { PrintFunction } from '../types.d.ts';
@@ -12,19 +12,13 @@ function createNonterminalVariant(
   variant: ast.ArgumentsDeclaration['variant'],
   options: ParserOptions<AstNode>
 ): ArgumentsDeclaration['variant'] {
-  switch (variant.cst.kind) {
-    case NonterminalKind.PositionalArgumentsDeclaration:
-      return new PositionalArgumentsDeclaration(
-        variant as ast.PositionalArgumentsDeclaration,
-        options
-      );
-    case NonterminalKind.NamedArgumentsDeclaration:
-      return new NamedArgumentsDeclaration(
-        variant as ast.NamedArgumentsDeclaration,
-        options
-      );
-    default:
-      throw new Error(`Unexpected variant: ${variant.cst.kind}`);
+  if (variant instanceof ast.PositionalArgumentsDeclaration) {
+    return new PositionalArgumentsDeclaration(variant, options);
+  } else if (variant instanceof ast.NamedArgumentsDeclaration) {
+    return new NamedArgumentsDeclaration(variant, options);
+  } else {
+    const exhaustiveCheck: never = variant;
+    return exhaustiveCheck;
   }
 }