avoid using the ast more than once since we can't ensure the pointer is preserved.

Author: Janther

src/clean.ts

@@ -5,7 +5,7 @@ const ignoredProperties = new Set([
   'comments',
   // this function is defined at constructor time so it won't pass AST
   // comparisons.
-  'cleanModifierInvocationArguments'
+  'isEmpty'
 ]);
 // eslint-disable-next-line @typescript-eslint/no-empty-function
 function clean(/* ast, newObj, parent */): void {}

src/slang-nodes/ModifierInvocation.ts

@@ -1,5 +1,4 @@
 import { NonterminalKind } from '@nomicfoundation/slang/cst';
-import { isBlockComment } from '../slang-utils/is-comment.js';
 import { getNodeMetadata, updateMetadata } from '../slang-utils/metadata.js';
 import { IdentifierPath } from './IdentifierPath.js';
 import { ArgumentsDeclaration } from './ArgumentsDeclaration.js';
@@ -16,8 +15,6 @@ export class ModifierInvocation implements SlangNode {
 
   loc;
 
-  cleanModifierInvocationArguments;
-
   name: IdentifierPath;
 
   arguments?: ArgumentsDeclaration;
@@ -43,20 +40,17 @@ export class ModifierInvocation implements SlangNode {
 
     this.comments = metadata.comments;
     this.loc = metadata.loc;
+  }
 
-    this.cleanModifierInvocationArguments = (): void => {
-      if (
-        this.arguments &&
-        this.arguments.variant.kind ===
-          NonterminalKind.PositionalArgumentsDeclaration &&
-        this.arguments.variant.arguments.items.length === 0 && // no arguments
-        !ast.arguments!.variant.cst.children.some((child) =>
-          isBlockComment(child.node)
-        ) // no comments, at this point we need to check the CST
-      ) {
-        delete this.arguments;
-      }
-    };
+  cleanModifierInvocationArguments(): void {
+    if (
+      this.arguments &&
+      this.arguments.variant.kind ===
+        NonterminalKind.PositionalArgumentsDeclaration &&
+      this.arguments.variant.isEmpty()
+    ) {
+      delete this.arguments;
+    }
   }
 
   print(path: AstPath<ModifierInvocation>, print: PrintFunction): Doc {

src/slang-nodes/PositionalArgumentsDeclaration.ts

@@ -1,5 +1,6 @@
 import { NonterminalKind } from '@nomicfoundation/slang/cst';
 import { getNodeMetadata, updateMetadata } from '../slang-utils/metadata.js';
+import { isBlockComment } from '../slang-utils/is-comment.js';
 import { PositionalArguments } from './PositionalArguments.js';
 
 import type * as ast from '@nomicfoundation/slang/ast';
@@ -14,6 +15,8 @@ export class PositionalArgumentsDeclaration implements SlangNode {
 
   loc;
 
+  isEmpty;
+
   arguments: PositionalArguments;
 
   constructor(
@@ -34,6 +37,14 @@ export class PositionalArgumentsDeclaration implements SlangNode {
 
     this.comments = metadata.comments;
     this.loc = metadata.loc;
+
+    // We need to check the comments at this point because they will be removed
+    // from this node into the root node.
+    const empty =
+      this.arguments.items.length === 0 && // no arguments
+      !this.comments.some((comment) => isBlockComment(comment)); // no block comments
+
+    this.isEmpty = (): boolean => empty;
   }
 
   print(