fix

src/environment.ts

@@ -88,6 +88,18 @@ export class Environment {
     return [...new Set(keys)];
   }
 
+  readonlyKeys(): symbol[] {
+    const keys: symbol[] = [...this.readonly.keys()];
+    if (this.parent) keys.push(...this.parent.readonlyKeys());
+    return [...new Set(keys)];
+  }
+
+  mutableKeys(): symbol[] {
+    const keys: symbol[] = [...this.mutable.keys()];
+    if (this.parent) keys.push(...this.parent.mutableKeys());
+    return [...new Set(keys)];
+  }
+
   shallowCopy(): Environment {
     const copy = new Environment({ parent: this.parent });
     copy.readonly = new Map(this.readonly);

src/evaluate/index.ts

@@ -133,7 +133,7 @@ const incAssign = (position: Position, context: CompileContext) => {
           context.env.has(patternKey),
           undeclaredName(
             patternKey.description!,
-            context.env.keys().map((k) => k.description ?? String(k))
+            context.env.mutableKeys().map((k) => k.description ?? String(k))
           )
         );
 
@@ -200,7 +200,7 @@ const assign = (position: Position, context: CompileContext) => {
           context.env.set(patternKey, value),
           undeclaredName(
             patternKey.description!,
-            context.env.keys().map((k) => k.description ?? String(k))
+            context.env.mutableKeys().map((k) => k.description ?? String(k))
           )
         );
       } else {

src/index.ts

@@ -29,6 +29,7 @@ program
     console.log('Starting REPL...');
     const file = '<repl>';
 
+    const context = newContext();
     console.log('Waiting for next input...');
     const rl = readline.createInterface({ input, output, prompt: '>> ' });
     rl.prompt();
@@ -42,7 +43,6 @@ program
         default: {
           const fileId = addFile(file, line);
           const compileContext = newCompileContext(fileId, file);
-          const context = newContext();
           const compiled = compileScriptString(line, compileContext);
           const result = await compiled(context);
           console.dir(result, { depth: null });