Remove need to avoid for..of loops. It's almost 2024.

.eslintrc.cjs

@@ -33,15 +33,10 @@ module.exports = {
 
     'no-restricted-syntax': [
       'error',
-      {
-        selector: 'ForOfStatement',
-        message:
-          'Avoid for..of loops in libraries, because they generate unneeded Babel iterator runtime support code in the bundle',
-      },
       {
         selector: 'ForInStatement',
         message:
-          'for..in loops are never what you want. Loop over Object.keys() instead.',
+          'for..in loops are never what you want. Use for..of, or use a .forEach() instead.',
       },
     ],
   },
@@ -52,7 +47,6 @@ module.exports = {
       files: ['test/**'],
       rules: {
         '@typescript-eslint/no-explicit-any': 'off',
-        'no-restricted-syntax': 'off',
       },
     },
   ],

src/_utils.ts

@@ -13,11 +13,11 @@ export function lazyval<V>(value: (() => V) | V): V {
  */
 export function subtract<C extends Scalar>(xs: Set<C>, ys: Set<C>): Set<C> {
   const result = new Set<C>();
-  xs.forEach((x) => {
+  for (const x of xs) {
     if (!ys.has(x)) {
       result.add(x);
     }
-  });
+  }
   return result;
 }
 
@@ -79,21 +79,21 @@ export function summarize(
   if (ann.type === 'array') {
     const items = ann.items;
     let index = 0;
-    items.forEach((ann) => {
-      summarize(ann, [...keypath, index++]).forEach((item) =>
+    for (const ann of items) {
+      for (const item of summarize(ann, [...keypath, index++])) {
         // Collect to results
-        result.push(item),
-      );
-    });
+        result.push(item);
+      }
+    }
   } else if (ann.type === 'object') {
     const fields = ann.fields;
-    Object.keys(fields).forEach((key) => {
+    for (const key of Object.keys(fields)) {
       const value = fields[key];
-      summarize(value, [...keypath, key]).forEach((item) =>
+      for (const item of summarize(value, [...keypath, key])) {
         // Collect to results
-        result.push(item),
-      );
-    });
+        result.push(item);
+      }
+    }
   }
 
   const text = ann.text;

src/annotate.ts

@@ -145,10 +145,10 @@ function annotateObject(
   seen.add(obj);
 
   const fields: Record<string, Annotation> = {};
-  Object.keys(obj).forEach((key) => {
+  for (const key of Object.keys(obj)) {
     const value = obj[key];
     fields[key] = annotate(value, undefined, seen);
-  });
+  }
   return object(fields, text);
 }
 

src/format.ts

@@ -24,13 +24,13 @@ function serializeArray(annotation: ArrayAnnotation, prefix: string): string {
   }
 
   const result: string[] = [];
-  items.forEach((item) => {
+  for (const item of items) {
     const [ser, ann] = serializeAnnotation(item, `${prefix}${INDENT}`);
     result.push(`${prefix}${INDENT}${ser}${','}`);
     if (ann !== undefined) {
       result.push(indent(ann, `${prefix}${INDENT}`));
     }
-  });
+  }
   return ['[', ...result, `${prefix}]`].join('\n');
 }
 
@@ -43,7 +43,7 @@ function serializeObject(annotation: ObjectAnnotation, prefix: string): string {
   }
 
   const result: string[] = [];
-  fieldNames.forEach((key) => {
+  for (const key of fieldNames) {
     const valueAnnotation = fields[key];
     const kser = serializeValue(key);
 
@@ -54,7 +54,7 @@ function serializeObject(annotation: ObjectAnnotation, prefix: string): string {
     if (vann !== undefined) {
       result.push(indent(vann, valPrefix));
     }
-  });
+  }
   return ['{', ...result, `${prefix}}`].join('\n');
 }
 

src/lib/objects.ts

@@ -45,7 +45,7 @@ export function object<DS extends Record<string, Decoder<any>>>(
     const record = {};
     let errors: Record<string, Annotation> | null = null;
 
-    Object.keys(decodersByKey).forEach((key) => {
+    for (const key of Object.keys(decodersByKey)) {
       const decoder = decodersByKey[key];
       const rawValue = plainObj[key];
       const result: DecodeResult<unknown> = decoder.decode(rawValue);
@@ -78,7 +78,7 @@ export function object<DS extends Record<string, Decoder<any>>>(
           errors[key] = ann;
         }
       }
-    });
+    }
 
     // Deal with errors now. There are two classes of errors we want to
     // report.  First of all, we want to report any inline errors in this
@@ -162,12 +162,12 @@ export function inexact<O extends Record<string, Decoder<any>>>(
       const safekeys = new Set(Object.keys(decodersByKey));
 
       // To account for hard-coded keys that aren't part of the input
-      safekeys.forEach((k) => allkeys.add(k));
+      for (const k of safekeys) allkeys.add(k);
 
       const rv = {} as {
         [K in keyof ObjectDecoderType<O>]: ObjectDecoderType<O>[K];
       } & Record<string, unknown>;
-      allkeys.forEach((k) => {
+      for (const k of allkeys) {
         if (safekeys.has(k)) {
           const value = safepart[k];
           if (value !== undefined) {
@@ -178,7 +178,7 @@ export function inexact<O extends Record<string, Decoder<any>>>(
           // @ts-expect-error - look into this later
           rv[k] = plainObj[k];
         }
-      });
+      }
       return rv;
     });
     return decoder.decode(plainObj);
@@ -200,7 +200,7 @@ export function dict<T>(decoder: Decoder<T>): Decoder<Record<string, T>> {
     let rv: Record<string, T> = {};
     let errors: Record<string, Annotation> | null = null;
 
-    Object.keys(plainObj).forEach((key: string) => {
+    for (const key of Object.keys(plainObj)) {
       const value = plainObj[key];
       const result = decoder.decode(value);
       if (result.ok) {
@@ -214,7 +214,7 @@ export function dict<T>(decoder: Decoder<T>): Decoder<Record<string, T>> {
         }
         errors[key] = result.error;
       }
-    });
+    }
 
     if (errors !== null) {
       return err(merge(annotateObject(plainObj), errors));