From 88cb13f775344539f39f73b0eba1b94bae80d466 Mon Sep 17 00:00:00 2001
From: Luca Casonato <hello@lcas.dev>
Date: Tue, 26 Mar 2024 15:11:24 +0100
Subject: [PATCH 1/8] feat: add support for parsing `async iterable<T>` type

---
 README.md                                     |   2 +-
 lib/productions/attribute.js                  |   4 +-
 lib/productions/callback.js                   |  13 ++
 lib/productions/iterable.js                   |  14 +-
 lib/productions/operation.js                  |   9 ++
 lib/productions/type.js                       |  14 ++
 test/invalid/baseline/invalid-attribute.txt   |  15 +-
 .../baseline/invalid-callback-argument.txt    |   3 +
 .../baseline/invalid-operation-return.txt     |   3 +
 test/invalid/idl/invalid-attribute.webidl     |   6 +
 .../idl/invalid-callback-argument.webidl      |   1 +
 .../idl/invalid-operation-return.webidl       |   4 +
 ...iterable.json => async-iterable-decl.json} |   0
 test/syntax/baseline/async-iterable-type.json | 131 ++++++++++++++++++
 ...able.webidl => async-iterable-decl.webidl} |   0
 test/syntax/idl/async-iterable-type.webidl    |   7 +
 16 files changed, 216 insertions(+), 10 deletions(-)
 create mode 100644 test/invalid/baseline/invalid-callback-argument.txt
 create mode 100644 test/invalid/baseline/invalid-operation-return.txt
 create mode 100644 test/invalid/idl/invalid-callback-argument.webidl
 create mode 100644 test/invalid/idl/invalid-operation-return.webidl
 rename test/syntax/baseline/{async-iterable.json => async-iterable-decl.json} (100%)
 create mode 100644 test/syntax/baseline/async-iterable-type.json
 rename test/syntax/idl/{async-iterable.webidl => async-iterable-decl.webidl} (100%)
 create mode 100644 test/syntax/idl/async-iterable-type.webidl

diff --git a/README.md b/README.md
index f45ee123..1a9c5bbf 100644
--- a/README.md
+++ b/README.md
@@ -236,7 +236,7 @@ attached to a field called `idlType`:
 Where the fields are as follows:
 
 * `type`: String indicating where this type is used. Can be `null` if not applicable.
-* `generic`: String indicating the generic type (e.g. "Promise", "sequence").
+* `generic`: String indicating the generic type (e.g. "Promise", "sequence", "async iterable").
 * `idlType`: String indicating the type name, or array of subtypes if the type is
   generic or a union.
 * `nullable`: `true` if the type is nullable.
diff --git a/lib/productions/attribute.js b/lib/productions/attribute.js
index 0dab2516..0c09a486 100644
--- a/lib/productions/attribute.js
+++ b/lib/productions/attribute.js
@@ -75,7 +75,9 @@ export class Attribute extends Base {
     yield* this.extAttrs.validate(defs);
     yield* this.idlType.validate(defs);
 
-    if (["sequence", "record"].includes(this.idlType.generic)) {
+    if (
+      ["async iterable", "sequence", "record"].includes(this.idlType.generic)
+    ) {
       const message = `Attributes cannot accept ${this.idlType.generic} types.`;
       yield validationError(
         this.tokens.name,
diff --git a/lib/productions/callback.js b/lib/productions/callback.js
index 56dba106..d8e15d50 100644
--- a/lib/productions/callback.js
+++ b/lib/productions/callback.js
@@ -5,6 +5,7 @@ import {
   unescape,
   autoParenter,
 } from "./helpers.js";
+import { validationError } from "../error.js";
 
 export class CallbackFunction extends Base {
   /**
@@ -44,6 +45,18 @@ export class CallbackFunction extends Base {
 
   *validate(defs) {
     yield* this.extAttrs.validate(defs);
+    for (const arg of this.arguments) {
+      yield* arg.validate(defs);
+      if (arg.idlType.generic === "async iterable") {
+        const message = `Callback function arguments can not be ${arg.idlType.generic} types.`;
+        yield validationError(
+          arg.tokens.name,
+          arg,
+          "operation-return-invalid-type",
+          message,
+        );
+      }
+    }
     yield* this.idlType.validate(defs);
   }
 
diff --git a/lib/productions/iterable.js b/lib/productions/iterable.js
index cfa93c54..baff2415 100644
--- a/lib/productions/iterable.js
+++ b/lib/productions/iterable.js
@@ -68,9 +68,19 @@ export class IterableLike extends Base {
       }
     }
 
-    tokens.termination =
-      tokeniser.consume(";") ||
+    tokens.termination = tokeniser.consume(";");
+    if (
+      !tokens.termination &&
+      tokens.async &&
+      tokens.base.value === "iterable"
+    ) {
+      // Instead of a missing semicolon, this could be an invalid async iterable
+      // return type for a regular operation. Let's bail out early in that case.
+      tokeniser.unconsume(start_position);
+      return;
+    } else if (!tokens.termination) {
       tokeniser.error(`Missing semicolon after ${type} declaration`);
+    }
 
     return ret.this;
   }
diff --git a/lib/productions/operation.js b/lib/productions/operation.js
index f4c561be..40b84b25 100644
--- a/lib/productions/operation.js
+++ b/lib/productions/operation.js
@@ -69,6 +69,15 @@ export class Operation extends Base {
     }
     if (this.idlType) {
       yield* this.idlType.validate(defs);
+      if (this.idlType.generic === "async iterable") {
+        const message = `Operations can not return ${this.idlType.generic} types.`;
+        yield validationError(
+          this.tokens.name,
+          this,
+          "operation-return-invalid-type",
+          message,
+        );
+      }
     }
     for (const argument of this.arguments) {
       yield* argument.validate(defs);
diff --git a/lib/productions/type.js b/lib/productions/type.js
index d4d64165..7429dfab 100644
--- a/lib/productions/type.js
+++ b/lib/productions/type.js
@@ -16,7 +16,9 @@ import { ExtendedAttributes } from "./extended-attributes.js";
  * @param {string} typeName
  */
 function generic_type(tokeniser, typeName) {
+  const prevPosition = tokeniser.position;
   const base = tokeniser.consume(
+    "async",
     "FrozenArray",
     "ObservableArray",
     "Promise",
@@ -29,6 +31,14 @@ function generic_type(tokeniser, typeName) {
   const ret = autoParenter(
     new Type({ source: tokeniser.source, tokens: { base } }),
   );
+  if (base.value === "async") {
+    ret.tokens.async = base;
+    ret.tokens.base = tokeniser.consume("iterable");
+    if (!ret.tokens.base) {
+      tokeniser.unconsume(prevPosition); // unconsume the "async" token
+      return;
+    }
+  }
   ret.tokens.open =
     tokeniser.consume("<") ||
     tokeniser.error(`No opening bracket after ${base.value}`);
@@ -42,6 +52,7 @@ function generic_type(tokeniser, typeName) {
       ret.subtype.push(subtype);
       break;
     }
+    case "async":
     case "sequence":
     case "FrozenArray":
     case "ObservableArray": {
@@ -169,6 +180,8 @@ export class Type extends Base {
 
   get generic() {
     if (this.subtype.length && this.tokens.base) {
+      if (this.tokens.base.value === "iterable" && this.tokens.async)
+        return "async iterable";
       return this.tokens.base.value;
     }
     return "";
@@ -259,6 +272,7 @@ for more information.`;
     const type_body = () => {
       if (this.union || this.generic) {
         return w.ts.wrap([
+          w.token(this.tokens.async, w.ts.generic),
           w.token(this.tokens.base, w.ts.generic),
           w.token(this.tokens.open),
           ...this.subtype.map((t) => t.write(w)),
diff --git a/test/invalid/baseline/invalid-attribute.txt b/test/invalid/baseline/invalid-attribute.txt
index 68b15c5e..eff26aa1 100644
--- a/test/invalid/baseline/invalid-attribute.txt
+++ b/test/invalid/baseline/invalid-attribute.txt
@@ -1,21 +1,24 @@
 (attr-invalid-type) Validation error at line 3 in invalid-attribute.webidl, inside `interface sequenceAsAttribute -> attribute invalid`:
   attribute sequence<short> invalid;
                             ^ Attributes cannot accept sequence types.
-(attr-invalid-type) Validation error at line 9 in invalid-attribute.webidl, inside `interface recordAsAttribute -> attribute invalid`:
+(attr-invalid-type) Validation error at line 9 in invalid-attribute.webidl, inside `interface asyncIterableAsAttribute -> attribute invalid`:
+ async iterable<short> invalid;
+                       ^ Attributes cannot accept async iterable types.
+(attr-invalid-type) Validation error at line 15 in invalid-attribute.webidl, inside `interface recordAsAttribute -> attribute invalid`:
 <DOMString, DOMString> invalid;
                        ^ Attributes cannot accept record types.
-(attr-invalid-type) Validation error at line 17 in invalid-attribute.webidl, inside `interface dictionaryAsAttribute -> attribute dict`:
+(attr-invalid-type) Validation error at line 23 in invalid-attribute.webidl, inside `interface dictionaryAsAttribute -> attribute dict`:
   attribute Dict dict;
             ^ Attributes cannot accept dictionary types.
-(attr-invalid-type) Validation error at line 18 in invalid-attribute.webidl, inside `interface dictionaryAsAttribute -> attribute dictUnion`:
+(attr-invalid-type) Validation error at line 24 in invalid-attribute.webidl, inside `interface dictionaryAsAttribute -> attribute dictUnion`:
   attribute (Dict or boolean) dictUnion
              ^ Attributes cannot accept dictionary types.
-(attr-invalid-type) Validation error at line 28 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr1`:
+(attr-invalid-type) Validation error at line 34 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr1`:
   readonly attribute [EnforceRange] long readOnlyAttr1;
                                     ^ Readonly attributes cannot accept [EnforceRange] extended attribute.
-(attr-invalid-type) Validation error at line 29 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr2`:
+(attr-invalid-type) Validation error at line 35 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr2`:
   readonly attribute [EnforceRange] GPUInt32In readOnlyAttr2;
                                     ^ Readonly attributes cannot accept [EnforceRange] extended attribute.
-(attr-invalid-type) Validation error at line 30 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr2`:
+(attr-invalid-type) Validation error at line 36 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr2`:
   readonly attribute GPUInt32 readOnlyAttr2;
                      ^ Readonly attributes cannot accept [EnforceRange] extended attribute.
diff --git a/test/invalid/baseline/invalid-callback-argument.txt b/test/invalid/baseline/invalid-callback-argument.txt
new file mode 100644
index 00000000..ad7c2399
--- /dev/null
+++ b/test/invalid/baseline/invalid-callback-argument.txt
@@ -0,0 +1,3 @@
+(operation-return-invalid-type) Validation error at line 1 in invalid-callback-argument.webidl, inside `callback DoSomething -> argument bool`:
+async iterable<DOMString> bool);
+                          ^ Callback function arguments can not be async iterable types.
diff --git a/test/invalid/baseline/invalid-operation-return.txt b/test/invalid/baseline/invalid-operation-return.txt
new file mode 100644
index 00000000..2bb314d7
--- /dev/null
+++ b/test/invalid/baseline/invalid-operation-return.txt
@@ -0,0 +1,3 @@
+(operation-return-invalid-type) Validation error at line 3 in invalid-operation-return.webidl, inside `interface asyncIterableReturn -> operation stream`:
+  async iterable<short> stream(async iterable<
+                        ^ Operations can not return async iterable types.
diff --git a/test/invalid/idl/invalid-attribute.webidl b/test/invalid/idl/invalid-attribute.webidl
index 8292e1fd..5f33c517 100644
--- a/test/invalid/idl/invalid-attribute.webidl
+++ b/test/invalid/idl/invalid-attribute.webidl
@@ -4,6 +4,12 @@ interface sequenceAsAttribute {
   attribute (sequence<short> or boolean) invalidUnion; // TODO
 };
 
+[Exposed=Window]
+interface asyncIterableAsAttribute {
+  attribute async iterable<short> invalid;
+  attribute (async iterable<short> or boolean) invalidUnion; // TODO
+};
+
 [Exposed=Window]
 interface recordAsAttribute {
   attribute record<DOMString, DOMString> invalid;
diff --git a/test/invalid/idl/invalid-callback-argument.webidl b/test/invalid/idl/invalid-callback-argument.webidl
new file mode 100644
index 00000000..c7ef1df6
--- /dev/null
+++ b/test/invalid/idl/invalid-callback-argument.webidl
@@ -0,0 +1 @@
+callback DoSomething = Promise<DOMString> (async iterable<DOMString> bool);
\ No newline at end of file
diff --git a/test/invalid/idl/invalid-operation-return.webidl b/test/invalid/idl/invalid-operation-return.webidl
new file mode 100644
index 00000000..a697a845
--- /dev/null
+++ b/test/invalid/idl/invalid-operation-return.webidl
@@ -0,0 +1,4 @@
+[Exposed=Window]
+interface asyncIterableReturn {
+  async iterable<short> stream(async iterable<short> foo);
+};
diff --git a/test/syntax/baseline/async-iterable.json b/test/syntax/baseline/async-iterable-decl.json
similarity index 100%
rename from test/syntax/baseline/async-iterable.json
rename to test/syntax/baseline/async-iterable-decl.json
diff --git a/test/syntax/baseline/async-iterable-type.json b/test/syntax/baseline/async-iterable-type.json
new file mode 100644
index 00000000..fb4ca4aa
--- /dev/null
+++ b/test/syntax/baseline/async-iterable-type.json
@@ -0,0 +1,131 @@
+[
+    {
+        "type": "interface",
+        "name": "Canvas",
+        "inheritance": null,
+        "members": [
+            {
+                "type": "operation",
+                "name": "drawPolygonAsync",
+                "idlType": {
+                    "type": "return-type",
+                    "extAttrs": [],
+                    "generic": "Promise",
+                    "nullable": false,
+                    "union": false,
+                    "idlType": [
+                        {
+                            "type": "return-type",
+                            "extAttrs": [],
+                            "generic": "",
+                            "nullable": false,
+                            "union": false,
+                            "idlType": "undefined"
+                        }
+                    ]
+                },
+                "arguments": [
+                    {
+                        "type": "argument",
+                        "name": "coordinates",
+                        "extAttrs": [],
+                        "idlType": {
+                            "type": "argument-type",
+                            "extAttrs": [],
+                            "generic": "async iterable",
+                            "nullable": false,
+                            "union": false,
+                            "idlType": [
+                                {
+                                    "type": "argument-type",
+                                    "extAttrs": [],
+                                    "generic": "",
+                                    "nullable": false,
+                                    "union": false,
+                                    "idlType": "float"
+                                }
+                            ]
+                        },
+                        "default": null,
+                        "optional": false,
+                        "variadic": false
+                    }
+                ],
+                "extAttrs": [],
+                "special": ""
+            }
+        ],
+        "extAttrs": [],
+        "partial": false
+    },
+    {
+        "type": "interface",
+        "name": "I",
+        "inheritance": null,
+        "members": [
+            {
+                "type": "operation",
+                "name": "f1",
+                "idlType": {
+                    "type": "return-type",
+                    "extAttrs": [],
+                    "generic": "Promise",
+                    "nullable": false,
+                    "union": false,
+                    "idlType": [
+                        {
+                            "type": "return-type",
+                            "extAttrs": [],
+                            "generic": "",
+                            "nullable": false,
+                            "union": false,
+                            "idlType": "undefined"
+                        }
+                    ]
+                },
+                "arguments": [
+                    {
+                        "type": "argument",
+                        "name": "arg",
+                        "extAttrs": [],
+                        "idlType": {
+                            "type": "argument-type",
+                            "extAttrs": [],
+                            "generic": "async iterable",
+                            "nullable": false,
+                            "union": false,
+                            "idlType": [
+                                {
+                                    "type": "argument-type",
+                                    "extAttrs": [
+                                        {
+                                            "type": "extended-attribute",
+                                            "name": "XAttr",
+                                            "rhs": null,
+                                            "arguments": []
+                                        }
+                                    ],
+                                    "generic": "",
+                                    "nullable": false,
+                                    "union": false,
+                                    "idlType": "float"
+                                }
+                            ]
+                        },
+                        "default": null,
+                        "optional": false,
+                        "variadic": false
+                    }
+                ],
+                "extAttrs": [],
+                "special": ""
+            }
+        ],
+        "extAttrs": [],
+        "partial": false
+    },
+    {
+        "type": "eof",
+        "value": ""
+    }
+]
diff --git a/test/syntax/idl/async-iterable.webidl b/test/syntax/idl/async-iterable-decl.webidl
similarity index 100%
rename from test/syntax/idl/async-iterable.webidl
rename to test/syntax/idl/async-iterable-decl.webidl
diff --git a/test/syntax/idl/async-iterable-type.webidl b/test/syntax/idl/async-iterable-type.webidl
new file mode 100644
index 00000000..1f9d0bd6
--- /dev/null
+++ b/test/syntax/idl/async-iterable-type.webidl
@@ -0,0 +1,7 @@
+interface Canvas {
+  Promise<undefined> drawPolygonAsync(async iterable<float> coordinates);
+};
+
+interface I {
+  Promise<undefined> f1(async iterable<[XAttr] float> arg);
+};

From 7d78f2c14bb1f4b93e265e619ebc99bf6ecd8975 Mon Sep 17 00:00:00 2001
From: Kagami Sascha Rosylight <saschanaz@outlook.com>
Date: Tue, 20 May 2025 00:20:24 +0200
Subject: [PATCH 2/8] it can be return type of operations

---
 lib/productions/iterable.js                   |  4 +-
 lib/productions/operation.js                  |  9 ---
 .../baseline/invalid-operation-return.txt     |  3 -
 .../idl/invalid-callback-argument.webidl      |  2 +-
 .../idl/invalid-operation-return.webidl       |  4 --
 test/syntax/baseline/async-iterable-type.json | 69 +++++++++++++++++++
 test/syntax/idl/async-iterable-type.webidl    |  5 ++
 7 files changed, 77 insertions(+), 19 deletions(-)
 delete mode 100644 test/invalid/baseline/invalid-operation-return.txt
 delete mode 100644 test/invalid/idl/invalid-operation-return.webidl

diff --git a/lib/productions/iterable.js b/lib/productions/iterable.js
index baff2415..d95f1e9a 100644
--- a/lib/productions/iterable.js
+++ b/lib/productions/iterable.js
@@ -74,8 +74,8 @@ export class IterableLike extends Base {
       tokens.async &&
       tokens.base.value === "iterable"
     ) {
-      // Instead of a missing semicolon, this could be an invalid async iterable
-      // return type for a regular operation. Let's bail out early in that case.
+      // Instead of a missing semicolon, this could be an async iterable return
+      // type for a regular operation. Let's bail out early in that case.
       tokeniser.unconsume(start_position);
       return;
     } else if (!tokens.termination) {
diff --git a/lib/productions/operation.js b/lib/productions/operation.js
index 40b84b25..f4c561be 100644
--- a/lib/productions/operation.js
+++ b/lib/productions/operation.js
@@ -69,15 +69,6 @@ export class Operation extends Base {
     }
     if (this.idlType) {
       yield* this.idlType.validate(defs);
-      if (this.idlType.generic === "async iterable") {
-        const message = `Operations can not return ${this.idlType.generic} types.`;
-        yield validationError(
-          this.tokens.name,
-          this,
-          "operation-return-invalid-type",
-          message,
-        );
-      }
     }
     for (const argument of this.arguments) {
       yield* argument.validate(defs);
diff --git a/test/invalid/baseline/invalid-operation-return.txt b/test/invalid/baseline/invalid-operation-return.txt
deleted file mode 100644
index 2bb314d7..00000000
--- a/test/invalid/baseline/invalid-operation-return.txt
+++ /dev/null
@@ -1,3 +0,0 @@
-(operation-return-invalid-type) Validation error at line 3 in invalid-operation-return.webidl, inside `interface asyncIterableReturn -> operation stream`:
-  async iterable<short> stream(async iterable<
-                        ^ Operations can not return async iterable types.
diff --git a/test/invalid/idl/invalid-callback-argument.webidl b/test/invalid/idl/invalid-callback-argument.webidl
index c7ef1df6..e609bad3 100644
--- a/test/invalid/idl/invalid-callback-argument.webidl
+++ b/test/invalid/idl/invalid-callback-argument.webidl
@@ -1 +1 @@
-callback DoSomething = Promise<DOMString> (async iterable<DOMString> bool);
\ No newline at end of file
+callback DoSomething = Promise<DOMString> (async iterable<DOMString> bool);
diff --git a/test/invalid/idl/invalid-operation-return.webidl b/test/invalid/idl/invalid-operation-return.webidl
deleted file mode 100644
index a697a845..00000000
--- a/test/invalid/idl/invalid-operation-return.webidl
+++ /dev/null
@@ -1,4 +0,0 @@
-[Exposed=Window]
-interface asyncIterableReturn {
-  async iterable<short> stream(async iterable<short> foo);
-};
diff --git a/test/syntax/baseline/async-iterable-type.json b/test/syntax/baseline/async-iterable-type.json
index fb4ca4aa..41340316 100644
--- a/test/syntax/baseline/async-iterable-type.json
+++ b/test/syntax/baseline/async-iterable-type.json
@@ -124,6 +124,75 @@
         "extAttrs": [],
         "partial": false
     },
+    {
+        "type": "interface",
+        "name": "asyncIterableReturn",
+        "inheritance": null,
+        "members": [
+            {
+                "type": "operation",
+                "name": "stream",
+                "idlType": {
+                    "type": "return-type",
+                    "extAttrs": [],
+                    "generic": "async iterable",
+                    "nullable": false,
+                    "union": false,
+                    "idlType": [
+                        {
+                            "type": "return-type",
+                            "extAttrs": [],
+                            "generic": "",
+                            "nullable": false,
+                            "union": false,
+                            "idlType": "short"
+                        }
+                    ]
+                },
+                "arguments": [
+                    {
+                        "type": "argument",
+                        "name": "foo",
+                        "extAttrs": [],
+                        "idlType": {
+                            "type": "argument-type",
+                            "extAttrs": [],
+                            "generic": "async iterable",
+                            "nullable": false,
+                            "union": false,
+                            "idlType": [
+                                {
+                                    "type": "argument-type",
+                                    "extAttrs": [],
+                                    "generic": "",
+                                    "nullable": false,
+                                    "union": false,
+                                    "idlType": "short"
+                                }
+                            ]
+                        },
+                        "default": null,
+                        "optional": false,
+                        "variadic": false
+                    }
+                ],
+                "extAttrs": [],
+                "special": ""
+            }
+        ],
+        "extAttrs": [
+            {
+                "type": "extended-attribute",
+                "name": "Exposed",
+                "rhs": {
+                    "type": "identifier",
+                    "value": "Window"
+                },
+                "arguments": []
+            }
+        ],
+        "partial": false
+    },
     {
         "type": "eof",
         "value": ""
diff --git a/test/syntax/idl/async-iterable-type.webidl b/test/syntax/idl/async-iterable-type.webidl
index 1f9d0bd6..f0e0f8d3 100644
--- a/test/syntax/idl/async-iterable-type.webidl
+++ b/test/syntax/idl/async-iterable-type.webidl
@@ -5,3 +5,8 @@ interface Canvas {
 interface I {
   Promise<undefined> f1(async iterable<[XAttr] float> arg);
 };
+
+[Exposed=Window]
+interface asyncIterableReturn {
+  async iterable<short> stream(async iterable<short> foo);
+};

From 21c5f8b8715a25ffb2f9d1f96fdebce0c45bc695 Mon Sep 17 00:00:00 2001
From: Kagami Sascha Rosylight <saschanaz@outlook.com>
Date: Wed, 23 Jul 2025 11:43:44 +0200
Subject: [PATCH 3/8] Update to async_sequence

---
 lib/productions/attribute.js                      |  2 +-
 lib/productions/callback.js                       |  6 +++---
 lib/productions/operation.js                      |  9 +++++++++
 lib/productions/type.js                           | 13 ++-----------
 lib/tokeniser.js                                  |  1 +
 test/invalid/baseline/async-sequence-const.txt    |  3 +++
 .../invalid/baseline/async-sequence-idl-to-js.txt |  9 +++++++++
 .../baseline/async-sequence-two-params.txt        |  3 +++
 test/invalid/baseline/invalid-attribute.txt       | 15 ++++++---------
 .../baseline/invalid-callback-argument.txt        |  3 ---
 test/invalid/idl/async-sequence-const.webidl      |  4 ++++
 test/invalid/idl/async-sequence-idl-to-js.webidl  |  9 +++++++++
 test/invalid/idl/async-sequence-two-params.webidl |  4 ++++
 test/invalid/idl/invalid-attribute.webidl         |  6 ------
 test/invalid/idl/invalid-callback-argument.webidl |  1 -
 ...ync-iterable-decl.json => async-iterable.json} |  0
 ...ync-iterable-type.json => async-sequence.json} |  8 ++++----
 test/syntax/idl/async-iterable-type.webidl        | 12 ------------
 ...iterable-decl.webidl => async-iterable.webidl} |  0
 test/syntax/idl/async-sequence.webidl             | 12 ++++++++++++
 20 files changed, 70 insertions(+), 50 deletions(-)
 create mode 100644 test/invalid/baseline/async-sequence-const.txt
 create mode 100644 test/invalid/baseline/async-sequence-idl-to-js.txt
 create mode 100644 test/invalid/baseline/async-sequence-two-params.txt
 delete mode 100644 test/invalid/baseline/invalid-callback-argument.txt
 create mode 100644 test/invalid/idl/async-sequence-const.webidl
 create mode 100644 test/invalid/idl/async-sequence-idl-to-js.webidl
 create mode 100644 test/invalid/idl/async-sequence-two-params.webidl
 delete mode 100644 test/invalid/idl/invalid-callback-argument.webidl
 rename test/syntax/baseline/{async-iterable-decl.json => async-iterable.json} (100%)
 rename test/syntax/baseline/{async-iterable-type.json => async-sequence.json} (96%)
 delete mode 100644 test/syntax/idl/async-iterable-type.webidl
 rename test/syntax/idl/{async-iterable-decl.webidl => async-iterable.webidl} (100%)
 create mode 100644 test/syntax/idl/async-sequence.webidl

diff --git a/lib/productions/attribute.js b/lib/productions/attribute.js
index 0c09a486..0c203a0b 100644
--- a/lib/productions/attribute.js
+++ b/lib/productions/attribute.js
@@ -76,7 +76,7 @@ export class Attribute extends Base {
     yield* this.idlType.validate(defs);
 
     if (
-      ["async iterable", "sequence", "record"].includes(this.idlType.generic)
+      ["async_sequence", "sequence", "record"].includes(this.idlType.generic)
     ) {
       const message = `Attributes cannot accept ${this.idlType.generic} types.`;
       yield validationError(
diff --git a/lib/productions/callback.js b/lib/productions/callback.js
index d8e15d50..815fe693 100644
--- a/lib/productions/callback.js
+++ b/lib/productions/callback.js
@@ -47,12 +47,12 @@ export class CallbackFunction extends Base {
     yield* this.extAttrs.validate(defs);
     for (const arg of this.arguments) {
       yield* arg.validate(defs);
-      if (arg.idlType.generic === "async iterable") {
-        const message = `Callback function arguments can not be ${arg.idlType.generic} types.`;
+      if (arg.idlType.generic === "async_sequence") {
+        const message = `async_sequence types can not returned as a callback argument.`;
         yield validationError(
           arg.tokens.name,
           arg,
-          "operation-return-invalid-type",
+          "async-sequence-idl-to-js",
           message,
         );
       }
diff --git a/lib/productions/operation.js b/lib/productions/operation.js
index f4c561be..ae888b81 100644
--- a/lib/productions/operation.js
+++ b/lib/productions/operation.js
@@ -68,6 +68,15 @@ export class Operation extends Base {
       yield validationError(this.tokens.open, this, "incomplete-op", message);
     }
     if (this.idlType) {
+      if (this.idlType.generic === "async_sequence") {
+        const message = `async_sequence types can not returned from an operation.`;
+        yield validationError(
+          this.idlType.tokens.base,
+          this,
+          "async-sequence-idl-to-js",
+          message,
+        );
+      }
       yield* this.idlType.validate(defs);
     }
     for (const argument of this.arguments) {
diff --git a/lib/productions/type.js b/lib/productions/type.js
index 7429dfab..7a51e5e1 100644
--- a/lib/productions/type.js
+++ b/lib/productions/type.js
@@ -16,12 +16,11 @@ import { ExtendedAttributes } from "./extended-attributes.js";
  * @param {string} typeName
  */
 function generic_type(tokeniser, typeName) {
-  const prevPosition = tokeniser.position;
   const base = tokeniser.consume(
-    "async",
     "FrozenArray",
     "ObservableArray",
     "Promise",
+    "async_sequence",
     "sequence",
     "record",
   );
@@ -31,14 +30,6 @@ function generic_type(tokeniser, typeName) {
   const ret = autoParenter(
     new Type({ source: tokeniser.source, tokens: { base } }),
   );
-  if (base.value === "async") {
-    ret.tokens.async = base;
-    ret.tokens.base = tokeniser.consume("iterable");
-    if (!ret.tokens.base) {
-      tokeniser.unconsume(prevPosition); // unconsume the "async" token
-      return;
-    }
-  }
   ret.tokens.open =
     tokeniser.consume("<") ||
     tokeniser.error(`No opening bracket after ${base.value}`);
@@ -52,7 +43,7 @@ function generic_type(tokeniser, typeName) {
       ret.subtype.push(subtype);
       break;
     }
-    case "async":
+    case "async_sequence":
     case "sequence":
     case "FrozenArray":
     case "ObservableArray": {
diff --git a/lib/tokeniser.js b/lib/tokeniser.js
index 7c787a1a..a934c52a 100644
--- a/lib/tokeniser.js
+++ b/lib/tokeniser.js
@@ -73,6 +73,7 @@ const nonRegexTerminals = [
   "ObservableArray",
   "Promise",
   "async_iterable",
+  "async_sequence",
   "bigint",
   "boolean",
   "byte",
diff --git a/test/invalid/baseline/async-sequence-const.txt b/test/invalid/baseline/async-sequence-const.txt
new file mode 100644
index 00000000..9cb28ef3
--- /dev/null
+++ b/test/invalid/baseline/async-sequence-const.txt
@@ -0,0 +1,3 @@
+Syntax error at line 3 in async-sequence-const.webidl, since `interface AsyncSequence`:
+  const async_sequence<long, short
+        ^ Const lacks a type
diff --git a/test/invalid/baseline/async-sequence-idl-to-js.txt b/test/invalid/baseline/async-sequence-idl-to-js.txt
new file mode 100644
index 00000000..b4bb0e82
--- /dev/null
+++ b/test/invalid/baseline/async-sequence-idl-to-js.txt
@@ -0,0 +1,9 @@
+(attr-invalid-type) Validation error at line 3 in async-sequence-idl-to-js.webidl, inside `interface asyncIterableAsAttribute -> attribute invalid`:
+  attribute async_sequence<short> invalid;
+                                  ^ Attributes cannot accept async_sequence types.
+(async-sequence-idl-to-js) Validation error at line 5 in async-sequence-idl-to-js.webidl, inside `interface asyncIterableAsAttribute -> operation invalidOp`:
+  async_sequence<DOMString> invalidOp
+  ^ async_sequence types can not returned from an operation.
+(async-sequence-idl-to-js) Validation error at line 8 in async-sequence-idl-to-js.webidl, inside `callback DoSomething -> argument bool`:
+ (async_sequence<DOMString> bool);
+                            ^ async_sequence types can not returned as a callback argument.
diff --git a/test/invalid/baseline/async-sequence-two-params.txt b/test/invalid/baseline/async-sequence-two-params.txt
new file mode 100644
index 00000000..b14f1242
--- /dev/null
+++ b/test/invalid/baseline/async-sequence-two-params.txt
@@ -0,0 +1,3 @@
+Syntax error at line 3 in async-sequence-two-params.webidl, since `interface AsyncSequence`:
+  async_sequence<long, short> foo(
+                     ^ Missing closing bracket after async_sequence
diff --git a/test/invalid/baseline/invalid-attribute.txt b/test/invalid/baseline/invalid-attribute.txt
index eff26aa1..68b15c5e 100644
--- a/test/invalid/baseline/invalid-attribute.txt
+++ b/test/invalid/baseline/invalid-attribute.txt
@@ -1,24 +1,21 @@
 (attr-invalid-type) Validation error at line 3 in invalid-attribute.webidl, inside `interface sequenceAsAttribute -> attribute invalid`:
   attribute sequence<short> invalid;
                             ^ Attributes cannot accept sequence types.
-(attr-invalid-type) Validation error at line 9 in invalid-attribute.webidl, inside `interface asyncIterableAsAttribute -> attribute invalid`:
- async iterable<short> invalid;
-                       ^ Attributes cannot accept async iterable types.
-(attr-invalid-type) Validation error at line 15 in invalid-attribute.webidl, inside `interface recordAsAttribute -> attribute invalid`:
+(attr-invalid-type) Validation error at line 9 in invalid-attribute.webidl, inside `interface recordAsAttribute -> attribute invalid`:
 <DOMString, DOMString> invalid;
                        ^ Attributes cannot accept record types.
-(attr-invalid-type) Validation error at line 23 in invalid-attribute.webidl, inside `interface dictionaryAsAttribute -> attribute dict`:
+(attr-invalid-type) Validation error at line 17 in invalid-attribute.webidl, inside `interface dictionaryAsAttribute -> attribute dict`:
   attribute Dict dict;
             ^ Attributes cannot accept dictionary types.
-(attr-invalid-type) Validation error at line 24 in invalid-attribute.webidl, inside `interface dictionaryAsAttribute -> attribute dictUnion`:
+(attr-invalid-type) Validation error at line 18 in invalid-attribute.webidl, inside `interface dictionaryAsAttribute -> attribute dictUnion`:
   attribute (Dict or boolean) dictUnion
              ^ Attributes cannot accept dictionary types.
-(attr-invalid-type) Validation error at line 34 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr1`:
+(attr-invalid-type) Validation error at line 28 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr1`:
   readonly attribute [EnforceRange] long readOnlyAttr1;
                                     ^ Readonly attributes cannot accept [EnforceRange] extended attribute.
-(attr-invalid-type) Validation error at line 35 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr2`:
+(attr-invalid-type) Validation error at line 29 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr2`:
   readonly attribute [EnforceRange] GPUInt32In readOnlyAttr2;
                                     ^ Readonly attributes cannot accept [EnforceRange] extended attribute.
-(attr-invalid-type) Validation error at line 36 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr2`:
+(attr-invalid-type) Validation error at line 30 in invalid-attribute.webidl, inside `interface EnforceRangeInReadonlyAttribute -> attribute readOnlyAttr2`:
   readonly attribute GPUInt32 readOnlyAttr2;
                      ^ Readonly attributes cannot accept [EnforceRange] extended attribute.
diff --git a/test/invalid/baseline/invalid-callback-argument.txt b/test/invalid/baseline/invalid-callback-argument.txt
deleted file mode 100644
index ad7c2399..00000000
--- a/test/invalid/baseline/invalid-callback-argument.txt
+++ /dev/null
@@ -1,3 +0,0 @@
-(operation-return-invalid-type) Validation error at line 1 in invalid-callback-argument.webidl, inside `callback DoSomething -> argument bool`:
-async iterable<DOMString> bool);
-                          ^ Callback function arguments can not be async iterable types.
diff --git a/test/invalid/idl/async-sequence-const.webidl b/test/invalid/idl/async-sequence-const.webidl
new file mode 100644
index 00000000..8d48f57d
--- /dev/null
+++ b/test/invalid/idl/async-sequence-const.webidl
@@ -0,0 +1,4 @@
+[Exposed=Window]
+interface AsyncSequence {
+  const async_sequence<long, short>  ASYNC_SEQUENCE = 0;
+};
diff --git a/test/invalid/idl/async-sequence-idl-to-js.webidl b/test/invalid/idl/async-sequence-idl-to-js.webidl
new file mode 100644
index 00000000..4e558581
--- /dev/null
+++ b/test/invalid/idl/async-sequence-idl-to-js.webidl
@@ -0,0 +1,9 @@
+[Exposed=Window]
+interface asyncIterableAsAttribute {
+  attribute async_sequence<short> invalid;
+  attribute (async_sequence<short> or boolean) invalidUnion; // TODO
+  async_sequence<DOMString> invalidOp();
+};
+
+callback DoSomething = Promise<DOMString> (async_sequence<DOMString> bool);
+
diff --git a/test/invalid/idl/async-sequence-two-params.webidl b/test/invalid/idl/async-sequence-two-params.webidl
new file mode 100644
index 00000000..472b556d
--- /dev/null
+++ b/test/invalid/idl/async-sequence-two-params.webidl
@@ -0,0 +1,4 @@
+[Exposed=Window]
+interface AsyncSequence {
+  async_sequence<long, short> foo();
+};
diff --git a/test/invalid/idl/invalid-attribute.webidl b/test/invalid/idl/invalid-attribute.webidl
index 5f33c517..8292e1fd 100644
--- a/test/invalid/idl/invalid-attribute.webidl
+++ b/test/invalid/idl/invalid-attribute.webidl
@@ -4,12 +4,6 @@ interface sequenceAsAttribute {
   attribute (sequence<short> or boolean) invalidUnion; // TODO
 };
 
-[Exposed=Window]
-interface asyncIterableAsAttribute {
-  attribute async iterable<short> invalid;
-  attribute (async iterable<short> or boolean) invalidUnion; // TODO
-};
-
 [Exposed=Window]
 interface recordAsAttribute {
   attribute record<DOMString, DOMString> invalid;
diff --git a/test/invalid/idl/invalid-callback-argument.webidl b/test/invalid/idl/invalid-callback-argument.webidl
deleted file mode 100644
index e609bad3..00000000
--- a/test/invalid/idl/invalid-callback-argument.webidl
+++ /dev/null
@@ -1 +0,0 @@
-callback DoSomething = Promise<DOMString> (async iterable<DOMString> bool);
diff --git a/test/syntax/baseline/async-iterable-decl.json b/test/syntax/baseline/async-iterable.json
similarity index 100%
rename from test/syntax/baseline/async-iterable-decl.json
rename to test/syntax/baseline/async-iterable.json
diff --git a/test/syntax/baseline/async-iterable-type.json b/test/syntax/baseline/async-sequence.json
similarity index 96%
rename from test/syntax/baseline/async-iterable-type.json
rename to test/syntax/baseline/async-sequence.json
index 41340316..837523a1 100644
--- a/test/syntax/baseline/async-iterable-type.json
+++ b/test/syntax/baseline/async-sequence.json
@@ -32,7 +32,7 @@
                         "idlType": {
                             "type": "argument-type",
                             "extAttrs": [],
-                            "generic": "async iterable",
+                            "generic": "async_sequence",
                             "nullable": false,
                             "union": false,
                             "idlType": [
@@ -91,7 +91,7 @@
                         "idlType": {
                             "type": "argument-type",
                             "extAttrs": [],
-                            "generic": "async iterable",
+                            "generic": "async_sequence",
                             "nullable": false,
                             "union": false,
                             "idlType": [
@@ -135,7 +135,7 @@
                 "idlType": {
                     "type": "return-type",
                     "extAttrs": [],
-                    "generic": "async iterable",
+                    "generic": "async_sequence",
                     "nullable": false,
                     "union": false,
                     "idlType": [
@@ -157,7 +157,7 @@
                         "idlType": {
                             "type": "argument-type",
                             "extAttrs": [],
-                            "generic": "async iterable",
+                            "generic": "async_sequence",
                             "nullable": false,
                             "union": false,
                             "idlType": [
diff --git a/test/syntax/idl/async-iterable-type.webidl b/test/syntax/idl/async-iterable-type.webidl
deleted file mode 100644
index f0e0f8d3..00000000
--- a/test/syntax/idl/async-iterable-type.webidl
+++ /dev/null
@@ -1,12 +0,0 @@
-interface Canvas {
-  Promise<undefined> drawPolygonAsync(async iterable<float> coordinates);
-};
-
-interface I {
-  Promise<undefined> f1(async iterable<[XAttr] float> arg);
-};
-
-[Exposed=Window]
-interface asyncIterableReturn {
-  async iterable<short> stream(async iterable<short> foo);
-};
diff --git a/test/syntax/idl/async-iterable-decl.webidl b/test/syntax/idl/async-iterable.webidl
similarity index 100%
rename from test/syntax/idl/async-iterable-decl.webidl
rename to test/syntax/idl/async-iterable.webidl
diff --git a/test/syntax/idl/async-sequence.webidl b/test/syntax/idl/async-sequence.webidl
new file mode 100644
index 00000000..199352bd
--- /dev/null
+++ b/test/syntax/idl/async-sequence.webidl
@@ -0,0 +1,12 @@
+interface Canvas {
+  Promise<undefined> drawPolygonAsync(async_sequence<float> coordinates);
+};
+
+interface I {
+  Promise<undefined> f1(async_sequence<[XAttr] float> arg);
+};
+
+[Exposed=Window]
+interface asyncIterableReturn {
+  async_sequence<short> stream(async_sequence<short> foo);
+};

From 7e1b0bfce4069b11faad856eebe787834a002216 Mon Sep 17 00:00:00 2001
From: Kagami Sascha Rosylight <saschanaz@outlook.com>
Date: Wed, 23 Jul 2025 11:48:27 +0200
Subject: [PATCH 4/8] Update README.md

---
 README.md | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 1558995b..7f488b06 100644
--- a/README.md
+++ b/README.md
@@ -186,6 +186,7 @@ properties:
 * `sourceName`: the source name you passed to `parse()`.
 * `level`: `"error"` by default, can be `"warning"` for some validations for e.g. potential future deprecations.
 * `ruleName`: Only for validations. Currently the followings are supported:
+   * `async-iterable-idl-to-js`: `async_iterable` types cannot be returned from the IDL to JS.
    * `attr-invalid-type`: Attributes cannot have sequences, records, nor dictionaries.
    * `dict-arg-default`: Optional dictionary type arguments must have a default value of `{}`.
    * `dict-arg-optional`: Dictionary type arguments must be optional if the type does not include a required field.
@@ -236,7 +237,7 @@ attached to a field called `idlType`:
 Where the fields are as follows:
 
 * `type`: String indicating where this type is used. Can be `null` if not applicable.
-* `generic`: String indicating the generic type (e.g. "Promise", "sequence", "async iterable").
+* `generic`: String indicating the generic type (e.g. "Promise", "sequence", "async_sequence").
 * `idlType`: String indicating the type name, or array of subtypes if the type is
   generic or a union.
 * `nullable`: `true` if the type is nullable.

From 3e1098a705d3ad63dec8f5b00416b556817561c3 Mon Sep 17 00:00:00 2001
From: Kagami Sascha Rosylight <saschanaz@outlook.com>
Date: Wed, 23 Jul 2025 11:53:11 +0200
Subject: [PATCH 5/8] revert the unconsume caused by LL(1) violation

---
 lib/productions/iterable.js | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/lib/productions/iterable.js b/lib/productions/iterable.js
index 79a6103a..22041800 100644
--- a/lib/productions/iterable.js
+++ b/lib/productions/iterable.js
@@ -71,19 +71,9 @@ export class IterableLike extends Base {
       }
     }
 
-    tokens.termination = tokeniser.consume(";");
-    if (
-      !tokens.termination &&
-      tokens.async &&
-      tokens.base.value === "iterable"
-    ) {
-      // Instead of a missing semicolon, this could be an async iterable return
-      // type for a regular operation. Let's bail out early in that case.
-      tokeniser.unconsume(start_position);
-      return;
-    } else if (!tokens.termination) {
+    tokens.termination =
+      tokeniser.consume(";") ||
       tokeniser.error(`Missing semicolon after ${type} declaration`);
-    }
 
     return ret.this;
   }

From 31fa8f9223cc178a7e6cad7dd08629bdd417819c Mon Sep 17 00:00:00 2001
From: Kagami Sascha Rosylight <saschanaz@outlook.com>
Date: Wed, 23 Jul 2025 12:06:52 +0200
Subject: [PATCH 6/8] revert usages of `async`

---
 lib/productions/type.js | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/lib/productions/type.js b/lib/productions/type.js
index 7a51e5e1..393743d0 100644
--- a/lib/productions/type.js
+++ b/lib/productions/type.js
@@ -171,8 +171,6 @@ export class Type extends Base {
 
   get generic() {
     if (this.subtype.length && this.tokens.base) {
-      if (this.tokens.base.value === "iterable" && this.tokens.async)
-        return "async iterable";
       return this.tokens.base.value;
     }
     return "";
@@ -263,7 +261,6 @@ for more information.`;
     const type_body = () => {
       if (this.union || this.generic) {
         return w.ts.wrap([
-          w.token(this.tokens.async, w.ts.generic),
           w.token(this.tokens.base, w.ts.generic),
           w.token(this.tokens.open),
           ...this.subtype.map((t) => t.write(w)),

From c29c1d581b72c2d1e07e7d900e1a5018ceedbaee Mon Sep 17 00:00:00 2001
From: Kagami Sascha Rosylight <saschanaz@outlook.com>
Date: Wed, 23 Jul 2025 14:13:55 +0200
Subject: [PATCH 7/8] remove async_sequence return

The grammar isn't wrong but it's not valid. It's covered in invalid/idl instead.
---
 test/syntax/baseline/async-sequence.json | 69 ------------------------
 test/syntax/idl/async-sequence.webidl    |  5 --
 2 files changed, 74 deletions(-)

diff --git a/test/syntax/baseline/async-sequence.json b/test/syntax/baseline/async-sequence.json
index 837523a1..6978e1fd 100644
--- a/test/syntax/baseline/async-sequence.json
+++ b/test/syntax/baseline/async-sequence.json
@@ -124,75 +124,6 @@
         "extAttrs": [],
         "partial": false
     },
-    {
-        "type": "interface",
-        "name": "asyncIterableReturn",
-        "inheritance": null,
-        "members": [
-            {
-                "type": "operation",
-                "name": "stream",
-                "idlType": {
-                    "type": "return-type",
-                    "extAttrs": [],
-                    "generic": "async_sequence",
-                    "nullable": false,
-                    "union": false,
-                    "idlType": [
-                        {
-                            "type": "return-type",
-                            "extAttrs": [],
-                            "generic": "",
-                            "nullable": false,
-                            "union": false,
-                            "idlType": "short"
-                        }
-                    ]
-                },
-                "arguments": [
-                    {
-                        "type": "argument",
-                        "name": "foo",
-                        "extAttrs": [],
-                        "idlType": {
-                            "type": "argument-type",
-                            "extAttrs": [],
-                            "generic": "async_sequence",
-                            "nullable": false,
-                            "union": false,
-                            "idlType": [
-                                {
-                                    "type": "argument-type",
-                                    "extAttrs": [],
-                                    "generic": "",
-                                    "nullable": false,
-                                    "union": false,
-                                    "idlType": "short"
-                                }
-                            ]
-                        },
-                        "default": null,
-                        "optional": false,
-                        "variadic": false
-                    }
-                ],
-                "extAttrs": [],
-                "special": ""
-            }
-        ],
-        "extAttrs": [
-            {
-                "type": "extended-attribute",
-                "name": "Exposed",
-                "rhs": {
-                    "type": "identifier",
-                    "value": "Window"
-                },
-                "arguments": []
-            }
-        ],
-        "partial": false
-    },
     {
         "type": "eof",
         "value": ""
diff --git a/test/syntax/idl/async-sequence.webidl b/test/syntax/idl/async-sequence.webidl
index 199352bd..6c5405a8 100644
--- a/test/syntax/idl/async-sequence.webidl
+++ b/test/syntax/idl/async-sequence.webidl
@@ -5,8 +5,3 @@ interface Canvas {
 interface I {
   Promise<undefined> f1(async_sequence<[XAttr] float> arg);
 };
-
-[Exposed=Window]
-interface asyncIterableReturn {
-  async_sequence<short> stream(async_sequence<short> foo);
-};

From 9ec23603af5a0dc58a6f98adf341e39b760be7d9 Mon Sep 17 00:00:00 2001
From: Kagami Sascha Rosylight <saschanaz@outlook.com>
Date: Wed, 23 Jul 2025 21:54:35 +0200
Subject: [PATCH 8/8] update validation message

---
 lib/productions/callback.js                        | 2 +-
 lib/productions/operation.js                       | 2 +-
 test/invalid/baseline/async-sequence-idl-to-js.txt | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/productions/callback.js b/lib/productions/callback.js
index 815fe693..316a19f1 100644
--- a/lib/productions/callback.js
+++ b/lib/productions/callback.js
@@ -48,7 +48,7 @@ export class CallbackFunction extends Base {
     for (const arg of this.arguments) {
       yield* arg.validate(defs);
       if (arg.idlType.generic === "async_sequence") {
-        const message = `async_sequence types can not returned as a callback argument.`;
+        const message = `async_sequence types cannot be returned as a callback argument.`;
         yield validationError(
           arg.tokens.name,
           arg,
diff --git a/lib/productions/operation.js b/lib/productions/operation.js
index ae888b81..bec24a00 100644
--- a/lib/productions/operation.js
+++ b/lib/productions/operation.js
@@ -69,7 +69,7 @@ export class Operation extends Base {
     }
     if (this.idlType) {
       if (this.idlType.generic === "async_sequence") {
-        const message = `async_sequence types can not returned from an operation.`;
+        const message = `async_sequence types cannot be returned by an operation.`;
         yield validationError(
           this.idlType.tokens.base,
           this,
diff --git a/test/invalid/baseline/async-sequence-idl-to-js.txt b/test/invalid/baseline/async-sequence-idl-to-js.txt
index b4bb0e82..cfcd7b5b 100644
--- a/test/invalid/baseline/async-sequence-idl-to-js.txt
+++ b/test/invalid/baseline/async-sequence-idl-to-js.txt
@@ -3,7 +3,7 @@
                                   ^ Attributes cannot accept async_sequence types.
 (async-sequence-idl-to-js) Validation error at line 5 in async-sequence-idl-to-js.webidl, inside `interface asyncIterableAsAttribute -> operation invalidOp`:
   async_sequence<DOMString> invalidOp
-  ^ async_sequence types can not returned from an operation.
+  ^ async_sequence types cannot be returned by an operation.
 (async-sequence-idl-to-js) Validation error at line 8 in async-sequence-idl-to-js.webidl, inside `callback DoSomething -> argument bool`:
  (async_sequence<DOMString> bool);
-                            ^ async_sequence types can not returned as a callback argument.
+                            ^ async_sequence types cannot be returned as a callback argument.