Add syntax tests for import.defer

These tests are all based on the existing dynamic import syntax tests, just updated to use the new syntax.

This PR does not contain any manually written tests -- they are all generated.

src/assignment-target-type/importcall-defer.case

@@ -0,0 +1,25 @@
+// Copyright (C) 2020 Rick Waldron. All rights reserved.
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-static-semantics-static-semantics-assignmenttargettype
+desc: >
+  Static Semantics AssignmentTargetType, Return invalid.
+info: |
+  ImportCall
+  Static Semantics AssignmentTargetType, Return invalid.
+template: invalid
+flags: [module]
+features: [import-defer]
+negative:
+  phase: parse
+  type: SyntaxError
+---*/
+
+//- assignmenttarget
+import.defer()
+//- operator
+=
+//- value
+1

src/dynamic-import/import-defer-assignment-expr-not-optional.case

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+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// Copyright (C) 2018 Rick Waldron. All rights reserved.
+// Copyright (C) 2018 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+desc: It's a SyntaxError if AssignmentExpression is omitted
+template: syntax/invalid
+info: |
+  ImportCall[Yield, Await] :
+      import . defer ( AssignmentExpression[+In, ?Yield, ?Await] )
+features: [import-defer]
+---*/
+//- import
+import.defer()
+//- teardown
+/* The params region intentionally empty */

src/dynamic-import/import-defer-empty-str-is-valid-assign-expr.case

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+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// Copyright (C) 2018 Rick Waldron. All rights reserved.
+// Copyright (C) 2018 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+desc: Calling import.defer('')
+template: syntax/valid
+features: [import-defer]
+---*/
+
+//- import
+import.defer('./empty_FIXTURE.js')

src/dynamic-import/import-defer-no-new-call-expression.case

@@ -0,0 +1,18 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// Copyright (C) 2018 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+desc: ImportCall is a CallExpression, it can't be preceded by the new keyword
+template: syntax/invalid
+info: |
+  CallExpression:
+    ImportCall
+
+  ImportCall :
+      import . defer ( AssignmentExpression[+In, ?Yield, ?Await] )
+
+features: [import-defer]
+---*/
+
+//- import
+new import.defer('./empty_FIXTURE.js')

src/dynamic-import/import-defer-no-rest-param.case

@@ -0,0 +1,18 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// Copyright (C) 2018 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+desc: ImportCall is not extensible - no rest parameter
+template: syntax/invalid
+info: |
+  ImportCall :
+      import . source ( AssignmentExpression[+In, ?Yield] )
+
+  This production doesn't allow the following production from ArgumentsList:
+
+  ... AssignmentExpression
+features: [import-defer]
+---*/
+
+//- import
+import.defer(...['./empty_FIXTURE.js'])

src/dynamic-import/import-defer-script-code-valid.case

@@ -0,0 +1,16 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// Copyright (C) 2018 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+desc: import.defer() can be used in script code
+template: syntax/valid
+features: [import-defer]
+---*/
+
+//- setup
+// This is still valid in script code, and should not be valid for module code
+// https://tc39.github.io/ecma262/#sec-scripts-static-semantics-lexicallydeclarednames
+var smoosh; function smoosh() {}
+
+//- import
+import.defer('./empty_FIXTURE.js')

src/dynamic-import/import-defer-specifier-tostring-abrupt-rejects.case

@@ -0,0 +1,40 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// Copyright (C) 2018 Rick Waldron. All rights reserved.
+// Copyright (C) 2018 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+desc: >
+    Abrupt from ToString(specifier) rejects the promise
+esid: sec-moduleevaluation
+info: |
+    Import Calls
+
+    Runtime Semantics: Evaluation
+
+    ImportCall : import . defer ( |AssignmentExpression| )
+        1. Return ? EvaluateImportCall(|AssignmentExpression|, ~defer~)
+
+    EvaluateImportCall ( specifierExpression, phase )
+        1. Let _referrer_ be GetActiveScriptOrModule().
+        1. If _referrer_ is *null*, set _referrer_ to the current Realm Record.
+        1. Let _specifierRef_ be ? Evaluation of _specifierExpression_.
+        1. Let _specifier_ be ? GetValue(_specifierRef_).
+        1. Let _promiseCapability_ be ! NewPromiseCapability(%Promise%).
+        1. Let _specifierString_ be Completion(ToString(_specifier_)).
+        1. IfAbruptRejectPromise(_specifierString_, _promiseCapability_).
+        ...
+template: catch
+features: [import-defer]
+---*/
+
+//- setup
+const obj = {
+    toString() {
+        throw 'custom error';
+    }
+};
+
+//- import
+import.defer(obj)
+//- body
+assert.sameValue(error, 'custom error');

test/language/expressions/assignmenttargettype/direct-importcall-defer.js

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+// This file was procedurally generated from the following sources:
+// - src/assignment-target-type/importcall-defer.case
+// - src/assignment-target-type/invalid/direct.template
+/*---
+description: Static Semantics AssignmentTargetType, Return invalid. (Direct assignment)
+features: [import-defer]
+flags: [generated, module]
+negative:
+  phase: parse
+  type: SyntaxError
+info: |
+    Direct assignment
+
+    ImportCall
+    Static Semantics AssignmentTargetType, Return invalid.
+
+---*/
+
+$DONOTEVALUATE();
+
+import.defer() = 1;

test/language/expressions/assignmenttargettype/parenthesized-importcall-defer.js

@@ -0,0 +1,24 @@
+// This file was procedurally generated from the following sources:
+// - src/assignment-target-type/importcall-defer.case
+// - src/assignment-target-type/invalid/parenthesized.template
+/*---
+description: Static Semantics AssignmentTargetType, Return invalid. (ParenthesizedExpression)
+esid: sec-grouping-operator-static-semantics-assignmenttargettype
+features: [import-defer]
+flags: [generated, module]
+negative:
+  phase: parse
+  type: SyntaxError
+info: |
+    ParenthesizedExpression: (Expression)
+
+    Return AssignmentTargetType of Expression.
+
+    ImportCall
+    Static Semantics AssignmentTargetType, Return invalid.
+
+---*/
+
+$DONOTEVALUATE();
+
+(import.defer()) = 1;

test/language/expressions/dynamic-import/catch/nested-arrow-import-catch-import-defer-specifier-tostring-abrupt-rejects.js

@@ -0,0 +1,57 @@
+// This file was procedurally generated from the following sources:
+// - src/dynamic-import/import-defer-specifier-tostring-abrupt-rejects.case
+// - src/dynamic-import/catch/nested-arrow.template
+/*---
+description: Abrupt from ToString(specifier) rejects the promise (nested arrow)
+esid: sec-import-call-runtime-semantics-evaluation
+features: [import-defer, dynamic-import]
+flags: [generated, async]
+info: |
+    ImportCall :
+        import( AssignmentExpression )
+
+    1. Let referencingScriptOrModule be ! GetActiveScriptOrModule().
+    2. Assert: referencingScriptOrModule is a Script Record or Module Record (i.e. is not null).
+    3. Let argRef be the result of evaluating AssignmentExpression.
+    4. Let specifier be ? GetValue(argRef).
+    5. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+    6. Let specifierString be ToString(specifier).
+    7. IfAbruptRejectPromise(specifierString, promiseCapability).
+    8. Perform ! HostImportModuleDynamically(referencingScriptOrModule, specifierString, promiseCapability).
+    9. Return promiseCapability.[[Promise]].
+
+
+    Import Calls
+
+    Runtime Semantics: Evaluation
+
+    ImportCall : import . defer ( |AssignmentExpression| )
+        1. Return ? EvaluateImportCall(|AssignmentExpression|, ~defer~)
+
+    EvaluateImportCall ( specifierExpression, phase )
+        1. Let _referrer_ be GetActiveScriptOrModule().
+        1. If _referrer_ is *null*, set _referrer_ to the current Realm Record.
+        1. Let _specifierRef_ be ? Evaluation of _specifierExpression_.
+        1. Let _specifier_ be ? GetValue(_specifierRef_).
+        1. Let _promiseCapability_ be ! NewPromiseCapability(%Promise%).
+        1. Let _specifierString_ be Completion(ToString(_specifier_)).
+        1. IfAbruptRejectPromise(_specifierString_, _promiseCapability_).
+        ...
+
+---*/
+const obj = {
+    toString() {
+        throw 'custom error';
+    }
+};
+
+
+let f = () => {
+  import.defer(obj).catch(error => {
+
+    assert.sameValue(error, 'custom error');
+
+  }).then($DONE, $DONE);
+};
+
+f();

test/language/expressions/dynamic-import/catch/nested-async-arrow-function-await-import-defer-specifier-tostring-abrupt-rejects.js

@@ -0,0 +1,57 @@
+// This file was procedurally generated from the following sources:
+// - src/dynamic-import/import-defer-specifier-tostring-abrupt-rejects.case
+// - src/dynamic-import/catch/nested-async-arrow-fn-await.template
+/*---
+description: Abrupt from ToString(specifier) rejects the promise (nested in async arrow function, awaited)
+esid: sec-import-call-runtime-semantics-evaluation
+features: [import-defer, dynamic-import]
+flags: [generated, async]
+info: |
+    ImportCall :
+        import( AssignmentExpression )
+
+    1. Let referencingScriptOrModule be ! GetActiveScriptOrModule().
+    2. Assert: referencingScriptOrModule is a Script Record or Module Record (i.e. is not null).
+    3. Let argRef be the result of evaluating AssignmentExpression.
+    4. Let specifier be ? GetValue(argRef).
+    5. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+    6. Let specifierString be ToString(specifier).
+    7. IfAbruptRejectPromise(specifierString, promiseCapability).
+    8. Perform ! HostImportModuleDynamically(referencingScriptOrModule, specifierString, promiseCapability).
+    9. Return promiseCapability.[[Promise]].
+
+
+    Import Calls
+
+    Runtime Semantics: Evaluation
+
+    ImportCall : import . defer ( |AssignmentExpression| )
+        1. Return ? EvaluateImportCall(|AssignmentExpression|, ~defer~)
+
+    EvaluateImportCall ( specifierExpression, phase )
+        1. Let _referrer_ be GetActiveScriptOrModule().
+        1. If _referrer_ is *null*, set _referrer_ to the current Realm Record.
+        1. Let _specifierRef_ be ? Evaluation of _specifierExpression_.
+        1. Let _specifier_ be ? GetValue(_specifierRef_).
+        1. Let _promiseCapability_ be ! NewPromiseCapability(%Promise%).
+        1. Let _specifierString_ be Completion(ToString(_specifier_)).
+        1. IfAbruptRejectPromise(_specifierString_, _promiseCapability_).
+        ...
+
+---*/
+const obj = {
+    toString() {
+        throw 'custom error';
+    }
+};
+
+
+const f = async () => {
+  await import.defer(obj);
+}
+
+f().catch(error => {
+
+  assert.sameValue(error, 'custom error');
+
+}).then($DONE, $DONE);

test/language/expressions/dynamic-import/catch/nested-async-arrow-function-return-await-import-defer-specifier-tostring-abrupt-rejects.js

@@ -0,0 +1,55 @@
+// This file was procedurally generated from the following sources:
+// - src/dynamic-import/import-defer-specifier-tostring-abrupt-rejects.case
+// - src/dynamic-import/catch/nested-async-arrow-fn-return-await.template
+/*---
+description: Abrupt from ToString(specifier) rejects the promise (nested in async arrow function, returned)
+esid: sec-import-call-runtime-semantics-evaluation
+features: [import-defer, dynamic-import]
+flags: [generated, async]
+info: |
+    ImportCall :
+        import( AssignmentExpression )
+
+    1. Let referencingScriptOrModule be ! GetActiveScriptOrModule().
+    2. Assert: referencingScriptOrModule is a Script Record or Module Record (i.e. is not null).
+    3. Let argRef be the result of evaluating AssignmentExpression.
+    4. Let specifier be ? GetValue(argRef).
+    5. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+    6. Let specifierString be ToString(specifier).
+    7. IfAbruptRejectPromise(specifierString, promiseCapability).
+    8. Perform ! HostImportModuleDynamically(referencingScriptOrModule, specifierString, promiseCapability).
+    9. Return promiseCapability.[[Promise]].
+
+
+    Import Calls
+
+    Runtime Semantics: Evaluation
+
+    ImportCall : import . defer ( |AssignmentExpression| )
+        1. Return ? EvaluateImportCall(|AssignmentExpression|, ~defer~)
+
+    EvaluateImportCall ( specifierExpression, phase )
+        1. Let _referrer_ be GetActiveScriptOrModule().
+        1. If _referrer_ is *null*, set _referrer_ to the current Realm Record.
+        1. Let _specifierRef_ be ? Evaluation of _specifierExpression_.
+        1. Let _specifier_ be ? GetValue(_specifierRef_).
+        1. Let _promiseCapability_ be ! NewPromiseCapability(%Promise%).
+        1. Let _specifierString_ be Completion(ToString(_specifier_)).
+        1. IfAbruptRejectPromise(_specifierString_, _promiseCapability_).
+        ...
+
+---*/
+const obj = {
+    toString() {
+        throw 'custom error';
+    }
+};
+
+
+const f = async () => await import.defer(obj);
+
+f().catch(error => {
+
+  assert.sameValue(error, 'custom error');
+
+}).then($DONE, $DONE);