[swift2objc] Support closure by Cairo09 · Pull Request #3207 · dart-lang/native

Cairo09 · 2026-03-06T19:12:58Z

Fixes: #1669

Changes made:

added closure parsing as a suffix parselet by supporting 'text: ->' in _suffixParsets, so any parsed type followed by -> ReturnType is converted into ClosureType
reused tuple parsing output as planned- parameterside parsing first produces either voidType, a single type, or TupleType then _closureParametersFromType converts that to closure parameter list that is () to [], (A, B)to [A, B] tuple elements to many params, single to one param (Int) or Int to [Int]
added _parseTypeExpressionUntilArrow so parser must stop parameter side parsing before ->
-> is in _suffixParsets, but async/ or throws before -> are handled in _maybeParseSuffixTypeExpression by _parseClosureModifiers
_sameAs and aliasedType are used so thunking happens only when closure signatures differ
Added ClosureType in AST with fields for parameters, return type, and isEscaping, isSendable, isAsync, isThrowing
7.Added visitClosureType to AST
Preserved @escaping , @sendable in parsing through _attributeParselet
9.Added closure effect parsing (for async, throws) using _parseClosureModifiers
Added closure adaptation in function transformation so wrapper methods generate closure thunks only when original and transformed closure signatures differ.

Tests added:

checks parsing of plain closures
2.attributed closures parsing
3.nested,optional closures, empty parameter closures parsing
4.checks closure flag preservation
5.method level closure param and return support
adapter behavior tests- thunk only when needed, sendable propagation, no @escaping on closure literals, wrap or unwrap direction correctness
added e2e test

PR Checklist

I’ve reviewed the contributor guide and applied the relevant portions to this PR.
I've run dart tool/ci.dart --all locally and resolved all issues identified. This ensures the PR is formatted, has no lint errors, and ran all code generators. This applies to the packages part of the toplevel pubspec.yaml workspace.
All existing and new tests are passing. I added new tests to check the change I am making.
The PR is actually solving the issue. PRs that don't solve the issue will be closed. Please be respectful of the maintainers' time. If it's not clear what the issue is, feel free to ask questions on the GitHub issue before submitting a PR.
I have updated CHANGELOG.md for the relevant packages. (Not needed for small changes such as doc typos).
I have updated the pubspec package version if necessary.

…osure

Cairo09 · 2026-03-06T21:49:00Z

I added : to splittables because in the e2e integration test for closure where there is (callback:
it split as ":(" so it produced an error of Malformed parameter list

github-actions · 2026-03-08T22:01:45Z

PR Health

Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?

This check can be disabled by tagging the PR with skip-breaking-check.

Changelog Entry ✔️

Package	Changed Files

Changes to files need to be accounted for in their respective changelogs.

This check can be disabled by tagging the PR with skip-changelog-check.

API leaks ✔️

The following packages contain symbols visible in the public API, but not exported by the library. Export these symbols or remove them from your publicly visible API.

Package	Leaked API symbol	Leaking sources

This check can be disabled by tagging the PR with skip-leaking-check.

liamappelbe · 2026-03-10T04:28:02Z

  TokenList fragments,
+) => _parseTypeExpression(context, symbolgraph, fragments);
+
+(ReferredType, TokenList) _parseTypeExpression(


What's the point of separating parseType and _parseTypeExpression?

liamappelbe · 2026-03-10T04:29:59Z

  return parselet(context, symbolgraph, token, fragments.slice(1));
 }

+(ReferredType, TokenList) _parseTypeExpressionUntilArrow(


This seems hacky. Ideally types should be self delimiting. That is, I'd expect parseType to already stop when it's done parsing the type. What happens if you just try to use parseType?

liamappelbe · 2026-03-10T04:31:25Z

 ) {
  if (fragments.isEmpty) return (null, fragments);
+
+  final (isAsync, isThrowing, afterEffects) = _parseClosureModifiers(fragments);


This whole chunk violates the parslet design. Why do you need it?

liamappelbe · 2026-03-10T04:34:04Z

-    shouldWrapPrimitives: originalFunction.throws,
  );

+  final (wrapperResult, type) = switch ((


Shouldn't all this logic live in maybeWrapValue?

liamappelbe · 2026-03-10T04:34:16Z

    );

-    final (unwrappedParamValue, unwrappedType) = maybeUnwrapValue(
+    final (unwrappedParamValue, unwrappedType) = switch ((


Shouldn't all this logic live in maybeUnwrapValue?

liamappelbe · 2026-03-10T04:46:03Z

@@ -0,0 +1,21 @@
+import Foundation
+
+public func applyGlobal(callback: (Int) -> Int, value: Int) -> Int {


This needs way more test cases. You're only testing (Int) -> Int. Also add tests for:

Zero args

Multiple args

Tuple returns

Void returns

Non-trivial arg and return types (ie types that themselves need to be transformed)

nested closures (ie closures that take closures as args, and return closures)

escaping

sendable

async

throwing

inout params

labeled params, (_ abc: String) -> Int

If any of those are going to be a lot of work to support, still write the test, but comment it out with a TODO. I'll file a bug for any such missing features, and we'll get to it later.

Cairo09 and others added 15 commits March 5, 2026 21:58

[swift2objc] Handle empty and async/throws closure type parsing

e62e039

[swift2objc] Fix nested closure optional expectation in test

0839191

[swift2objc] Add closure thunk adaptation in function transform

cf674a6

Propagate sendable attribute in adapted closure expressions

6655b81

Parsing handled

06e3057

Merge branch 'pr-11' into pr-10

340d830

Fix initializer call to generateInvocationParams signature

ed7c801

Fix closure transform test to match primitive wrapping behavior

494059e

Merge branch 'pr-fix' into pr-10

0b48351

Fix swift2objc long-line lints in closure transformer and tests

6d1fc37

Clarify closure adaptation flow and extend closure thunk tests

fd4beda

Disallow throws-async closure order and add method closure coverage

84eec73

fix

21dfccf

Merge branch 'pr-fix2' into pr-10

517790e

Added e2e test

255668d

github-actions bot added the package:swift2objc label Mar 6, 2026

Cairo09 and others added 4 commits March 7, 2026 00:43

Merge branch 'main' into support-closure

a5121f7

Changelog

7b84cfc

Merge remote-tracking branch 'origin/support-closure' into support-cl…

8173569

…osure

fixed changelog

20b3044

Cairo09 and others added 3 commits March 9, 2026 04:27

Fixed issue

3cad681

Merge branch 'main' into support-closure

2069238

Merge branch 'main' into support-closure

68da46e

liamappelbe reviewed Mar 10, 2026

View reviewed changes

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

[swift2objc] Support closure#3207

[swift2objc] Support closure#3207
Cairo09 wants to merge 22 commits intodart-lang:mainfrom
Cairo09:support-closure

Cairo09 commented Mar 6, 2026 •

edited

Loading

Uh oh!

Cairo09 commented Mar 6, 2026 •

edited

Loading

Uh oh!

github-actions bot commented Mar 8, 2026

Uh oh!

liamappelbe Mar 10, 2026

Uh oh!

liamappelbe Mar 10, 2026

Uh oh!

liamappelbe Mar 10, 2026

Uh oh!

liamappelbe Mar 10, 2026

Uh oh!

liamappelbe Mar 10, 2026

Uh oh!

liamappelbe Mar 10, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

		@@ -0,0 +1,21 @@
		import Foundation

		public func applyGlobal(callback: (Int) -> Int, value: Int) -> Int {

Conversation

Cairo09 commented Mar 6, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

PR Checklist

Uh oh!

Cairo09 commented Mar 6, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

github-actions bot commented Mar 8, 2026

PR Health

Uh oh!

liamappelbe Mar 10, 2026

Choose a reason for hiding this comment

Uh oh!

liamappelbe Mar 10, 2026

Choose a reason for hiding this comment

Uh oh!

liamappelbe Mar 10, 2026

Choose a reason for hiding this comment

Uh oh!

liamappelbe Mar 10, 2026

Choose a reason for hiding this comment

Uh oh!

liamappelbe Mar 10, 2026

Choose a reason for hiding this comment

Uh oh!

liamappelbe Mar 10, 2026

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Cairo09 commented Mar 6, 2026 •

edited

Loading

Cairo09 commented Mar 6, 2026 •

edited

Loading