Fix #19905 - expand type tuples in delegate params during IFTI#22262
Merged
thewilsonator merged 1 commit intodlang:masterfrom Jan 21, 2026
Merged
Fix #19905 - expand type tuples in delegate params during IFTI#22262thewilsonator merged 1 commit intodlang:masterfrom
thewilsonator merged 1 commit intodlang:masterfrom
Conversation
When matching a lambda against a delegate type like `R delegate(Args)` during IFTI, parameter types that resolve to TypeTuples (e.g. from AliasSeq) were not being expanded before comparing parameter counts. This caused IFTI to fail for lambdas like `(a) => a.m()` when matched against `R delegate(AliasSeq!S)`, even though explicit instantiation `fun!void((a) => a.m())` worked correctly. The fix resolves and expands TypeTuple parameters before comparing counts, similar to what TypeFunction.typeSemantic does, but only for parameters that don't rely on template parameters being deduced. 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <noreply@anthropic.com>
Contributor
|
Thanks for your pull request, @CyberShadow! Bugzilla referencesYour PR doesn't reference any Bugzilla issue. If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog.
|
rikkimax
reviewed
Dec 18, 2025
| Type pt = pto.type; | ||
| if (!reliesOnTemplateParameters(pt, parameters[inferStart .. parameters.length])) | ||
| { | ||
| pt = pt.syntaxCopy().typeSemantic(e.loc, sc); |
Contributor
There was a problem hiding this comment.
Something about that syntaxCopy call doesn't seem necessary.
Needs further review.
Member
Author
There was a problem hiding this comment.
Claude says:
syntaxCopy is needed because typeSemantic may modify the type in-place
(setting deco), and we don't want to contaminate the template's
parameter list for future instantiations.
CyberShadow
commented
Dec 19, 2025
thewilsonator
approved these changes
Jan 21, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
LLM disclosure: this entire PR is AI-generated. It might be OK, or it might be slop. The fix looks sensible on the surface, and it passes the test suite, however, so does most slop in general. Still, I'd really like this bug to be fixed, so off the chance that this is actually OK, it seems worth a shot.
When matching a lambda against a delegate type like
R delegate(Args)during IFTI, parameter types that resolve to TypeTuples (e.g. from AliasSeq) were not being expanded before comparing parameter counts.This caused IFTI to fail for lambdas like
(a) => a.m()when matched againstR delegate(AliasSeq!S), even though explicit instantiationfun!void((a) => a.m())worked correctly.The fix resolves and expands TypeTuple parameters before comparing counts, similar to what TypeFunction.typeSemantic does, but only for parameters that don't rely on template parameters being deduced.
🤖 Generated with Claude Code