Avoid silentNeverType leaking into generator types inferred based on inner generic calls at yields#62283
Merged
jakebailey merged 2 commits intomicrosoft:mainfrom Dec 5, 2025
Conversation
…n inner generic calls at `yield`s
typescript-bot
added
the
For Uncommitted Bug
Collaborator
|
This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise. |
1 similar comment
Collaborator
|
This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise. |
Contributor
There was a problem hiding this comment.
Pull Request Overview
This PR fixes an issue where silentNeverType was incorrectly leaking into generator types when inferring types based on inner generic calls at yield expressions. The change improves type inference for generators that use yield* with generic function calls by preventing premature type narrowing to never.
Key changes:
- Removes special handling of
silentNeverTypein yield expression type checking - Modifies check mode for yield expressions to skip generic function checks
- Updates test baselines to reflect improved type inference from
nevertoany
Reviewed Changes
Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.
Show a summary per file
| File | Description |
|---|---|
| src/compiler/checker.ts | Core fix removing silentNeverType handling and adjusting check modes |
| tests/cases/compiler/genericCallAtYieldExpressionInGenericCall1.ts | Additional test cases for the fix |
| tests/baselines/reference/*.types | Updated type baselines showing improved inference |
| tests/baselines/reference/*.errors.txt | New error baselines for test cases |
| tests/baselines/reference/*.symbols | Symbol baselines for new test cases |
Andarist
commented
Aug 13, 2025
src/compiler/checker.ts
Outdated
| const isAsync = (getFunctionFlags(func) & FunctionFlags.Async) !== 0; | ||
| forEachYieldExpression(func.body as Block, yieldExpression => { | ||
| const yieldExpressionType = yieldExpression.expression ? checkExpression(yieldExpression.expression, checkMode) : undefinedWideningType; | ||
| const yieldExpressionType = yieldExpression.expression ? checkExpression(yieldExpression.expression, checkMode && checkMode & ~CheckMode.SkipGenericFunctions) : undefinedWideningType; |
Contributor
Author
There was a problem hiding this comment.
this is exactly what the cousin (checkAndAggregateReturnExpressionTypes) of this function (checkAndAggregateYieldOperandTypes) does
Andarist
commented
Aug 13, 2025
| > : ^ ^^ ^^ ^^^^^ | ||
| >function* <T>(value: T) { const result = yield* inner(value); // ok} : <T>(value: T) => Generator<never, void, never> | ||
| > : ^ ^^ ^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| >function* <T>(value: T) { const result = yield* inner(value); // ok} : <T>(value: T) => Generator<any, void, any> |
Contributor
Author
There was a problem hiding this comment.
the new results here are better and match the other results that have inner~ function called beforehand (when its precomputed result is yield*ed)
Member
|
@typescript-bot test it |
Collaborator
Collaborator
|
Hey @jakebailey, the results of running the DT tests are ready. Everything looks the same! |
Collaborator
|
@jakebailey Here are the results of running the user tests with tsc comparing There were infrastructure failures potentially unrelated to your change:
Otherwise... Everything looks good! |
Collaborator
|
@jakebailey Here they are:
tscComparison Report - baseline..pr
System info unknown
Hosts
Scenarios
Developer Information: |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Collaborator
|
@jakebailey Here are the results of running the top 400 repos with tsc comparing Everything looks good! |
jakebailey
approved these changes
Dec 5, 2025
jakebailey
approved these changes
Dec 5, 2025
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
3 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.
This is an improvement over one of the recent PRs: #61317