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Show incompatible union members in discriminated union discriminator errors

2

### 🔍 Search Terms discriminated union error message, union type assignability error, misleading error message, discriminator property, wider union error, union literal type error, type narrowing error message ### ✅...

janpaepke

Don't defer index types for non-generic substitution types

7

fixes https://github.com/microsoft/TypeScript/issues/61728

Andarist

Regression performance compiling types in version 5.4.2

20

### 🔎 Search Terms "regression", "5.4.2", "performance" ### 🕗 Version & Regression Information - This changed between versions 5.3.3 and 5.4.2 ### ⏯ Playground Link _No response_ ### 💻 Code...

georgekaran

Closing TS 6.0 LS issues

9

### Acknowledgement - [x] I acknowledge that issues using this template may be closed without further explanation at the maintainer's discretion. ### Comment [As discussed in our December blog post](https://devblogs.microsoft.com/typescript/progress-on-typescript-7-december-2025/#resetting-language-service-issues),...

RyanCavanaugh

[Feature Request] fieldof similar to keyof but include private and protected field

5

# Suggestion ## 🔍 Search Terms fieldof , mapped type, mapped private protected Can maybe related: https://github.com/microsoft/TypeScript/issues/35416 https://github.com/microsoft/TypeScript/issues/4822 ## ✅ Viability Checklist My suggestion meets these guidelines: * ✅ This...

jonlepage

Unwrap substitution types early in `getPropertyTypeForIndexType`

6

fixes https://github.com/microsoft/TypeScript/issues/57109 fixes https://github.com/microsoft/TypeScript/issues/54886

Andarist

Deprecation error message reporting method type as deprecated instead of method name

1

### 🔎 Search Terms deprecated type ### 🕗 Version & Regression Information - This is the behavior in every version I tried, and I reviewed the FAQ for entries about...

andrewbranch

Fix "never nullish" diagnostic missing expressions wrapped in parentheses

7

The "never nullish" diagnostic (TS2881) was not reported when the left operand of a `??` operator was wrapped in parentheses, causing valid errors to be silently ignored. ```typescript const x:...

Copilot

"Never nullish" checks miss "never nullish" through parens

1

### 🔎 Search Terms never nullish parenthesis ### 🕗 Version & Regression Information - This changed between versions 5.8 and 5.9 ### ⏯ Playground Link https://www.typescriptlang.org/play/?#code/MYewdgzgLgBAHgLhgbxgTydATgSzAcxgB8YBXMAEwFMAzPKimAX2LMtvsYF43q6wGMAIYRhYNAG4AsAChZs0JFg0QIGDzgB+AHRoYmzTAAGqgA4Qj+wwCJr0mYugwARkKzqYACi26rxsxYAlH629grgECAANlTaUSD4nioggfaO0bHxia5YqUA ### 💻 Code ```ts...

jakebailey