Port fix to crash in mixin checking #2431
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Pull request overview
This PR ports a crash fix from TypeScript PR #62928 that prevents a nil pointer dereference in mixin type checking. The fix adds a guard condition in the getBaseTypes function to check if a type has the appropriate object flags before attempting to access its interface type data.
- Added guard condition to prevent crash when
getBaseTypesis called on types without class/interface/reference object flags - Added regression test case
noCrashOnMixin2.tsthat demonstrates the previously crashing mixin pattern - Test properly produces type-checking errors without crashing the compiler
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.
Show a summary per file
| File | Description |
|---|---|
| testdata/tests/cases/compiler/noCrashOnMixin2.ts | Adds regression test for mixin crash scenario with protected constructors |
| testdata/baselines/reference/compiler/noCrashOnMixin2.types | Expected type inference output for the test case |
| testdata/baselines/reference/compiler/noCrashOnMixin2.symbols | Expected symbol resolution output for the test case |
| testdata/baselines/reference/compiler/noCrashOnMixin2.errors.txt | Expected error messages showing proper error reporting without crash |
| internal/checker/checker.go | Adds guard condition in getBaseTypes to prevent nil pointer dereference on types without appropriate object flags |
jakebailey
approved these changes
Dec 28, 2025
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Ports microsoft/TypeScript#62928.