Use strict subtype relation in getCommonSupertype
#1288
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Pull Request Overview
This PR ports the fix from the TypeScript repo to use a strict subtype relation in the getCommonSupertype functionality, addressing issue #1222. Key changes include:
- Adding a test case (strictBestCommonSupertype.ts) to validate the fix.
- Updating baseline output files (types and symbols) to reflect the new behavior.
- Refactoring the common supertype computation in internal/checker/inference.go to use a dedicated getSingleCommonSupertype helper.
Reviewed Changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| testdata/tests/cases/compiler/strictBestCommonSupertype.ts | New test case verifying the strict subtype logic for selecting a common supertype. |
| testdata/baselines/reference/compiler/strictBestCommonSupertype.types | Updated expected types baseline to match the new algorithm output. |
| testdata/baselines/reference/compiler/strictBestCommonSupertype.symbols | Updated expected symbols baseline reflecting changes in type resolution. |
| internal/checker/inference.go | Refactored common supertype logic to use getSingleCommonSupertype for stricter subtype validation. |
jakebailey
approved these changes
Jun 25, 2025
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This is a port of microsoft/TypeScript#61903.
Fixes #1222.