Fix: Correct constructor type inference in checker.ts (#29707).

[aman1-2]

Fixes #29707

This PR fixes an issue where the constructor type was incorrectly inferred in checker.ts. The fix ensures that the correct type is assigned, preventing potential type errors in class instantiation.
Adjusted type-checking logic in checker.ts to correctly infer the constructor type.

Changes Made

• Updated logic in checker.ts to handle constructor type inference correctly.
• Added/updated unit tests to validate the fix.

Verification Steps

• Ran hereby runtests locally to confirm all tests pass.
• Code is up-to-date with the main branch.

Please do Guide if my approach was wrong or if further refinements are needed!

[aman1-2]

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