Fix: Compiler now memoizes when const is between hooks (#35355)

[pritjasani08]

Summary

Fixes #35355

The React Compiler was not properly memoizing values when a const declaration appeared between React hooks. This fix ensures that const declarations don't break the memoization analysis chain.

Problem

When a const declaration appears between React hooks, the compiler's memoization logic was incorrectly pruning all active scopes, causing useMemo and other memoized values to not be properly optimized.

**Example of the bug:**pt
function Component() {
const [state, setState] = useState(0);
const someConst = 42; // ← This const between hooks breaks memoization
const memoized = useMemo(() => someConst * 2, [someConst]);
return

{memoized}

;
}## Solution
Updated the memoization logic in FlattenScopesWithHooksOrUseHIR.ts to only prune scopes whose body blocks actually contain hooks, rather than pruning all active scopes when a hook is encountered. This allows scopes created between hooks (like const declarations) to be properly memoized.

Changes

• Modified FlattenScopesWithHooksOrUseHIR.ts to identify blocks containing hooks in a first pass
• Updated pruning logic to only prune scopes that contain hooks, not all active scopes
• Scopes created between hooks are now properly tracked and memoized

Test Plan

• Verified the fix works with the playground example from issue [Compiler Bug]: Compiler doesn't memoize if const is between hooks #35061
• All existing compiler tests pass
• The fix ensures scopes without hooks are not incorrectly pruned