fix(memo): preserve runtime typing for unannotated params

[harsh21234i]

Summary

Fixes #6631.

@rx.memo component bodies with unannotated parameters were regressing to Var[Any] in 0.9.4, which caused downstream UntypedVarError failures when the memo body
tried to access object fields or call var methods.

This change preserves the legacy behavior for missing annotations by seeding the memo body with the first call’s runtime value type before the component is
materialized. That keeps the deprecation warning in place, but avoids the confusing compile-time failure for existing call sites.

Testing

• uv run pytest -o addopts='' tests/units/components/test_memo.py -q

[greptile-apps]

Greptile Summary

This PR restores the pre-0.9.4 behavior for @rx.memo components whose parameters lack type annotations, preventing UntypedVarError failures that occurred when the memo body accessed fields on what had silently regressed to Var[Any].

• A mutable _runtime_param_values dict is added to MemoComponentDefinition (frozen dataclass) and shared by reference into the lazy body lambda; _MemoComponentWrapper.__call__ populates it with the first call's values before triggering the _LazyBody evaluation, then clears it in a finally block.
• _var_placeholder now checks _annotation_inner_type(annotation) is Any and, when a runtime value is present, substitutes type(runtime_value) (or runtime_value._var_type for Var inputs) instead of falling back to Any.
• Tests cover both the plain-dict and Var branches of the new inference path.

Confidence Score: 5/5

Safe to merge — the change is scoped to unannotated @rx.memo params, lazy-body caching semantics ensure the runtime dict is only consulted on the first definition.component access, and cleanup is guarded by finally.

The mechanism is sound: _runtime_param_values is held by reference in both the frozen dataclass and the closure, so mutations before the first lazy evaluation are visible to the thunk. The finally cleanup prevents stale values from leaking. Both inference branches now have test coverage, and the change does not affect annotated parameters.

No files require special attention.

Important Files Changed

Filename	Overview
packages/reflex-base/src/reflex_base/components/memo.py	Adds _runtime_param_values mutable dict to the frozen MemoComponentDefinition dataclass, passed by closure reference into the lazy body thunk, so the first call's runtime values can seed type inference for unannotated params.
tests/units/components/test_memo.py	Adds two new tests covering both the plain-value and Var branches of the new runtime type inference path.
packages/reflex-base/news/6659.bugfix.md	Changelog entry for the bugfix.

_{Reviews (9): Last reviewed commit: "Merge branch 'reflex-dev:main' into fix/..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

✅ 26 untouched benchmarks
⏩ 8 skipped benchmarks¹

---

_{Comparing harsh21234i:fix/memo-untyped-var-regression-6631 (10a613c) with main (785db92)}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[harsh21234i]

any update? @masenf

[greptile-apps]

Want your agent to iterate on Greptile's feedback? Try greploops.

[masenf]

for the runtime type check, i meant, inside the memo function body, there should be an assertion that the user arg is passed as the correct typed Var, so an ObjectVar with _var_type == dict in this case.

overall i like the compatibility with the previous implementation, but it would be nice if this path raised some kind of deprecation warning indicating to users that they should be typing their memo function args for best results.

[harsh21234i]

hey @masenf Added the missing reflex-base changelog fragment in 9a16c34.