Problem

Two independent handle[State<Int>] handlers in nested scope both read/write the same global WASM cell ($vera.state_get_Int / $vera.state_put_Int), so they do not have independent state. The inner handler overwrites the outer handler's state.

-- Expected: outer state = 10, inner state = 99 (independent)
-- Actual:   inner handler corrupts outer state
let @Int = handle[State<Int>](10) {
  let @Int = handle[State<Int>](99) {
    State.put(42)    -- should only affect inner handler
  };
  State.get()        -- returns 42, not 10
};

Root Cause

The current State effect implementation maps each State<T> operation to a single global WASM mutable global ($vera.state_Int). Nested handlers of the same type overwrite this shared cell rather than maintaining a separate cell per handler scope.

A correct implementation requires either:

• A handler stack per type (push on enter, pop on exit), or
• CPS/continuation-passing transformation of handlers so each handler closure captures its own cell

Workaround

Use different state types for nested handlers (e.g., State<Int> + State<Bool>), or restructure code to use sequential (non-nested) handlers of the same type.

Impact

Any program using nested handle[State<T>] of the same type produces incorrect results. This was discovered while writing tests/conformance/ch07_nested_handlers.vera, which avoids the pattern for this reason.