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Merge pull request #45 from nixops4/doc-shared-value-state

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doc: Shared Value state
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Robert Hensing 2026-01-15 18:56:08 +01:00 • committed by GitHub
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4
nix-bindings-expr/src/eval_state.rs
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@ -442,6 +442,8 @@ impl EvalState {
/// Converts [thunks](https://nix.dev/manual/nix/latest/language/evaluation.html#laziness) to their evaluated form. Does not modify already-evaluated values.
///
/// Does not perform deep evaluation of nested structures.
///
/// See also: [Shared Evaluation State](Value#shared-evaluation-state)
#[doc(alias = "evaluate")]
#[doc(alias = "strict")]
pub fn force(&mut self, v: &Value) -> Result<()> {
@ -460,6 +462,8 @@ impl EvalState {
/// Returns [`None`] if the value is an unevaluated [thunk](https://nix.dev/manual/nix/latest/language/evaluation.html#laziness).
///
/// Returns [`Some`] if the value is already evaluated.
///
/// See also: [Shared Evaluation State](Value#shared-evaluation-state)
#[doc(alias = "type_of")]
#[doc(alias = "value_type_lazy")]
#[doc(alias = "nix_get_type")]

15
nix-bindings-expr/src/value.rs
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@ -65,6 +65,21 @@ impl ValueType {
}
/// A pointer to a [value](https://nix.dev/manual/nix/latest/language/types.html) or [thunk](https://nix.dev/manual/nix/2.31/language/evaluation.html?highlight=thunk#laziness), to be used with [`EvalState`][`crate::eval_state::EvalState`] methods.
///
/// # Shared Evaluation State
///
/// Multiple `Value` instances can reference the same underlying Nix value.
/// This occurs when a `Value` is [cloned](Clone), or when multiple Nix
/// expressions reference the same binding.
///
/// When any reference to a thunk is evaluated—whether through
/// [`force`](crate::eval_state::EvalState::force), other `EvalState` methods,
/// or indirectly as a consequence of evaluating something else—all references
/// observe the evaluated result. This means
/// [`value_type_unforced`](crate::eval_state::EvalState::value_type_unforced)
/// can return `None` (thunk) initially but a specific type later, even without
/// directly operating on that `Value`. The state will not regress back to a
/// less determined state.
pub struct Value {
inner: NonNull<raw::Value>,
}