Struct RuleConstraint 

pub struct RuleConstraint { /* private fields */ }

Compiled representation of a single TLExpr constraint.

Two forms coexist:

1. Eager table (allow_set) — populated when the constraint compiles to a finite predicate list over a user-supplied vocabulary mapper. This path is the fast path and is used by the hard/soft masks.
2. Fallback pass-through — used when the expression hit an unsupported variant. In that case RuleConstraint::evaluate returns ConstraintVerdict::SoftPenalty(0.0) and the decoder behaves as if no constraint was present.

Implementations

impl RuleConstraint

pub fn compile<M>(expr: TLExpr, mapper: M) -> RuleGuidedResult<Self>

where M: Fn(TokenId) -> Option<String> + Send + Sync + 'static,

Compile a constraint from a TLExpr and a token → symbol-name mapper.

• If the expression only uses supported variants, the returned constraint eagerly enumerates allowed symbol names into a HashSet.
• Otherwise, the constraint is still constructed but evaluates to a no-op (soft-penalty of zero). This makes the decoder forward- compatible: new TLExpr variants don’t break existing call sites.

pub fn evaluate( &self, prefix: &[TokenId], candidate: TokenId, ) -> ConstraintVerdict

Evaluate the constraint against (prefix, candidate).

prefix is the token sequence already committed to the beam; it is not used by the current allow-list compiler but is part of the contract so stateful constraints (e.g. “no token X after token Y”) remain implementable without an API break — see extend_tlexpr_support.

pub fn allow_set(&self) -> Option<&HashSet<String>>

Read-only access to the compiled allow-list, if any.

pub fn is_supported(&self) -> bool

true when the constraint was compiled against a supported subset of TLExpr. false means the constraint is a no-op.

pub fn source(&self) -> &TLExpr

Original expression.

Trait Implementations

impl Debug for RuleConstraint

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.