Enum UnknownSemanticPolicy 

pub enum UnknownSemanticPolicy {
    AssumeTrue,
    AssumeFalse,
    Error,
}

Policy for semantic predicate coordinates that have no runtime implementation.

ANTLR grammars may embed target-language predicates that the metadata generator could not translate into a ParserPredicate table entry. When recognition reaches such a coordinate the runtime cannot know the grammar author’s intent, so the caller chooses how to proceed.

The default is Self::AssumeTrue, matching the historical behavior of this runtime. That default is deprecated and will change to Self::Error in a future minor release; grammars relying on unconditional predicates should opt in explicitly.

Variants

AssumeTrue

Treat the predicate as passing, as if it were absent from the grammar.

AssumeFalse

Treat the predicate as failing, removing the guarded alternative.

Error

Fail the parse with AntlrError::Unsupported naming every unknown coordinate that recognition evaluated.

Trait Implementations

impl Clone for UnknownSemanticPolicy

fn clone(&self) -> UnknownSemanticPolicy

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for UnknownSemanticPolicy

impl Debug for UnknownSemanticPolicy

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

Formats the value using the given formatter.

impl Default for UnknownSemanticPolicy

fn default() -> UnknownSemanticPolicy

Returns the “default value” for a type.

impl Eq for UnknownSemanticPolicy

impl PartialEq for UnknownSemanticPolicy

fn eq(&self, other: &UnknownSemanticPolicy) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for UnknownSemanticPolicy