Struct ThunkSignature 

pub struct ThunkSignature {
    pub impl_type_id: u32,
    pub trait_id: u32,
    pub method_name: String,
    pub flags: VTableEntryFlags,
    pub wrap_targets: SmallVec<[WrapTarget; 2]>,
    pub self_arg_positions: SmallVec<[u8; 4]>,
    pub type_param_count: u8,
}

Per-(impl, method) thunk descriptor — the data the emission tier needs to generate a thunk function for one method of one impl.

The emission tier walks each impl’s method list, runs Erase_T on each method’s signature, and either emits a VTableEntry::Direct (no rewriting needed) or a thunk + the corresponding VTableEntry::{BoxedReturn, SelfArg, Generic, Compound} per §Q25.C.5.

Per-(impl, method) cardinality. One thunk per pair, NOT one per trait — different impls of the same trait method may need different thunks because the concrete return type differs. (E.g. impl Animal for Dog { fn clone_me(&self) -> Dog } vs impl Animal for Cat { fn clone_me(&self) -> Cat } — each clones a different concrete type and boxes it under the same trait id.)

Fields

impl_type_id: u32

Impl that owns the method (concrete-type id from the impl’s matching VTable::concrete_type_id).

trait_id: u32

Trait the method belongs to (VTable::trait_names first entry, or the surrounding trait for multi-impl cases).

method_name: String

Method name as declared in the trait.

flags: VTableEntryFlags

Erasure flags — which of (BoxedReturn / SelfArg / Generic) apply. Empty → emission tier emits VTableEntry::Direct and no thunk. Single bit → emission emits the corresponding single-shape VTableEntry::* variant. Multiple bits → VTableEntry::Compound.

wrap_targets: SmallVec<[WrapTarget; 2]>

Wrap-targets if BOXED_RETURN is set (empty otherwise).

self_arg_positions: SmallVec<[u8; 4]>

Self-arg positions if SELF_ARG is set (empty otherwise).

type_param_count: u8

Number of method-generic parameters if GENERIC is set (zero otherwise).

Implementations

impl ThunkSignature

pub fn build( impl_type_id: u32, trait_id: u32, method_name: String, return_wrap_targets: SmallVec<[WrapTarget; 2]>, self_arg_positions: SmallVec<[u8; 4]>, type_param_count: u8, ) -> Self

Build a thunk signature from per-arg / per-return erasure results. The emission tier calls this once per (impl, method) pair after running Erase_T on each component of the signature.

• return_wrap_targets — wrap_targets from running Erase_T on the method’s return type. Non-empty ⇒ BOXED_RETURN.
• self_arg_positions — indices (0-based, excluding receiver) of arguments declared as Self in the trait signature. Non-empty ⇒ SELF_ARG.
• type_param_count — number of <G> method-generic parameters. Non-zero ⇒ GENERIC.

pub fn is_direct(&self) -> bool

Whether this method needs no thunk at all (Direct dispatch).

pub fn to_vtable_entry(&self, function_or_thunk_id: u16) -> VTableEntry

Build the corresponding VTableEntry once the emission tier has assigned function_id (for Direct) / thunk_id (otherwise). Direct entries get function_id; Compound / shape entries get the thunk id and the emission-tier- allocated thunk function id is stored elsewhere.

Trait Implementations

impl Clone for ThunkSignature

fn clone(&self) -> ThunkSignature

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ThunkSignature

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

Formats the value using the given formatter.