Module default_fsharp 

The value an F# member takes when the stream does not carry it.

Table 9 of DDS-XTypes 1.3, as F# — deliberately a further derivation and not a call into any sibling’s, for the reason default_zig.rs’s own documentation gives: the columns are compared against each other and a shared helper would make them agree about a mistake.

Two uses, and only one of them needs a generated function

default_expr answers Table 9’s value as one expression, and crates/lang-rules/src/adapter/fsharp.rs calls it directly to give every fsharp::ClassField::default its value at the moment a class is declared — no function needed there, because the value is written once, at the declaration, and never repeated.

crates/lang-rules/src/emit/fsharp.rs’s crate::emit::Routine carries no Ast and no Id<TypeNode> — only the already-materialised fsharp::Type — so a decoder’s own starting value cannot call default_expr directly the way the adapter does; it needs a name it can build a call to, exactly the shape default_zig.rs’s defaulter_from_decoder answers for Zig and for the same reason. defaulter_name, defaulter_from_decoder, fsharp_defaulters_over and fsharp_defaulters_called_by are that machinery, generating let zd_def_X () : T = <Table 9's value> — a unit -> T function and not a plain value, because a plain let zd_def_X : T = Pose() would construct one Pose at module load and hand every caller the same mutable object; every one of crates/lang-rules/src/emit/fsharp.rs’s three call sites — crate::emit::CodecTarget::routine’s decode start, crate::emit::CodecTarget::default_into and crate::emit::CodecTarget::member_default’s implicit branch — call zd_def_X () and expect a fresh one each time.

What makes this machinery shorter than default_zig.rs’s own copy of it is the body each generated function answers with: for an aggregate it is T(), one call, because crates/lang-cst/src/fsharp/mod.rs’s module documentation is where the design that makes T() already Table 9’s value is argued — Zig has to build a whole struct literal there and this column does not.

Functions

default_expr

DDS-XTypes 1.3 Table 9’s value for id, as an F# expression.

defaulter_from_decoder

The defaulter that goes with a decoder, by name.

defaulter_name

The defaulter function name for a type, keyed the way the decoder is: by the IDL kind for a primitive and by the codec tag for everything else — default_zig.rs’s defaulter_name read onto this column’s tag function.

discriminator_default

A union discriminator’s own Table 9 default, in the discriminator’s F# form: the enumerator for an enumeration, the boolean literal for a boolean, and the number for everything else — a char and a wchar discriminator hold their code unit as an integer here, as default_zig.rs’s discriminant_literal does for Zig.

fsharp_defaulters_called_by

The defaulters decls call, and exactly those — read off the emitted calls rather than derived a second time from the model, the same reachability walk default_zig.rs’s zig_defaulters_called_by runs.

fsharp_defaulters_over

Build the defaulter for each of types, once per name: let zd_def_X () : T = <Table 9's value>, a unit -> T function so every caller gets a fresh, unaliased value — the module documentation says why a plain value would be wrong for a mutable class.

member_value

One member’s default: its @default, or its type’s Table 9 value. §7.2.2.4.4.4.9 puts the explicit one first.