Module markers 

Marker traits for proc-macro derived types. Marker traits for proc-macro derived types.

These marker traits identify types that have been derived with specific proc-macros. They enable compile-time type checking and blanket implementations.

Pattern

Each derive macro generates an impl of its corresponding marker trait:

Derive Macro	Marker Trait
#[derive(DataFrameRow)]	DataFrameRow
#[derive(PreferList)]	crate::markers::PrefersList
#[derive(PreferExternalPtr)]	crate::markers::PrefersExternalPtr
#[derive(PreferRNativeType)]	crate::markers::PrefersRNativeType
#[derive(PreferDataFrame)]	crate::markers::PrefersDataFrame

Traits

DataFramePayloadFields 👻

Reflection trait for #[derive(DataFrameRow)] types, used for compile-time collision detection in outer DataFrameRow enums.

DataFrameRow

Marker trait for types generated by #[derive(DataFrameRow)].

PrefersDataFrame

Marker trait for types that should be converted to R data frames via IntoR.

PrefersExternalPtr

Marker trait for types that prefer ExternalPtr conversion.

PrefersList

Marker trait for types that should be converted to R lists via IntoR.

PrefersRNativeType

Marker trait for types that prefer native SEXP conversion.

WidensToF64

Marker trait for types that can widen to f64 without loss.

WidensToI32

Marker trait for types that can widen to i32 without loss.

Functions

assert_no_payload_field_collision 👻

Compile-time assertion: no element of fields equals discriminant_suffix (the inner-enum’s #[dataframe(tag)] value).

assert_no_sibling_field_collision 👻

Compile-time assertion: no element of sibling_cols matches concat!(base, "_", tag).

const_str_eq 🔒

Const-eval equality check for two &str values (stable since Rust 1.46).