Module rust_conversion_builder 

Shared utilities for converting R SEXP parameters to Rust types.

This module provides a builder for generating Rust conversion code from R SEXP arguments, ensuring consistent behavior across standalone functions and impl methods.

Structs

ArgContext 🔒

The R-facing context of one argument’s conversion failure (#1591).

ConversionSubject 🔒

What a conversion failure is about: the value it names and how.

LayeredValue 🔒

The innermost value of a layered choice parameter.

RustConversionBuilder

Builder for generating Rust conversion statements from R SEXP parameters.

Enums

ChoiceLayer 🔒

A layer around a choice parameter’s value, outermost first.

ChoiceLeaf

Where the innermost value of a layered choice parameter comes from.

Expected 🔒

Where the <expected> of a conversion failure’s '<p>' must be <expected> comes from.

Functions

conversion_err_arm 🔒

The Err(e) arm of a conversion binding: return the tagged kind = "conversion" value. __mx_conversion_err_parts! takes the class vector, message and data from an RConditionData error type, the R-worded reason from a built-in conversion error and the Display text otherwise; conversion_condition_value puts the context’s prefix before it, appends the crate’s conversion_error_class and adds e$param and e$rust_type.

conversion_err_arm_with_call 🔒

conversion_value_tokens 🔒

The conversion_condition_value(...) expression for the error bound as e on subject, with the crate class and call.

declared_expectation 🔒

The expression, on a conversion failure’s path, for what a parameter of type ty declares when the macro has no wording for it: an Option<String>, with the error bound as e. Only for a type the binding converts with TryFromSexp, whose __MX_EXPECTATION it reads.

either_arm_guards 🔒

One compile-time assertion per leaf of the R arm of an Either choice parameter param of type ty (nested Eithers on the R side peeled): compilation fails when the leaf’s TryFromSexp is CHARACTER_ONLY, since the choice check never sends character or factor input there. Read through EitherArmProbe, so a leaf without TryFromSexp adds no error of its own. Empty without an Either layer.

expected_arm 🔒

The from_r::ExpectedArm of one side of an Either, of type ty: the macro’s wording when it has one (crate::r_preconditions::conversion_expectation), a nested Either side by side, NULL or <T> for an Option<T> or Result<T, ()> side, else the type’s __MX_EXPECTATION, with its @param noun (crate::type_inspect::r_value_noun) for when neither the type nor its error names it. Every side is a TryFromSexp type, as Either’s own impl requires (and the Option / Result impls of their T).

layered_choice_expr 🔒

The decoding expression for a choice parameter of type ty whose value sits under Missing / Option / Either layers (#1473, #1551), applied to the SEXP binding sexp. Each layer is one miniextendr_api::match_arg_* helper that takes the decoder of the layers below it, so Missing<Option<Mode>> becomes

names_impl_trait 🔒

Whether ty spells an impl Trait anywhere (impl AsRef<str>, Vec<impl Display>).

no_na_value_stmt 🔒

The post-conversion no_na check of the binding ident (R name r_name): when the value holds what its type reads as NA (TryFromSexp::__mx_has_na), return the tagged kind = "conversion" value no_na’s R guard would raise, with message verbatim, the crate’s conversion_error_class and e$param (arg_check_condition_value). The call is the wrapper’s call slot, as for a conversion failure.

shim_conversion_err_arm 🔒

Trait shims have no R call slot. They return the same structured argument error as C wrappers; a View re-panic attributes it to the consumer’s call. read_ty supplies TryFromSexp expectations when the conversion uses that trait; rooted views instead derive their expectation from the error.

try_from_sexp 🔒

TryFromSexp on sexp_ident, and the type its binding names: ty, or for a copied trait signature (#2123) _, with the conversion through the witness target inferred from the concrete method, so a declaration-local type is never spelled in the impl’s module.

unit_result_ok_type 🔒

T for a Result<T, ()> type, which reads NULL as Err(()).

worker_native_storage 🔒

Shared native worker inputs are snapshots of their R-thread conversion. Copy before dispatch, then form every reference inside the worker closure. Mutable inputs keep their separate write-through conversion path.

worker_string_storage 🔒

The four borrowed character shapes supported by the raw converters. Keep their worker storage owned; do not generalize this to arbitrary list nesting, which has different conversion and rooting requirements (#1427).