rust/compiler/rustc_monomorphize/src/lib.rs

// tidy-alphabetical-start
#![feature(array_windows)]
#![feature(if_let_guard)]
#![feature(let_chains)]
#![warn(unreachable_pub)]
// tidy-alphabetical-end

use rustc_hir::lang_items::LangItem;
use rustc_middle::query::TyCtxtAt;
use rustc_middle::ty::adjustment::CustomCoerceUnsized;
use rustc_middle::ty::{self, Ty};
use rustc_middle::util::Providers;
use rustc_middle::{bug, traits};
use rustc_span::ErrorGuaranteed;

mod collector;
mod errors;
mod partitioning;
mod polymorphize;
mod util;

rustc_fluent_macro::fluent_messages! { "../messages.ftl" }

fn custom_coerce_unsize_info<'tcx>(
    tcx: TyCtxtAt<'tcx>,
    source_ty: Ty<'tcx>,
    target_ty: Ty<'tcx>,
) -> Result<CustomCoerceUnsized, ErrorGuaranteed> {
    let trait_ref = ty::TraitRef::new(
        tcx.tcx,
        tcx.require_lang_item(LangItem::CoerceUnsized, Some(tcx.span)),
        [source_ty, target_ty],
    );

    match tcx.codegen_select_candidate((ty::ParamEnv::reveal_all(), trait_ref)) {
        Ok(traits::ImplSource::UserDefined(traits::ImplSourceUserDefinedData {
            impl_def_id,
            ..
        })) => Ok(tcx.coerce_unsized_info(impl_def_id)?.custom_kind.unwrap()),
        impl_source => {
            bug!("invalid `CoerceUnsized` impl_source: {:?}", impl_source);
        }
    }
}

pub fn provide(providers: &mut Providers) {
    partitioning::provide(providers);
    polymorphize::provide(providers);
}