rust/tests/ui-fulldeps/stable-mir/check_layout.rs

// run-pass
//! Test information regarding type layout.

// ignore-stage1
// ignore-cross-compile
// ignore-remote
// ignore-windows-gnu mingw has troubles with linking https://github.com/rust-lang/rust/pull/116837

#![feature(rustc_private)]
#![feature(assert_matches)]
#![feature(control_flow_enum)]
#![feature(ascii_char, ascii_char_variants)]

extern crate rustc_hir;
extern crate rustc_middle;
#[macro_use]
extern crate rustc_smir;
extern crate rustc_driver;
extern crate rustc_interface;
extern crate stable_mir;

use rustc_middle::ty::TyCtxt;
use rustc_smir::rustc_internal;
use stable_mir::abi::{ArgAbi, CallConvention, FieldsShape, PassMode, VariantsShape};
use stable_mir::mir::mono::Instance;
use stable_mir::{CrateDef, CrateItems, ItemKind};
use std::assert_matches::assert_matches;
use std::convert::TryFrom;
use std::io::Write;
use std::ops::ControlFlow;

const CRATE_NAME: &str = "input";

/// This function uses the Stable MIR APIs to get information about the test crate.
fn test_stable_mir(_tcx: TyCtxt<'_>) -> ControlFlow<()> {
    // Find items in the local crate.
    let items = stable_mir::all_local_items();
    let target_fn = *get_item(&items, (ItemKind::Fn, "fn_abi")).unwrap();
    let instance = Instance::try_from(target_fn).unwrap();
    let fn_abi = instance.fn_abi().unwrap();
    assert_eq!(fn_abi.conv, CallConvention::Rust);
    assert_eq!(fn_abi.args.len(), 2);

    check_ignore(&fn_abi.args[0]);
    check_primitive(&fn_abi.args[1]);
    check_result(fn_abi.ret);

    ControlFlow::Continue(())
}

/// Check the argument to be ignored: `ignore: [u8; 0]`.
fn check_ignore(abi: &ArgAbi) {
    assert!(abi.ty.kind().is_array());
    assert_eq!(abi.mode, PassMode::Ignore);
    let layout = abi.layout.shape();
    assert!(layout.is_sized());
    assert!(layout.is_1zst());
}

/// Check the primitive argument: `primitive: char`.
fn check_primitive(abi: &ArgAbi) {
    assert!(abi.ty.kind().is_char());
    assert_eq!(abi.mode, PassMode::Direct);
    let layout = abi.layout.shape();
    assert!(layout.is_sized());
    assert!(!layout.is_1zst());
    assert_matches!(layout.fields, FieldsShape::Primitive);
}

/// Check the return value: `Result<usize, &str>`.
fn check_result(abi: ArgAbi) {
    assert!(abi.ty.kind().is_enum());
    assert_eq!(abi.mode, PassMode::Indirect);
    let layout = abi.layout.shape();
    assert!(layout.is_sized());
    assert_matches!(layout.fields, FieldsShape::Arbitrary { .. });
    assert_matches!(layout.variants, VariantsShape::Multiple { .. })
}

fn get_item<'a>(
    items: &'a CrateItems,
    item: (ItemKind, &str),
) -> Option<&'a stable_mir::CrateItem> {
    items.iter().find(|crate_item| (item.0 == crate_item.kind()) && crate_item.name() == item.1)
}

/// This test will generate and analyze a dummy crate using the stable mir.
/// For that, it will first write the dummy crate into a file.
/// Then it will create a `StableMir` using custom arguments and then
/// it will run the compiler.
fn main() {
    let path = "alloc_input.rs";
    generate_input(&path).unwrap();
    let args = vec![
        "rustc".to_string(),
        "--crate-type=lib".to_string(),
        "--crate-name".to_string(),
        CRATE_NAME.to_string(),
        path.to_string(),
    ];
    run!(args, tcx, test_stable_mir(tcx)).unwrap();
}

fn generate_input(path: &str) -> std::io::Result<()> {
    let mut file = std::fs::File::create(path)?;
    write!(
        file,
        r#"
        #[allow(unused_variables)]
        pub fn fn_abi(ignore: [u8; 0], primitive: char) -> Result<usize, &'static str> {{
            // We only care about the signature.
            todo!()
        }}
        "#
    )?;
    Ok(())
}