1 files changed, 139 insertions, 0 deletions
diff --git a/tests/ui-fulldeps/rustc_public/check_defs.rs b/tests/ui-fulldeps/rustc_public/check_defs.rs
new file mode 100644
index 00000000000..0c45859a132
--- /dev/null
+++ b/tests/ui-fulldeps/rustc_public/check_defs.rs
@@ -0,0 +1,139 @@
+//@ run-pass
+//! Test that users are able to use stable mir APIs to retrieve information about crate definitions.
+
+//@ ignore-stage1
+//@ ignore-cross-compile
+//@ ignore-remote
+//@ edition: 2021
+
+#![feature(rustc_private)]
+#![feature(assert_matches)]
+
+extern crate rustc_middle;
+
+extern crate rustc_driver;
+extern crate rustc_interface;
+extern crate rustc_public;
+
+use std::assert_matches::assert_matches;
+use mir::{mono::Instance, TerminatorKind::*};
+use rustc_public::mir::mono::InstanceKind;
+use rustc_public::ty::{RigidTy, TyKind, Ty, UintTy};
+use rustc_public::*;
+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() -> ControlFlow<()> {
+    let entry = rustc_public::entry_fn().unwrap();
+    let main_fn = Instance::try_from(entry).unwrap();
+    assert_eq!(main_fn.name(), "main");
+    assert_eq!(main_fn.trimmed_name(), "main");
+
+    let instances = get_instances(main_fn.body().unwrap());
+    assert_eq!(instances.len(), 3);
+    test_fn(instances[0], "from_u32", "std::char::from_u32", "core");
+    test_fn(instances[1], "Vec::<u8>::new", "std::vec::Vec::<u8>::new", "alloc");
+    test_fn(instances[2], "ctpop::<u8>", "std::intrinsics::ctpop::<u8>", "core");
+    test_vec_new(instances[1]);
+    ControlFlow::Continue(())
+}
+
+fn test_fn(instance: Instance, expected_trimmed: &str, expected_qualified: &str, krate: &str) {
+    let trimmed = instance.trimmed_name();
+    let qualified = instance.name();
+    assert_eq!(&trimmed, expected_trimmed);
+    assert_eq!(&qualified, expected_qualified);
+
+    if instance.kind == InstanceKind::Intrinsic {
+        let intrinsic = instance.intrinsic_name().unwrap();
+        let (trimmed_base, _trimmed_args) = trimmed.split_once("::").unwrap();
+        assert_eq!(intrinsic, trimmed_base);
+        return;
+    }
+    assert!(instance.intrinsic_name().is_none());
+
+    let item = CrateItem::try_from(instance).unwrap();
+    let trimmed = item.trimmed_name();
+    let qualified = item.name();
+    assert_eq!(trimmed, expected_trimmed.replace("u8", "T"));
+    assert_eq!(qualified, expected_qualified.replace("u8", "T"));
+    assert_eq!(&item.krate().name, krate);
+}
+
+fn extract_elem_ty(ty: Ty) -> Ty {
+    match ty.kind() {
+        TyKind::RigidTy(RigidTy::Adt(_, args)) => {
+            *args.0[0].expect_ty()
+        }
+        _ => unreachable!("Expected Vec ADT, but found: {ty:?}")
+    }
+}
+
+/// Check signature and type of `Vec::<u8>::new` and its generic version.
+fn test_vec_new(instance: mir::mono::Instance) {
+    let sig = instance.fn_abi().unwrap();
+    assert_eq!(&sig.args, &[]);
+    let elem_ty = extract_elem_ty(sig.ret.ty);
+    assert_matches!(elem_ty.kind(), TyKind::RigidTy(RigidTy::Uint(UintTy::U8)));
+
+    // Get the signature for Vec::<T>::new.
+    let item = CrateItem::try_from(instance).unwrap();
+    let ty = item.ty();
+    let gen_sig = ty.kind().fn_sig().unwrap().skip_binder();
+    let gen_ty = extract_elem_ty(gen_sig.output());
+    assert_matches!(gen_ty.kind(), TyKind::Param(_));
+}
+
+/// Inspect the instance body
+fn get_instances(body: mir::Body) -> Vec<Instance> {
+    body.blocks.iter().filter_map(|bb| {
+        match &bb.terminator.kind {
+            Call { func, .. } => {
+                let TyKind::RigidTy(ty) = func.ty(body.locals()).unwrap().kind() else { unreachable!
+                () };
+                let RigidTy::FnDef(def, args) = ty else { unreachable!() };
+                Instance::resolve(def, &args).ok()
+            }
+            _ => {
+                None
+            }
+        }
+    }).collect::<Vec<_>>()
+}
+
+/// 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 `RustcPublic` using custom arguments and then
+/// it will run the compiler.
+fn main() {
+    let path = "defs_input.rs";
+    generate_input(&path).unwrap();
+    let args = &[
+        "rustc".to_string(),
+        "-Cpanic=abort".to_string(),
+        "--crate-name".to_string(),
+        CRATE_NAME.to_string(),
+        path.to_string(),
+    ];
+    run!(args, test_stable_mir).unwrap();
+}
+
+fn generate_input(path: &str) -> std::io::Result<()> {
+    let mut file = std::fs::File::create(path)?;
+    write!(
+        file,
+        r#"
+        #![feature(core_intrinsics)]
+
+        fn main() {{
+            let _c = core::char::from_u32(99);
+            let _v = Vec::<u8>::new();
+            let _i = std::intrinsics::ctpop::<u8>(0);
+        }}
+    "#
+    )?;
+    Ok(())
+}