Add a new trait to retrieve StableMir definition Ty

We implement the trait only for definitions that should have a type.
It's possible that I missed a few definitions, but we can add them later
if needed.

compiler/stable_mir/src/crate_def.rs

@@ -1,7 +1,7 @@
 //! Module that define a common trait for things that represent a crate definition,
 //! such as, a function, a trait, an enum, and any other definitions.
 
-use crate::ty::Span;
+use crate::ty::{GenericArgs, Span, Ty};
 use crate::{with, Crate, Symbol};
 
 /// A unique identification number for each item accessible for the current compilation unit.
@@ -52,6 +52,23 @@ fn span(&self) -> Span {
     }
 }
 
+/// A trait that can be used to retrieve a definition's type.
+///
+/// Note that not every CrateDef has a type `Ty`. They should not implement this trait.
+pub trait CrateDefType: CrateDef {
+    /// Returns the type of this crate item.
+    fn ty(&self) -> Ty {
+        with(|cx| cx.def_ty(self.def_id()))
+    }
+
+    /// Retrieve the type of this definition by instantiating and normalizing it with `args`.
+    ///
+    /// This will panic if instantiation fails.
+    fn ty_with_args(&self, args: &GenericArgs) -> Ty {
+        with(|cx| cx.def_ty_with_args(self.def_id(), args))
+    }
+}
+
 macro_rules! crate_def {
     ( $(#[$attr:meta])*
       $vis:vis $name:ident $(;)?
@@ -67,3 +84,21 @@ fn def_id(&self) -> DefId {
         }
     };
 }
+
+macro_rules! crate_def_with_ty {
+    ( $(#[$attr:meta])*
+      $vis:vis $name:ident $(;)?
+    ) => {
+        $(#[$attr])*
+        #[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
+        $vis struct $name(pub DefId);
+
+        impl CrateDef for $name {
+            fn def_id(&self) -> DefId {
+                self.0
+            }
+        }
+
+        impl CrateDefType for $name {}
+    };
+}

compiler/stable_mir/src/lib.rs

@@ -22,8 +22,7 @@
 use std::io;
 
 use crate::compiler_interface::with;
-pub use crate::crate_def::CrateDef;
-pub use crate::crate_def::DefId;
+pub use crate::crate_def::{CrateDef, CrateDefType, DefId};
 pub use crate::error::*;
 use crate::mir::Body;
 use crate::mir::Mutability;
@@ -115,12 +114,15 @@ pub enum CtorKind {
 
 pub type Filename = String;
 
-crate_def! {
+crate_def_with_ty! {
     /// Holds information about an item in a crate.
     pub CrateItem;
 }
 
 impl CrateItem {
+    /// This will return the body of an item.
+    ///
+    /// This will panic if no body is available.
     pub fn body(&self) -> mir::Body {
         with(|cx| cx.mir_body(self.0))
     }

compiler/stable_mir/src/ty.rs

@@ -3,9 +3,10 @@
     with, DefId, Error, Symbol,
 };
 use crate::abi::Layout;
+use crate::crate_def::{CrateDef, CrateDefType};
 use crate::mir::alloc::{read_target_int, read_target_uint, AllocId};
+use crate::mir::mono::StaticDef;
 use crate::target::MachineInfo;
-use crate::{crate_def::CrateDef, mir::mono::StaticDef};
 use crate::{Filename, Opaque};
 use std::fmt::{self, Debug, Display, Formatter};
 use std::ops::Range;
@@ -504,6 +505,15 @@ pub fn fn_sig(&self) -> Option<PolyFnSig> {
     pub fn discriminant_ty(&self) -> Option<Ty> {
         self.rigid().map(|ty| with(|cx| cx.rigid_ty_discriminant_ty(ty)))
     }
+
+    /// Deconstruct a function type if this is one.
+    pub fn fn_def(&self) -> Option<(FnDef, &GenericArgs)> {
+        if let TyKind::RigidTy(RigidTy::FnDef(def, args)) = self {
+            Some((*def, args))
+        } else {
+            None
+        }
+    }
 }
 
 pub struct TypeAndMut {
@@ -629,7 +639,7 @@ pub fn items(&self) -> Vec<ForeignDef> {
     }
 }
 
-crate_def! {
+crate_def_with_ty! {
     /// Hold information about a ForeignItem in a crate.
     pub ForeignDef;
 }
@@ -647,7 +657,7 @@ pub enum ForeignItemKind {
     Type(Ty),
 }
 
-crate_def! {
+crate_def_with_ty! {
     /// Hold information about a function definition in a crate.
     pub FnDef;
 }
@@ -668,9 +678,15 @@ pub fn as_intrinsic(&self) -> Option<IntrinsicDef> {
     pub fn is_intrinsic(&self) -> bool {
         self.as_intrinsic().is_some()
     }
+
+    /// Get the function signature for this function definition.
+    pub fn fn_sig(&self) -> PolyFnSig {
+        let kind = self.ty().kind();
+        kind.fn_sig().unwrap()
+    }
 }
 
-crate_def! {
+crate_def_with_ty! {
     pub IntrinsicDef;
 }
 
@@ -710,7 +726,7 @@ fn from(def: IntrinsicDef) -> Self {
     pub BrNamedDef;
 }
 
-crate_def! {
+crate_def_with_ty! {
     pub AdtDef;
 }
 
@@ -866,7 +882,7 @@ pub fn declaration(trait_def: &TraitDef) -> TraitDecl {
     pub GenericDef;
 }
 
-crate_def! {
+crate_def_with_ty! {
     pub ConstDef;
 }
 

tests/ui-fulldeps/stable-mir/check_def_ty.rs

@@ -0,0 +1,114 @@
+//@ run-pass
+//! Test that users are able to use stable mir APIs to retrieve type information from a crate item
+//! definition.
+
+//@ ignore-stage1
+//@ ignore-cross-compile
+//@ ignore-remote
+//@ ignore-windows-gnu mingw has troubles with linking https://github.com/rust-lang/rust/pull/116837
+//@ edition: 2021
+
+#![feature(rustc_private)]
+#![feature(assert_matches)]
+#![feature(control_flow_enum)]
+
+#[macro_use]
+extern crate rustc_smir;
+extern crate rustc_driver;
+extern crate rustc_interface;
+extern crate stable_mir;
+
+use rustc_smir::rustc_internal;
+use stable_mir::ty::{Ty, ForeignItemKind};
+use stable_mir::*;
+use std::io::Write;
+use std::ops::ControlFlow;
+
+const CRATE_NAME: &str = "crate_def_ty";
+
+/// Test if we can retrieve type information from different definitions.
+fn test_def_tys() -> ControlFlow<()> {
+    let items = stable_mir::all_local_items();
+    for item in &items {
+        // Type from crate items.
+        let ty = item.ty();
+        match item.name().as_str() {
+            "STATIC_STR" => assert!(ty.kind().is_ref()),
+            "CONST_U32" => assert!(ty.kind().is_integral()),
+            "main" => { check_fn_def(ty) }
+            _ => unreachable!("Unexpected item: `{item:?}`")
+        }
+    }
+
+    let foreign_items = stable_mir::local_crate().foreign_modules();
+    for item in foreign_items[0].module().items() {
+        // Type from foreign items.
+        let ty = item.ty();
+        let item_kind = item.kind();
+        let name = item.name();
+        match item_kind {
+            ForeignItemKind::Fn(fn_def) => {
+                assert_eq!(&name, "extern_fn");
+                assert_eq!(ty, fn_def.ty());
+                check_fn_def(ty)
+            }
+            ForeignItemKind::Static(def) => {
+                assert_eq!(&name, "EXT_STATIC");
+                assert_eq!(ty, def.ty());
+                assert!(ty.kind().is_integral())
+            }
+            _ => unreachable!("Unexpected kind: {item_kind:?}")
+        };
+    }
+
+    ControlFlow::Continue(())
+}
+
+fn check_fn_def(ty: Ty) {
+    let kind = ty.kind();
+    let (def, args) = kind.fn_def().expect(&format!("Expected function type, but found: {ty}"));
+    assert!(def.ty().kind().is_fn());
+    assert_eq!(def.ty_with_args(args), ty);
+}
+
+/// 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 = "defs_ty_input.rs";
+    generate_input(&path).unwrap();
+    let args = vec![
+        "rustc".to_string(),
+        "-Cpanic=abort".to_string(),
+        "--crate-name".to_string(),
+        CRATE_NAME.to_string(),
+        path.to_string(),
+    ];
+    run!(args, test_def_tys).unwrap();
+}
+
+fn generate_input(path: &str) -> std::io::Result<()> {
+    let mut file = std::fs::File::create(path)?;
+    write!(
+        file,
+        r#"
+        // We would like to check intrinsic definition.
+        #![feature(core_intrinsics)]
+        static STATIC_STR: &str = "foo";
+        const CONST_U32: u32 = 0u32;
+
+        fn main() {{
+            let _c = core::char::from_u32(99);
+            let _v = Vec::<u8>::new();
+            let _i = std::intrinsics::size_of::<u8>();
+        }}
+
+        extern "C" {{
+            fn extern_fn(x: i32) -> i32;
+            static EXT_STATIC: i32;
+        }}
+    "#
+    )?;
+    Ok(())
+}