Rollup of 4 pull requests

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -1799,9 +1799,10 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                         .iter()
                         .find(|cand| self.matches_by_doc_alias(cand.def_id))
                         .map(|cand| cand.name)
-                })
-                .unwrap();
-                Ok(applicable_close_candidates.into_iter().find(|method| method.name == best_name))
+                });
+                Ok(best_name.and_then(|best_name| {
+                    applicable_close_candidates.into_iter().find(|method| method.name == best_name)
+                }))
             }
         })
     }

compiler/rustc_smir/src/rustc_smir/context.rs

@@ -3,6 +3,7 @@
 //! This trait is currently the main interface between the Rust compiler,
 //! and the `stable_mir` crate.
 
+use rustc_middle::ty;
 use rustc_middle::ty::print::{with_forced_trimmed_paths, with_no_trimmed_paths};
 use rustc_middle::ty::{GenericPredicates, Instance, ParamEnv, ScalarInt, ValTree};
 use rustc_span::def_id::LOCAL_CRATE;
@@ -12,9 +13,9 @@ use stable_mir::mir::mono::{InstanceDef, StaticDef};
 use stable_mir::mir::Body;
 use stable_mir::ty::{
     AdtDef, AdtKind, Allocation, ClosureDef, ClosureKind, Const, FnDef, GenericArgs, LineInfo,
-    RigidTy, Span, TyKind,
+    PolyFnSig, RigidTy, Span, TyKind,
 };
-use stable_mir::{self, Crate, CrateItem, Error, Filename, ItemKind, Symbol};
+use stable_mir::{self, Crate, CrateItem, DefId, Error, Filename, ItemKind, Symbol};
 use std::cell::RefCell;
 
 use crate::rustc_internal::{internal, RustcInternal};
@@ -39,6 +40,12 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
         tables.tcx.instance_mir(rustc_middle::ty::InstanceDef::Item(def_id)).stable(&mut tables)
     }
 
+    fn has_body(&self, def: DefId) -> bool {
+        let tables = self.0.borrow();
+        let def_id = tables[def];
+        tables.tcx.is_mir_available(def_id)
+    }
+
     fn all_trait_decls(&self) -> stable_mir::TraitDecls {
         let mut tables = self.0.borrow_mut();
         tables
@@ -195,6 +202,13 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
         def.internal(&mut *tables).is_box()
     }
 
+    fn fn_sig(&self, def: FnDef, args: &GenericArgs) -> PolyFnSig {
+        let mut tables = self.0.borrow_mut();
+        let def_id = def.0.internal(&mut *tables);
+        let sig = tables.tcx.fn_sig(def_id).instantiate(tables.tcx, args.internal(&mut *tables));
+        sig.stable(&mut *tables)
+    }
+
     fn eval_target_usize(&self, cnst: &Const) -> Result<u64, Error> {
         let mut tables = self.0.borrow_mut();
         let mir_const = cnst.internal(&mut *tables);
@@ -266,6 +280,12 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
         tables.tcx.symbol_name(instance).name.to_string()
     }
 
+    fn is_empty_drop_shim(&self, def: InstanceDef) -> bool {
+        let tables = self.0.borrow_mut();
+        let instance = tables.instances[def];
+        matches!(instance.def, ty::InstanceDef::DropGlue(_, None))
+    }
+
     fn mono_instance(&self, item: stable_mir::CrateItem) -> stable_mir::mir::mono::Instance {
         let mut tables = self.0.borrow_mut();
         let def_id = tables[item.0];

compiler/rustc_smir/src/rustc_smir/convert/ty.rs

@@ -777,7 +777,9 @@ impl<'tcx> Stable<'tcx> for ty::Instance<'tcx> {
         let kind = match self.def {
             ty::InstanceDef::Item(..) => stable_mir::mir::mono::InstanceKind::Item,
             ty::InstanceDef::Intrinsic(..) => stable_mir::mir::mono::InstanceKind::Intrinsic,
-            ty::InstanceDef::Virtual(..) => stable_mir::mir::mono::InstanceKind::Virtual,
+            ty::InstanceDef::Virtual(_def_id, idx) => {
+                stable_mir::mir::mono::InstanceKind::Virtual { idx }
+            }
             ty::InstanceDef::VTableShim(..)
             | ty::InstanceDef::ReifyShim(..)
             | ty::InstanceDef::FnPtrAddrShim(..)

compiler/stable_mir/src/compiler_interface.rs

@@ -10,8 +10,8 @@ use crate::mir::mono::{Instance, InstanceDef, StaticDef};
 use crate::mir::Body;
 use crate::ty::{
     AdtDef, AdtKind, Allocation, ClosureDef, ClosureKind, Const, FnDef, GenericArgs,
-    GenericPredicates, Generics, ImplDef, ImplTrait, LineInfo, RigidTy, Span, TraitDecl, TraitDef,
-    Ty, TyKind,
+    GenericPredicates, Generics, ImplDef, ImplTrait, LineInfo, PolyFnSig, RigidTy, Span, TraitDecl,
+    TraitDef, Ty, TyKind,
 };
 use crate::{
     mir, Crate, CrateItem, CrateItems, DefId, Error, Filename, ImplTraitDecls, ItemKind, Symbol,
@@ -24,7 +24,11 @@ pub trait Context {
     fn entry_fn(&self) -> Option<CrateItem>;
     /// Retrieve all items of the local crate that have a MIR associated with them.
     fn all_local_items(&self) -> CrateItems;
+    /// Retrieve the body of a function.
+    /// This function will panic if the body is not available.
     fn mir_body(&self, item: DefId) -> mir::Body;
+    /// Check whether the body of a function is available.
+    fn has_body(&self, item: DefId) -> bool;
     fn all_trait_decls(&self) -> TraitDecls;
     fn trait_decl(&self, trait_def: &TraitDef) -> TraitDecl;
     fn all_trait_impls(&self) -> ImplTraitDecls;
@@ -64,6 +68,9 @@ pub trait Context {
     /// Returns if the ADT is a box.
     fn adt_is_box(&self, def: AdtDef) -> bool;
 
+    /// Retrieve the function signature for the given generic arguments.
+    fn fn_sig(&self, def: FnDef, args: &GenericArgs) -> PolyFnSig;
+
     /// Evaluate constant as a target usize.
     fn eval_target_usize(&self, cnst: &Const) -> Result<u64, Error>;
 
@@ -85,8 +92,7 @@ pub trait Context {
     /// Obtain the representation of a type.
     fn ty_kind(&self, ty: Ty) -> TyKind;
 
-    /// Get the body of an Instance.
-    /// FIXME: Monomorphize the body.
+    /// Get the body of an Instance which is already monomorphized.
     fn instance_body(&self, instance: InstanceDef) -> Option<Body>;
 
     /// Get the instance type with generic substitutions applied and lifetimes erased.
@@ -98,6 +104,9 @@ pub trait Context {
     /// Get the instance mangled name.
     fn instance_mangled_name(&self, instance: InstanceDef) -> Symbol;
 
+    /// Check if this is an empty DropGlue shim.
+    fn is_empty_drop_shim(&self, def: InstanceDef) -> bool;
+
     /// Convert a non-generic crate item into an instance.
     /// This function will panic if the item is generic.
     fn mono_instance(&self, item: CrateItem) -> Instance;

compiler/stable_mir/src/mir/mono.rs

@@ -1,6 +1,6 @@
 use crate::crate_def::CrateDef;
 use crate::mir::Body;
-use crate::ty::{Allocation, ClosureDef, ClosureKind, FnDef, GenericArgs, IndexedVal, Ty};
+use crate::ty::{Allocation, ClosureDef, ClosureKind, FnDef, FnSig, GenericArgs, IndexedVal, Ty};
 use crate::{with, CrateItem, DefId, Error, ItemKind, Opaque, Symbol};
 use std::fmt::{Debug, Formatter};
 
@@ -27,7 +27,8 @@ pub enum InstanceKind {
     /// A compiler intrinsic function.
     Intrinsic,
     /// A virtual function definition stored in a VTable.
-    Virtual,
+    /// The `idx` field indicates the position in the VTable for this instance.
+    Virtual { idx: usize },
     /// A compiler generated shim.
     Shim,
 }
@@ -106,6 +107,24 @@ impl Instance {
             })
         })
     }
+
+    /// Get this function signature with all types already instantiated.
+    pub fn fn_sig(&self) -> FnSig {
+        self.ty().kind().fn_sig().unwrap().skip_binder()
+    }
+
+    /// Check whether this instance is an empty shim.
+    ///
+    /// Allow users to check if this shim can be ignored when called directly.
+    ///
+    /// We have decided not to export different types of Shims to StableMIR users, however, this
+    /// is a query that can be very helpful for users when processing DropGlue.
+    ///
+    /// When generating code for a Drop terminator, users can ignore an empty drop glue.
+    /// These shims are only needed to generate a valid Drop call done via VTable.
+    pub fn is_empty_shim(&self) -> bool {
+        self.kind == InstanceKind::Shim && with(|cx| cx.is_empty_drop_shim(self.def))
+    }
 }
 
 impl Debug for Instance {
@@ -124,8 +143,6 @@ impl TryFrom<CrateItem> for Instance {
 
     fn try_from(item: CrateItem) -> Result<Self, Self::Error> {
         with(|context| {
-            // FIXME(celinval):
-            // - Return `Err` if instance does not have a body.
             if !context.requires_monomorphization(item.0) {
                 Ok(context.mono_instance(item))
             } else {
@@ -141,11 +158,13 @@ impl TryFrom<Instance> for CrateItem {
     type Error = crate::Error;
 
     fn try_from(value: Instance) -> Result<Self, Self::Error> {
-        if value.kind == InstanceKind::Item {
-            Ok(CrateItem(with(|context| context.instance_def_id(value.def))))
-        } else {
-            Err(Error::new(format!("Item kind `{:?}` cannot be converted", value.kind)))
-        }
+        with(|context| {
+            if value.kind == InstanceKind::Item && context.has_body(value.def.def_id()) {
+                Ok(CrateItem(context.instance_def_id(value.def)))
+            } else {
+                Err(Error::new(format!("Item kind `{:?}` cannot be converted", value.kind)))
+            }
+        })
     }
 }
 
@@ -170,6 +189,12 @@ impl From<StaticDef> for CrateItem {
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub struct InstanceDef(usize);
 
+impl CrateDef for InstanceDef {
+    fn def_id(&self) -> DefId {
+        with(|context| context.instance_def_id(*self))
+    }
+}
+
 crate_def! {
     /// Holds information about a static variable definition.
     pub StaticDef;

compiler/stable_mir/src/ty.rs

@@ -168,7 +168,11 @@ impl TyKind {
     }
 
     pub fn is_unit(&self) -> bool {
-        matches!(self, TyKind::RigidTy(RigidTy::Tuple(data)) if data.len() == 0)
+        matches!(self, TyKind::RigidTy(RigidTy::Tuple(data)) if data.is_empty())
+    }
+
+    pub fn is_bool(&self) -> bool {
+        matches!(self, TyKind::RigidTy(RigidTy::Bool))
     }
 
     pub fn is_trait(&self) -> bool {
@@ -187,6 +191,14 @@ impl TyKind {
         matches!(self, TyKind::RigidTy(RigidTy::Adt(def, _)) if def.kind() == AdtKind::Union)
     }
 
+    pub fn is_fn(&self) -> bool {
+        matches!(self, TyKind::RigidTy(RigidTy::FnDef(..)))
+    }
+
+    pub fn is_fn_ptr(&self) -> bool {
+        matches!(self, TyKind::RigidTy(RigidTy::FnPtr(..)))
+    }
+
     pub fn trait_principal(&self) -> Option<Binder<ExistentialTraitRef>> {
         if let TyKind::RigidTy(RigidTy::Dynamic(predicates, _, _)) = self {
             if let Some(Binder { value: ExistentialPredicate::Trait(trait_ref), bound_vars }) =
@@ -227,6 +239,15 @@ impl TyKind {
             _ => None,
         }
     }
+
+    /// Get the function signature for function like types (Fn, FnPtr, Closure, Coroutine)
+    pub fn fn_sig(&self) -> Option<PolyFnSig> {
+        match self {
+            TyKind::RigidTy(RigidTy::FnDef(def, args)) => Some(with(|cx| cx.fn_sig(*def, args))),
+            TyKind::RigidTy(RigidTy::FnPtr(sig)) => Some(sig.clone()),
+            _ => None,
+        }
+    }
 }
 
 pub struct TypeAndMut {
@@ -307,8 +328,9 @@ crate_def! {
 }
 
 impl FnDef {
-    pub fn body(&self) -> Body {
-        with(|ctx| ctx.mir_body(self.0))
+    // Get the function body if available.
+    pub fn body(&self) -> Option<Body> {
+        with(|ctx| ctx.has_body(self.0).then(|| ctx.mir_body(self.0)))
     }
 }
 
@@ -488,6 +510,16 @@ pub struct FnSig {
     pub abi: Abi,
 }
 
+impl FnSig {
+    pub fn output(&self) -> Ty {
+        self.inputs_and_output[self.inputs_and_output.len() - 1]
+    }
+
+    pub fn inputs(&self) -> &[Ty] {
+        &self.inputs_and_output[..self.inputs_and_output.len() - 1]
+    }
+}
+
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub enum Abi {
     Rust,

src/bootstrap/src/core/builder.rs

@@ -10,6 +10,7 @@ use std::io::{BufRead, BufReader};
 use std::ops::Deref;
 use std::path::{Path, PathBuf};
 use std::process::Command;
+use std::sync::OnceLock;
 use std::time::{Duration, Instant};
 
 use crate::core::build_steps::llvm;
@@ -25,12 +26,10 @@ use crate::EXTRA_CHECK_CFGS;
 use crate::{Build, CLang, DocTests, GitRepo, Mode};
 
 pub use crate::Compiler;
-// FIXME:
-// - use std::lazy for `Lazy`
-// - use std::cell for `OnceCell`
-// Once they get stabilized and reach beta.
+
 use clap::ValueEnum;
-use once_cell::sync::{Lazy, OnceCell};
+// FIXME: replace with std::lazy after it gets stabilized and reaches beta
+use once_cell::sync::Lazy;
 
 #[cfg(test)]
 #[path = "../tests/builder.rs"]
@@ -496,7 +495,7 @@ impl<'a> ShouldRun<'a> {
     ///
     /// [`path`]: ShouldRun::path
     pub fn paths(mut self, paths: &[&str]) -> Self {
-        static SUBMODULES_PATHS: OnceCell<Vec<String>> = OnceCell::new();
+        static SUBMODULES_PATHS: OnceLock<Vec<String>> = OnceLock::new();
 
         let init_submodules_paths = |src: &PathBuf| {
             let file = File::open(src.join(".gitmodules")).unwrap();

src/bootstrap/src/core/config/config.rs

@@ -17,6 +17,7 @@ use std::io::IsTerminal;
 use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::str::FromStr;
+use std::sync::OnceLock;
 
 use crate::core::build_steps::compile::CODEGEN_BACKEND_PREFIX;
 use crate::core::build_steps::llvm;
@@ -25,7 +26,6 @@ use crate::utils::cache::{Interned, INTERNER};
 use crate::utils::channel::{self, GitInfo};
 use crate::utils::helpers::{exe, output, t};
 use build_helper::exit;
-use once_cell::sync::OnceCell;
 use semver::Version;
 use serde::{Deserialize, Deserializer};
 use serde_derive::Deserialize;
@@ -1907,7 +1907,7 @@ impl Config {
     }
 
     pub(crate) fn download_rustc_commit(&self) -> Option<&str> {
-        static DOWNLOAD_RUSTC: OnceCell<Option<String>> = OnceCell::new();
+        static DOWNLOAD_RUSTC: OnceLock<Option<String>> = OnceLock::new();
         if self.dry_run() && DOWNLOAD_RUSTC.get().is_none() {
             // avoid trying to actually download the commit
             return self.download_rustc_commit.as_deref();

src/bootstrap/src/core/download.rs

@@ -5,18 +5,18 @@ use std::{
     io::{BufRead, BufReader, BufWriter, ErrorKind, Write},
     path::{Path, PathBuf},
     process::{Command, Stdio},
+    sync::OnceLock,
 };
 
 use build_helper::ci::CiEnv;
-use once_cell::sync::OnceCell;
 use xz2::bufread::XzDecoder;
 
 use crate::core::build_steps::llvm::detect_llvm_sha;
 use crate::core::config::RustfmtMetadata;
 use crate::utils::helpers::{check_run, exe, program_out_of_date};
 use crate::{t, Config};
 
-static SHOULD_FIX_BINS_AND_DYLIBS: OnceCell<bool> = OnceCell::new();
+static SHOULD_FIX_BINS_AND_DYLIBS: OnceLock<bool> = OnceLock::new();
 
 /// `Config::try_run` wrapper for this module to avoid warnings on `try_run`, since we don't have access to a `builder` yet.
 fn try_run(config: &Config, cmd: &mut Command) -> Result<(), ()> {
@@ -131,7 +131,7 @@ impl Config {
         println!("attempting to patch {}", fname.display());
 
         // Only build `.nix-deps` once.
-        static NIX_DEPS_DIR: OnceCell<PathBuf> = OnceCell::new();
+        static NIX_DEPS_DIR: OnceLock<PathBuf> = OnceLock::new();
         let mut nix_build_succeeded = true;
         let nix_deps_dir = NIX_DEPS_DIR.get_or_init(|| {
             // Run `nix-build` to "build" each dependency (which will likely reuse