Split out the stable part of smir into its own crate to prevent accidental usage of forever unstable things

compiler/stable_mir/src/lib.rs

@@ -0,0 +1,242 @@
+//! The WIP stable interface to rustc internals.
+//!
+//! For more information see <https://github.com/rust-lang/project-stable-mir>
+//!
+//! # Note
+//!
+//! This API is still completely unstable and subject to change.
+
+#![doc(
+    html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/",
+    test(attr(allow(unused_variables), deny(warnings)))
+)]
+//!
+//! This crate shall contain all type definitions and APIs that we expect third-party tools to invoke to
+//! interact with the compiler.
+//!
+//! The goal is to eventually be published on
+//! [crates.io](https://crates.io).
+
+use std::cell::Cell;
+use std::fmt;
+use std::fmt::Debug;
+
+use self::ty::{
+    GenericPredicates, Generics, ImplDef, ImplTrait, Span, TraitDecl, TraitDef, Ty, TyKind,
+};
+
+#[macro_use]
+extern crate scoped_tls;
+
+pub mod fold;
+pub mod mir;
+pub mod ty;
+pub mod visitor;
+
+/// Use String for now but we should replace it.
+pub type Symbol = String;
+
+/// The number that identifies a crate.
+pub type CrateNum = usize;
+
+/// A unique identification number for each item accessible for the current compilation unit.
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub struct DefId(pub usize);
+
+impl Debug for DefId {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("DefId")
+            .field("id", &self.0)
+            .field("name", &with(|cx| cx.name_of_def_id(*self)))
+            .finish()
+    }
+}
+
+/// A unique identification number for each provenance
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub struct AllocId(pub usize);
+
+/// A list of crate items.
+pub type CrateItems = Vec<CrateItem>;
+
+/// A list of trait decls.
+pub type TraitDecls = Vec<TraitDef>;
+
+/// A list of impl trait decls.
+pub type ImplTraitDecls = Vec<ImplDef>;
+
+/// An error type used to represent an error that has already been reported by the compiler.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum CompilerError<T> {
+    /// Internal compiler error (I.e.: Compiler crashed).
+    ICE,
+    /// Compilation failed.
+    CompilationFailed,
+    /// Compilation was interrupted.
+    Interrupted(T),
+    /// Compilation skipped. This happens when users invoke rustc to retrieve information such as
+    /// --version.
+    Skipped,
+}
+
+/// Holds information about a crate.
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct Crate {
+    pub id: CrateNum,
+    pub name: Symbol,
+    pub is_local: bool,
+}
+
+pub type DefKind = Opaque;
+
+/// Holds information about an item in the crate.
+/// For now, it only stores the item DefId. Use functions inside `rustc_internal` module to
+/// use this item.
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct CrateItem(pub DefId);
+
+impl CrateItem {
+    pub fn body(&self) -> mir::Body {
+        with(|cx| cx.mir_body(self.0))
+    }
+
+    pub fn span(&self) -> Span {
+        with(|cx| cx.span_of_an_item(self.0))
+    }
+
+    pub fn name(&self) -> String {
+        with(|cx| cx.name_of_def_id(self.0))
+    }
+
+    pub fn kind(&self) -> DefKind {
+        with(|cx| cx.def_kind(self.0))
+    }
+}
+
+/// Return the function where execution starts if the current
+/// crate defines that. This is usually `main`, but could be
+/// `start` if the crate is a no-std crate.
+pub fn entry_fn() -> Option<CrateItem> {
+    with(|cx| cx.entry_fn())
+}
+
+/// Access to the local crate.
+pub fn local_crate() -> Crate {
+    with(|cx| cx.local_crate())
+}
+
+/// Try to find a crate with the given name.
+pub fn find_crate(name: &str) -> Option<Crate> {
+    with(|cx| cx.find_crate(name))
+}
+
+/// Try to find a crate with the given name.
+pub fn external_crates() -> Vec<Crate> {
+    with(|cx| cx.external_crates())
+}
+
+/// Retrieve all items in the local crate that have a MIR associated with them.
+pub fn all_local_items() -> CrateItems {
+    with(|cx| cx.all_local_items())
+}
+
+pub fn all_trait_decls() -> TraitDecls {
+    with(|cx| cx.all_trait_decls())
+}
+
+pub fn trait_decl(trait_def: &TraitDef) -> TraitDecl {
+    with(|cx| cx.trait_decl(trait_def))
+}
+
+pub fn all_trait_impls() -> ImplTraitDecls {
+    with(|cx| cx.all_trait_impls())
+}
+
+pub fn trait_impl(trait_impl: &ImplDef) -> ImplTrait {
+    with(|cx| cx.trait_impl(trait_impl))
+}
+
+pub trait Context {
+    fn entry_fn(&mut self) -> Option<CrateItem>;
+    /// Retrieve all items of the local crate that have a MIR associated with them.
+    fn all_local_items(&mut self) -> CrateItems;
+    fn mir_body(&mut self, item: DefId) -> mir::Body;
+    fn all_trait_decls(&mut self) -> TraitDecls;
+    fn trait_decl(&mut self, trait_def: &TraitDef) -> TraitDecl;
+    fn all_trait_impls(&mut self) -> ImplTraitDecls;
+    fn trait_impl(&mut self, trait_impl: &ImplDef) -> ImplTrait;
+    fn generics_of(&mut self, def_id: DefId) -> Generics;
+    fn predicates_of(&mut self, def_id: DefId) -> GenericPredicates;
+    fn explicit_predicates_of(&mut self, def_id: DefId) -> GenericPredicates;
+    /// Get information about the local crate.
+    fn local_crate(&self) -> Crate;
+    /// Retrieve a list of all external crates.
+    fn external_crates(&self) -> Vec<Crate>;
+
+    /// Find a crate with the given name.
+    fn find_crate(&self, name: &str) -> Option<Crate>;
+
+    /// Prints the name of given `DefId`
+    fn name_of_def_id(&self, def_id: DefId) -> String;
+
+    /// Prints a human readable form of `Span`
+    fn print_span(&self, span: Span) -> String;
+
+    /// Prints the kind of given `DefId`
+    fn def_kind(&mut self, def_id: DefId) -> DefKind;
+
+    /// `Span` of an item
+    fn span_of_an_item(&mut self, def_id: DefId) -> Span;
+
+    /// Obtain the representation of a type.
+    fn ty_kind(&mut self, ty: Ty) -> TyKind;
+
+    /// Create a new `Ty` from scratch without information from rustc.
+    fn mk_ty(&mut self, kind: TyKind) -> Ty;
+}
+
+// A thread local variable that stores a pointer to the tables mapping between TyCtxt
+// datastructures and stable MIR datastructures
+scoped_thread_local! (static TLV: Cell<*mut ()>);
+
+pub fn run(mut context: impl Context, f: impl FnOnce()) {
+    assert!(!TLV.is_set());
+    fn g<'a>(mut context: &mut (dyn Context + 'a), f: impl FnOnce()) {
+        let ptr: *mut () = &mut context as *mut &mut _ as _;
+        TLV.set(&Cell::new(ptr), || {
+            f();
+        });
+    }
+    g(&mut context, f);
+}
+
+/// Loads the current context and calls a function with it.
+/// Do not nest these, as that will ICE.
+pub fn with<R>(f: impl FnOnce(&mut dyn Context) -> R) -> R {
+    assert!(TLV.is_set());
+    TLV.with(|tlv| {
+        let ptr = tlv.get();
+        assert!(!ptr.is_null());
+        f(unsafe { *(ptr as *mut &mut dyn Context) })
+    })
+}
+
+/// A type that provides internal information but that can still be used for debug purpose.
+#[derive(Clone)]
+pub struct Opaque(String);
+
+impl std::fmt::Display for Opaque {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
+impl std::fmt::Debug for Opaque {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{:?}", self.0)
+    }
+}
+
+pub fn opaque<T: Debug>(value: &T) -> Opaque {
+    Opaque(format!("{value:?}"))
+}