Add a test for get_body_with_borrowck_facts.

compiler/rustc_mir/src/borrow_check/consumers.rs

@@ -15,6 +15,15 @@ pub use super::{
 
 /// This function computes Polonius facts for the given body. It makes a copy of
 /// the body because it needs to regenerate the region identifiers.
+///
+/// Note:
+/// *   This function will panic if the required body was already stolen. This
+///     can, for example, happen when requesting a body of a `const` function
+///     because they are evaluated during typechecking. The panic can be avoided
+///     by overriding the `mir_borrowck` query. You can find a complete example
+///     that shows how to do this at `src/test/run-make/obtain-borrowck/`.
+/// *   This function will also panic if computation of Polonius facts
+///     (`-Zpolonius` flag) is not enabled.
 pub fn get_body_with_borrowck_facts<'tcx>(
     tcx: TyCtxt<'tcx>,
     def: ty::WithOptConstParam<LocalDefId>,

src/test/run-make/obtain-borrowck/Makefile

@@ -0,0 +1,25 @@
+-include ../../run-make-fulldeps/tools.mk
+
+# This example shows how to implement a rustc driver that retrieves MIR bodies
+# together with the borrow checker information.
+
+# How to run this
+# $ ./x.py test src/test/run-make/obtain-borrowck
+
+DRIVER_BINARY := "$(TMPDIR)"/driver
+BUILD_STAGE := $(RUST_BUILD_STAGE:$(TARGET)=)
+RUSTC_SRC_LIB_DEPS := $(BUILD_DIR)/$(TARGET)/$(BUILD_STAGE)rustc/release/deps/
+RUSTC_SRC_LIB := $(BUILD_DIR)/$(TARGET)/$(BUILD_STAGE)rustc/$(TARGET)/release/deps/
+SYSROOT := $(shell $(RUSTC) --print sysroot)
+DRIVER_RPATH_ENV = \
+	$(LD_LIB_PATH_ENVVAR)="${RUSTC_SRC_LIB}:$(HOST_RPATH_DIR)/rustlib/$(TARGET)/lib/:$($(LD_LIB_PATH_ENVVAR))"
+
+all:
+	$(RUSTC) -L $(RUSTC_SRC_LIB) -L $(RUSTC_SRC_LIB_DEPS) driver.rs -o "$(DRIVER_BINARY)"
+	$(DRIVER_RPATH_ENV) "$(DRIVER_BINARY)" --sysroot $(SYSROOT) test.rs -o "$(TMPDIR)/driver_test" > "$(TMPDIR)"/output.stdout
+
+ifdef RUSTC_BLESS_TEST
+	cp "$(TMPDIR)"/output.stdout output.stdout
+else
+	$(DIFF) output.stdout "$(TMPDIR)"/output.stdout
+endif

src/test/run-make/obtain-borrowck/driver.rs

@@ -0,0 +1,171 @@
+#![feature(rustc_private)]
+
+//! This program implements a rustc driver that retrieves MIR bodies with
+//! borrowck information. This cannot be done in a straightforward way because
+//! `get_body_with_borrowck_facts`–the function for retrieving a MIR body with
+//! borrowck facts–can panic if the body is stolen before it is invoked.
+//! Therefore, the driver overrides `mir_borrowck` query (this is done in the
+//! `config` callback), which retrieves the body that is about to be borrow
+//! checked and stores it in a thread local `MIR_BODIES`. Then, `after_analysis`
+//! callback triggers borrow checking of all MIR bodies by retrieving
+//! `optimized_mir` and pulls out the MIR bodies with the borrowck information
+//! from the thread local storage.
+
+extern crate rustc_driver;
+extern crate rustc_hir;
+extern crate rustc_interface;
+extern crate rustc_middle;
+extern crate rustc_mir;
+extern crate rustc_session;
+
+use rustc_driver::Compilation;
+use rustc_hir::def_id::LocalDefId;
+use rustc_hir::itemlikevisit::ItemLikeVisitor;
+use rustc_interface::interface::Compiler;
+use rustc_interface::{Config, Queries};
+use rustc_middle::ty::query::query_values::mir_borrowck;
+use rustc_middle::ty::query::Providers;
+use rustc_middle::ty::{self, TyCtxt};
+use rustc_mir::consumers::BodyWithBorrowckFacts;
+use rustc_session::Session;
+use std::cell::RefCell;
+use std::collections::HashMap;
+use std::thread_local;
+
+fn main() {
+    let exit_code = rustc_driver::catch_with_exit_code(move || {
+        let mut rustc_args: Vec<_> = std::env::args().collect();
+        // We must pass -Zpolonius so that the borrowck information is computed.
+        rustc_args.push("-Zpolonius".to_owned());
+        let mut callbacks = CompilerCalls::default();
+        // Call the Rust compiler with our callbacks.
+        rustc_driver::RunCompiler::new(&rustc_args, &mut callbacks).run()
+    });
+    std::process::exit(exit_code);
+}
+
+#[derive(Default)]
+pub struct CompilerCalls;
+
+impl rustc_driver::Callbacks for CompilerCalls {
+
+    // In this callback we override the mir_borrowck query.
+    fn config(&mut self, config: &mut Config) {
+        assert!(config.override_queries.is_none());
+        config.override_queries = Some(override_queries);
+    }
+
+    // In this callback we trigger borrow checking of all functions and obtain
+    // the result.
+    fn after_analysis<'tcx>(
+        &mut self,
+        compiler: &Compiler,
+        queries: &'tcx Queries<'tcx>,
+    ) -> Compilation {
+        compiler.session().abort_if_errors();
+        queries.global_ctxt().unwrap().peek_mut().enter(|tcx| {
+
+            // Collect definition ids of MIR bodies.
+            let hir = tcx.hir();
+            let krate = hir.krate();
+            let mut visitor = HirVisitor { bodies: Vec::new() };
+            krate.visit_all_item_likes(&mut visitor);
+
+            // Trigger borrow checking of all bodies.
+            for def_id in visitor.bodies {
+                let _ = tcx.optimized_mir(def_id);
+            }
+
+            // See what bodies were borrow checked.
+            let mut bodies = get_bodies(tcx);
+            bodies.sort_by(|(def_id1, _), (def_id2, _)| def_id1.cmp(def_id2));
+            println!("Bodies retrieved for:");
+            for (def_id, body) in bodies {
+                println!("{}", def_id);
+                assert!(body.input_facts.cfg_edge.len() > 0);
+            }
+        });
+
+        Compilation::Continue
+    }
+}
+
+fn override_queries(_session: &Session, local: &mut Providers, external: &mut Providers) {
+    local.mir_borrowck = mir_borrowck;
+    external.mir_borrowck = mir_borrowck;
+}
+
+// Since mir_borrowck does not have access to any other state, we need to use a
+// thread-local for storing the obtained MIR bodies.
+//
+// Note: We are using 'static lifetime here, which is in general unsound.
+// Unfortunately, that is the only lifetime allowed here. Our use is safe
+// because we cast it back to `'tcx` before using.
+thread_local! {
+    pub static MIR_BODIES:
+        RefCell<HashMap<LocalDefId, BodyWithBorrowckFacts<'static>>> =
+        RefCell::new(HashMap::new());
+}
+
+fn mir_borrowck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> mir_borrowck<'tcx> {
+    let body_with_facts = rustc_mir::consumers::get_body_with_borrowck_facts(
+        tcx,
+        ty::WithOptConstParam::unknown(def_id),
+    );
+    // SAFETY: The reader casts the 'static lifetime to 'tcx before using it.
+    let body_with_facts: BodyWithBorrowckFacts<'static> =
+        unsafe { std::mem::transmute(body_with_facts) };
+    MIR_BODIES.with(|state| {
+        let mut map = state.borrow_mut();
+        assert!(map.insert(def_id, body_with_facts).is_none());
+    });
+    let mut providers = Providers::default();
+    rustc_mir::provide(&mut providers);
+    let original_mir_borrowck = providers.mir_borrowck;
+    original_mir_borrowck(tcx, def_id)
+}
+
+/// Visitor that collects all body definition ids mentioned in the program.
+struct HirVisitor {
+    bodies: Vec<LocalDefId>,
+}
+
+impl<'tcx> ItemLikeVisitor<'tcx> for HirVisitor {
+    fn visit_item(&mut self, item: &rustc_hir::Item) {
+        if let rustc_hir::ItemKind::Fn(..) = item.kind {
+            self.bodies.push(item.def_id);
+        }
+    }
+
+    fn visit_trait_item(&mut self, trait_item: &rustc_hir::TraitItem) {
+        if let rustc_hir::TraitItemKind::Fn(_, trait_fn) = &trait_item.kind {
+            if let rustc_hir::TraitFn::Provided(_) = trait_fn {
+                self.bodies.push(trait_item.def_id);
+            }
+        }
+    }
+
+    fn visit_impl_item(&mut self, impl_item: &rustc_hir::ImplItem) {
+        if let rustc_hir::ImplItemKind::Fn(..) = impl_item.kind {
+            self.bodies.push(impl_item.def_id);
+        }
+    }
+
+    fn visit_foreign_item(&mut self, _foreign_item: &rustc_hir::ForeignItem) {}
+}
+
+/// Pull MIR bodies stored in the thread-local.
+fn get_bodies<'tcx>(tcx: TyCtxt<'tcx>) -> Vec<(String, BodyWithBorrowckFacts<'tcx>)> {
+    MIR_BODIES.with(|state| {
+        let mut map = state.borrow_mut();
+        map.drain()
+            .map(|(def_id, body)| {
+                let def_path = tcx.def_path(def_id.to_def_id());
+                // SAFETY: For soundness we need to ensure that the bodies have
+                // the same lifetime (`'tcx`), which they had before they were
+                // stored in the thread local.
+                (def_path.to_string_no_crate_verbose(), body)
+            })
+            .collect()
+    })
+}

src/test/run-make/obtain-borrowck/output.stdout

@@ -0,0 +1,8 @@
+Bodies retrieved for:
+::X::provided
+::foo
+::main
+::main::{constant#0}
+::{impl#0}::new
+::{impl#1}::provided
+::{impl#1}::required

src/test/run-make/obtain-borrowck/test.rs

@@ -0,0 +1,32 @@
+trait X {
+    fn provided(&self) -> usize {
+        5
+    }
+    fn required(&self) -> u32;
+}
+
+struct Bar;
+
+impl Bar {
+    fn new() -> Self {
+        Self
+    }
+}
+
+impl X for Bar {
+    fn provided(&self) -> usize {
+        1
+    }
+    fn required(&self) -> u32 {
+        7
+    }
+}
+
+const fn foo() -> usize {
+    1
+}
+
+fn main() {
+    let bar: [Bar; foo()] = [Bar::new()];
+    assert_eq!(bar[0].provided(), foo());
+}