WIP Add a shim for functions annotated with #[track_caller] (RFC 2091 #2/N)

src/doc/unstable-book/src/language-features/track-caller.md

@@ -0,0 +1,5 @@
+# `track_caller`
+
+The tracking issue for this feature is: [#47809](https://github.com/rust-lang/rust/issues/47809).
+
+------------------------

src/librustc/error_codes.rs

@@ -2234,6 +2234,25 @@ These attributes are meant to only be used by the standard library and are
 rejected in your own crates.
 "##,
 
+E0736: r##"
+#[track_caller] and #[naked] cannot be applied to the same function.
+
+Erroneous code example:
+
+```compile_fail,E0736
+#![feature(track_caller)]
+
+#[naked]
+#[track_caller]
+fn foo() {}
+```
+
+This is primarily due to ABI incompatibilities between the two attributes.
+See [RFC 2091] for details on this and other limitations.
+
+[RFC 2091]: https://github.com/rust-lang/rfcs/blob/master/text/2091-inline-semantic.md
+"##,
+
 ;
 //  E0006, // merged with E0005
 //  E0101, // replaced with E0282
@@ -2296,4 +2315,5 @@ rejected in your own crates.
     E0726, // non-explicit (not `'_`) elided lifetime in unsupported position
     E0727, // `async` generators are not yet supported
     E0728, // `await` must be in an `async` function or block
+    E0739, // invalid track_caller application/syntax
 }

src/librustc/hir/check_attr.rs

@@ -11,7 +11,7 @@ use crate::ty::TyCtxt;
 use crate::ty::query::Providers;
 
 use std::fmt::{self, Display};
-use syntax::symbol::sym;
+use syntax::{attr, symbol::sym};
 use syntax_pos::Span;
 
 #[derive(Copy, Clone, PartialEq)]
@@ -103,6 +103,8 @@ impl CheckAttrVisitor<'tcx> {
                 self.check_marker(attr, item, target)
             } else if attr.check_name(sym::target_feature) {
                 self.check_target_feature(attr, item, target)
+            } else if attr.check_name(sym::track_caller) {
+                self.check_track_caller(attr, &item, target)
             } else {
                 true
             };
@@ -135,6 +137,32 @@ impl CheckAttrVisitor<'tcx> {
         }
     }
 
+    /// Checks if a `#[track_caller]` is applied to a non-naked function. Returns `true` if valid.
+    fn check_track_caller(&self, attr: &hir::Attribute, item: &hir::Item, target: Target) -> bool {
+        if target != Target::Fn {
+            struct_span_err!(
+                self.tcx.sess,
+                attr.span,
+                E0739,
+                "attribute should be applied to function"
+            )
+            .span_label(item.span, "not a function")
+            .emit();
+            false
+        } else if attr::contains_name(&item.attrs, sym::naked) {
+            struct_span_err!(
+                self.tcx.sess,
+                attr.span,
+                E0736,
+                "cannot use `#[track_caller]` with `#[naked]`",
+            )
+            .emit();
+            false
+        } else {
+            true
+        }
+    }
+
     /// Checks if the `#[non_exhaustive]` attribute on an `item` is valid. Returns `true` if valid.
     fn check_non_exhaustive(
         &self,

src/librustc/hir/mod.rs

@@ -2716,7 +2716,9 @@ bitflags! {
         const USED                      = 1 << 9;
         /// #[ffi_returns_twice], indicates that an extern function can return
         /// multiple times
-        const FFI_RETURNS_TWICE = 1 << 10;
+        const FFI_RETURNS_TWICE         = 1 << 10;
+        /// #[track_caller]: allow access to the caller location
+        const TRACK_CALLER              = 1 << 11;
     }
 }
 

src/librustc/mir/mono.rs

@@ -386,6 +386,7 @@ impl<'tcx> CodegenUnit<'tcx> {
                             tcx.hir().as_local_hir_id(def_id)
                         }
                         InstanceDef::VtableShim(..) |
+                        InstanceDef::ReifyShim(..) |
                         InstanceDef::Intrinsic(..) |
                         InstanceDef::FnPtrShim(..) |
                         InstanceDef::Virtual(..) |

src/librustc/ty/instance.rs

@@ -25,6 +25,9 @@ pub enum InstanceDef<'tcx> {
     /// `<T as Trait>::method` where `method` receives unsizeable `self: Self`.
     VtableShim(DefId),
 
+    /// `fn()` pointer where the function is annotated with `#[track_caller]`.
+    ReifyShim(DefId),
+
     /// `<fn() as FnTrait>::call_*`
     /// `DefId` is `FnTrait::call_*`
     FnPtrShim(DefId, Ty<'tcx>),
@@ -123,6 +126,7 @@ impl<'tcx> InstanceDef<'tcx> {
         match *self {
             InstanceDef::Item(def_id) |
             InstanceDef::VtableShim(def_id) |
+            InstanceDef::ReifyShim(def_id) |
             InstanceDef::FnPtrShim(def_id, _) |
             InstanceDef::Virtual(def_id, _) |
             InstanceDef::Intrinsic(def_id, ) |
@@ -178,6 +182,9 @@ impl<'tcx> fmt::Display for Instance<'tcx> {
             InstanceDef::VtableShim(_) => {
                 write!(f, " - shim(vtable)")
             }
+            InstanceDef::ReifyShim(_) => {
+                write!(f, " - shim(reify)")
+            }
             InstanceDef::Intrinsic(_) => {
                 write!(f, " - intrinsic")
             }
@@ -290,6 +297,28 @@ impl<'tcx> Instance<'tcx> {
         result
     }
 
+    pub fn resolve_for_fn_ptr(
+        tcx: TyCtxt<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        def_id: DefId,
+        substs: SubstsRef<'tcx>,
+    ) -> Option<Instance<'tcx>> {
+        debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
+        let fn_sig = tcx.fn_sig(def_id);
+        // let is_reify_shim = fn_sig.inputs().skip_binder().len() > 0
+        //     && fn_sig.input(0).skip_binder().is_param(0)
+        //     && tcx.generics_of(def_id).has_self;
+        if is_reify_shim {
+            debug!(" => fn ptr with implicit caller location");
+            Some(Instance {
+                def: InstanceDef::ReifyShim(def_id),
+                substs,
+            })
+        } else {
+            Instance::resolve(tcx, param_env, def_id, substs)
+        }
+    }
+
     pub fn resolve_for_vtable(
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,

src/librustc/ty/mod.rs

@@ -3026,6 +3026,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 self.optimized_mir(did)
             }
             ty::InstanceDef::VtableShim(..) |
+            ty::InstanceDef::ReifyShim(..) |
             ty::InstanceDef::Intrinsic(..) |
             ty::InstanceDef::FnPtrShim(..) |
             ty::InstanceDef::Virtual(..) |

src/librustc/ty/structural_impls.rs

@@ -761,6 +761,8 @@ impl<'a, 'tcx> Lift<'tcx> for ty::InstanceDef<'a> {
                 Some(ty::InstanceDef::Item(def_id)),
             ty::InstanceDef::VtableShim(def_id) =>
                 Some(ty::InstanceDef::VtableShim(def_id)),
+            ty::InstanceDef::ReifyShim(def_id) =>
+                Some(ty::InstanceDef::ReifyShim(def_id)),
             ty::InstanceDef::Intrinsic(def_id) =>
                 Some(ty::InstanceDef::Intrinsic(def_id)),
             ty::InstanceDef::FnPtrShim(def_id, ref ty) =>
@@ -966,6 +968,7 @@ impl<'tcx> TypeFoldable<'tcx> for ty::instance::Instance<'tcx> {
             def: match self.def {
                 Item(did) => Item(did.fold_with(folder)),
                 VtableShim(did) => VtableShim(did.fold_with(folder)),
+                ReifyShim(did) => ReifyShim(did.fold_with(folder)),
                 Intrinsic(did) => Intrinsic(did.fold_with(folder)),
                 FnPtrShim(did, ty) => FnPtrShim(
                     did.fold_with(folder),
@@ -994,7 +997,7 @@ impl<'tcx> TypeFoldable<'tcx> for ty::instance::Instance<'tcx> {
         use crate::ty::InstanceDef::*;
         self.substs.visit_with(visitor) ||
         match self.def {
-            Item(did) | VtableShim(did) | Intrinsic(did) | Virtual(did, _) => {
+            Item(did) | VtableShim(did) | ReifyShim(did) | Intrinsic(did) | Virtual(did, _) => {
                 did.visit_with(visitor)
             },
             FnPtrShim(did, ty) | CloneShim(did, ty) => {

src/librustc_mir/interpret/terminator.rs

@@ -263,6 +263,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 Ok(())
             }
             ty::InstanceDef::VtableShim(..) |
+            ty::InstanceDef::ReifyShim(..) |
             ty::InstanceDef::ClosureOnceShim { .. } |
             ty::InstanceDef::FnPtrShim(..) |
             ty::InstanceDef::DropGlue(..) |

src/librustc_mir/monomorphize/collector.rs

@@ -740,6 +740,7 @@ fn visit_instance_use<'tcx>(
             }
         }
         ty::InstanceDef::VtableShim(..) |
+        ty::InstanceDef::ReifyShim(..) |
         ty::InstanceDef::Virtual(..) |
         ty::InstanceDef::DropGlue(_, None) => {
             // don't need to emit shim if we are calling directly.
@@ -766,6 +767,7 @@ fn should_monomorphize_locally<'tcx>(tcx: TyCtxt<'tcx>, instance: &Instance<'tcx
     let def_id = match instance.def {
         ty::InstanceDef::Item(def_id) => def_id,
         ty::InstanceDef::VtableShim(..) |
+        ty::InstanceDef::ReifyShim(..) |
         ty::InstanceDef::ClosureOnceShim { .. } |
         ty::InstanceDef::Virtual(..) |
         ty::InstanceDef::FnPtrShim(..) |

src/librustc_mir/monomorphize/partitioning.rs

@@ -329,6 +329,7 @@ fn mono_item_visibility(
 
         // These are all compiler glue and such, never exported, always hidden.
         InstanceDef::VtableShim(..) |
+        InstanceDef::ReifyShim(..) |
         InstanceDef::FnPtrShim(..) |
         InstanceDef::Virtual(..) |
         InstanceDef::Intrinsic(..) |
@@ -664,6 +665,7 @@ fn characteristic_def_id_of_mono_item<'tcx>(
             let def_id = match instance.def {
                 ty::InstanceDef::Item(def_id) => def_id,
                 ty::InstanceDef::VtableShim(..) |
+                ty::InstanceDef::ReifyShim(..) |
                 ty::InstanceDef::FnPtrShim(..) |
                 ty::InstanceDef::ClosureOnceShim { .. } |
                 ty::InstanceDef::Intrinsic(..) |

src/librustc_mir/shim.rs

@@ -41,6 +41,15 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>) -> &'tcx
                 None,
             )
         }
+        ty::InstanceDef::ReifyShim(def_id) => {
+            build_call_shim(
+                tcx,
+                def_id,
+                Adjustment::DerefMove,
+                CallKind::Direct(def_id),
+                None,
+            )
+        }
         ty::InstanceDef::FnPtrShim(def_id, ty) => {
             let trait_ = tcx.trait_of_item(def_id).unwrap();
             let adjustment = match tcx.lang_items().fn_trait_kind(trait_) {

src/librustc_typeck/check/wfcheck.rs

@@ -172,6 +172,18 @@ pub fn check_trait_item(tcx: TyCtxt<'_>, def_id: DefId) {
         _ => None
     };
     check_associated_item(tcx, trait_item.hir_id, trait_item.span, method_sig);
+
+    // Prohibits applying `#[track_caller]` to trait decls
+    for attr in &trait_item.attrs {
+        if attr.check_name(sym::track_caller) {
+            struct_span_err!(
+                tcx.sess,
+                attr.span,
+                E0738,
+                "`#[track_caller]` is not supported in trait declarations."
+            ).emit();
+        }
+    }
 }
 
 pub fn check_impl_item(tcx: TyCtxt<'_>, def_id: DefId) {
@@ -182,6 +194,30 @@ pub fn check_impl_item(tcx: TyCtxt<'_>, def_id: DefId) {
         hir::ImplItemKind::Method(ref sig, _) => Some(sig),
         _ => None
     };
+
+    // Prohibits applying `#[track_caller]` to trait impls
+    if method_sig.is_some() {
+        let track_caller_attr = impl_item.attrs.iter()
+            .find(|a| a.check_name(sym::track_caller));
+        if let Some(tc_attr) = track_caller_attr {
+            let parent_hir_id = tcx.hir().get_parent_item(hir_id);
+            let containing_item = tcx.hir().expect_item(parent_hir_id);
+            let containing_impl_is_for_trait = match &containing_item.kind {
+                hir::ItemKind::Impl(_, _, _, _, tr, _, _) => tr.is_some(),
+                _ => bug!("parent of an ImplItem must be an Impl"),
+            };
+
+            if containing_impl_is_for_trait {
+                struct_span_err!(
+                    tcx.sess,
+                    tc_attr.span,
+                    E0738,
+                    "`#[track_caller]` is not supported in traits yet."
+                ).emit();
+            }
+        }
+    }
+
     check_associated_item(tcx, impl_item.hir_id, impl_item.span, method_sig);
 }
 

src/librustc_typeck/collect.rs

@@ -2593,6 +2593,16 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
         } else if attr.check_name(sym::thread_local) {
             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
+        } else if attr.check_name(sym::track_caller) {
+            if tcx.fn_sig(id).abi() != abi::Abi::Rust {
+                struct_span_err!(
+                    tcx.sess,
+                    attr.span,
+                    E0737,
+                    "rust ABI is required to use `#[track_caller]`"
+                ).emit();
+            }
+            codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
         } else if attr.check_name(sym::export_name) {
             if let Some(s) = attr.value_str() {
                 if s.as_str().contains("\0") {

src/librustc_typeck/error_codes.rs

@@ -4907,6 +4907,75 @@ fn foo_recursive(n: usize) -> Pin<Box<dyn Future<Output = ()>>> {
 The `Box<...>` ensures that the result is of known size,
 and the pin is required to keep it in the same place in memory.
 "##,
+
+E0737: r##"
+#[track_caller] requires functions to have the "Rust" ABI for implicitly
+receiving caller location. See [RFC 2091] for details on this and other
+restrictions.
+
+Erroneous code example:
+
+```compile_fail,E0737
+#![feature(track_caller)]
+
+#[track_caller]
+extern "C" fn foo() {}
+```
+
+[RFC 2091]: https://github.com/rust-lang/rfcs/blob/master/text/2091-inline-semantic.md
+"##,
+
+E0738: r##"
+#[track_caller] cannot be used in traits yet.  This is due to limitations in the
+compiler which are likely to be temporary. See [RFC 2091] for details on this
+and other restrictions.
+
+Erroneous example with a trait method implementation:
+
+```compile_fail,E0738
+#![feature(track_caller)]
+
+trait Foo {
+    fn bar(&self);
+}
+
+impl Foo for u64 {
+    #[track_caller]
+    fn bar(&self) {}
+}
+```
+
+Erroneous example with a blanket trait method implementation:
+
+```compile_fail,E0738
+#![feature(track_caller)]
+
+trait Foo {
+    #[track_caller]
+    fn bar(&self) {}
+    fn baz(&self);
+}
+```
+
+Erroneous example with a trait method declaration:
+
+```compile_fail,E0738
+#[!feature(track_caller)]
+
+trait Foo {
+    fn bar(&self) {}
+
+    #[track_caller]
+    fn baz(&self);
+}
+```
+
+Note that while the compiler may be able to support the attribute in traits in
+the future, [RFC 2091] prohibits their implementation without a follow-up RFC.
+
+[RFC 2091]: https://github.com/rust-lang/rfcs/blob/master/text/2091-inline-semantic.md
+"##,
+
 ;
 //  E0035, merged into E0087/E0089
 //  E0036, merged into E0087/E0089