Rollup of 9 pull requests

src/doc/rustc/src/profile-guided-optimization.md

@@ -125,6 +125,17 @@ RUSTFLAGS="-Cprofile-use=/tmp/pgo-data/merged.profdata" \
     cargo build --release --target=x86_64-unknown-linux-gnu
 ```
 
+### Troubleshooting
+
+- It is recommended to pass `-Cllvm-args=-pgo-warn-missing-function` during the
+  `-Cprofile-use` phase. LLVM by default does not warn if it cannot find
+  profiling data for a given function. Enabling this warning will make it
+  easier to spot errors in your setup.
+
+- There is a [known issue](https://github.com/rust-lang/cargo/issues/7416) in
+  Cargo prior to version 1.39 that will prevent PGO from working correctly. Be
+  sure to use Cargo 1.39 or newer when doing PGO.
+
 ## Further Reading
 
 `rustc`'s PGO support relies entirely on LLVM's implementation of the feature

src/librustc/hir/lowering.rs

@@ -3291,10 +3291,14 @@ impl<'a> LoweringContext<'a> {
                 let id = self.sess.next_node_id();
                 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
             }
-            // This is the normal case.
-            AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
-
-            AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
+            // `PassThrough` is the normal case.
+            // `new_error_lifetime`, which would usually be used in the case of `ReportError`,
+            // is unsuitable here, as these can occur from missing lifetime parameters in a
+            // `PathSegment`, for which there is no associated `'_` or `&T` with no explicit
+            // lifetime. Instead, we simply create an implicit lifetime, which will be checked
+            // later, at which point a suitable error will be emitted.
+          | AnonymousLifetimeMode::PassThrough
+          | AnonymousLifetimeMode::ReportError => self.new_implicit_lifetime(span),
         }
     }
 

src/librustc/ty/mod.rs

@@ -701,6 +701,13 @@ impl<T> Deref for List<T> {
     type Target = [T];
     #[inline(always)]
     fn deref(&self) -> &[T] {
+        self.as_ref()
+    }
+}
+
+impl<T> AsRef<[T]> for List<T> {
+    #[inline(always)]
+    fn as_ref(&self) -> &[T] {
         unsafe {
             slice::from_raw_parts(self.data.as_ptr(), self.len)
         }

src/librustc/ty/util.rs

@@ -1096,6 +1096,9 @@ fn needs_drop_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>
 
         ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
 
+        // Zero-length arrays never contain anything to drop.
+        ty::Array(_, len) if len.try_eval_usize(tcx, param_env) == Some(0) => false,
+
         // Structural recursion.
         ty::Array(ty, _) | ty::Slice(ty) => needs_drop(ty),
 

src/librustc_codegen_llvm/back/archive.rs

@@ -9,7 +9,9 @@ use std::str;
 
 use crate::llvm::archive_ro::{ArchiveRO, Child};
 use crate::llvm::{self, ArchiveKind};
-use rustc_codegen_ssa::{METADATA_FILENAME, RLIB_BYTECODE_EXTENSION};
+use rustc_codegen_ssa::{
+    METADATA_FILENAME, RLIB_BYTECODE_EXTENSION, looks_like_rust_object_file
+};
 use rustc_codegen_ssa::back::archive::{ArchiveBuilder, find_library};
 use rustc::session::Session;
 use syntax::symbol::Symbol;
@@ -141,7 +143,7 @@ impl<'a> ArchiveBuilder<'a> for LlvmArchiveBuilder<'a> {
             }
 
             // Don't include Rust objects if LTO is enabled
-            if lto && fname.starts_with(&obj_start) && fname.ends_with(".o") {
+            if lto && looks_like_rust_object_file(fname) {
                 return true
             }
 

src/librustc_codegen_ssa/back/link.rs

@@ -3,7 +3,7 @@
 
 use rustc::session::{Session, filesearch};
 use rustc::session::config::{
-    self, RUST_CGU_EXT, DebugInfo, OutputFilenames, OutputType, PrintRequest, Sanitizer
+    self, DebugInfo, OutputFilenames, OutputType, PrintRequest, Sanitizer
 };
 use rustc::session::search_paths::PathKind;
 use rustc::middle::dependency_format::Linkage;
@@ -15,7 +15,8 @@ use rustc_fs_util::fix_windows_verbatim_for_gcc;
 use rustc_target::spec::{PanicStrategy, RelroLevel, LinkerFlavor};
 use syntax::symbol::Symbol;
 
-use crate::{METADATA_FILENAME, RLIB_BYTECODE_EXTENSION, CrateInfo, CodegenResults};
+use crate::{METADATA_FILENAME, RLIB_BYTECODE_EXTENSION, CrateInfo,
+    looks_like_rust_object_file, CodegenResults};
 use super::archive::ArchiveBuilder;
 use super::command::Command;
 use super::linker::Linker;
@@ -1549,23 +1550,9 @@ fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(
                 let canonical = f.replace("-", "_");
                 let canonical_name = name.replace("-", "_");
 
-                // Look for `.rcgu.o` at the end of the filename to conclude
-                // that this is a Rust-related object file.
-                fn looks_like_rust(s: &str) -> bool {
-                    let path = Path::new(s);
-                    let ext = path.extension().and_then(|s| s.to_str());
-                    if ext != Some(OutputType::Object.extension()) {
-                        return false
-                    }
-                    let ext2 = path.file_stem()
-                        .and_then(|s| Path::new(s).extension())
-                        .and_then(|s| s.to_str());
-                    ext2 == Some(RUST_CGU_EXT)
-                }
-
                 let is_rust_object =
                     canonical.starts_with(&canonical_name) &&
-                    looks_like_rust(&f);
+                    looks_like_rust_object_file(&f);
 
                 // If we've been requested to skip all native object files
                 // (those not generated by the rust compiler) then we can skip

src/librustc_codegen_ssa/lib.rs

@@ -22,9 +22,9 @@
 #[macro_use] extern crate rustc;
 #[macro_use] extern crate syntax;
 
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use rustc::dep_graph::WorkProduct;
-use rustc::session::config::{OutputFilenames, OutputType};
+use rustc::session::config::{OutputFilenames, OutputType, RUST_CGU_EXT};
 use rustc::middle::lang_items::LangItem;
 use rustc::hir::def_id::CrateNum;
 use rustc::ty::query::Providers;
@@ -62,6 +62,7 @@ pub struct ModuleCodegen<M> {
 pub const METADATA_FILENAME: &str = "rust.metadata.bin";
 pub const RLIB_BYTECODE_EXTENSION: &str = "bc.z";
 
+
 impl<M> ModuleCodegen<M> {
     pub fn into_compiled_module(self,
                             emit_obj: bool,
@@ -166,3 +167,22 @@ pub fn provide_extern(providers: &mut Providers<'_>) {
     crate::back::symbol_export::provide_extern(providers);
     crate::base::provide_both(providers);
 }
+
+/// Checks if the given filename ends with the `.rcgu.o` extension that `rustc`
+/// uses for the object files it generates.
+pub fn looks_like_rust_object_file(filename: &str) -> bool {
+    let path = Path::new(filename);
+    let ext = path.extension().and_then(|s| s.to_str());
+    if ext != Some(OutputType::Object.extension()) {
+        // The file name does not end with ".o", so it can't be an object file.
+        return false
+    }
+
+    // Strip the ".o" at the end
+    let ext2 = path.file_stem()
+        .and_then(|s| Path::new(s).extension())
+        .and_then(|s| s.to_str());
+
+    // Check if the "inner" extension
+    ext2 == Some(RUST_CGU_EXT)
+}

src/librustc_mir/dataflow/impls/indirect_mutation.rs

@@ -104,25 +104,16 @@ impl<'tcx> TransferFunction<'_, '_, 'tcx> {
         kind: mir::BorrowKind,
         borrowed_place: &mir::Place<'tcx>,
     ) -> bool {
-        let borrowed_ty = borrowed_place.ty(self.body, self.tcx).ty;
-
-        // Zero-sized types cannot be mutated, since there is nothing inside to mutate.
-        //
-        // FIXME: For now, we only exempt arrays of length zero. We need to carefully
-        // consider the effects before extending this to all ZSTs.
-        if let ty::Array(_, len) = borrowed_ty.kind {
-            if len.try_eval_usize(self.tcx, self.param_env) == Some(0) {
-                return false;
-            }
-        }
-
         match kind {
             mir::BorrowKind::Mut { .. } => true,
 
             | mir::BorrowKind::Shared
             | mir::BorrowKind::Shallow
             | mir::BorrowKind::Unique
-            => !borrowed_ty.is_freeze(self.tcx, self.param_env, DUMMY_SP),
+            => !borrowed_place
+                .ty(self.body, self.tcx)
+                .ty
+                .is_freeze(self.tcx, self.param_env, DUMMY_SP),
         }
     }
 }

src/librustc_typeck/check/closure.rs

@@ -611,6 +611,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 Some(hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Fn)) => {
                     debug!("supplied_sig_of_closure: closure is async fn body");
                     self.deduce_future_output_from_obligations(expr_def_id)
+                        .unwrap_or_else(|| {
+                            // AFAIK, deducing the future output
+                            // always succeeds *except* in error cases
+                            // like #65159. I'd like to return Error
+                            // here, but I can't because I can't
+                            // easily (and locally) prove that we
+                            // *have* reported an
+                            // error. --nikomatsakis
+                            astconv.ty_infer(None, decl.output.span())
+                        })
                 }
 
                 _ => astconv.ty_infer(None, decl.output.span()),
@@ -645,7 +655,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     fn deduce_future_output_from_obligations(
         &self,
         expr_def_id: DefId,
-    ) -> Ty<'tcx> {
+    ) -> Option<Ty<'tcx>> {
         debug!("deduce_future_output_from_obligations(expr_def_id={:?})", expr_def_id);
 
         let ret_coercion =
@@ -688,8 +698,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 } else {
                     None
                 }
-            })
-            .unwrap();
+            });
 
         debug!("deduce_future_output_from_obligations: output_ty={:?}", output_ty);
         output_ty

src/librustc_typeck/check/method/suggest.rs

@@ -777,19 +777,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             } else {
                 "items from traits can only be used if the trait is implemented and in scope"
             });
-            let mut msg = format!(
+            let message = |action| format!(
                 "the following {traits_define} an item `{name}`, perhaps you need to {action} \
                  {one_of_them}:",
                 traits_define = if candidates.len() == 1 {
                     "trait defines"
                 } else {
                     "traits define"
                 },
-                action = if let Some(param) = param_type {
-                    format!("restrict type parameter `{}` with", param)
-                } else {
-                    "implement".to_string()
-                },
+                action = action,
                 one_of_them = if candidates.len() == 1 {
                     "it"
                 } else {
@@ -809,50 +805,81 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         // Get the `hir::Param` to verify whether it already has any bounds.
                         // We do this to avoid suggesting code that ends up as `T: FooBar`,
                         // instead we suggest `T: Foo + Bar` in that case.
-                        let mut has_bounds = None;
-                        let mut impl_trait = false;
-                        if let Node::GenericParam(ref param) = hir.get(id) {
-                            let kind = &param.kind;
-                            if let hir::GenericParamKind::Type { synthetic: Some(_), .. } = kind {
-                                // We've found `fn foo(x: impl Trait)` instead of
-                                // `fn foo<T>(x: T)`. We want to suggest the correct
-                                // `fn foo(x: impl Trait + TraitBound)` instead of
-                                // `fn foo<T: TraitBound>(x: T)`. (See #63706.)
-                                impl_trait = true;
-                                has_bounds = param.bounds.get(1);
-                            } else {
-                                has_bounds = param.bounds.get(0);
+                        match hir.get(id) {
+                            Node::GenericParam(ref param) => {
+                                let mut impl_trait = false;
+                                let has_bounds = if let hir::GenericParamKind::Type {
+                                    synthetic: Some(_), ..
+                                } = &param.kind {
+                                    // We've found `fn foo(x: impl Trait)` instead of
+                                    // `fn foo<T>(x: T)`. We want to suggest the correct
+                                    // `fn foo(x: impl Trait + TraitBound)` instead of
+                                    // `fn foo<T: TraitBound>(x: T)`. (#63706)
+                                    impl_trait = true;
+                                    param.bounds.get(1)
+                                } else {
+                                    param.bounds.get(0)
+                                };
+                                let sp = hir.span(id);
+                                let sp = if let Some(first_bound) = has_bounds {
+                                    // `sp` only covers `T`, change it so that it covers
+                                    // `T:` when appropriate
+                                    sp.until(first_bound.span())
+                                } else {
+                                    sp
+                                };
+                                // FIXME: contrast `t.def_id` against `param.bounds` to not suggest
+                                // traits already there. That can happen when the cause is that
+                                // we're in a const scope or associated function used as a method.
+                                err.span_suggestions(
+                                    sp,
+                                    &message(format!(
+                                        "restrict type parameter `{}` with",
+                                        param.name.ident().as_str(),
+                                    )),
+                                    candidates.iter().map(|t| format!(
+                                        "{}{} {}{}",
+                                        param.name.ident().as_str(),
+                                        if impl_trait { " +" } else { ":" },
+                                        self.tcx.def_path_str(t.def_id),
+                                        if has_bounds.is_some() { " + "} else { "" },
+                                    )),
+                                    Applicability::MaybeIncorrect,
+                                );
+                                suggested = true;
+                            }
+                            Node::Item(hir::Item {
+                                kind: hir::ItemKind::Trait(.., bounds, _), ident, ..
+                            }) => {
+                                let (sp, sep, article) = if bounds.is_empty() {
+                                    (ident.span.shrink_to_hi(), ":", "a")
+                                } else {
+                                    (bounds.last().unwrap().span().shrink_to_hi(), " +", "another")
+                                };
+                                err.span_suggestions(
+                                    sp,
+                                    &message(format!("add {} supertrait for", article)),
+                                    candidates.iter().map(|t| format!(
+                                        "{} {}",
+                                        sep,
+                                        self.tcx.def_path_str(t.def_id),
+                                    )),
+                                    Applicability::MaybeIncorrect,
+                                );
+                                suggested = true;
                             }
+                            _ => {}
                         }
-                        let sp = hir.span(id);
-                        // `sp` only covers `T`, change it so that it covers `T:` when appropriate.
-                        let sp = if let Some(first_bound) = has_bounds {
-                            sp.until(first_bound.span())
-                        } else {
-                            sp
-                        };
-
-                        // FIXME: contrast `t.def_id` against `param.bounds` to not suggest traits
-                        // already there. That can happen when the cause is that we're in a const
-                        // scope or associated function used as a method.
-                        err.span_suggestions(
-                            sp,
-                            &msg[..],
-                            candidates.iter().map(|t| format!(
-                                "{}{} {}{}",
-                                param,
-                                if impl_trait { " +" } else { ":" },
-                                self.tcx.def_path_str(t.def_id),
-                                if has_bounds.is_some() { " + " } else { "" },
-                            )),
-                            Applicability::MaybeIncorrect,
-                        );
-                        suggested = true;
                     }
                 };
             }
 
             if !suggested {
+                let mut msg = message(if let Some(param) = param_type {
+                    format!("restrict type parameter `{}` with", param)
+                } else {
+                    "implement".to_string()
+                });
                 for (i, trait_info) in candidates.iter().enumerate() {
                     msg.push_str(&format!(
                         "\ncandidate #{}: `{}`",