Rollup of 9 pull requests

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -2077,7 +2077,6 @@ impl<'a> State<'a> {
             ast::ExprKind::Async(capture_clause, _, ref blk) => {
                 self.word_nbsp("async");
                 self.print_capture_clause(capture_clause);
-                self.s.space();
                 // cbox/ibox in analogy to the `ExprKind::Block` arm above
                 self.cbox(INDENT_UNIT);
                 self.ibox(0);

compiler/rustc_incremental/src/assert_dep_graph.rs

@@ -52,6 +52,7 @@ use std::env;
 use std::fs::{self, File};
 use std::io::{BufWriter, Write};
 
+#[allow(missing_docs)]
 pub fn assert_dep_graph(tcx: TyCtxt<'_>) {
     tcx.dep_graph.with_ignore(|| {
         if tcx.sess.opts.debugging_opts.dump_dep_graph {
@@ -262,6 +263,7 @@ fn dump_graph(query: &DepGraphQuery) {
     }
 }
 
+#[allow(missing_docs)]
 pub struct GraphvizDepGraph<'q>(FxHashSet<&'q DepNode>, Vec<(&'q DepNode, &'q DepNode)>);
 
 impl<'a, 'q> dot::GraphWalk<'a> for GraphvizDepGraph<'q> {

compiler/rustc_incremental/src/assert_module_sources.rs

@@ -29,6 +29,7 @@ use rustc_session::cgu_reuse_tracker::*;
 use rustc_span::symbol::{sym, Symbol};
 use std::collections::BTreeSet;
 
+#[allow(missing_docs)]
 pub fn assert_module_sources(tcx: TyCtxt<'_>) {
     tcx.dep_graph.with_ignore(|| {
         if tcx.sess.opts.incremental.is_none() {

compiler/rustc_incremental/src/lib.rs

@@ -1,5 +1,6 @@
 //! Support for serializing the dep-graph and reloading it.
 
+#![deny(missing_docs)]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(in_band_lifetimes)]
 #![feature(let_else)]

compiler/rustc_incremental/src/persist/fs.rs

@@ -133,21 +133,26 @@ const QUERY_CACHE_FILENAME: &str = "query-cache.bin";
 // case-sensitive (as opposed to base64, for example).
 const INT_ENCODE_BASE: usize = base_n::CASE_INSENSITIVE;
 
+/// Returns the path to a session's dependency graph.
 pub fn dep_graph_path(sess: &Session) -> PathBuf {
     in_incr_comp_dir_sess(sess, DEP_GRAPH_FILENAME)
 }
+/// Returns the path to a session's staging dependency graph.
+///
+/// On the difference between dep-graph and staging dep-graph,
+/// see [`rustc_incremental::persist::save::build_dep_graph`].
 pub fn staging_dep_graph_path(sess: &Session) -> PathBuf {
     in_incr_comp_dir_sess(sess, STAGING_DEP_GRAPH_FILENAME)
 }
-
 pub fn work_products_path(sess: &Session) -> PathBuf {
     in_incr_comp_dir_sess(sess, WORK_PRODUCTS_FILENAME)
 }
-
+/// Returns the path to a session's query cache.
 pub fn query_cache_path(sess: &Session) -> PathBuf {
     in_incr_comp_dir_sess(sess, QUERY_CACHE_FILENAME)
 }
 
+/// Locks a given session directory.
 pub fn lock_file_path(session_dir: &Path) -> PathBuf {
     let crate_dir = session_dir.parent().unwrap();
 
@@ -166,23 +171,35 @@ pub fn lock_file_path(session_dir: &Path) -> PathBuf {
     crate_dir.join(&directory_name[0..dash_indices[2]]).with_extension(&LOCK_FILE_EXT[1..])
 }
 
+/// Returns the path for a given filename within the incremental compilation directory
+/// in the current session.
 pub fn in_incr_comp_dir_sess(sess: &Session, file_name: &str) -> PathBuf {
     in_incr_comp_dir(&sess.incr_comp_session_dir(), file_name)
 }
 
+/// Returns the path for a given filename within the incremental compilation directory,
+/// not necessarily from the current session.
+///
+/// To ensure the file is part of the current session, use [`in_incr_comp_dir_sess`].
 pub fn in_incr_comp_dir(incr_comp_session_dir: &Path, file_name: &str) -> PathBuf {
     incr_comp_session_dir.join(file_name)
 }
 
-/// Allocates the private session directory. The boolean in the Ok() result
-/// indicates whether we should try loading a dep graph from the successfully
-/// initialized directory, or not.
-/// The post-condition of this fn is that we have a valid incremental
-/// compilation session directory, if the result is `Ok`. A valid session
+/// Allocates the private session directory.
+///
+/// If the result of this function is `Ok`, we have a valid incremental
+/// compilation session directory. A valid session
 /// directory is one that contains a locked lock file. It may or may not contain
 /// a dep-graph and work products from a previous session.
-/// If the call fails, the fn may leave behind an invalid session directory.
+///
+/// This always attempts to load a dep-graph from the directory.
+/// If loading fails for some reason, we fallback to a disabled [`DepGraph`].
+/// See [`rustc_interface::queries::dep_graph`].
+///
+/// If this function returns an error, it may leave behind an invalid session directory.
 /// The garbage collection will take care of it.
+///
+/// [`rustc_interface::queries::dep_graph`]: ../../rustc_interface/struct.Queries.html#structfield.dep_graph
 pub fn prepare_session_directory(
     sess: &Session,
     crate_name: &str,
@@ -661,6 +678,7 @@ fn is_old_enough_to_be_collected(timestamp: SystemTime) -> bool {
     timestamp < SystemTime::now() - Duration::from_secs(10)
 }
 
+/// Runs garbage collection for the current session.
 pub fn garbage_collect_session_directories(sess: &Session) -> io::Result<()> {
     debug!("garbage_collect_session_directories() - begin");
 

compiler/rustc_incremental/src/persist/load.rs

@@ -18,13 +18,24 @@ use super::work_product;
 type WorkProductMap = FxHashMap<WorkProductId, WorkProduct>;
 
 #[derive(Debug)]
+/// Represents the result of an attempt to load incremental compilation data.
 pub enum LoadResult<T> {
-    Ok { data: T },
+    /// Loading was successful.
+    Ok {
+        #[allow(missing_docs)]
+        data: T,
+    },
+    /// The file either didn't exist or was produced by an incompatible compiler version.
     DataOutOfDate,
-    Error { message: String },
+    /// An error occured.
+    Error {
+        #[allow(missing_docs)]
+        message: String,
+    },
 }
 
 impl<T: Default> LoadResult<T> {
+    /// Accesses the data returned in [`LoadResult::Ok`].
     pub fn open(self, sess: &Session) -> T {
         // Check for errors when using `-Zassert-incremental-state`
         match (sess.opts.assert_incr_state, &self) {
@@ -99,6 +110,7 @@ pub enum MaybeAsync<T> {
 }
 
 impl<T> MaybeAsync<LoadResult<T>> {
+    /// Accesses the data returned in [`LoadResult::Ok`] in an asynchronous way if possible.
     pub fn open(self) -> LoadResult<T> {
         match self {
             MaybeAsync::Sync(result) => result,
@@ -109,6 +121,7 @@ impl<T> MaybeAsync<LoadResult<T>> {
     }
 }
 
+/// An asynchronous type for computing the dependency graph.
 pub type DepGraphFuture = MaybeAsync<LoadResult<(SerializedDepGraph, WorkProductMap)>>;
 
 /// Launch a thread and load the dependency graph in the background.

compiler/rustc_incremental/src/persist/save.rs

@@ -13,9 +13,13 @@ use super::file_format;
 use super::fs::*;
 use super::work_product;
 
-/// Save and dump the DepGraph.
+/// Saves and writes the [`DepGraph`] to the file system.
 ///
-/// No query must be invoked after this function.
+/// This function saves both the dep-graph and the query result cache,
+/// and drops the result cache.
+///
+/// This function should only run after all queries have completed.
+/// Trying to execute a query afterwards would attempt to read the result cache we just dropped.
 pub fn save_dep_graph(tcx: TyCtxt<'_>) {
     debug!("save_dep_graph()");
     tcx.dep_graph.with_ignore(|| {
@@ -75,6 +79,7 @@ pub fn save_dep_graph(tcx: TyCtxt<'_>) {
     })
 }
 
+/// Saves the work product index.
 pub fn save_work_product_index(
     sess: &Session,
     dep_graph: &DepGraph,
@@ -139,6 +144,12 @@ fn encode_query_cache(tcx: TyCtxt<'_>, encoder: &mut FileEncoder) -> FileEncodeR
     tcx.sess.time("incr_comp_serialize_result_cache", || tcx.serialize_query_result_cache(encoder))
 }
 
+/// Builds the dependency graph.
+///
+/// This function breates the *staging dep-graph*. When the dep-graph is modified by a query
+/// execution, the new dependency information is not kept in memory but directly
+/// output to this file. `save_dep_graph` then finalizes the staging dep-graph
+/// and moves it to the permanent dep-graph path
 pub fn build_dep_graph(
     sess: &Session,
     prev_graph: SerializedDepGraph,

compiler/rustc_incremental/src/persist/work_product.rs

@@ -1,4 +1,6 @@
-//! This module contains files for saving intermediate work-products.
+//! Functions for saving and removing intermediate [work products].
+//!
+//! [work products]: WorkProduct
 
 use crate::persist::fs::*;
 use rustc_fs_util::link_or_copy;
@@ -7,6 +9,7 @@ use rustc_session::Session;
 use std::fs as std_fs;
 use std::path::PathBuf;
 
+/// Copies a CGU work product to the incremental compilation directory, so next compilation can find and reuse it.
 pub fn copy_cgu_workproduct_to_incr_comp_cache_dir(
     sess: &Session,
     cgu_name: &str,
@@ -40,6 +43,7 @@ pub fn copy_cgu_workproduct_to_incr_comp_cache_dir(
     Some((work_product_id, work_product))
 }
 
+/// Removes files for a given work product.
 pub fn delete_workproduct_files(sess: &Session, work_product: &WorkProduct) {
     if let Some(ref file_name) = work_product.saved_file {
         let path = in_incr_comp_dir_sess(sess, file_name);

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -461,10 +461,6 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
                     if let Some(def_id) = def_id.as_local() {
                         let opaque_hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
                         let parent_def_id = self.infcx.defining_use_anchor;
-                        let def_scope_default = || {
-                            let opaque_parent_hir_id = tcx.hir().get_parent_item(opaque_hir_id);
-                            parent_def_id == tcx.hir().local_def_id(opaque_parent_hir_id)
-                        };
                         let (in_definition_scope, origin) = match tcx.hir().expect_item(def_id).kind
                         {
                             // Anonymous `impl Trait`
@@ -481,7 +477,14 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
                             }) => {
                                 (may_define_opaque_type(tcx, parent_def_id, opaque_hir_id), origin)
                             }
-                            _ => (def_scope_default(), hir::OpaqueTyOrigin::TyAlias),
+                            ref itemkind => {
+                                span_bug!(
+                                    self.value_span,
+                                    "weird opaque type: {:#?}, {:#?}",
+                                    ty.kind(),
+                                    itemkind
+                                )
+                            }
                         };
                         if in_definition_scope {
                             let opaque_type_key =

compiler/rustc_span/src/symbol.rs

@@ -499,6 +499,7 @@ symbols! {
         core_panic_macro,
         cosf32,
         cosf64,
+        count,
         cr,
         crate_id,
         crate_in_paths,

compiler/rustc_typeck/src/check/method/suggest.rs

@@ -67,6 +67,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
+    fn is_slice_ty(&self, ty: Ty<'tcx>, span: Span) -> bool {
+        self.autoderef(span, ty).any(|(ty, _)| matches!(ty.kind(), ty::Slice(..) | ty::Array(..)))
+    }
+
     pub fn report_method_error(
         &self,
         mut span: Span,
@@ -691,7 +695,23 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                 let mut restrict_type_params = false;
                 let mut unsatisfied_bounds = false;
-                if !unsatisfied_predicates.is_empty() {
+                if item_name.name == sym::count && self.is_slice_ty(actual, span) {
+                    let msg = "consider using `len` instead";
+                    if let SelfSource::MethodCall(_expr) = source {
+                        err.span_suggestion_short(
+                            span,
+                            msg,
+                            String::from("len"),
+                            Applicability::MachineApplicable,
+                        );
+                    } else {
+                        err.span_label(span, msg);
+                    }
+                    if let Some(iterator_trait) = self.tcx.get_diagnostic_item(sym::Iterator) {
+                        let iterator_trait = self.tcx.def_path_str(iterator_trait);
+                        err.note(&format!("`count` is defined on `{iterator_trait}`, which `{actual}` does not implement"));
+                    }
+                } else if !unsatisfied_predicates.is_empty() {
                     let def_span = |def_id| {
                         self.tcx.sess.source_map().guess_head_span(self.tcx.def_span(def_id))
                     };
@@ -990,9 +1010,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     }
                 }
 
-                let mut fallback_span = true;
-                let msg = "remove this method call";
                 if item_name.name == sym::as_str && actual.peel_refs().is_str() {
+                    let msg = "remove this method call";
+                    let mut fallback_span = true;
                     if let SelfSource::MethodCall(expr) = source {
                         let call_expr =
                             self.tcx.hir().expect_expr(self.tcx.hir().get_parent_node(expr.hir_id));

compiler/rustc_typeck/src/check/op.rs

@@ -492,7 +492,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> bool /* did we suggest to call a function because of missing parentheses? */ {
         err.span_label(span, ty.to_string());
         if let FnDef(def_id, _) = *ty.kind() {
-            let source_map = self.tcx.sess.source_map();
             if !self.tcx.has_typeck_results(def_id) {
                 return false;
             }
@@ -517,20 +516,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .lookup_op_method(fn_sig.output(), &[other_ty], Op::Binary(op, is_assign))
                 .is_ok()
             {
-                if let Ok(snippet) = source_map.span_to_snippet(span) {
-                    let (variable_snippet, applicability) = if !fn_sig.inputs().is_empty() {
-                        (format!("{}( /* arguments */ )", snippet), Applicability::HasPlaceholders)
-                    } else {
-                        (format!("{}()", snippet), Applicability::MaybeIncorrect)
-                    };
+                let (variable_snippet, applicability) = if !fn_sig.inputs().is_empty() {
+                    ("( /* arguments */ )".to_string(), Applicability::HasPlaceholders)
+                } else {
+                    ("()".to_string(), Applicability::MaybeIncorrect)
+                };
 
-                    err.span_suggestion(
-                        span,
-                        "you might have forgotten to call this function",
-                        variable_snippet,
-                        applicability,
-                    );
-                }
+                err.span_suggestion_verbose(
+                    span.shrink_to_hi(),
+                    "you might have forgotten to call this function",
+                    variable_snippet,
+                    applicability,
+                );
                 return true;
             }
         }

compiler/rustc_typeck/src/collect/type_of.rs

@@ -172,7 +172,7 @@ pub(super) fn opt_const_param_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<
                 // We've encountered an `AnonConst` in some path, so we need to
                 // figure out which generic parameter it corresponds to and return
                 // the relevant type.
-                let (arg_index, segment) = path
+                let filtered = path
                     .segments
                     .iter()
                     .filter_map(|seg| seg.args.map(|args| (args.args, seg)))
@@ -181,10 +181,17 @@ pub(super) fn opt_const_param_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<
                             .filter(|arg| arg.is_const())
                             .position(|arg| arg.id() == hir_id)
                             .map(|index| (index, seg))
-                    })
-                    .unwrap_or_else(|| {
-                        bug!("no arg matching AnonConst in path");
                     });
+                let (arg_index, segment) = match filtered {
+                    None => {
+                        tcx.sess.delay_span_bug(
+                            tcx.def_span(def_id),
+                            "no arg matching AnonConst in path",
+                        );
+                        return None;
+                    }
+                    Some(inner) => inner,
+                };
 
                 // Try to use the segment resolution if it is valid, otherwise we
                 // default to the path resolution.

library/alloc/src/collections/vec_deque/mod.rs

@@ -720,9 +720,9 @@ impl<T, A: Allocator> VecDeque<T, A> {
     ///
     /// Note that the allocator may give the collection more space than it
     /// requests. Therefore, capacity can not be relied upon to be precisely
-    /// minimal. Prefer [`reserve`] if future insertions are expected.
+    /// minimal. Prefer [`try_reserve`] if future insertions are expected.
     ///
-    /// [`reserve`]: VecDeque::reserve
+    /// [`try_reserve`]: VecDeque::try_reserve
     ///
     /// # Errors
     ///

library/alloc/src/string.rs

@@ -1044,9 +1044,9 @@ impl String {
     ///
     /// Note that the allocator may give the collection more space than it
     /// requests. Therefore, capacity can not be relied upon to be precisely
-    /// minimal. Prefer [`reserve`] if future insertions are expected.
+    /// minimal. Prefer [`try_reserve`] if future insertions are expected.
     ///
-    /// [`reserve`]: String::reserve
+    /// [`try_reserve`]: String::try_reserve
     ///
     /// # Errors
     ///