Auto merge of #98335 - JohnTitor:rollup-j2zudxv, r=JohnTitor

Rollup of 11 pull requests

Successful merges:

 - #94033 (Improve docs for `is_running` to explain use case)
 - #97269 (adjust transmute const stabilization version)
 - #97805 (Add proper tracing spans to rustc_trait_selection::traits::error_reporting)
 - #98022 (Fix erroneous span for borrowck error)
 - #98124 (Improve loading of crates.js and sidebar-items.js)
 - #98278 (Some token stream cleanups)
 - #98306 (`try_fold_unevaluated` for infallible folders)
 - #98313 (Remove lies in comments.)
 - #98323 (:arrow_up: rust-analyzer)
 - #98329 (Avoid an ICE and instead let the compiler report a useful error)
 - #98330 (update ioslice docs to use shared slices)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_ast/src/tokenstream.rs

@@ -25,7 +25,7 @@ use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use rustc_span::{Span, DUMMY_SP};
 use smallvec::{smallvec, SmallVec};
 
-use std::{fmt, iter, mem};
+use std::{fmt, iter};
 
 /// When the main Rust parser encounters a syntax-extension invocation, it
 /// parses the arguments to the invocation as a token tree. This is a very
@@ -399,45 +399,6 @@ impl TokenStream {
         self.0.len()
     }
 
-    pub fn from_streams(mut streams: SmallVec<[TokenStream; 2]>) -> TokenStream {
-        match streams.len() {
-            0 => TokenStream::default(),
-            1 => streams.pop().unwrap(),
-            _ => {
-                // We are going to extend the first stream in `streams` with
-                // the elements from the subsequent streams. This requires
-                // using `make_mut()` on the first stream, and in practice this
-                // doesn't cause cloning 99.9% of the time.
-                //
-                // One very common use case is when `streams` has two elements,
-                // where the first stream has any number of elements within
-                // (often 1, but sometimes many more) and the second stream has
-                // a single element within.
-
-                // Determine how much the first stream will be extended.
-                // Needed to avoid quadratic blow up from on-the-fly
-                // reallocations (#57735).
-                let num_appends = streams.iter().skip(1).map(|ts| ts.len()).sum();
-
-                // Get the first stream. If it's `None`, create an empty
-                // stream.
-                let mut iter = streams.drain(..);
-                let mut first_stream_lrc = iter.next().unwrap().0;
-
-                // Append the elements to the first stream, after reserving
-                // space for them.
-                let first_vec_mut = Lrc::make_mut(&mut first_stream_lrc);
-                first_vec_mut.reserve(num_appends);
-                for stream in iter {
-                    first_vec_mut.extend(stream.0.iter().cloned());
-                }
-
-                // Create the final `TokenStream`.
-                TokenStream(first_stream_lrc)
-            }
-        }
-    }
-
     pub fn trees(&self) -> CursorRef<'_> {
         CursorRef::new(self)
     }
@@ -562,50 +523,65 @@ impl TokenStreamBuilder {
     }
 
     pub fn push<T: Into<TokenStream>>(&mut self, stream: T) {
-        let mut stream = stream.into();
-
-        // If `self` is not empty and the last tree within the last stream is a
-        // token tree marked with `Joint`...
-        if let Some(TokenStream(ref mut last_stream_lrc)) = self.0.last_mut()
-            && let Some((TokenTree::Token(last_token), Spacing::Joint)) = last_stream_lrc.last()
-            // ...and `stream` is not empty and the first tree within it is
-            // a token tree...
-            && let TokenStream(ref mut stream_lrc) = stream
-            && let Some((TokenTree::Token(token), spacing)) = stream_lrc.first()
-            // ...and the two tokens can be glued together...
-            && let Some(glued_tok) = last_token.glue(&token)
-        {
-            // ...then do so, by overwriting the last token
-            // tree in `self` and removing the first token tree
-            // from `stream`. This requires using `make_mut()`
-            // on the last stream in `self` and on `stream`,
-            // and in practice this doesn't cause cloning 99.9%
-            // of the time.
-
-            // Overwrite the last token tree with the merged
-            // token.
-            let last_vec_mut = Lrc::make_mut(last_stream_lrc);
-            *last_vec_mut.last_mut().unwrap() = (TokenTree::Token(glued_tok), *spacing);
-
-            // Remove the first token tree from `stream`. (This
-            // is almost always the only tree in `stream`.)
-            let stream_vec_mut = Lrc::make_mut(stream_lrc);
-            stream_vec_mut.remove(0);
-
-            // Don't push `stream` if it's empty -- that could
-            // block subsequent token gluing, by getting
-            // between two token trees that should be glued
-            // together.
-            if !stream.is_empty() {
-                self.0.push(stream);
-            }
-            return;
-        }
-        self.0.push(stream);
+        self.0.push(stream.into());
     }
 
     pub fn build(self) -> TokenStream {
-        TokenStream::from_streams(self.0)
+        let mut streams = self.0;
+        match streams.len() {
+            0 => TokenStream::default(),
+            1 => streams.pop().unwrap(),
+            _ => {
+                // We will extend the first stream in `streams` with the
+                // elements from the subsequent streams. This requires using
+                // `make_mut()` on the first stream, and in practice this
+                // doesn't cause cloning 99.9% of the time.
+                //
+                // One very common use case is when `streams` has two elements,
+                // where the first stream has any number of elements within
+                // (often 1, but sometimes many more) and the second stream has
+                // a single element within.
+
+                // Determine how much the first stream will be extended.
+                // Needed to avoid quadratic blow up from on-the-fly
+                // reallocations (#57735).
+                let num_appends = streams.iter().skip(1).map(|ts| ts.len()).sum();
+
+                // Get the first stream, which will become the result stream.
+                // If it's `None`, create an empty stream.
+                let mut iter = streams.drain(..);
+                let mut res_stream_lrc = iter.next().unwrap().0;
+
+                // Append the subsequent elements to the result stream, after
+                // reserving space for them.
+                let res_vec_mut = Lrc::make_mut(&mut res_stream_lrc);
+                res_vec_mut.reserve(num_appends);
+                for stream in iter {
+                    let stream_iter = stream.0.iter().cloned();
+
+                    // If (a) `res_mut_vec` is not empty and the last tree
+                    // within it is a token tree marked with `Joint`, and (b)
+                    // `stream` is not empty and the first tree within it is a
+                    // token tree, and (c) the two tokens can be glued
+                    // together...
+                    if let Some((TokenTree::Token(last_tok), Spacing::Joint)) = res_vec_mut.last()
+                        && let Some((TokenTree::Token(tok), spacing)) = stream.0.first()
+                        && let Some(glued_tok) = last_tok.glue(&tok)
+                    {
+                        // ...then overwrite the last token tree in
+                        // `res_vec_mut` with the glued token, and skip the
+                        // first token tree from `stream`.
+                        *res_vec_mut.last_mut().unwrap() = (TokenTree::Token(glued_tok), *spacing);
+                        res_vec_mut.extend(stream_iter.skip(1));
+                    } else {
+                        // Append all of `stream`.
+                        res_vec_mut.extend(stream_iter);
+                    }
+                }
+
+                TokenStream(res_stream_lrc)
+            }
+        }
     }
 }
 
@@ -679,20 +655,6 @@ impl Cursor {
         })
     }
 
-    pub fn index(&self) -> usize {
-        self.index
-    }
-
-    pub fn append(&mut self, new_stream: TokenStream) {
-        if new_stream.is_empty() {
-            return;
-        }
-        let index = self.index;
-        let stream = mem::take(&mut self.stream);
-        *self = TokenStream::from_streams(smallvec![stream, new_stream]).into_trees();
-        self.index = index;
-    }
-
     pub fn look_ahead(&self, n: usize) -> Option<&TokenTree> {
         self.stream.0[self.index..].get(n).map(|(tree, _)| tree)
     }

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -357,12 +357,20 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                 .add_element(live_region_vid, location);
         });
 
+        // HACK(compiler-errors): Constants that are gathered into Body.required_consts
+        // have their locations erased...
+        let locations = if location != Location::START {
+            location.to_locations()
+        } else {
+            Locations::All(constant.span)
+        };
+
         if let Some(annotation_index) = constant.user_ty {
             if let Err(terr) = self.cx.relate_type_and_user_type(
                 constant.literal.ty(),
                 ty::Variance::Invariant,
                 &UserTypeProjection { base: annotation_index, projs: vec![] },
-                location.to_locations(),
+                locations,
                 ConstraintCategory::Boring,
             ) {
                 let annotation = &self.cx.user_type_annotations[annotation_index];
@@ -390,12 +398,9 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                                      promoted: &Body<'tcx>,
                                      ty,
                                      san_ty| {
-                        if let Err(terr) = verifier.cx.eq_types(
-                            ty,
-                            san_ty,
-                            location.to_locations(),
-                            ConstraintCategory::Boring,
-                        ) {
+                        if let Err(terr) =
+                            verifier.cx.eq_types(ty, san_ty, locations, ConstraintCategory::Boring)
+                        {
                             span_mirbug!(
                                 verifier,
                                 promoted,
@@ -416,7 +421,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                     }
                 } else {
                     if let Err(terr) = self.cx.fully_perform_op(
-                        location.to_locations(),
+                        locations,
                         ConstraintCategory::Boring,
                         self.cx.param_env.and(type_op::ascribe_user_type::AscribeUserType::new(
                             constant.literal.ty(),
@@ -435,7 +440,6 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                 }
             } else if let Some(static_def_id) = constant.check_static_ptr(tcx) {
                 let unnormalized_ty = tcx.type_of(static_def_id);
-                let locations = location.to_locations();
                 let normalized_ty = self.cx.normalize(unnormalized_ty, locations);
                 let literal_ty = constant.literal.ty().builtin_deref(true).unwrap().ty;
 
@@ -454,7 +458,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                 self.cx.normalize_and_prove_instantiated_predicates(
                     def_id,
                     instantiated_predicates,
-                    location.to_locations(),
+                    locations,
                 );
             }
         }