Auto merge of rust-lang#73692 - Dylan-DPC:rollup-ehzsbfw, r=Dylan-DPC

Rollup of 6 pull requests

Successful merges:

 - rust-lang#73638 (Remove unused crate imports in 2018 edition crates)
 - rust-lang#73639 (Change heuristic for determining range literal)
 - rust-lang#73646 (Add some regression tests)
 - rust-lang#73652 (Add re-exports to use suggestions)
 - rust-lang#73667 (Update BTreeMap::new() doc)
 - rust-lang#73675 (Update books)

Failed merges:

r? @ghost

src/liballoc/collections/btree/map.rs

@@ -488,7 +488,7 @@ struct MergeIter<K, V, I: Iterator<Item = (K, V)>> {
 }
 
 impl<K: Ord, V> BTreeMap<K, V> {
-    /// Makes a new empty BTreeMap with a reasonable choice for B.
+    /// Makes a new empty BTreeMap.
     ///
     /// Does not allocate anything on its own.
     ///

src/liballoc/collections/vec_deque/tests.rs

@@ -1,7 +1,5 @@
 use super::*;
 
-use test;
-
 #[bench]
 #[cfg_attr(miri, ignore)] // isolated Miri does not support benchmarks
 fn bench_push_back_100(b: &mut test::Bencher) {

src/librustc_ast_pretty/pprust/tests.rs

@@ -2,7 +2,6 @@ use super::*;
 
 use rustc_ast::ast;
 use rustc_ast::with_default_globals;
-use rustc_span;
 use rustc_span::source_map::respan;
 use rustc_span::symbol::Ident;
 

src/librustc_data_structures/sync.rs

@@ -358,7 +358,6 @@ cfg_if! {
         use parking_lot::Mutex as InnerLock;
         use parking_lot::RwLock as InnerRwLock;
 
-        use std;
         use std::thread;
         pub use rayon::{join, scope};
 

src/librustc_hir/hir.rs

@@ -1511,13 +1511,7 @@ pub fn is_range_literal(sm: &SourceMap, expr: &Expr<'_>) -> bool {
     // Check whether a span corresponding to a range expression is a
     // range literal, rather than an explicit struct or `new()` call.
     fn is_lit(sm: &SourceMap, span: &Span) -> bool {
-        let end_point = sm.end_point(*span);
-
-        if let Ok(end_string) = sm.span_to_snippet(end_point) {
-            !(end_string.ends_with('}') || end_string.ends_with(')'))
-        } else {
-            false
-        }
+        sm.span_to_snippet(*span).map(|range_src| range_src.contains("..")).unwrap_or(false)
     };
 
     match expr.kind {

src/librustc_resolve/diagnostics.rs

@@ -643,18 +643,18 @@ impl<'a> Resolver<'a> {
         let not_local_module = crate_name.name != kw::Crate;
         let mut worklist =
             vec![(start_module, Vec::<ast::PathSegment>::new(), true, not_local_module)];
+        let mut worklist_via_import = vec![];
 
-        while let Some((in_module, path_segments, accessible, in_module_is_extern)) = worklist.pop()
+        while let Some((in_module, path_segments, accessible, in_module_is_extern)) =
+            match worklist.pop() {
+                None => worklist_via_import.pop(),
+                Some(x) => Some(x),
+            }
         {
             // We have to visit module children in deterministic order to avoid
             // instabilities in reported imports (#43552).
             in_module.for_each_child(self, |this, ident, ns, name_binding| {
-                // avoid imports entirely
-                if name_binding.is_import() && !name_binding.is_extern_crate() {
-                    return;
-                }
-
-                // avoid non-importable candidates as well
+                // avoid non-importable candidates
                 if !name_binding.is_importable() {
                     return;
                 }
@@ -667,6 +667,17 @@ impl<'a> Resolver<'a> {
                     return;
                 }
 
+                let via_import = name_binding.is_import() && !name_binding.is_extern_crate();
+
+                // There is an assumption elsewhere that paths of variants are in the enum's
+                // declaration and not imported. With this assumption, the variant component is
+                // chopped and the rest of the path is assumed to be the enum's own path. For
+                // errors where a variant is used as the type instead of the enum, this causes
+                // funny looking invalid suggestions, i.e `foo` instead of `foo::MyEnum`.
+                if via_import && name_binding.is_possibly_imported_variant() {
+                    return;
+                }
+
                 // collect results based on the filter function
                 // avoid suggesting anything from the same module in which we are resolving
                 if ident.name == lookup_ident.name
@@ -724,7 +735,8 @@ impl<'a> Resolver<'a> {
                         let is_extern = in_module_is_extern || name_binding.is_extern_crate();
                         // add the module to the lookup
                         if seen_modules.insert(module.def_id().unwrap()) {
-                            worklist.push((module, path_segments, child_accessible, is_extern));
+                            if via_import { &mut worklist_via_import } else { &mut worklist }
+                                .push((module, path_segments, child_accessible, is_extern));
                         }
                     }
                 }

src/librustc_resolve/lib.rs

@@ -703,6 +703,13 @@ impl<'a> NameBinding<'a> {
             }
     }
 
+    fn is_possibly_imported_variant(&self) -> bool {
+        match self.kind {
+            NameBindingKind::Import { binding, .. } => binding.is_possibly_imported_variant(),
+            _ => self.is_variant(),
+        }
+    }
+
     // We sometimes need to treat variants as `pub` for backwards compatibility.
     fn pseudo_vis(&self) -> ty::Visibility {
         if self.is_variant() && self.res().def_id().is_local() {

src/libstd/os/illumos/fs.rs

@@ -1,7 +1,5 @@
 #![stable(feature = "metadata_ext", since = "1.1.0")]
 
-use libc;
-
 use crate::fs::Metadata;
 use crate::sys_common::AsInner;
 

src/libstd/sys/unix/ext/net.rs

@@ -2,9 +2,6 @@
 
 //! Unix-specific networking functionality
 
-#[cfg(unix)]
-use libc;
-
 // FIXME(#43348): Make libc adapt #[doc(cfg(...))] so we don't need these fake definitions here?
 #[cfg(not(unix))]
 #[allow(non_camel_case_types)]

src/libstd/sys/vxworks/args.rs

@@ -56,7 +56,6 @@ mod imp {
     use crate::ffi::{CStr, OsString};
     use crate::marker::PhantomData;
     use crate::ptr;
-    use libc;
 
     use crate::sys_common::mutex::Mutex;
 

src/libstd/sys/vxworks/ext/fs.rs

@@ -6,7 +6,6 @@ use crate::path::Path;
 use crate::sys;
 use crate::sys::platform::fs::MetadataExt as UnixMetadataExt;
 use crate::sys_common::{AsInner, AsInnerMut, FromInner};
-use libc;
 
 /// Unix-specific extensions to [`File`].
 ///

src/libstd/sys/vxworks/rand.rs

@@ -13,7 +13,6 @@ pub fn hashmap_random_keys() -> (u64, u64) {
 mod imp {
     use crate::io;
     use core::sync::atomic::{AtomicBool, Ordering::Relaxed};
-    use libc;
 
     pub fn fill_bytes(v: &mut [u8]) {
         static RNG_INIT: AtomicBool = AtomicBool::new(false);

src/libstd/sys/vxworks/rwlock.rs

@@ -1,6 +1,5 @@
 use crate::cell::UnsafeCell;
 use crate::sync::atomic::{AtomicUsize, Ordering};
-use libc;
 
 pub struct RWLock {
     inner: UnsafeCell<libc::pthread_rwlock_t>,

src/libstd/sys/vxworks/time.rs

@@ -1,7 +1,6 @@
 use crate::cmp::Ordering;
 use crate::time::Duration;
 use ::core::hash::{Hash, Hasher};
-use libc;
 
 pub use self::inner::{Instant, SystemTime, UNIX_EPOCH};
 use crate::convert::TryInto;
@@ -104,7 +103,6 @@ mod inner {
     use crate::fmt;
     use crate::sys::cvt;
     use crate::time::Duration;
-    use libc;
 
     use super::Timespec;
 

src/libstd/sys/wasi/alloc.rs

@@ -1,7 +1,6 @@
 use crate::alloc::{GlobalAlloc, Layout, System};
 use crate::ptr;
 use crate::sys_common::alloc::{realloc_fallback, MIN_ALIGN};
-use libc;
 
 #[stable(feature = "alloc_system_type", since = "1.28.0")]
 unsafe impl GlobalAlloc for System {

src/test/ui/glob-resolve1.rs

@@ -29,3 +29,7 @@ fn main() {
     foo::<C>(); //~ ERROR: cannot find type `C` in this scope
     foo::<D>(); //~ ERROR: cannot find type `D` in this scope
 }
+
+mod other {
+    pub fn import() {}
+}

src/test/ui/glob-resolve1.stderr

@@ -42,6 +42,11 @@ error[E0425]: cannot find function `import` in this scope
    |
 LL |     import();
    |     ^^^^^^ not found in this scope
+   |
+help: consider importing this function
+   |
+LL | use other::import;
+   |
 
 error[E0412]: cannot find type `A` in this scope
   --> $DIR/glob-resolve1.rs:28:11

src/test/ui/impl-trait/issue-69840.rs

@@ -0,0 +1,16 @@
+// check-pass
+
+#![feature(impl_trait_in_bindings)]
+#![allow(incomplete_features)]
+
+struct A<'a>(&'a ());
+
+trait Trait<T> {}
+
+impl<T> Trait<T> for () {}
+
+pub fn foo<'a>() {
+    let _x: impl Trait<A<'a>> = ();
+}
+
+fn main() {}

src/test/ui/namespace/namespace-mix.stderr

@@ -16,7 +16,7 @@ help: consider importing one of these items instead
    |
 LL | use m2::S;
    |
-LL | use namespace_mix::xm2::S;
+LL | use xm2::S;
    |
 
 error[E0423]: expected value, found type alias `xm1::S`
@@ -39,7 +39,7 @@ help: consider importing one of these items instead
    |
 LL | use m2::S;
    |
-LL | use namespace_mix::xm2::S;
+LL | use xm2::S;
    |
 
 error[E0423]: expected value, found struct variant `m7::V`
@@ -61,7 +61,7 @@ help: consider importing one of these items instead
    |
 LL | use m8::V;
    |
-LL | use namespace_mix::xm8::V;
+LL | use xm8::V;
    |
 
 error[E0423]: expected value, found struct variant `xm7::V`
@@ -83,7 +83,7 @@ help: consider importing one of these items instead
    |
 LL | use m8::V;
    |
-LL | use namespace_mix::xm8::V;
+LL | use xm8::V;
    |
 
 error[E0277]: the trait bound `c::Item: Impossible` is not satisfied

src/test/ui/never_type/issue-51506.rs

@@ -0,0 +1,41 @@
+#![feature(never_type, specialization)]
+#![allow(incomplete_features)]
+
+use std::iter::{self, Empty};
+
+trait Trait {
+    type Out: Iterator<Item = u32>;
+
+    fn f(&self) -> Option<Self::Out>;
+}
+
+impl<T> Trait for T {
+    default type Out = !; //~ ERROR: `!` is not an iterator
+
+    default fn f(&self) -> Option<Self::Out> {
+        None
+    }
+}
+
+struct X;
+
+impl Trait for X {
+    type Out = Empty<u32>;
+
+    fn f(&self) -> Option<Self::Out> {
+        Some(iter::empty())
+    }
+}
+
+fn f<T: Trait>(a: T) {
+    if let Some(iter) = a.f() {
+        println!("Some");
+        for x in iter {
+            println!("x = {}", x);
+        }
+    }
+}
+
+pub fn main() {
+    f(10);
+}

src/test/ui/never_type/issue-51506.stderr

@@ -0,0 +1,14 @@
+error[E0277]: `!` is not an iterator
+  --> $DIR/issue-51506.rs:13:5
+   |
+LL |     type Out: Iterator<Item = u32>;
+   |     ------------------------------- required by `Trait::Out`
+...
+LL |     default type Out = !;
+   |     ^^^^^^^^^^^^^^^^^^^^^ `!` is not an iterator
+   |
+   = help: the trait `std::iter::Iterator` is not implemented for `!`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.

src/test/ui/range/issue-73553-misinterp-range-literal.rs

@@ -0,0 +1,16 @@
+type Range = std::ops::Range<usize>;
+
+fn demo(r: &Range) {
+    println!("{:?}", r);
+}
+
+fn tell(x: usize) -> usize {
+    x
+}
+
+fn main() {
+    demo(tell(1)..tell(10));
+    //~^ ERROR mismatched types
+    demo(1..10);
+    //~^ ERROR mismatched types
+}

src/test/ui/range/issue-73553-misinterp-range-literal.stderr

@@ -0,0 +1,27 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-73553-misinterp-range-literal.rs:12:10
+   |
+LL |     demo(tell(1)..tell(10));
+   |          ^^^^^^^^^^^^^^^^^
+   |          |
+   |          expected reference, found struct `std::ops::Range`
+   |          help: consider borrowing here: `&(tell(1)..tell(10))`
+   |
+   = note: expected reference `&std::ops::Range<usize>`
+                 found struct `std::ops::Range<usize>`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-73553-misinterp-range-literal.rs:14:10
+   |
+LL |     demo(1..10);
+   |          ^^^^^
+   |          |
+   |          expected reference, found struct `std::ops::Range`
+   |          help: consider borrowing here: `&(1..10)`
+   |
+   = note: expected reference `&std::ops::Range<usize>`
+                 found struct `std::ops::Range<{integer}>`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/resolve/issue-21221-2.stderr

@@ -4,7 +4,9 @@ error[E0405]: cannot find trait `T` in this scope
 LL | impl T for Foo { }
    |      ^ not found in this scope
    |
-help: consider importing this trait
+help: consider importing one of these items
+   |
+LL | use baz::T;
    |
 LL | use foo::bar::T;
    |