Rollup of 5 pull requests

compiler/rustc_driver/src/lib.rs

@@ -1055,13 +1055,7 @@ pub fn handle_options(args: &[String]) -> Option<getopts::Matches> {
     }
 
     if cg_flags.iter().any(|x| *x == "passes=list") {
-        let backend_name = debug_flags.iter().find_map(|x| {
-            if x.starts_with("codegen-backend=") {
-                Some(&x["codegen-backends=".len()..])
-            } else {
-                None
-            }
-        });
+        let backend_name = debug_flags.iter().find_map(|x| x.strip_prefix("codegen-backend="));
         get_codegen_backend(&None, backend_name).print_passes();
         return None;
     }

compiler/rustc_hir/src/hir.rs

@@ -734,7 +734,7 @@ impl<'hir> WherePredicate<'hir> {
     }
 }
 
-#[derive(Debug, HashStable_Generic, PartialEq, Eq)]
+#[derive(Copy, Clone, Debug, HashStable_Generic, PartialEq, Eq)]
 pub enum PredicateOrigin {
     WhereClause,
     GenericParam,

compiler/rustc_resolve/src/late/lifetimes.rs

@@ -207,6 +207,13 @@ enum Scope<'a> {
         /// In some cases not allowing late bounds allows us to avoid ICEs.
         /// This is almost ways set to true.
         allow_late_bound: bool,
+
+        /// If this binder comes from a where clause, specify how it was created.
+        /// This is used to diagnose inaccessible lifetimes in APIT:
+        /// ```ignore (illustrative)
+        /// fn foo(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {}
+        /// ```
+        where_bound_origin: Option<hir::PredicateOrigin>,
     },
 
     /// Lifetimes introduced by a fn are scoped to the call-site for that fn,
@@ -277,17 +284,19 @@ impl<'a> fmt::Debug for TruncatedScopeDebug<'a> {
                 opaque_type_parent,
                 scope_type,
                 hir_id,
-                s: _,
                 allow_late_bound,
+                where_bound_origin,
+                s: _,
             } => f
                 .debug_struct("Binder")
                 .field("lifetimes", lifetimes)
                 .field("next_early_index", next_early_index)
                 .field("opaque_type_parent", opaque_type_parent)
                 .field("scope_type", scope_type)
                 .field("hir_id", hir_id)
-                .field("s", &"..")
                 .field("allow_late_bound", allow_late_bound)
+                .field("where_bound_origin", where_bound_origin)
+                .field("s", &"..")
                 .finish(),
             Scope::Body { id, s: _ } => {
                 f.debug_struct("Body").field("id", id).field("s", &"..").finish()
@@ -638,6 +647,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     opaque_type_parent: false,
                     scope_type: BinderScopeType::Normal,
                     allow_late_bound: true,
+                    where_bound_origin: None,
                 };
                 self.with(scope, move |this| intravisit::walk_fn(this, fk, fd, b, s, hir_id));
             }
@@ -753,6 +763,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     scope_type: BinderScopeType::Normal,
                     s: ROOT_SCOPE,
                     allow_late_bound: false,
+                    where_bound_origin: None,
                 };
                 self.with(scope, |this| {
                     let scope = Scope::TraitRefBoundary { s: this.scope };
@@ -818,6 +829,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     opaque_type_parent: false,
                     scope_type: BinderScopeType::Normal,
                     allow_late_bound: true,
+                    where_bound_origin: None,
                 };
                 self.with(scope, |this| {
                     // a bare fn has no bounds, so everything
@@ -1006,6 +1018,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                             opaque_type_parent: false,
                             scope_type: BinderScopeType::Normal,
                             allow_late_bound: false,
+                            where_bound_origin: None,
                         };
                         this.with(scope, |this| {
                             this.visit_generics(generics);
@@ -1026,6 +1039,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                         opaque_type_parent: false,
                         scope_type: BinderScopeType::Normal,
                         allow_late_bound: false,
+                        where_bound_origin: None,
                     };
                     self.with(scope, |this| {
                         let scope = Scope::TraitRefBoundary { s: this.scope };
@@ -1084,6 +1098,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     opaque_type_parent: true,
                     scope_type: BinderScopeType::Normal,
                     allow_late_bound: false,
+                    where_bound_origin: None,
                 };
                 self.with(scope, |this| {
                     let scope = Scope::TraitRefBoundary { s: this.scope };
@@ -1151,6 +1166,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     opaque_type_parent: true,
                     scope_type: BinderScopeType::Normal,
                     allow_late_bound: true,
+                    where_bound_origin: None,
                 };
                 self.with(scope, |this| {
                     let scope = Scope::TraitRefBoundary { s: this.scope };
@@ -1266,6 +1282,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                         ref bounded_ty,
                         bounds,
                         ref bound_generic_params,
+                        origin,
                         ..
                     }) => {
                         let (lifetimes, binders): (FxIndexMap<LocalDefId, Region>, Vec<_>) =
@@ -1296,6 +1313,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                             opaque_type_parent: false,
                             scope_type: BinderScopeType::Normal,
                             allow_late_bound: true,
+                            where_bound_origin: Some(origin),
                         };
                         this.with(scope, |this| {
                             this.visit_ty(&bounded_ty);
@@ -1368,6 +1386,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     opaque_type_parent: false,
                     scope_type,
                     allow_late_bound: true,
+                    where_bound_origin: None,
                 };
                 self.with(scope, |this| {
                     intravisit::walk_param_bound(this, bound);
@@ -1420,6 +1439,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
             opaque_type_parent: false,
             scope_type,
             allow_late_bound: true,
+            where_bound_origin: None,
         };
         self.with(scope, |this| {
             walk_list!(this, visit_generic_param, trait_ref.bound_generic_params);
@@ -1680,6 +1700,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
             opaque_type_parent: true,
             scope_type: BinderScopeType::Normal,
             allow_late_bound: true,
+            where_bound_origin: None,
         };
         self.with(scope, walk);
     }
@@ -1783,12 +1804,48 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
             }
 
             self.insert_lifetime(lifetime_ref, def);
-        } else {
-            self.tcx.sess.delay_span_bug(
-                lifetime_ref.span,
-                &format!("Could not resolve {:?} in scope {:#?}", lifetime_ref, self.scope,),
-            );
+            return;
         }
+
+        // We may fail to resolve higher-ranked lifetimes that are mentionned by APIT.
+        // AST-based resolution does not care for impl-trait desugaring, which are the
+        // responibility of lowering.  This may create a mismatch between the resolution
+        // AST found (`region_def_id`) which points to HRTB, and what HIR allows.
+        // ```
+        // fn foo(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {}
+        // ```
+        //
+        // In such case, walk back the binders to diagnose it properly.
+        let mut scope = self.scope;
+        loop {
+            match *scope {
+                Scope::Binder {
+                    where_bound_origin: Some(hir::PredicateOrigin::ImplTrait), ..
+                } => {
+                    let mut err = self.tcx.sess.struct_span_err(
+                        lifetime_ref.span,
+                        "`impl Trait` can only mention lifetimes bound at the fn or impl level",
+                    );
+                    err.span_note(self.tcx.def_span(region_def_id), "lifetime declared here");
+                    err.emit();
+                    return;
+                }
+                Scope::Root => break,
+                Scope::Binder { s, .. }
+                | Scope::Body { s, .. }
+                | Scope::Elision { s, .. }
+                | Scope::ObjectLifetimeDefault { s, .. }
+                | Scope::Supertrait { s, .. }
+                | Scope::TraitRefBoundary { s, .. } => {
+                    scope = s;
+                }
+            }
+        }
+
+        self.tcx.sess.delay_span_bug(
+            lifetime_ref.span,
+            &format!("Could not resolve {:?} in scope {:#?}", lifetime_ref, self.scope,),
+        );
     }
 
     fn visit_segment_args(

library/core/src/ptr/mod.rs

@@ -532,7 +532,7 @@ pub const fn null<T>() -> *const T {
 #[rustc_diagnostic_item = "ptr_null"]
 #[cfg(not(bootstrap))]
 pub const fn null<T: ?Sized + Thin>() -> *const T {
-    from_raw_parts(0 as *const (), ())
+    from_raw_parts(invalid(0), ())
 }
 
 /// Creates a null mutable raw pointer.
@@ -709,7 +709,7 @@ where
 #[rustc_diagnostic_item = "ptr_null_mut"]
 #[cfg(not(bootstrap))]
 pub const fn null_mut<T: ?Sized + Thin>() -> *mut T {
-    from_raw_parts_mut(0 as *mut (), ())
+    from_raw_parts_mut(invalid_mut(0), ())
 }
 
 /// Forms a raw slice from a pointer and a length.

src/etc/htmldocck.py

@@ -94,6 +94,10 @@
   in the specified file. The number of occurrences must match the given
   count.
 
+* `@count PATH XPATH TEXT COUNT` checks for the occurrence of the given XPath
+  with the given text in the specified file. The number of occurrences must
+  match the given count.
+
 * `@snapshot NAME PATH XPATH` creates a snapshot test named NAME.
   A snapshot test captures a subtree of the DOM, at the location
   determined by the XPath, and compares it to a pre-recorded value
@@ -382,23 +386,25 @@ def check_tree_attr(tree, path, attr, pat, regexp):
     return ret
 
 
-def check_tree_text(tree, path, pat, regexp):
+# Returns the number of occurences matching the regex (`regexp`) and the text (`pat`).
+def check_tree_text(tree, path, pat, regexp, stop_at_first):
     path = normalize_xpath(path)
-    ret = False
+    match_count = 0
     try:
         for e in tree.findall(path):
             try:
                 value = flatten(e)
             except KeyError:
                 continue
             else:
-                ret = check_string(value, pat, regexp)
-                if ret:
-                    break
+                if check_string(value, pat, regexp):
+                    match_count += 1
+                    if stop_at_first:
+                        break
     except Exception:
         print('Failed to get path "{}"'.format(path))
         raise
-    return ret
+    return match_count
 
 
 def get_tree_count(tree, path):
@@ -518,6 +524,19 @@ def print_err(lineno, context, err, message=None):
         stderr("\t{}".format(context))
 
 
+def get_nb_matching_elements(cache, c, regexp, stop_at_first):
+    tree = cache.get_tree(c.args[0])
+    pat, sep, attr = c.args[1].partition('/@')
+    if sep:  # attribute
+        tree = cache.get_tree(c.args[0])
+        return check_tree_attr(tree, pat, attr, c.args[2], False)
+    else:  # normalized text
+        pat = c.args[1]
+        if pat.endswith('/text()'):
+            pat = pat[:-7]
+        return check_tree_text(cache.get_tree(c.args[0]), pat, c.args[2], regexp, stop_at_first)
+
+
 ERR_COUNT = 0
 
 
@@ -538,16 +557,7 @@ def check_command(c, cache):
                 ret = check_string(cache.get_file(c.args[0]), c.args[1], regexp)
             elif len(c.args) == 3:  # @has/matches <path> <pat> <match> = XML tree test
                 cerr = "`XPATH PATTERN` did not match"
-                tree = cache.get_tree(c.args[0])
-                pat, sep, attr = c.args[1].partition('/@')
-                if sep:  # attribute
-                    tree = cache.get_tree(c.args[0])
-                    ret = check_tree_attr(tree, pat, attr, c.args[2], regexp)
-                else:  # normalized text
-                    pat = c.args[1]
-                    if pat.endswith('/text()'):
-                        pat = pat[:-7]
-                    ret = check_tree_text(cache.get_tree(c.args[0]), pat, c.args[2], regexp)
+                ret = get_nb_matching_elements(cache, c, regexp, True) != 0
             else:
                 raise InvalidCheck('Invalid number of @{} arguments'.format(c.cmd))
 
@@ -557,6 +567,11 @@ def check_command(c, cache):
                 found = get_tree_count(cache.get_tree(c.args[0]), c.args[1])
                 cerr = "Expected {} occurrences but found {}".format(expected, found)
                 ret = expected == found
+            elif len(c.args) == 4:  # @count <path> <pat> <text> <count> = count test
+                expected = int(c.args[3])
+                found = get_nb_matching_elements(cache, c, False, False)
+                cerr = "Expected {} occurrences but found {}".format(expected, found)
+                ret = found == expected
             else:
                 raise InvalidCheck('Invalid number of @{} arguments'.format(c.cmd))
 

src/librustdoc/html/render/mod.rs

@@ -1600,6 +1600,13 @@ fn render_impl(
         }
 
         if let Some(ref dox) = i.impl_item.collapsed_doc_value() {
+            if trait_.is_none() && i.inner_impl().items.is_empty() {
+                w.write_str(
+                    "<div class=\"item-info\">\
+                    <div class=\"stab empty-impl\">This impl block contains no items.</div>
+                </div>",
+                );
+            }
             write!(
                 w,
                 "<div class=\"docblock\">{}</div>",

src/librustdoc/html/static/css/themes/ayu.css

@@ -281,9 +281,13 @@ details.undocumented > summary::before {
 	color: #000;
 }
 
+/* Created this empty rule to satisfy the theme checks. */
+.stab.empty-impl {}
+
 .stab.unstable,
 .stab.deprecated,
-.stab.portability {
+.stab.portability,
+.stab.empty-impl {
 	color: #c5c5c5;
 	background: #314559 !important;
 	border-style: none !important;

src/librustdoc/html/static/css/themes/dark.css

@@ -266,6 +266,7 @@ details.undocumented > summary::before {
 	color: #ddd;
 }
 
+.stab.empty-impl { background: #FFF5D6; border-color: #FFC600; color: #2f2f2f; }
 .stab.unstable { background: #FFF5D6; border-color: #FFC600; color: #2f2f2f; }
 .stab.deprecated { background: #ffc4c4; border-color: #db7b7b; color: #2f2f2f; }
 .stab.portability { background: #F3DFFF; border-color: #b07bdb; color: #2f2f2f; }

src/librustdoc/html/static/css/themes/light.css

@@ -255,6 +255,7 @@ details.undocumented > summary::before {
 	color: #000;
 }
 
+.stab.empty-impl { background: #FFF5D6; border-color: #FFC600; }
 .stab.unstable { background: #FFF5D6; border-color: #FFC600; }
 .stab.deprecated { background: #ffc4c4; border-color: #db7b7b; }
 .stab.portability { background: #F3DFFF; border-color: #b07bdb; }

src/librustdoc/passes/stripper.rs

@@ -124,8 +124,9 @@ pub(crate) struct ImplStripper<'a> {
 impl<'a> DocFolder for ImplStripper<'a> {
     fn fold_item(&mut self, i: Item) -> Option<Item> {
         if let clean::ImplItem(ref imp) = *i.kind {
-            // emptied none trait impls can be stripped
-            if imp.trait_.is_none() && imp.items.is_empty() {
+            // Impl blocks can be skipped if they are: empty; not a trait impl; and have no
+            // documentation.
+            if imp.trait_.is_none() && imp.items.is_empty() && i.doc_value().is_none() {
                 return None;
             }
             if let Some(did) = imp.for_.def_id(self.cache) {

src/test/rustdoc/empty-impl-block.rs

@@ -0,0 +1,20 @@
+#![crate_name = "foo"]
+
+// @has 'foo/struct.Foo.html'
+pub struct Foo;
+
+// @has - '//*[@class="docblock"]' 'Hello empty impl block!'
+// @has - '//*[@class="item-info"]' 'This impl block contains no items.'
+/// Hello empty impl block!
+impl Foo {}
+// We ensure that this empty impl block without doc isn't rendered.
+// @count - '//*[@class="impl has-srclink"]' 'impl Foo' 1
+impl Foo {}
+
+// Just to ensure that empty trait impl blocks are rendered.
+pub struct Another;
+pub trait Bar {}
+
+// @has 'foo/struct.Another.html'
+// @has - '//h3[@class="code-header in-band"]' 'impl Bar for Another'
+impl Bar for Another {}