Auto merge of #84112 - Dylan-DPC:rollup-tapsrzz, r=Dylan-DPC

Rollup of 7 pull requests

Successful merges:

 - #83669 (Issue 81508 fix)
 - #84014 (Improve trait/impl method discrepancy errors)
 - #84059 (Bump libc dependency of std to 0.2.93)
 - #84067 (clean up example on read_to_string)
 - #84079 (Improve test for `rustdoc::bare_urls` lint)
 - #84094 (Remove FixedSizeArray)
 - #84101 (rustdoc: Move crate loader to collect_intra_doc_links::early )

Failed merges:

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

24 files changed, 498 insertions, 182 deletions

diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index c9fdaa50534..be7bff1a29c 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -5,8 +5,8 @@ use rustc_driver::abort_on_err;
 use rustc_errors::emitter::{Emitter, EmitterWriter};
 use rustc_errors::json::JsonEmitter;
 use rustc_feature::UnstableFeatures;
-use rustc_hir::def::{Namespace::TypeNS, Res};
-use rustc_hir::def_id::{CrateNum, DefId, DefIndex, LocalDefId, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def::Res;
+use rustc_hir::def_id::{CrateNum, DefId, DefIndex, LocalDefId, LOCAL_CRATE};
 use rustc_hir::HirId;
 use rustc_hir::{
     intravisit::{self, NestedVisitorMap, Visitor},
@@ -356,55 +356,7 @@ crate fn create_resolver<'a>(
     let (krate, resolver, _) = &*parts;
     let resolver = resolver.borrow().clone();
 
-    // Letting the resolver escape at the end of the function leads to inconsistencies between the
-    // crates the TyCtxt sees and the resolver sees (because the resolver could load more crates
-    // after escaping). Hopefully `IntraLinkCrateLoader` gets all the crates we need ...
-    struct IntraLinkCrateLoader {
-        current_mod: DefId,
-        resolver: Rc<RefCell<interface::BoxedResolver>>,
-    }
-    impl ast::visit::Visitor<'_> for IntraLinkCrateLoader {
-        fn visit_attribute(&mut self, attr: &ast::Attribute) {
-            use crate::html::markdown::{markdown_links, MarkdownLink};
-            use crate::passes::collect_intra_doc_links::Disambiguator;
-
-            if let Some(doc) = attr.doc_str() {
-                for MarkdownLink { link, .. } in markdown_links(&doc.as_str()) {
-                    // FIXME: this misses a *lot* of the preprocessing done in collect_intra_doc_links
-                    // I think most of it shouldn't be necessary since we only need the crate prefix?
-                    let path_str = match Disambiguator::from_str(&link) {
-                        Ok(x) => x.map_or(link.as_str(), |(_, p)| p),
-                        Err(_) => continue,
-                    };
-                    self.resolver.borrow_mut().access(|resolver| {
-                        let _ = resolver.resolve_str_path_error(
-                            attr.span,
-                            path_str,
-                            TypeNS,
-                            self.current_mod,
-                        );
-                    });
-                }
-            }
-            ast::visit::walk_attribute(self, attr);
-        }
-
-        fn visit_item(&mut self, item: &ast::Item) {
-            use rustc_ast_lowering::ResolverAstLowering;
-
-            if let ast::ItemKind::Mod(..) = item.kind {
-                let new_mod =
-                    self.resolver.borrow_mut().access(|resolver| resolver.local_def_id(item.id));
-                let old_mod = mem::replace(&mut self.current_mod, new_mod.to_def_id());
-                ast::visit::walk_item(self, item);
-                self.current_mod = old_mod;
-            } else {
-                ast::visit::walk_item(self, item);
-            }
-        }
-    }
-    let crate_id = LocalDefId { local_def_index: CRATE_DEF_INDEX }.to_def_id();
-    let mut loader = IntraLinkCrateLoader { current_mod: crate_id, resolver };
+    let mut loader = crate::passes::collect_intra_doc_links::IntraLinkCrateLoader::new(resolver);
     ast::visit::walk_crate(&mut loader, krate);
 
     loader.resolver
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index 4bc7544e33d..6342110adfe 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -39,13 +39,16 @@ use crate::passes::Pass;
 
 use super::span_of_attrs;
 
+mod early;
+crate use early::IntraLinkCrateLoader;
+
 crate const COLLECT_INTRA_DOC_LINKS: Pass = Pass {
     name: "collect-intra-doc-links",
     run: collect_intra_doc_links,
     description: "resolves intra-doc links",
 };
 
-crate fn collect_intra_doc_links(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
+fn collect_intra_doc_links(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
     LinkCollector {
         cx,
         mod_ids: Vec::new(),
@@ -892,6 +895,117 @@ impl<'a, 'tcx> DocFolder for LinkCollector<'a, 'tcx> {
     }
 }
 
+enum PreprocessingError<'a> {
+    Anchor(AnchorFailure),
+    Disambiguator(Range<usize>, String),
+    Resolution(ResolutionFailure<'a>, String, Option<Disambiguator>),
+}
+
+impl From<AnchorFailure> for PreprocessingError<'_> {
+    fn from(err: AnchorFailure) -> Self {
+        Self::Anchor(err)
+    }
+}
+
+struct PreprocessingInfo {
+    path_str: String,
+    disambiguator: Option<Disambiguator>,
+    extra_fragment: Option<String>,
+    link_text: String,
+}
+
+/// Returns:
+/// - `None` if the link should be ignored.
+/// - `Some(Err)` if the link should emit an error
+/// - `Some(Ok)` if the link is valid
+///
+/// `link_buffer` is needed for lifetime reasons; it will always be overwritten and the contents ignored.
+fn preprocess_link<'a>(
+    ori_link: &'a MarkdownLink,
+) -> Option<Result<PreprocessingInfo, PreprocessingError<'a>>> {
+    // [] is mostly likely not supposed to be a link
+    if ori_link.link.is_empty() {
+        return None;
+    }
+
+    // Bail early for real links.
+    if ori_link.link.contains('/') {
+        return None;
+    }
+
+    let stripped = ori_link.link.replace("`", "");
+    let mut parts = stripped.split('#');
+
+    let link = parts.next().unwrap();
+    if link.trim().is_empty() {
+        // This is an anchor to an element of the current page, nothing to do in here!
+        return None;
+    }
+    let extra_fragment = parts.next();
+    if parts.next().is_some() {
+        // A valid link can't have multiple #'s
+        return Some(Err(AnchorFailure::MultipleAnchors.into()));
+    }
+
+    // Parse and strip the disambiguator from the link, if present.
+    let (path_str, disambiguator) = match Disambiguator::from_str(&link) {
+        Ok(Some((d, path))) => (path.trim(), Some(d)),
+        Ok(None) => (link.trim(), None),
+        Err((err_msg, relative_range)) => {
+            // Only report error if we would not have ignored this link. See issue #83859.
+            if !should_ignore_link_with_disambiguators(link) {
+                let no_backticks_range = range_between_backticks(&ori_link);
+                let disambiguator_range = (no_backticks_range.start + relative_range.start)
+                    ..(no_backticks_range.start + relative_range.end);
+                return Some(Err(PreprocessingError::Disambiguator(disambiguator_range, err_msg)));
+            } else {
+                return None;
+            }
+        }
+    };
+
+    if should_ignore_link(path_str) {
+        return None;
+    }
+
+    // We stripped `()` and `!` when parsing the disambiguator.
+    // Add them back to be displayed, but not prefix disambiguators.
+    let link_text =
+        disambiguator.map(|d| d.display_for(path_str)).unwrap_or_else(|| path_str.to_owned());
+
+    // Strip generics from the path.
+    let path_str = if path_str.contains(['<', '>'].as_slice()) {
+        match strip_generics_from_path(&path_str) {
+            Ok(path) => path,
+            Err(err_kind) => {
+                debug!("link has malformed generics: {}", path_str);
+                return Some(Err(PreprocessingError::Resolution(
+                    err_kind,
+                    path_str.to_owned(),
+                    disambiguator,
+                )));
+            }
+        }
+    } else {
+        path_str.to_owned()
+    };
+
+    // Sanity check to make sure we don't have any angle brackets after stripping generics.
+    assert!(!path_str.contains(['<', '>'].as_slice()));
+
+    // The link is not an intra-doc link if it still contains spaces after stripping generics.
+    if path_str.contains(' ') {
+        return None;
+    }
+
+    Some(Ok(PreprocessingInfo {
+        path_str,
+        disambiguator,
+        extra_fragment: extra_fragment.map(String::from),
+        link_text,
+    }))
+}
+
 impl LinkCollector<'_, '_> {
     /// This is the entry point for resolving an intra-doc link.
     ///
@@ -907,16 +1021,6 @@ impl LinkCollector<'_, '_> {
     ) -> Option<ItemLink> {
         trace!("considering link '{}'", ori_link.link);
 
-        // Bail early for real links.
-        if ori_link.link.contains('/') {
-            return None;
-        }
-
-        // [] is mostly likely not supposed to be a link
-        if ori_link.link.is_empty() {
-            return None;
-        }
-
         let diag_info = DiagnosticInfo {
             item,
             dox,
@@ -924,47 +1028,29 @@ impl LinkCollector<'_, '_> {
             link_range: ori_link.range.clone(),
         };
 
-        let link = ori_link.link.replace("`", "");
-        let no_backticks_range = range_between_backticks(&ori_link);
-        let parts = link.split('#').collect::<Vec<_>>();
-        let (link, extra_fragment) = if parts.len() > 2 {
-            // A valid link can't have multiple #'s
-            anchor_failure(self.cx, diag_info, AnchorFailure::MultipleAnchors);
-            return None;
-        } else if parts.len() == 2 {
-            if parts[0].trim().is_empty() {
-                // This is an anchor to an element of the current page, nothing to do in here!
-                return None;
-            }
-            (parts[0], Some(parts[1].to_owned()))
-        } else {
-            (parts[0], None)
-        };
-
-        // Parse and strip the disambiguator from the link, if present.
-        let (mut path_str, disambiguator) = match Disambiguator::from_str(&link) {
-            Ok(Some((d, path))) => (path.trim(), Some(d)),
-            Ok(None) => (link.trim(), None),
-            Err((err_msg, relative_range)) => {
-                if !should_ignore_link_with_disambiguators(link) {
-                    // Only report error if we would not have ignored this link.
-                    // See issue #83859.
-                    let disambiguator_range = (no_backticks_range.start + relative_range.start)
-                        ..(no_backticks_range.start + relative_range.end);
-                    disambiguator_error(self.cx, diag_info, disambiguator_range, &err_msg);
+        let PreprocessingInfo { path_str, disambiguator, extra_fragment, link_text } =
+            match preprocess_link(&ori_link)? {
+                Ok(x) => x,
+                Err(err) => {
+                    match err {
+                        PreprocessingError::Anchor(err) => anchor_failure(self.cx, diag_info, err),
+                        PreprocessingError::Disambiguator(range, msg) => {
+                            disambiguator_error(self.cx, diag_info, range, &msg)
+                        }
+                        PreprocessingError::Resolution(err, path_str, disambiguator) => {
+                            resolution_failure(
+                                self,
+                                diag_info,
+                                &path_str,
+                                disambiguator,
+                                smallvec![err],
+                            );
+                        }
+                    }
+                    return None;
                 }
-                return None;
-            }
-        };
-
-        if should_ignore_link(path_str) {
-            return None;
-        }
-
-        // We stripped `()` and `!` when parsing the disambiguator.
-        // Add them back to be displayed, but not prefix disambiguators.
-        let link_text =
-            disambiguator.map(|d| d.display_for(path_str)).unwrap_or_else(|| path_str.to_owned());
+            };
+        let mut path_str = &*path_str;
 
         // In order to correctly resolve intra-doc links we need to
         // pick a base AST node to work from.  If the documentation for
@@ -1029,39 +1115,12 @@ impl LinkCollector<'_, '_> {
             module_id = DefId { krate, index: CRATE_DEF_INDEX };
         }
 
-        // Strip generics from the path.
-        let stripped_path_string;
-        if path_str.contains(['<', '>'].as_slice()) {
-            stripped_path_string = match strip_generics_from_path(path_str) {
-                Ok(path) => path,
-                Err(err_kind) => {
-                    debug!("link has malformed generics: {}", path_str);
-                    resolution_failure(
-                        self,
-                        diag_info,
-                        path_str,
-                        disambiguator,
-                        smallvec![err_kind],
-                    );
-                    return None;
-                }
-            };
-            path_str = &stripped_path_string;
-        }
-        // Sanity check to make sure we don't have any angle brackets after stripping generics.
-        assert!(!path_str.contains(['<', '>'].as_slice()));
-
-        // The link is not an intra-doc link if it still contains spaces after stripping generics.
-        if path_str.contains(' ') {
-            return None;
-        }
-
         let (mut res, mut fragment) = self.resolve_with_disambiguator_cached(
             ResolutionInfo {
                 module_id,
                 dis: disambiguator,
                 path_str: path_str.to_owned(),
-                extra_fragment,
+                extra_fragment: extra_fragment.map(String::from),
             },
             diag_info.clone(), // this struct should really be Copy, but Range is not :(
             matches!(ori_link.kind, LinkType::Reference | LinkType::Shortcut),
@@ -1438,7 +1497,7 @@ fn should_ignore_link(path_str: &str) -> bool {
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
 /// Disambiguators for a link.
-crate enum Disambiguator {
+enum Disambiguator {
     /// `prim@`
     ///
     /// This is buggy, see <https://github.com/rust-lang/rust/pull/77875#discussion_r503583103>
@@ -1467,7 +1526,7 @@ impl Disambiguator {
     /// This returns `Ok(Some(...))` if a disambiguator was found,
     /// `Ok(None)` if no disambiguator was found, or `Err(...)`
     /// if there was a problem with the disambiguator.
-    crate fn from_str(link: &str) -> Result<Option<(Self, &str)>, (String, Range<usize>)> {
+    fn from_str(link: &str) -> Result<Option<(Self, &str)>, (String, Range<usize>)> {
         use Disambiguator::{Kind, Namespace as NS, Primitive};
 
         if let Some(idx) = link.find('@') {
diff --git a/src/librustdoc/passes/collect_intra_doc_links/early.rs b/src/librustdoc/passes/collect_intra_doc_links/early.rs
new file mode 100644
index 00000000000..7cba2523d1a
--- /dev/null
+++ b/src/librustdoc/passes/collect_intra_doc_links/early.rs
@@ -0,0 +1,63 @@
+use rustc_ast as ast;
+use rustc_hir::def::Namespace::TypeNS;
+use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_INDEX};
+use rustc_interface::interface;
+
+use std::cell::RefCell;
+use std::mem;
+use std::rc::Rc;
+
+// Letting the resolver escape at the end of the function leads to inconsistencies between the
+// crates the TyCtxt sees and the resolver sees (because the resolver could load more crates
+// after escaping). Hopefully `IntraLinkCrateLoader` gets all the crates we need ...
+crate struct IntraLinkCrateLoader {
+    current_mod: DefId,
+    crate resolver: Rc<RefCell<interface::BoxedResolver>>,
+}
+
+impl IntraLinkCrateLoader {
+    crate fn new(resolver: Rc<RefCell<interface::BoxedResolver>>) -> Self {
+        let crate_id = LocalDefId { local_def_index: CRATE_DEF_INDEX }.to_def_id();
+        Self { current_mod: crate_id, resolver }
+    }
+}
+
+impl ast::visit::Visitor<'_> for IntraLinkCrateLoader {
+    fn visit_attribute(&mut self, attr: &ast::Attribute) {
+        use crate::html::markdown::markdown_links;
+        use crate::passes::collect_intra_doc_links::preprocess_link;
+
+        if let Some(doc) = attr.doc_str() {
+            for link in markdown_links(&doc.as_str()) {
+                let path_str = if let Some(Ok(x)) = preprocess_link(&link) {
+                    x.path_str
+                } else {
+                    continue;
+                };
+                self.resolver.borrow_mut().access(|resolver| {
+                    let _ = resolver.resolve_str_path_error(
+                        attr.span,
+                        &path_str,
+                        TypeNS,
+                        self.current_mod,
+                    );
+                });
+            }
+        }
+        ast::visit::walk_attribute(self, attr);
+    }
+
+    fn visit_item(&mut self, item: &ast::Item) {
+        use rustc_ast_lowering::ResolverAstLowering;
+
+        if let ast::ItemKind::Mod(..) = item.kind {
+            let new_mod =
+                self.resolver.borrow_mut().access(|resolver| resolver.local_def_id(item.id));
+            let old_mod = mem::replace(&mut self.current_mod, new_mod.to_def_id());
+            ast::visit::walk_item(self, item);
+            self.current_mod = old_mod;
+        } else {
+            ast::visit::walk_item(self, item);
+        }
+    }
+}
diff --git a/src/test/rustdoc-ui/bare-urls.fixed b/src/test/rustdoc-ui/bare-urls.fixed
new file mode 100644
index 00000000000..23aa5c44c21
--- /dev/null
+++ b/src/test/rustdoc-ui/bare-urls.fixed
@@ -0,0 +1,60 @@
+// run-rustfix
+
+#![deny(rustdoc::bare_urls)]
+
+/// <https://somewhere.com>
+//~^ ERROR this URL is not a hyperlink
+/// <https://somewhere.com/a>
+//~^ ERROR this URL is not a hyperlink
+/// <https://www.somewhere.com>
+//~^ ERROR this URL is not a hyperlink
+/// <https://www.somewhere.com/a>
+//~^ ERROR this URL is not a hyperlink
+/// <https://subdomain.example.com>
+//~^ ERROR not a hyperlink
+/// <https://somewhere.com?>
+//~^ ERROR this URL is not a hyperlink
+/// <https://somewhere.com/a?>
+//~^ ERROR this URL is not a hyperlink
+/// <https://somewhere.com?hello=12>
+//~^ ERROR this URL is not a hyperlink
+/// <https://somewhere.com/a?hello=12>
+//~^ ERROR this URL is not a hyperlink
+/// <https://example.com?hello=12#xyz>
+//~^ ERROR this URL is not a hyperlink
+/// <https://example.com/a?hello=12#xyz>
+//~^ ERROR this URL is not a hyperlink
+/// <https://example.com#xyz>
+//~^ ERROR this URL is not a hyperlink
+/// <https://example.com/a#xyz>
+//~^ ERROR this URL is not a hyperlink
+/// <https://somewhere.com?hello=12&bye=11>
+//~^ ERROR this URL is not a hyperlink
+/// <https://somewhere.com/a?hello=12&bye=11>
+//~^ ERROR this URL is not a hyperlink
+/// <https://somewhere.com?hello=12&bye=11#xyz>
+//~^ ERROR this URL is not a hyperlink
+/// hey! <https://somewhere.com/a?hello=12&bye=11#xyz>
+//~^ ERROR this URL is not a hyperlink
+pub fn c() {}
+
+/// <https://somewhere.com>
+/// [a](http://a.com)
+/// [b]
+///
+/// [b]: http://b.com
+///
+/// ```
+/// This link should not be linted: http://example.com
+///
+/// Nor this one: <http://example.com> or this one: [x](http://example.com)
+/// ```
+///
+/// [should_not.lint](should_not.lint)
+pub fn everything_is_fine_here() {}
+
+#[allow(rustdoc::bare_urls)]
+pub mod foo {
+    /// https://somewhere.com/a?hello=12&bye=11#xyz
+    pub fn bar() {}
+}
diff --git a/src/test/rustdoc-ui/url-improvements.rs b/src/test/rustdoc-ui/bare-urls.rs
index 43a13b02d0a..592f57343bc 100644
--- a/src/test/rustdoc-ui/url-improvements.rs
+++ b/src/test/rustdoc-ui/bare-urls.rs
@@ -1,3 +1,5 @@
+// run-rustfix
+
 #![deny(rustdoc::bare_urls)]
 
 /// https://somewhere.com
diff --git a/src/test/rustdoc-ui/url-improvements.stderr b/src/test/rustdoc-ui/bare-urls.stderr
index 3d5ebd8be6b..6b612f81590 100644
--- a/src/test/rustdoc-ui/url-improvements.stderr
+++ b/src/test/rustdoc-ui/bare-urls.stderr
@@ -1,107 +1,107 @@
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:3:5
+  --> $DIR/bare-urls.rs:5:5
    |
 LL | /// https://somewhere.com
    |     ^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://somewhere.com>`
    |
 note: the lint level is defined here
-  --> $DIR/url-improvements.rs:1:9
+  --> $DIR/bare-urls.rs:3:9
    |
 LL | #![deny(rustdoc::bare_urls)]
    |         ^^^^^^^^^^^^^^^^^^
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:5:5
+  --> $DIR/bare-urls.rs:7:5
    |
 LL | /// https://somewhere.com/a
    |     ^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://somewhere.com/a>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:7:5
+  --> $DIR/bare-urls.rs:9:5
    |
 LL | /// https://www.somewhere.com
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://www.somewhere.com>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:9:5
+  --> $DIR/bare-urls.rs:11:5
    |
 LL | /// https://www.somewhere.com/a
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://www.somewhere.com/a>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:11:5
+  --> $DIR/bare-urls.rs:13:5
    |
 LL | /// https://subdomain.example.com
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://subdomain.example.com>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:13:5
+  --> $DIR/bare-urls.rs:15:5
    |
 LL | /// https://somewhere.com?
    |     ^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://somewhere.com?>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:15:5
+  --> $DIR/bare-urls.rs:17:5
    |
 LL | /// https://somewhere.com/a?
    |     ^^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://somewhere.com/a?>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:17:5
+  --> $DIR/bare-urls.rs:19:5
    |
 LL | /// https://somewhere.com?hello=12
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://somewhere.com?hello=12>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:19:5
+  --> $DIR/bare-urls.rs:21:5
    |
 LL | /// https://somewhere.com/a?hello=12
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://somewhere.com/a?hello=12>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:21:5
+  --> $DIR/bare-urls.rs:23:5
    |
 LL | /// https://example.com?hello=12#xyz
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://example.com?hello=12#xyz>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:23:5
+  --> $DIR/bare-urls.rs:25:5
    |
 LL | /// https://example.com/a?hello=12#xyz
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://example.com/a?hello=12#xyz>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:25:5
+  --> $DIR/bare-urls.rs:27:5
    |
 LL | /// https://example.com#xyz
    |     ^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://example.com#xyz>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:27:5
+  --> $DIR/bare-urls.rs:29:5
    |
 LL | /// https://example.com/a#xyz
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://example.com/a#xyz>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:29:5
+  --> $DIR/bare-urls.rs:31:5
    |
 LL | /// https://somewhere.com?hello=12&bye=11
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://somewhere.com?hello=12&bye=11>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:31:5
+  --> $DIR/bare-urls.rs:33:5
    |
 LL | /// https://somewhere.com/a?hello=12&bye=11
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://somewhere.com/a?hello=12&bye=11>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:33:5
+  --> $DIR/bare-urls.rs:35:5
    |
 LL | /// https://somewhere.com?hello=12&bye=11#xyz
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://somewhere.com?hello=12&bye=11#xyz>`
 
 error: this URL is not a hyperlink
-  --> $DIR/url-improvements.rs:35:10
+  --> $DIR/bare-urls.rs:37:10
    |
 LL | /// hey! https://somewhere.com/a?hello=12&bye=11#xyz
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<https://somewhere.com/a?hello=12&bye=11#xyz>`
diff --git a/src/test/rustdoc/intra-doc/auxiliary/empty.rs b/src/test/rustdoc/intra-doc/auxiliary/empty.rs
new file mode 100644
index 00000000000..d11c69f812a
--- /dev/null
+++ b/src/test/rustdoc/intra-doc/auxiliary/empty.rs
@@ -0,0 +1 @@
+// intentionally empty
diff --git a/src/test/rustdoc/intra-doc/auxiliary/empty2.rs b/src/test/rustdoc/intra-doc/auxiliary/empty2.rs
new file mode 100644
index 00000000000..d11c69f812a
--- /dev/null
+++ b/src/test/rustdoc/intra-doc/auxiliary/empty2.rs
@@ -0,0 +1 @@
+// intentionally empty
diff --git a/src/test/rustdoc/intra-doc/extern-crate-only-used-in-link.rs b/src/test/rustdoc/intra-doc/extern-crate-only-used-in-link.rs
index 0964c79de06..5d8dcf8bc1d 100644
--- a/src/test/rustdoc/intra-doc/extern-crate-only-used-in-link.rs
+++ b/src/test/rustdoc/intra-doc/extern-crate-only-used-in-link.rs
@@ -1,8 +1,19 @@
+// This test is just a little cursed.
 // aux-build:issue-66159-1.rs
 // aux-crate:priv:issue_66159_1=issue-66159-1.rs
+// aux-build:empty.rs
+// aux-crate:priv:empty=empty.rs
+// aux-build:empty2.rs
+// aux-crate:priv:empty2=empty2.rs
 // build-aux-docs
-// compile-flags:-Z unstable-options
+// compile-flags:-Z unstable-options --edition 2018
 
 // @has extern_crate_only_used_in_link/index.html
 // @has - '//a[@href="../issue_66159_1/struct.Something.html"]' 'issue_66159_1::Something'
 //! [issue_66159_1::Something]
+
+// @has - '//a[@href="../empty/index.html"]' 'empty'
+//! [`empty`]
+
+// @has - '//a[@href="../empty2/index.html"]' 'empty2'
+//! [empty2<x>]
diff --git a/src/test/ui/associated-types/defaults-specialization.stderr b/src/test/ui/associated-types/defaults-specialization.stderr
index 920f8322813..3c7dc1fc3c9 100644
--- a/src/test/ui/associated-types/defaults-specialization.stderr
+++ b/src/test/ui/associated-types/defaults-specialization.stderr
@@ -15,7 +15,10 @@ LL |     fn make() -> Self::Ty {
    |                  -------- type in trait
 ...
 LL |     fn make() -> u8 { 0 }
-   |                  ^^ expected associated type, found `u8`
+   |                  ^^
+   |                  |
+   |                  expected associated type, found `u8`
+   |                  help: change the output type to match the trait: `<A<T> as Tr>::Ty`
    |
    = note: expected fn pointer `fn() -> <A<T> as Tr>::Ty`
               found fn pointer `fn() -> u8`
@@ -30,7 +33,10 @@ LL |     default type Ty = bool;
    |     ----------------------- expected this associated type
 LL | 
 LL |     fn make() -> bool { true }
-   |                  ^^^^ expected associated type, found `bool`
+   |                  ^^^^
+   |                  |
+   |                  expected associated type, found `bool`
+   |                  help: change the output type to match the trait: `<B<T> as Tr>::Ty`
    |
    = note: expected fn pointer `fn() -> <B<T> as Tr>::Ty`
               found fn pointer `fn() -> bool`
diff --git a/src/test/ui/compare-method/bad-self-type.rs b/src/test/ui/compare-method/bad-self-type.rs
new file mode 100644
index 00000000000..f42a9e49abd
--- /dev/null
+++ b/src/test/ui/compare-method/bad-self-type.rs
@@ -0,0 +1,26 @@
+use std::future::Future;
+use std::task::{Context, Poll};
+
+fn main() {}
+
+struct MyFuture {}
+
+impl Future for MyFuture {
+    type Output = ();
+    fn poll(self, _: &mut Context<'_>) -> Poll<()> {
+    //~^ ERROR method `poll` has an incompatible type for trait
+        todo!()
+    }
+}
+
+trait T {
+    fn foo(self);
+    fn bar(self) -> Option<()>;
+}
+
+impl T for MyFuture {
+    fn foo(self: Box<Self>) {}
+    //~^ ERROR method `foo` has an incompatible type for trait
+    fn bar(self) {}
+    //~^ ERROR method `bar` has an incompatible type for trait
+}
diff --git a/src/test/ui/compare-method/bad-self-type.stderr b/src/test/ui/compare-method/bad-self-type.stderr
new file mode 100644
index 00000000000..76f91fbf241
--- /dev/null
+++ b/src/test/ui/compare-method/bad-self-type.stderr
@@ -0,0 +1,46 @@
+error[E0053]: method `poll` has an incompatible type for trait
+  --> $DIR/bad-self-type.rs:10:13
+   |
+LL |     fn poll(self, _: &mut Context<'_>) -> Poll<()> {
+   |             ^^^^
+   |             |
+   |             expected struct `Pin`, found struct `MyFuture`
+   |             help: change the self-receiver type to match the trait: `self: Pin<&mut MyFuture>`
+   |
+   = note: expected fn pointer `fn(Pin<&mut MyFuture>, &mut Context<'_>) -> Poll<_>`
+              found fn pointer `fn(MyFuture, &mut Context<'_>) -> Poll<_>`
+
+error[E0053]: method `foo` has an incompatible type for trait
+  --> $DIR/bad-self-type.rs:22:18
+   |
+LL |     fn foo(self);
+   |            ---- type in trait
+...
+LL |     fn foo(self: Box<Self>) {}
+   |            ------^^^^^^^^^
+   |            |     |
+   |            |     expected struct `MyFuture`, found struct `Box`
+   |            help: change the self-receiver type to match the trait: `self`
+   |
+   = note: expected fn pointer `fn(MyFuture)`
+              found fn pointer `fn(Box<MyFuture>)`
+
+error[E0053]: method `bar` has an incompatible type for trait
+  --> $DIR/bad-self-type.rs:24:18
+   |
+LL |     fn bar(self) -> Option<()>;
+   |                     ---------- type in trait
+...
+LL |     fn bar(self) {}
+   |                  ^ expected enum `Option`, found `()`
+   |
+   = note: expected fn pointer `fn(MyFuture) -> Option<()>`
+              found fn pointer `fn(MyFuture)`
+help: change the output type to match the trait
+   |
+LL |     fn bar(self) -> Option<()> {}
+   |                  ^^^^^^^^^^^^^
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0053`.
diff --git a/src/test/ui/compare-method/reordered-type-param.stderr b/src/test/ui/compare-method/reordered-type-param.stderr
index f1f8a663f21..d581628ea48 100644
--- a/src/test/ui/compare-method/reordered-type-param.stderr
+++ b/src/test/ui/compare-method/reordered-type-param.stderr
@@ -5,8 +5,10 @@ LL |   fn b<C:Clone,D>(&self, x: C) -> C;
    |                             - type in trait
 ...
 LL |   fn b<F:Clone,G>(&self, _x: G) -> G { panic!() }
-   |        -       -             ^ expected type parameter `F`, found type parameter `G`
-   |        |       |
+   |        -       -             ^
+   |        |       |             |
+   |        |       |             expected type parameter `F`, found type parameter `G`
+   |        |       |             help: change the parameter type to match the trait: `F`
    |        |       found type parameter
    |        expected type parameter
    |
diff --git a/src/test/ui/impl-trait/impl-generic-mismatch-ab.stderr b/src/test/ui/impl-trait/impl-generic-mismatch-ab.stderr
index 638a0093fb2..d37670db085 100644
--- a/src/test/ui/impl-trait/impl-generic-mismatch-ab.stderr
+++ b/src/test/ui/impl-trait/impl-generic-mismatch-ab.stderr
@@ -5,8 +5,10 @@ LL |     fn foo<A: Debug>(&self, a: &A, b: &impl Debug);
    |                                -- type in trait
 ...
 LL |     fn foo<B: Debug>(&self, a: &impl Debug, b: &B) { }
-   |            -                   ^^^^^^^^^^^ expected type parameter `B`, found type parameter `impl Debug`
-   |            |
+   |            -                   ^^^^^^^^^^^
+   |            |                   |
+   |            |                   expected type parameter `B`, found type parameter `impl Debug`
+   |            |                   help: change the parameter type to match the trait: `&B`
    |            expected type parameter
    |
    = note: expected fn pointer `fn(&(), &B, &impl Debug)`
diff --git a/src/test/ui/impl-trait/trait_type.stderr b/src/test/ui/impl-trait/trait_type.stderr
index 961bb735118..bea24339837 100644
--- a/src/test/ui/impl-trait/trait_type.stderr
+++ b/src/test/ui/impl-trait/trait_type.stderr
@@ -1,8 +1,11 @@
 error[E0053]: method `fmt` has an incompatible type for trait
-  --> $DIR/trait_type.rs:7:4
+  --> $DIR/trait_type.rs:7:21
    |
 LL |    fn fmt(&self, x: &str) -> () { }
-   |    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ types differ in mutability
+   |                     ^^^^
+   |                     |
+   |                     types differ in mutability
+   |                     help: change the parameter type to match the trait: `&mut Formatter<'_>`
    |
    = note: expected fn pointer `fn(&MyType, &mut Formatter<'_>) -> Result<(), std::fmt::Error>`
               found fn pointer `fn(&MyType, &str)`
diff --git a/src/test/ui/issues/issue-13033.stderr b/src/test/ui/issues/issue-13033.stderr
index 57447fa48aa..6c3651ff121 100644
--- a/src/test/ui/issues/issue-13033.stderr
+++ b/src/test/ui/issues/issue-13033.stderr
@@ -8,7 +8,7 @@ LL |     fn bar(&mut self, other: &dyn Foo) {}
    |                              ^^^^^^^^
    |                              |
    |                              types differ in mutability
-   |                              help: consider changing the mutability to match the trait: `&mut dyn Foo`
+   |                              help: change the parameter type to match the trait: `&mut dyn Foo`
    |
    = note: expected fn pointer `fn(&mut Baz, &mut dyn Foo)`
               found fn pointer `fn(&mut Baz, &dyn Foo)`
diff --git a/src/test/ui/issues/issue-20225.stderr b/src/test/ui/issues/issue-20225.stderr
index 3bcc50ded84..6f4813ca623 100644
--- a/src/test/ui/issues/issue-20225.stderr
+++ b/src/test/ui/issues/issue-20225.stderr
@@ -1,33 +1,42 @@
 error[E0053]: method `call` has an incompatible type for trait
-  --> $DIR/issue-20225.rs:6:3
+  --> $DIR/issue-20225.rs:6:43
    |
 LL | impl<'a, T> Fn<(&'a T,)> for Foo {
    |          - this type parameter
 LL |   extern "rust-call" fn call(&self, (_,): (T,)) {}
-   |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `&T`, found type parameter `T`
+   |                                           ^^^^
+   |                                           |
+   |                                           expected `&T`, found type parameter `T`
+   |                                           help: change the parameter type to match the trait: `(&'a T,)`
    |
    = note: expected fn pointer `extern "rust-call" fn(&Foo, (&'a T,))`
               found fn pointer `extern "rust-call" fn(&Foo, (T,))`
 
 error[E0053]: method `call_mut` has an incompatible type for trait
-  --> $DIR/issue-20225.rs:11:3
+  --> $DIR/issue-20225.rs:11:51
    |
 LL | impl<'a, T> FnMut<(&'a T,)> for Foo {
    |          - this type parameter
 LL |   extern "rust-call" fn call_mut(&mut self, (_,): (T,)) {}
-   |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `&T`, found type parameter `T`
+   |                                                   ^^^^
+   |                                                   |
+   |                                                   expected `&T`, found type parameter `T`
+   |                                                   help: change the parameter type to match the trait: `(&'a T,)`
    |
    = note: expected fn pointer `extern "rust-call" fn(&mut Foo, (&'a T,))`
               found fn pointer `extern "rust-call" fn(&mut Foo, (T,))`
 
 error[E0053]: method `call_once` has an incompatible type for trait
-  --> $DIR/issue-20225.rs:18:3
+  --> $DIR/issue-20225.rs:18:47
    |
 LL | impl<'a, T> FnOnce<(&'a T,)> for Foo {
    |          - this type parameter
 ...
 LL |   extern "rust-call" fn call_once(self, (_,): (T,)) {}
-   |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `&T`, found type parameter `T`
+   |                                               ^^^^
+   |                                               |
+   |                                               expected `&T`, found type parameter `T`
+   |                                               help: change the parameter type to match the trait: `(&'a T,)`
    |
    = note: expected fn pointer `extern "rust-call" fn(Foo, (&'a T,))`
               found fn pointer `extern "rust-call" fn(Foo, (T,))`
diff --git a/src/test/ui/issues/issue-21332.stderr b/src/test/ui/issues/issue-21332.stderr
index 35863fbebe3..d92966da17c 100644
--- a/src/test/ui/issues/issue-21332.stderr
+++ b/src/test/ui/issues/issue-21332.stderr
@@ -1,8 +1,11 @@
 error[E0053]: method `next` has an incompatible type for trait
-  --> $DIR/issue-21332.rs:5:5
+  --> $DIR/issue-21332.rs:5:27
    |
 LL |     fn next(&mut self) -> Result<i32, i32> { Ok(7) }
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected enum `Option`, found enum `Result`
+   |                           ^^^^^^^^^^^^^^^^
+   |                           |
+   |                           expected enum `Option`, found enum `Result`
+   |                           help: change the output type to match the trait: `Option<i32>`
    |
    = note: expected fn pointer `fn(&mut S) -> Option<i32>`
               found fn pointer `fn(&mut S) -> Result<i32, i32>`
diff --git a/src/test/ui/issues/issue-35869.stderr b/src/test/ui/issues/issue-35869.stderr
index f80561bf6be..71b2a9df095 100644
--- a/src/test/ui/issues/issue-35869.stderr
+++ b/src/test/ui/issues/issue-35869.stderr
@@ -5,7 +5,10 @@ LL |     fn foo(_: fn(u8) -> ());
    |               ------------ type in trait
 ...
 LL |     fn foo(_: fn(u16) -> ()) {}
-   |               ^^^^^^^^^^^^^ expected `u8`, found `u16`
+   |               ^^^^^^^^^^^^^
+   |               |
+   |               expected `u8`, found `u16`
+   |               help: change the parameter type to match the trait: `fn(u8)`
    |
    = note: expected fn pointer `fn(fn(u8))`
               found fn pointer `fn(fn(u16))`
@@ -17,7 +20,10 @@ LL |     fn bar(_: Option<u8>);
    |               ---------- type in trait
 ...
 LL |     fn bar(_: Option<u16>) {}
-   |               ^^^^^^^^^^^ expected `u8`, found `u16`
+   |               ^^^^^^^^^^^
+   |               |
+   |               expected `u8`, found `u16`
+   |               help: change the parameter type to match the trait: `Option<u8>`
    |
    = note: expected fn pointer `fn(Option<u8>)`
               found fn pointer `fn(Option<u16>)`
@@ -29,7 +35,10 @@ LL |     fn baz(_: (u8, u16));
    |               --------- type in trait
 ...
 LL |     fn baz(_: (u16, u16)) {}
-   |               ^^^^^^^^^^ expected `u8`, found `u16`
+   |               ^^^^^^^^^^
+   |               |
+   |               expected `u8`, found `u16`
+   |               help: change the parameter type to match the trait: `(u8, u16)`
    |
    = note: expected fn pointer `fn((u8, _))`
               found fn pointer `fn((u16, _))`
@@ -41,7 +50,10 @@ LL |     fn qux() -> u8;
    |                 -- type in trait
 ...
 LL |     fn qux() -> u16 { 5u16 }
-   |                 ^^^ expected `u8`, found `u16`
+   |                 ^^^
+   |                 |
+   |                 expected `u8`, found `u16`
+   |                 help: change the output type to match the trait: `u8`
    |
    = note: expected fn pointer `fn() -> u8`
               found fn pointer `fn() -> u16`
diff --git a/src/test/ui/mismatched_types/E0053.stderr b/src/test/ui/mismatched_types/E0053.stderr
index e0a3ce922b9..6ce8126b9f9 100644
--- a/src/test/ui/mismatched_types/E0053.stderr
+++ b/src/test/ui/mismatched_types/E0053.stderr
@@ -5,7 +5,10 @@ LL |     fn foo(x: u16);
    |               --- type in trait
 ...
 LL |     fn foo(x: i16) { }
-   |               ^^^ expected `u16`, found `i16`
+   |               ^^^
+   |               |
+   |               expected `u16`, found `i16`
+   |               help: change the parameter type to match the trait: `u16`
    |
    = note: expected fn pointer `fn(u16)`
               found fn pointer `fn(i16)`
@@ -20,7 +23,7 @@ LL |     fn bar(&mut self) { }
    |            ^^^^^^^^^
    |            |
    |            types differ in mutability
-   |            help: consider changing the mutability to match the trait: `&self`
+   |            help: change the self-receiver type to match the trait: `self: &Bar`
    |
    = note: expected fn pointer `fn(&Bar)`
               found fn pointer `fn(&mut Bar)`
diff --git a/src/test/ui/mismatched_types/trait-impl-fn-incompatibility.stderr b/src/test/ui/mismatched_types/trait-impl-fn-incompatibility.stderr
index 161843473b6..2ac4d1c33a9 100644
--- a/src/test/ui/mismatched_types/trait-impl-fn-incompatibility.stderr
+++ b/src/test/ui/mismatched_types/trait-impl-fn-incompatibility.stderr
@@ -5,7 +5,10 @@ LL |     fn foo(x: u16);
    |               --- type in trait
 ...
 LL |     fn foo(x: i16) { }
-   |               ^^^ expected `u16`, found `i16`
+   |               ^^^
+   |               |
+   |               expected `u16`, found `i16`
+   |               help: change the parameter type to match the trait: `u16`
    |
    = note: expected fn pointer `fn(u16)`
               found fn pointer `fn(i16)`
@@ -20,7 +23,7 @@ LL |     fn bar(&mut self, bar: &Bar) { }
    |                            ^^^^
    |                            |
    |                            types differ in mutability
-   |                            help: consider changing the mutability to match the trait: `&mut Bar`
+   |                            help: change the parameter type to match the trait: `&mut Bar`
    |
    = note: expected fn pointer `fn(&mut Bar, &mut Bar)`
               found fn pointer `fn(&mut Bar, &Bar)`
diff --git a/src/test/ui/resolve/issue-81508.rs b/src/test/ui/resolve/issue-81508.rs
new file mode 100644
index 00000000000..23605cd2fd9
--- /dev/null
+++ b/src/test/ui/resolve/issue-81508.rs
@@ -0,0 +1,22 @@
+// Confusing diagnostic when using variable as a type:
+//
+// Previous warnings indicate Foo is not used, when in fact it is
+// used improperly as a variable or constant. New warning points
+// out user may be trying to use variable as a type. Test demonstrates
+// cases for both local variable and const.
+
+fn main() {
+    let Baz: &str = "";
+
+    println!("{}", Baz::Bar); //~ ERROR: failed to resolve: use of undeclared type `Baz`
+}
+
+#[allow(non_upper_case_globals)]
+pub const Foo: &str = "";
+
+mod submod {
+    use super::Foo;
+    fn function() {
+        println!("{}", Foo::Bar); //~ ERROR: failed to resolve: use of undeclared type `Foo`
+    }
+}
diff --git a/src/test/ui/resolve/issue-81508.stderr b/src/test/ui/resolve/issue-81508.stderr
new file mode 100644
index 00000000000..15555631b90
--- /dev/null
+++ b/src/test/ui/resolve/issue-81508.stderr
@@ -0,0 +1,21 @@
+error[E0433]: failed to resolve: use of undeclared type `Baz`
+  --> $DIR/issue-81508.rs:11:20
+   |
+LL |     let Baz: &str = "";
+   |         --- help: `Baz` is defined here, but is not a type
+LL | 
+LL |     println!("{}", Baz::Bar);
+   |                    ^^^ use of undeclared type `Baz`
+
+error[E0433]: failed to resolve: use of undeclared type `Foo`
+  --> $DIR/issue-81508.rs:20:24
+   |
+LL |     use super::Foo;
+   |         ---------- help: `Foo` is defined here, but is not a type
+LL |     fn function() {
+LL |         println!("{}", Foo::Bar);
+   |                        ^^^ use of undeclared type `Foo`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0433`.
diff --git a/src/test/ui/wrong-mul-method-signature.stderr b/src/test/ui/wrong-mul-method-signature.stderr
index 4c367fb9e9c..9f8896f01ee 100644
--- a/src/test/ui/wrong-mul-method-signature.stderr
+++ b/src/test/ui/wrong-mul-method-signature.stderr
@@ -1,26 +1,35 @@
 error[E0053]: method `mul` has an incompatible type for trait
-  --> $DIR/wrong-mul-method-signature.rs:16:5
+  --> $DIR/wrong-mul-method-signature.rs:16:21
    |
 LL |     fn mul(self, s: &f64) -> Vec1 {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `f64`, found `&f64`
+   |                     ^^^^
+   |                     |
+   |                     expected `f64`, found `&f64`
+   |                     help: change the parameter type to match the trait: `f64`
    |
    = note: expected fn pointer `fn(Vec1, f64) -> Vec1`
               found fn pointer `fn(Vec1, &f64) -> Vec1`
 
 error[E0053]: method `mul` has an incompatible type for trait
-  --> $DIR/wrong-mul-method-signature.rs:33:5
+  --> $DIR/wrong-mul-method-signature.rs:33:21
    |
 LL |     fn mul(self, s: f64) -> Vec2 {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `Vec2`, found `f64`
+   |                     ^^^
+   |                     |
+   |                     expected struct `Vec2`, found `f64`
+   |                     help: change the parameter type to match the trait: `Vec2`
    |
    = note: expected fn pointer `fn(Vec2, Vec2) -> f64`
               found fn pointer `fn(Vec2, f64) -> Vec2`
 
 error[E0053]: method `mul` has an incompatible type for trait
-  --> $DIR/wrong-mul-method-signature.rs:52:5
+  --> $DIR/wrong-mul-method-signature.rs:52:29
    |
 LL |     fn mul(self, s: f64) -> f64 {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `f64`
+   |                             ^^^
+   |                             |
+   |                             expected `i32`, found `f64`
+   |                             help: change the output type to match the trait: `i32`
    |
    = note: expected fn pointer `fn(Vec3, _) -> i32`
               found fn pointer `fn(Vec3, _) -> f64`