Auto merge of rust-lang#80138 - Dylan-DPC:rollup-qamsfyh, r=Dylan-DPC

Rollup of 5 pull requests

Successful merges:

 - rust-lang#78164 (Prefer regions with an `external_name` in `approx_universal_upper_bound`)
 - rust-lang#80003 (Fix overflow when converting ZST Vec to VecDeque)
 - rust-lang#80023 (Enhance error message when misspelled label to value in break expression)
 - rust-lang#80046 (Add more documentation to `Diagnostic` and `DiagnosticBuilder`)
 - rust-lang#80109 (Remove redundant and unreliable coverage test results)

Failed merges:

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

compiler/rustc_errors/src/diagnostic.rs

@@ -30,7 +30,8 @@ pub enum DiagnosticId {
     Lint { name: String, has_future_breakage: bool },
 }
 
-/// For example a note attached to an error.
+/// A "sub"-diagnostic attached to a parent diagnostic.
+/// For example, a note attached to an error.
 #[derive(Clone, Debug, PartialEq, Hash, Encodable, Decodable)]
 pub struct SubDiagnostic {
     pub level: Level,
@@ -124,6 +125,7 @@ impl Diagnostic {
         self.level = Level::Cancelled;
     }
 
+    /// Check if this diagnostic [was cancelled][Self::cancel()].
     pub fn cancelled(&self) -> bool {
         self.level == Level::Cancelled
     }
@@ -164,7 +166,7 @@ impl Diagnostic {
         self.note_expected_found_extra(expected_label, expected, found_label, found, &"", &"")
     }
 
-    pub fn note_unsuccessfull_coercion(
+    pub fn note_unsuccessful_coercion(
         &mut self,
         expected: DiagnosticStyledString,
         found: DiagnosticStyledString,
@@ -241,6 +243,7 @@ impl Diagnostic {
         self
     }
 
+    /// Add a note attached to this diagnostic.
     pub fn note(&mut self, msg: &str) -> &mut Self {
         self.sub(Level::Note, msg, MultiSpan::new(), None);
         self
@@ -252,33 +255,40 @@ impl Diagnostic {
     }
 
     /// Prints the span with a note above it.
+    /// This is like [`Diagnostic::note()`], but it gets its own span.
     pub fn span_note<S: Into<MultiSpan>>(&mut self, sp: S, msg: &str) -> &mut Self {
         self.sub(Level::Note, msg, sp.into(), None);
         self
     }
 
+    /// Add a warning attached to this diagnostic.
     pub fn warn(&mut self, msg: &str) -> &mut Self {
         self.sub(Level::Warning, msg, MultiSpan::new(), None);
         self
     }
 
-    /// Prints the span with a warn above it.
+    /// Prints the span with a warning above it.
+    /// This is like [`Diagnostic::warn()`], but it gets its own span.
     pub fn span_warn<S: Into<MultiSpan>>(&mut self, sp: S, msg: &str) -> &mut Self {
         self.sub(Level::Warning, msg, sp.into(), None);
         self
     }
 
+    /// Add a help message attached to this diagnostic.
     pub fn help(&mut self, msg: &str) -> &mut Self {
         self.sub(Level::Help, msg, MultiSpan::new(), None);
         self
     }
 
     /// Prints the span with some help above it.
+    /// This is like [`Diagnostic::help()`], but it gets its own span.
     pub fn span_help<S: Into<MultiSpan>>(&mut self, sp: S, msg: &str) -> &mut Self {
         self.sub(Level::Help, msg, sp.into(), None);
         self
     }
 
+    /// Show a suggestion that has multiple parts to it.
+    /// In other words, multiple changes need to be applied as part of this suggestion.
     pub fn multipart_suggestion(
         &mut self,
         msg: &str,
@@ -299,6 +309,8 @@ impl Diagnostic {
         self
     }
 
+    /// Show multiple suggestions that have multiple parts.
+    /// See also [`Diagnostic::multipart_suggestion()`].
     pub fn multipart_suggestions(
         &mut self,
         msg: &str,
@@ -382,6 +394,7 @@ impl Diagnostic {
         self
     }
 
+    /// [`Diagnostic::span_suggestion()`] but you can set the [`SuggestionStyle`].
     pub fn span_suggestion_with_style(
         &mut self,
         sp: Span,
@@ -401,6 +414,7 @@ impl Diagnostic {
         self
     }
 
+    /// Always show the suggested change.
     pub fn span_suggestion_verbose(
         &mut self,
         sp: Span,
@@ -419,6 +433,7 @@ impl Diagnostic {
     }
 
     /// Prints out a message with multiple suggested edits of the code.
+    /// See also [`Diagnostic::span_suggestion()`].
     pub fn span_suggestions(
         &mut self,
         sp: Span,
@@ -458,7 +473,7 @@ impl Diagnostic {
         self
     }
 
-    /// Prints out a message with for a suggestion without showing the suggested code.
+    /// Prints out a message for a suggestion without showing the suggested code.
     ///
     /// This is intended to be used for suggestions that are obvious in what the changes need to
     /// be from the message, showing the span label inline would be visually unpleasant
@@ -481,7 +496,7 @@ impl Diagnostic {
         self
     }
 
-    /// Adds a suggestion to the json output, but otherwise remains silent/undisplayed in the cli.
+    /// Adds a suggestion to the JSON output that will not be shown in the CLI.
     ///
     /// This is intended to be used for suggestions that are *very* obvious in what the changes
     /// need to be from the message, but we still want other tools to be able to apply them.

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -30,6 +30,15 @@ struct DiagnosticBuilderInner<'a> {
     allow_suggestions: bool,
 }
 
+/// This is a helper macro for [`forward!`] that allows automatically adding documentation
+/// that uses tokens from [`forward!`]'s input.
+macro_rules! forward_inner_docs {
+    ($e:expr => $i:item) => {
+        #[doc = $e]
+        $i
+    }
+}
+
 /// In general, the `DiagnosticBuilder` uses deref to allow access to
 /// the fields and methods of the embedded `diagnostic` in a
 /// transparent way. *However,* many of the methods are intended to
@@ -45,10 +54,11 @@ macro_rules! forward {
         pub fn $n:ident(&self, $($name:ident: $ty:ty),* $(,)?) -> &Self
     ) => {
         $(#[$attrs])*
+        forward_inner_docs!(concat!("See [`Diagnostic::", stringify!($n), "()`].") =>
         pub fn $n(&self, $($name: $ty),*) -> &Self {
             self.diagnostic.$n($($name),*);
             self
-        }
+        });
     };
 
     // Forward pattern for &mut self -> &mut Self
@@ -57,10 +67,11 @@ macro_rules! forward {
         pub fn $n:ident(&mut self, $($name:ident: $ty:ty),* $(,)?) -> &mut Self
     ) => {
         $(#[$attrs])*
+        forward_inner_docs!(concat!("See [`Diagnostic::", stringify!($n), "()`].") =>
         pub fn $n(&mut self, $($name: $ty),*) -> &mut Self {
             self.0.diagnostic.$n($($name),*);
             self
-        }
+        });
     };
 
     // Forward pattern for &mut self -> &mut Self, with S: Into<MultiSpan>
@@ -74,10 +85,11 @@ macro_rules! forward {
         ) -> &mut Self
     ) => {
         $(#[$attrs])*
+        forward_inner_docs!(concat!("See [`Diagnostic::", stringify!($n), "()`].") =>
         pub fn $n<S: Into<MultiSpan>>(&mut self, $($name: $ty),*) -> &mut Self {
             self.0.diagnostic.$n($($name),*);
             self
-        }
+        });
     };
 }
 
@@ -116,7 +128,7 @@ impl<'a> DiagnosticBuilder<'a> {
 
     /// Stashes diagnostic for possible later improvement in a different,
     /// later stage of the compiler. The diagnostic can be accessed with
-    /// the provided `span` and `key` through `.steal_diagnostic` on `Handler`.
+    /// the provided `span` and `key` through [`Handler::steal_diagnostic()`].
     ///
     /// As with `buffer`, this is unless the handler has disabled such buffering.
     pub fn stash(self, span: Span, key: StashKey) {
@@ -202,7 +214,7 @@ impl<'a> DiagnosticBuilder<'a> {
     }
 
     /// Labels all the given spans with the provided label.
-    /// See `span_label` for more information.
+    /// See [`Diagnostic::span_label()`] for more information.
     pub fn span_labels(
         &mut self,
         spans: impl IntoIterator<Item = Span>,
@@ -233,7 +245,7 @@ impl<'a> DiagnosticBuilder<'a> {
         found_extra: &dyn fmt::Display,
     ) -> &mut Self);
 
-    forward!(pub fn note_unsuccessfull_coercion(
+    forward!(pub fn note_unsuccessful_coercion(
         &mut self,
         expected: DiagnosticStyledString,
         found: DiagnosticStyledString,
@@ -254,6 +266,7 @@ impl<'a> DiagnosticBuilder<'a> {
         msg: &str,
     ) -> &mut Self);
 
+    /// See [`Diagnostic::multipart_suggestion()`].
     pub fn multipart_suggestion(
         &mut self,
         msg: &str,
@@ -267,6 +280,7 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    /// See [`Diagnostic::multipart_suggestions()`].
     pub fn multipart_suggestions(
         &mut self,
         msg: &str,
@@ -280,6 +294,7 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    /// See [`Diagnostic::tool_only_multipart_suggestion()`].
     pub fn tool_only_multipart_suggestion(
         &mut self,
         msg: &str,
@@ -293,6 +308,7 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    /// See [`Diagnostic::span_suggestion()`].
     pub fn span_suggestion(
         &mut self,
         sp: Span,
@@ -307,6 +323,7 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    /// See [`Diagnostic::span_suggestions()`].
     pub fn span_suggestions(
         &mut self,
         sp: Span,
@@ -321,6 +338,7 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    /// See [`Diagnostic::span_suggestion_short()`].
     pub fn span_suggestion_short(
         &mut self,
         sp: Span,
@@ -335,6 +353,7 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    /// See [`Diagnostic::span_suggestion_verbose()`].
     pub fn span_suggestion_verbose(
         &mut self,
         sp: Span,
@@ -349,6 +368,7 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    /// See [`Diagnostic::span_suggestion_hidden()`].
     pub fn span_suggestion_hidden(
         &mut self,
         sp: Span,
@@ -363,6 +383,7 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    /// See [`Diagnostic::tool_only_span_suggestion()`] for more information.
     pub fn tool_only_span_suggestion(
         &mut self,
         sp: Span,
@@ -380,19 +401,22 @@ impl<'a> DiagnosticBuilder<'a> {
     forward!(pub fn set_span<S: Into<MultiSpan>>(&mut self, sp: S) -> &mut Self);
     forward!(pub fn code(&mut self, s: DiagnosticId) -> &mut Self);
 
+    /// Allow attaching suggestions this diagnostic.
+    /// If this is set to `false`, then any suggestions attached with the `span_suggestion_*`
+    /// methods after this is set to `false` will be ignored.
     pub fn allow_suggestions(&mut self, allow: bool) -> &mut Self {
         self.0.allow_suggestions = allow;
         self
     }
 
     /// Convenience function for internal use, clients should use one of the
-    /// struct_* methods on Handler.
+    /// `struct_*` methods on [`Handler`].
     crate fn new(handler: &'a Handler, level: Level, message: &str) -> DiagnosticBuilder<'a> {
         DiagnosticBuilder::new_with_code(handler, level, None, message)
     }
 
     /// Convenience function for internal use, clients should use one of the
-    /// struct_* methods on Handler.
+    /// `struct_*` methods on [`Handler`].
     crate fn new_with_code(
         handler: &'a Handler,
         level: Level,

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -1622,7 +1622,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                     }
                 }
                 (TypeError::ObjectUnsafeCoercion(_), _) => {
-                    diag.note_unsuccessfull_coercion(found, expected);
+                    diag.note_unsuccessful_coercion(found, expected);
                 }
                 (_, _) => {
                     debug!(

compiler/rustc_mir/src/borrow_check/region_infer/mod.rs

@@ -1145,8 +1145,24 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         for ur in self.scc_values.universal_regions_outlived_by(r_scc) {
             let new_lub = self.universal_region_relations.postdom_upper_bound(lub, ur);
             debug!("approx_universal_upper_bound: ur={:?} lub={:?} new_lub={:?}", ur, lub, new_lub);
+            // The upper bound of two non-static regions is static: this
+            // means we know nothing about the relationship between these
+            // two regions. Pick a 'better' one to use when constructing
+            // a diagnostic
             if ur != static_r && lub != static_r && new_lub == static_r {
-                lub = std::cmp::min(ur, lub);
+                // Prefer the region with an `external_name` - this
+                // indicates that the region is early-bound, so working with
+                // it can produce a nicer error.
+                if self.region_definition(ur).external_name.is_some() {
+                    lub = ur;
+                } else if self.region_definition(lub).external_name.is_some() {
+                    // Leave lub unchanged
+                } else {
+                    // If we get here, we don't have any reason to prefer
+                    // one region over the other. Just pick the
+                    // one with the lower index for now.
+                    lub = std::cmp::min(ur, lub);
+                }
             } else {
                 lub = new_lub;
             }

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -542,6 +542,26 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
                 err.span_label(base_span, fallback_label);
             }
         }
+        if let Some(err_code) = &err.code {
+            if err_code == &rustc_errors::error_code!(E0425) {
+                for label_rib in &self.label_ribs {
+                    for (label_ident, _) in &label_rib.bindings {
+                        if format!("'{}", ident) == label_ident.to_string() {
+                            let msg = "a label with a similar name exists";
+                            // FIXME: consider only emitting this suggestion if a label would be valid here
+                            // which is pretty much only the case for `break` expressions.
+                            err.span_suggestion(
+                                span,
+                                &msg,
+                                label_ident.name.to_string(),
+                                Applicability::MaybeIncorrect,
+                            );
+                        }
+                    }
+                }
+            }
+        }
+
         (err, candidates)
     }
 

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

@@ -2793,8 +2793,12 @@ impl<T> From<Vec<T>> for VecDeque<T> {
             let len = other.len();
 
             // We need to extend the buf if it's not a power of two, too small
-            // or doesn't have at least one free space
-            if !buf.capacity().is_power_of_two()
+            // or doesn't have at least one free space.
+            // We check if `T` is a ZST in the first condition,
+            // because `usize::MAX` (the capacity returned by `capacity()` for ZST)
+            // is not a power of two and thus it'll always try
+            // to reserve more memory which will panic for ZST (rust-lang/rust#78532)
+            if (!buf.capacity().is_power_of_two() && mem::size_of::<T>() != 0)
                 || (buf.capacity() < (MINIMUM_CAPACITY + 1))
                 || (buf.capacity() == len)
             {

library/alloc/tests/vec_deque.rs

@@ -1728,3 +1728,10 @@ fn test_zero_sized_push() {
         }
     }
 }
+
+#[test]
+fn test_from_zero_sized_vec() {
+    let v = vec![(); 100];
+    let queue = VecDeque::from(v);
+    assert_eq!(queue.len(), 100);
+}