Remove one remaining use of Level::Help

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -74,20 +74,6 @@ pub(super) struct DescribePlaceOpt {
 
 pub(super) struct IncludingTupleField(pub(super) bool);
 
-pub(crate) enum BufferedDiag<'diag> {
-    Error(Diag<'diag>),
-    NonError(Diag<'diag, ()>),
-}
-
-impl<'diag> BufferedDiag<'diag> {
-    fn sort_span(&self) -> Span {
-        match self {
-            BufferedDiag::Error(diag) => diag.sort_span,
-            BufferedDiag::NonError(diag) => diag.sort_span,
-        }
-    }
-}
-
 #[derive(Default)]
 pub(crate) struct BorrowckDiagnosticsBuffer<'diag, 'tcx> {
     /// This field keeps track of move errors that are to be reported for given move indices.
@@ -108,16 +94,13 @@ pub(crate) struct BorrowckDiagnosticsBuffer<'diag, 'tcx> {
 
     buffered_mut_errors: FxIndexMap<Span, (Diag<'diag>, usize)>,
 
-    /// Buffer of diagnostics to be reported. A mixture of error and non-error diagnostics.
-    buffered_diags: Vec<BufferedDiag<'diag>>,
+    /// Buffer of diagnostics to be reported.
+    buffered_diags: Vec<Diag<'diag>>,
 }
 
 impl<'diag, 'tcx> BorrowckDiagnosticsBuffer<'diag, 'tcx> {
-    pub(crate) fn buffer_non_error(&mut self, diag: Diag<'diag, ()>) {
-        self.buffered_diags.push(BufferedDiag::NonError(diag));
-    }
     pub(crate) fn buffer_error(&mut self, diag: Diag<'diag>) {
-        self.buffered_diags.push(BufferedDiag::Error(diag));
+        self.buffered_diags.push(diag);
     }
 
     pub(crate) fn emit_errors(&mut self) {
@@ -134,14 +117,9 @@ impl<'diag, 'tcx> BorrowckDiagnosticsBuffer<'diag, 'tcx> {
         }
 
         if !self.buffered_diags.is_empty() {
-            self.buffered_diags.sort_by_key(|buffered_diag| buffered_diag.sort_span());
-            for buffered_diag in self.buffered_diags.drain(..) {
-                match buffered_diag {
-                    BufferedDiag::Error(diag) => {
-                        diag.emit();
-                    }
-                    BufferedDiag::NonError(diag) => diag.emit(),
-                }
+            self.buffered_diags.sort_by_key(|diag| diag.sort_span);
+            for diag in self.buffered_diags.drain(..) {
+                diag.emit();
             }
         }
     }
@@ -152,10 +130,6 @@ impl<'diag, 'tcx> MirBorrowckCtxt<'_, 'diag, 'tcx> {
         self.diags_buffer.buffer_error(diag.with_dcx(self.dcx()));
     }
 
-    pub(crate) fn buffer_non_error(&mut self, diag: Diag<'_, ()>) {
-        self.diags_buffer.buffer_non_error(diag.with_dcx(self.dcx()));
-    }
-
     pub(crate) fn buffer_move_error(
         &mut self,
         move_out_indices: Vec<MoveOutIndex>,

compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs

@@ -14,9 +14,6 @@ use crate::MirBorrowckCtxt;
 
 /// The different things we could suggest.
 enum SuggestedConstraint {
-    /// Outlives(a, [b, c, d, ...]) => 'a: 'b + 'c + 'd + ...
-    Outlives(RegionName, SmallVec<[RegionName; 2]>),
-
     /// 'a = 'b
     Equal(RegionName, RegionName),
 
@@ -106,11 +103,10 @@ impl OutlivesSuggestionBuilder {
                 continue;
             }
 
-            // There are three types of suggestions we can make:
-            // 1) Suggest a bound: 'a: 'b
-            // 2) Suggest replacing 'a with 'static. If any of `outlived` is `'static`, then we
+            // There are two types of suggestions we can make:
+            // 1) Suggest replacing 'a with 'static. If any of `outlived` is `'static`, then we
             //    should just replace 'a with 'static.
-            // 3) Suggest unifying 'a with 'b if we have both 'a: 'b and 'b: 'a
+            // 2) Suggest unifying 'a with 'b if we have both 'a: 'b and 'b: 'a
 
             if outlived
                 .iter()
@@ -121,7 +117,7 @@ impl OutlivesSuggestionBuilder {
                 // We want to isolate out all lifetimes that should be unified and print out
                 // separate messages for them.
 
-                let (unified, other): (Vec<_>, Vec<_>) = outlived.into_iter().partition(
+                let unified = outlived.into_iter().filter(
                     // Do we have both 'fr: 'r and 'r: 'fr?
                     |(r, _)| {
                         self.constraints_to_add
@@ -130,17 +126,12 @@ impl OutlivesSuggestionBuilder {
                     },
                 );
 
-                for (r, bound) in unified.into_iter() {
+                for (r, bound) in unified {
                     if !unified_already.contains(fr) {
                         suggested.push(SuggestedConstraint::Equal(fr_name, bound));
                         unified_already.insert(r);
                     }
                 }
-
-                if !other.is_empty() {
-                    let other = other.iter().map(|(_, rname)| *rname).collect::<SmallVec<_>>();
-                    suggested.push(SuggestedConstraint::Outlives(fr_name, other))
-                }
             }
         }
 
@@ -202,54 +193,36 @@ impl OutlivesSuggestionBuilder {
             return;
         }
 
-        // If there is exactly one suggestable constraints, then just suggest it. Otherwise, emit a
-        // list of diagnostics.
-        let mut diag = if let [constraint] = suggested.as_slice() {
-            mbcx.dcx().struct_help(match constraint {
-                SuggestedConstraint::Outlives(a, bs) => {
-                    let bs: SmallVec<[String; 2]> = bs.iter().map(|r| r.to_string()).collect();
-                    format!("add bound `{a}: {}`", bs.join(" + "))
-                }
-
+        // Emit an error with a list of one or more help suggestions. This is a weird error because
+        // it's just there to provide somewhere to put the help suggestions that describe how to
+        // fix the one or more borrow errors already reported within the item.
+        let tcx = mbcx.infcx.tcx;
+        let def_id = mbcx.mir_def_id();
+        let span = tcx.def_ident_span(def_id).unwrap_or_else(|| tcx.def_span(def_id));
+        let mut diag = tcx
+            .dcx()
+            .struct_err("one or more lifetime errors were found in this item")
+            .with_span(span);
+
+        // Add suggestions.
+        for constraint in suggested {
+            match constraint {
                 SuggestedConstraint::Equal(a, b) => {
-                    format!("`{a}` and `{b}` must be the same: replace one with the other")
+                    diag.help(format!(
+                        "`{a}` and `{b}` must be the same: replace one with the other",
+                    ));
                 }
-                SuggestedConstraint::Static(a) => format!("replace `{a}` with `'static`"),
-            })
-        } else {
-            // Create a new diagnostic.
-            let mut diag = mbcx
-                .infcx
-                .tcx
-                .dcx()
-                .struct_help("the following changes may resolve your lifetime errors");
-
-            // Add suggestions.
-            for constraint in suggested {
-                match constraint {
-                    SuggestedConstraint::Outlives(a, bs) => {
-                        let bs: SmallVec<[String; 2]> = bs.iter().map(|r| r.to_string()).collect();
-                        diag.help(format!("add bound `{a}: {}`", bs.join(" + ")));
-                    }
-                    SuggestedConstraint::Equal(a, b) => {
-                        diag.help(format!(
-                            "`{a}` and `{b}` must be the same: replace one with the other",
-                        ));
-                    }
-                    SuggestedConstraint::Static(a) => {
-                        diag.help(format!("replace `{a}` with `'static`"));
-                    }
+                SuggestedConstraint::Static(a) => {
+                    diag.help(format!("replace `{a}` with `'static`"));
                 }
             }
-
-            diag
-        };
+        }
 
         // We want this message to appear after other messages on the mir def.
         let mir_span = mbcx.body.span;
         diag.sort_span = mir_span.shrink_to_hi();
 
         // Buffer the diagnostic
-        mbcx.buffer_non_error(diag);
+        mbcx.buffer_error(diag);
     }
 }

compiler/rustc_errors/src/lib.rs

@@ -1148,11 +1148,6 @@ impl<'a> DiagCtxtHandle<'a> {
         self.create_note(note).emit()
     }
 
-    #[track_caller]
-    pub fn struct_help(self, msg: impl Into<DiagMessage>) -> Diag<'a, ()> {
-        Diag::new(self, Help, msg)
-    }
-
     #[track_caller]
     pub fn struct_failure_note(self, msg: impl Into<DiagMessage>) -> Diag<'a, ()> {
         Diag::new(self, FailureNote, msg)
@@ -1572,7 +1567,7 @@ impl DelayedDiagInner {
 /// | ForceWarning | -        | ()               | yes       | lint-only
 /// | Warning      | -        | ()               | yes       | yes
 /// | Note         | -        | ()               | rare      | -
-/// | Help         | -        | ()               | rare      | -
+/// | Help         | -        | ()               | don't use | -
 /// | FailureNote  | -        | ()               | rare      | -
 /// | Allow        | -        | ()               | yes       | lint-only
 /// | Expect       | -        | ()               | yes       | lint-only
@@ -1607,14 +1602,18 @@ pub enum Level {
     /// Will be skipped if `can_emit_warnings` is false.
     Warning,
 
-    /// A message giving additional context.
+    /// A rarely-used level for output that isn't an error or a warning.
     Note,
 
     /// A message suggesting how to fix something.
+    ///
+    /// FIXME(nnethercote) Do not use this! Currently only exists to support `proc_macro::Help`,
+    /// part of the unstable `proc_macro_diagnostic` feature (see #54140). Should be removed
+    /// because help messages are fine as subdiagnostics but are silly as top-level diagnostics.
     Help,
 
-    /// Similar to `Note`, but used in cases where compilation has failed. When printed for human
-    /// consumption, it doesn't have any kind of `note:` label.
+    /// Similar to `Note`, but even rarer. Lacks the a trailing blank line that all other
+    /// diagnostics have. Also, when printed for human consumption it doesn't have a `note:` label.
     FailureNote,
 
     /// Only used for lints.
@@ -1666,13 +1665,13 @@ pub enum Sublevel {
     /// See `Level::Warning`.
     Warning,
 
-    /// See `Level::Note`.
+    /// A message giving additional context.
     Note,
 
     /// A note that is only emitted once.
     OnceNote,
 
-    /// See `Level::Help`.
+    /// A message suggesting how to fix something.
     Help,
 
     /// A help that is only emitted once.

tests/ui/associated-types/associated-types-project-from-hrtb-in-fn-body.rs

@@ -13,7 +13,7 @@ fn foo<'a, I : for<'x> Foo<&'x isize>>(
     let y: I::A = x;
 }
 
-fn bar<'a, 'b, I : for<'x> Foo<&'x isize>>(
+fn bar<'a, 'b, I : for<'x> Foo<&'x isize>>( //~ ERROR one or more lifetime errors
     x: <I as Foo<&'a isize>>::A,
     y: <I as Foo<&'b isize>>::A,
     cond: bool)

tests/ui/associated-types/associated-types-project-from-hrtb-in-fn-body.stderr

@@ -24,7 +24,13 @@ LL |     let z: I::A = if cond { x } else { y };
    |
    = help: consider adding the following bound: `'a: 'b`
 
-help: `'a` and `'b` must be the same: replace one with the other
+error: one or more lifetime errors were found in this item
+  --> $DIR/associated-types-project-from-hrtb-in-fn-body.rs:16:4
+   |
+LL | fn bar<'a, 'b, I : for<'x> Foo<&'x isize>>(
+   |    ^^^
+   |
+   = help: `'a` and `'b` must be the same: replace one with the other
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 

tests/ui/associated-types/cache/project-fn-ret-contravariant.krisskross.stderr

@@ -1,5 +1,5 @@
 error: lifetime may not live long enough
-  --> $DIR/project-fn-ret-contravariant.rs:46:4
+  --> $DIR/project-fn-ret-contravariant.rs:47:4
    |
 LL | fn transmute<'a,'b>(x: &'a u32, y: &'b u32) -> (&'a u32, &'b u32) {
    |              -- -- lifetime `'b` defined here
@@ -12,7 +12,7 @@ LL |    (a, b)
    = help: consider adding the following bound: `'a: 'b`
 
 error: lifetime may not live long enough
-  --> $DIR/project-fn-ret-contravariant.rs:46:4
+  --> $DIR/project-fn-ret-contravariant.rs:47:4
    |
 LL | fn transmute<'a,'b>(x: &'a u32, y: &'b u32) -> (&'a u32, &'b u32) {
    |              -- -- lifetime `'b` defined here
@@ -24,7 +24,13 @@ LL |    (a, b)
    |
    = help: consider adding the following bound: `'b: 'a`
 
-help: `'a` and `'b` must be the same: replace one with the other
+error: one or more lifetime errors were found in this item
+  --> $DIR/project-fn-ret-contravariant.rs:43:4
+   |
+LL | fn transmute<'a,'b>(x: &'a u32, y: &'b u32) -> (&'a u32, &'b u32) {
+   |    ^^^^^^^^^
+   |
+   = help: `'a` and `'b` must be the same: replace one with the other
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 

tests/ui/associated-types/cache/project-fn-ret-contravariant.rs

@@ -41,6 +41,7 @@ fn baz<'a,'b>(x: &'a u32) -> &'static u32 {
 
 #[cfg(krisskross)] // two instantiations, mixing and matching: BAD
 fn transmute<'a,'b>(x: &'a u32, y: &'b u32) -> (&'a u32, &'b u32) {
+   //[krisskross]~^ ERROR one or more lifetime errors
    let a = bar(foo, y);
    let b = bar(foo, x);
    (a, b) //[krisskross]~ ERROR lifetime may not live long enough

tests/ui/associated-types/cache/project-fn-ret-invariant.krisskross.stderr

@@ -1,5 +1,5 @@
 error: lifetime may not live long enough
-  --> $DIR/project-fn-ret-invariant.rs:59:5
+  --> $DIR/project-fn-ret-invariant.rs:61:5
    |
 LL | fn transmute<'a, 'b>(x: Type<'a>, y: Type<'b>) -> (Type<'a>, Type<'b>) {
    |              --  -- lifetime `'b` defined here
@@ -15,7 +15,7 @@ LL |     (a, b)
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 error: lifetime may not live long enough
-  --> $DIR/project-fn-ret-invariant.rs:59:5
+  --> $DIR/project-fn-ret-invariant.rs:61:5
    |
 LL | fn transmute<'a, 'b>(x: Type<'a>, y: Type<'b>) -> (Type<'a>, Type<'b>) {
    |              --  -- lifetime `'b` defined here
@@ -30,7 +30,13 @@ LL |     (a, b)
    = note: the struct `Type<'a>` is invariant over the parameter `'a`
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
-help: `'a` and `'b` must be the same: replace one with the other
+error: one or more lifetime errors were found in this item
+  --> $DIR/project-fn-ret-invariant.rs:57:4
+   |
+LL | fn transmute<'a, 'b>(x: Type<'a>, y: Type<'b>) -> (Type<'a>, Type<'b>) {
+   |    ^^^^^^^^^
+   |
+   = help: `'a` and `'b` must be the same: replace one with the other
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 

tests/ui/associated-types/cache/project-fn-ret-invariant.oneuse.stderr

@@ -1,11 +1,11 @@
 error: lifetime may not live long enough
-  --> $DIR/project-fn-ret-invariant.rs:40:13
+  --> $DIR/project-fn-ret-invariant.rs:41:13
    |
 LL | fn baz<'a, 'b>(x: Type<'a>, y: Type<'b>) -> (Type<'a>, Type<'b>) {
    |        --  -- lifetime `'b` defined here
    |        |
    |        lifetime `'a` defined here
-LL |     let f = foo; // <-- No consistent type can be inferred for `f` here.
+...
 LL |     let a = bar(f, x);
    |             ^^^^^^^^^ argument requires that `'b` must outlive `'a`
    |
@@ -15,7 +15,7 @@ LL |     let a = bar(f, x);
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 error: lifetime may not live long enough
-  --> $DIR/project-fn-ret-invariant.rs:42:13
+  --> $DIR/project-fn-ret-invariant.rs:43:13
    |
 LL | fn baz<'a, 'b>(x: Type<'a>, y: Type<'b>) -> (Type<'a>, Type<'b>) {
    |        --  -- lifetime `'b` defined here
@@ -30,7 +30,13 @@ LL |     let b = bar(f, y);
    = note: the struct `Type<'a>` is invariant over the parameter `'a`
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
-help: `'a` and `'b` must be the same: replace one with the other
+error: one or more lifetime errors were found in this item
+  --> $DIR/project-fn-ret-invariant.rs:38:4
+   |
+LL | fn baz<'a, 'b>(x: Type<'a>, y: Type<'b>) -> (Type<'a>, Type<'b>) {
+   |    ^^^
+   |
+   = help: `'a` and `'b` must be the same: replace one with the other
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors