Putting help message only under the identifier that needs to be prefixed

Author: sunjay

compiler/rustc_passes/src/dead.rs

@@ -16,7 +16,7 @@ use rustc_middle::middle::privacy;
 use rustc_middle::ty::{self, DefIdTree, TyCtxt};
 use rustc_session::lint;
 
-use rustc_span::symbol::{sym, Symbol};
+use rustc_span::symbol::{sym, Ident, Symbol};
 
 // Any local node that may call something in its body block should be
 // explored. For example, if it's a live Node::Item that is a
@@ -589,7 +589,7 @@ impl DeadVisitor<'tcx> {
         &mut self,
         id: hir::HirId,
         span: rustc_span::Span,
-        name: Symbol,
+        name: Ident,
         participle: &str,
         extra_note: Option<ExtraNote>,
     ) {
@@ -598,7 +598,7 @@ impl DeadVisitor<'tcx> {
                 let def_id = self.tcx.hir().local_def_id(id);
                 let descr = self.tcx.def_kind(def_id).descr(def_id.to_def_id());
 
-                let prefixed = vec![(span, format!("_{}", name))];
+                let prefixed = vec![(name.span, format!("_{}", name))];
 
                 let mut diag =
                     lint.build(&format!("{} is never {}: `{}`", descr, participle, name));
@@ -611,11 +611,11 @@ impl DeadVisitor<'tcx> {
 
                 let mut note = format!(
                     "the leading underscore signals that this {} serves some other \
-                    purpose\neven if it isn't used in a way that we can detect.",
+                    purpose even if it isn't used in a way that we can detect.",
                     descr,
                 );
                 if matches!(extra_note, Some(ExtraNote::OtherPurposeExamples)) {
-                    note += " (e.g. for its effect\nwhen dropped or in foreign code)";
+                    note += " (e.g. for its effect when dropped or in foreign code)";
                 }
 
                 diag.note(&note);
@@ -670,7 +670,7 @@ impl Visitor<'tcx> for DeadVisitor<'tcx> {
                 hir::ItemKind::Struct(..) => "constructed", // Issue #52325
                 _ => "used",
             };
-            self.warn_dead_code(item.hir_id(), span, item.ident.name, participle, None);
+            self.warn_dead_code(item.hir_id(), span, item.ident, participle, None);
         } else {
             // Only continue if we didn't warn
             intravisit::walk_item(self, item);
@@ -684,15 +684,15 @@ impl Visitor<'tcx> for DeadVisitor<'tcx> {
         id: hir::HirId,
     ) {
         if self.should_warn_about_variant(&variant) {
-            self.warn_dead_code(variant.id, variant.span, variant.ident.name, "constructed", None);
+            self.warn_dead_code(variant.id, variant.span, variant.ident, "constructed", None);
         } else {
             intravisit::walk_variant(self, variant, g, id);
         }
     }
 
     fn visit_foreign_item(&mut self, fi: &'tcx hir::ForeignItem<'tcx>) {
         if self.should_warn_about_foreign_item(fi) {
-            self.warn_dead_code(fi.hir_id(), fi.span, fi.ident.name, "used", None);
+            self.warn_dead_code(fi.hir_id(), fi.span, fi.ident, "used", None);
         }
         intravisit::walk_foreign_item(self, fi);
     }
@@ -702,7 +702,7 @@ impl Visitor<'tcx> for DeadVisitor<'tcx> {
             self.warn_dead_code(
                 field.hir_id,
                 field.span,
-                field.ident.name,
+                field.ident,
                 "read",
                 Some(ExtraNote::OtherPurposeExamples),
             );
@@ -717,7 +717,7 @@ impl Visitor<'tcx> for DeadVisitor<'tcx> {
                     self.warn_dead_code(
                         impl_item.hir_id(),
                         impl_item.span,
-                        impl_item.ident.name,
+                        impl_item.ident,
                         "used",
                         None,
                     );
@@ -737,13 +737,7 @@ impl Visitor<'tcx> for DeadVisitor<'tcx> {
                     } else {
                         impl_item.ident.span
                     };
-                    self.warn_dead_code(
-                        impl_item.hir_id(),
-                        span,
-                        impl_item.ident.name,
-                        "used",
-                        None,
-                    );
+                    self.warn_dead_code(impl_item.hir_id(), span, impl_item.ident, "used", None);
                 }
                 self.visit_nested_body(body_id)
             }

src/test/ui/associated-consts/associated-const-dead-code.stderr

@@ -2,10 +2,11 @@ error: associated constant is never used: `BAR`
   --> $DIR/associated-const-dead-code.rs:6:5
    |
 LL |     const BAR: u32 = 1;
-   |     ^^^^^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_BAR`
+   |     ^^^^^^---^^^^^^^^^^
+   |           |
+   |           help: if this is intentional, prefix it with an underscore: `_BAR`
    |
-   = note: the leading underscore signals that this associated constant serves some other purpose
-           even if it isn't used in a way that we can detect.
+   = note: the leading underscore signals that this associated constant serves some other purpose even if it isn't used in a way that we can detect.
 note: the lint level is defined here
   --> $DIR/associated-const-dead-code.rs:1:9
    |

src/test/ui/derive-uninhabited-enum-38885.stderr

@@ -2,10 +2,11 @@ warning: variant is never constructed: `Void`
   --> $DIR/derive-uninhabited-enum-38885.rs:13:5
    |
 LL |     Void(Void),
-   |     ^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_Void`
+   |     ----^^^^^^
+   |     |
+   |     help: if this is intentional, prefix it with an underscore: `_Void`
    |
-   = note: the leading underscore signals that this variant serves some other purpose
-           even if it isn't used in a way that we can detect.
+   = note: the leading underscore signals that this variant serves some other purpose even if it isn't used in a way that we can detect.
    = note: `-W dead-code` implied by `-W unused`
 
 warning: 1 warning emitted

src/test/ui/issues/issue-37515.stderr

@@ -2,10 +2,11 @@ warning: type alias is never used: `Z`
   --> $DIR/issue-37515.rs:5:1
    |
 LL | type Z = dyn for<'x> Send;
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_Z`
+   | ^^^^^-^^^^^^^^^^^^^^^^^^^^
+   |      |
+   |      help: if this is intentional, prefix it with an underscore: `_Z`
    |
-   = note: the leading underscore signals that this type alias serves some other purpose
-           even if it isn't used in a way that we can detect.
+   = note: the leading underscore signals that this type alias serves some other purpose even if it isn't used in a way that we can detect.
 note: the lint level is defined here
   --> $DIR/issue-37515.rs:3:9
    |

src/test/ui/lint/dead-code/basic.stderr

@@ -4,8 +4,7 @@ error: function is never used: `foo`
 LL | fn foo() {
    |    ^^^ help: if this is intentional, prefix it with an underscore: `_foo`
    |
-   = note: the leading underscore signals that this function serves some other purpose
-           even if it isn't used in a way that we can detect.
+   = note: the leading underscore signals that this function serves some other purpose even if it isn't used in a way that we can detect.
 note: the lint level is defined here
   --> $DIR/basic.rs:1:9
    |

src/test/ui/lint/dead-code/const-and-self.stderr

@@ -4,8 +4,7 @@ warning: variant is never constructed: `B`
 LL |     B,
    |     ^ help: if this is intentional, prefix it with an underscore: `_B`
    |
-   = note: the leading underscore signals that this variant serves some other purpose
-           even if it isn't used in a way that we can detect.
+   = note: the leading underscore signals that this variant serves some other purpose even if it isn't used in a way that we can detect.
 note: the lint level is defined here
   --> $DIR/const-and-self.rs:3:9
    |
@@ -18,8 +17,7 @@ warning: variant is never constructed: `C`
 LL |     C,
    |     ^ help: if this is intentional, prefix it with an underscore: `_C`
    |
-   = note: the leading underscore signals that this variant serves some other purpose
-           even if it isn't used in a way that we can detect.
+   = note: the leading underscore signals that this variant serves some other purpose even if it isn't used in a way that we can detect.
 
 warning: 2 warnings emitted
 

src/test/ui/lint/dead-code/drop-only-field-issue-81658.stderr

@@ -2,11 +2,11 @@ error: field is never read: `guard`
   --> $DIR/drop-only-field-issue-81658.rs:15:5
    |
 LL |     guard: MutexGuard<'a, T>,
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_guard`
+   |     -----^^^^^^^^^^^^^^^^^^^
+   |     |
+   |     help: if this is intentional, prefix it with an underscore: `_guard`
    |
-   = note: the leading underscore signals that this field serves some other purpose
-           even if it isn't used in a way that we can detect. (e.g. for its effect
-           when dropped or in foreign code)
+   = note: the leading underscore signals that this field serves some other purpose even if it isn't used in a way that we can detect. (e.g. for its effect when dropped or in foreign code)
 note: the lint level is defined here
   --> $DIR/drop-only-field-issue-81658.rs:8:9
    |

src/test/ui/lint/dead-code/empty-unused-enum.stderr

@@ -4,8 +4,7 @@ error: enum is never used: `E`
 LL | enum E {}
    |      ^ help: if this is intentional, prefix it with an underscore: `_E`
    |
-   = note: the leading underscore signals that this enum serves some other purpose
-           even if it isn't used in a way that we can detect.
+   = note: the leading underscore signals that this enum serves some other purpose even if it isn't used in a way that we can detect.
 note: the lint level is defined here
   --> $DIR/empty-unused-enum.rs:1:9
    |

src/test/ui/lint/dead-code/field-used-in-ffi-issue-81658.stderr

@@ -2,11 +2,11 @@ error: field is never read: `items`
   --> $DIR/field-used-in-ffi-issue-81658.rs:13:5
    |
 LL |     items: Option<Vec<T>>,
-   |     ^^^^^^^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_items`
+   |     -----^^^^^^^^^^^^^^^^
+   |     |
+   |     help: if this is intentional, prefix it with an underscore: `_items`
    |
-   = note: the leading underscore signals that this field serves some other purpose
-           even if it isn't used in a way that we can detect. (e.g. for its effect
-           when dropped or in foreign code)
+   = note: the leading underscore signals that this field serves some other purpose even if it isn't used in a way that we can detect. (e.g. for its effect when dropped or in foreign code)
 note: the lint level is defined here
   --> $DIR/field-used-in-ffi-issue-81658.rs:7:9
    |

src/test/ui/lint/dead-code/impl-trait.stderr

@@ -2,10 +2,11 @@ error: type alias is never used: `Unused`
   --> $DIR/impl-trait.rs:12:1
    |
 LL | type Unused = ();
-   | ^^^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_Unused`
+   | ^^^^^------^^^^^^
+   |      |
+   |      help: if this is intentional, prefix it with an underscore: `_Unused`
    |
-   = note: the leading underscore signals that this type alias serves some other purpose
-           even if it isn't used in a way that we can detect.
+   = note: the leading underscore signals that this type alias serves some other purpose even if it isn't used in a way that we can detect.
 note: the lint level is defined here
   --> $DIR/impl-trait.rs:1:9
    |