review comments

Author: estebank

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

@@ -54,7 +54,7 @@ pub fn report_object_safety_error(
         "the trait `{}` cannot be made into an object",
         trait_str
     );
-    err.span_label(span, format!("the trait `{}` cannot be made into an object", trait_str));
+    err.span_label(span, format!("`{}` cannot be made into an object", trait_str));
 
     let mut reported_violations = FxHashSet::default();
     let mut multi_span = vec![];

compiler/rustc_middle/src/traits/mod.rs

@@ -647,7 +647,7 @@ impl ObjectSafetyViolation {
             ObjectSafetyViolation::SizedSelf(_) => "it requires `Self: Sized`".into(),
             ObjectSafetyViolation::SupertraitSelf(ref spans) => {
                 if spans.iter().any(|sp| *sp != DUMMY_SP) {
-                    "it uses `Self` as a type parameter in this".into()
+                    "it uses `Self` as a type parameter".into()
                 } else {
                     "it cannot use `Self` as a type parameter in a supertrait or `where`-clause"
                         .into()

compiler/rustc_trait_selection/src/traits/object_safety.rs

@@ -100,51 +100,7 @@ fn object_safety_violations_for_trait(
                 span,
             ) = violation
             {
-                // Using `CRATE_NODE_ID` is wrong, but it's hard to get a more precise id.
-                // It's also hard to get a use site span, so we use the method definition span.
-                tcx.struct_span_lint_hir(
-                    WHERE_CLAUSES_OBJECT_SAFETY,
-                    hir::CRATE_HIR_ID,
-                    *span,
-                    |lint| {
-                        let mut err = lint.build(&format!(
-                            "the trait `{}` cannot be made into an object",
-                            tcx.def_path_str(trait_def_id)
-                        ));
-                        let node = tcx.hir().get_if_local(trait_def_id);
-                        let mut spans = MultiSpan::from_span(*span);
-                        if let Some(hir::Node::Item(item)) = node {
-                            spans.push_span_label(
-                                item.ident.span,
-                                "this trait cannot be made into an object...".into(),
-                            );
-                            spans.push_span_label(
-                                *span,
-                                format!("...because {}", violation.error_msg()),
-                            );
-                        } else {
-                            spans.push_span_label(
-                                *span,
-                                format!(
-                                    "the trait cannot be made into an object because {}",
-                                    violation.error_msg()
-                                ),
-                            );
-                        };
-                        err.span_note(
-                            spans,
-                            "for a trait to be \"object safe\" it needs to allow building a vtable \
-                             to allow the call to be resolvable dynamically; for more information \
-                             visit <https://doc.rust-lang.org/reference/items/traits.html\
-                             #object-safety>",
-                        );
-                        if node.is_some() {
-                            // Only provide the help if its a local trait, otherwise it's not
-                            violation.solution(&mut err);
-                        }
-                        err.emit();
-                    },
-                );
+                lint_object_unsafe_trait(tcx, *span, trait_def_id, violation);
                 false
             } else {
                 true
@@ -182,6 +138,51 @@ fn object_safety_violations_for_trait(
     violations
 }
 
+/// Lint object-unsafe trait.
+fn lint_object_unsafe_trait(
+    tcx: TyCtxt<'_>,
+    span: Span,
+    trait_def_id: DefId,
+    violation: &ObjectSafetyViolation,
+) {
+    // Using `CRATE_NODE_ID` is wrong, but it's hard to get a more precise id.
+    // It's also hard to get a use site span, so we use the method definition span.
+    tcx.struct_span_lint_hir(WHERE_CLAUSES_OBJECT_SAFETY, hir::CRATE_HIR_ID, span, |lint| {
+        let mut err = lint.build(&format!(
+            "the trait `{}` cannot be made into an object",
+            tcx.def_path_str(trait_def_id)
+        ));
+        let node = tcx.hir().get_if_local(trait_def_id);
+        let mut spans = MultiSpan::from_span(span);
+        if let Some(hir::Node::Item(item)) = node {
+            spans.push_span_label(
+                item.ident.span,
+                "this trait cannot be made into an object...".into(),
+            );
+            spans.push_span_label(span, format!("...because {}", violation.error_msg()));
+        } else {
+            spans.push_span_label(
+                span,
+                format!(
+                    "the trait cannot be made into an object because {}",
+                    violation.error_msg()
+                ),
+            );
+        };
+        err.span_note(
+            spans,
+            "for a trait to be \"object safe\" it needs to allow building a vtable to allow the \
+             call to be resolvable dynamically; for more information visit \
+             <https://doc.rust-lang.org/reference/items/traits.html#object-safety>",
+        );
+        if node.is_some() {
+            // Only provide the help if its a local trait, otherwise it's not
+            violation.solution(&mut err);
+        }
+        err.emit();
+    });
+}
+
 fn sized_trait_bound_spans<'tcx>(
     tcx: TyCtxt<'tcx>,
     bounds: hir::GenericBounds<'tcx>,

src/test/ui/associated-consts/associated-const-in-trait.stderr

@@ -2,7 +2,7 @@ error[E0038]: the trait `Trait` cannot be made into an object
   --> $DIR/associated-const-in-trait.rs:9:6
    |
 LL | impl dyn Trait {
-   |      ^^^^^^^^^ the trait `Trait` cannot be made into an object
+   |      ^^^^^^^^^ `Trait` cannot be made into an object
    |
    = help: consider moving `N` to another trait
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>

src/test/ui/associated-item/issue-48027.stderr

@@ -2,7 +2,7 @@ error[E0038]: the trait `Bar` cannot be made into an object
   --> $DIR/issue-48027.rs:6:6
    |
 LL | impl dyn Bar {}
-   |      ^^^^^^^ the trait `Bar` cannot be made into an object
+   |      ^^^^^^^ `Bar` cannot be made into an object
    |
    = help: consider moving `X` to another trait
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>

src/test/ui/coherence/coherence-impl-trait-for-trait-object-safe.stderr

@@ -2,7 +2,7 @@ error[E0038]: the trait `NotObjectSafe` cannot be made into an object
   --> $DIR/coherence-impl-trait-for-trait-object-safe.rs:7:24
    |
 LL | impl NotObjectSafe for dyn NotObjectSafe { }
-   |                        ^^^^^^^^^^^^^^^^^ the trait `NotObjectSafe` cannot be made into an object
+   |                        ^^^^^^^^^^^^^^^^^ `NotObjectSafe` cannot be made into an object
    |
    = help: consider moving `eq` to another trait
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>

src/test/ui/did_you_mean/trait-object-reference-without-parens-suggestion.stderr

@@ -14,7 +14,7 @@ error[E0038]: the trait `Copy` cannot be made into an object
   --> $DIR/trait-object-reference-without-parens-suggestion.rs:4:12
    |
 LL |     let _: &Copy + 'static;
-   |            ^^^^^ the trait `Copy` cannot be made into an object
+   |            ^^^^^ `Copy` cannot be made into an object
    |
    = note: the trait cannot be made into an object because it requires `Self: Sized`
    = note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>

src/test/ui/error-codes/E0033-teach.stderr

@@ -8,7 +8,7 @@ error[E0038]: the trait `SomeTrait` cannot be made into an object
   --> $DIR/E0033-teach.rs:8:20
    |
 LL |     let trait_obj: &dyn SomeTrait = SomeTrait;
-   |                    ^^^^^^^^^^^^^^ the trait `SomeTrait` cannot be made into an object
+   |                    ^^^^^^^^^^^^^^ `SomeTrait` cannot be made into an object
    |
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/E0033-teach.rs:4:8

src/test/ui/error-codes/E0033.stderr

@@ -8,7 +8,7 @@ error[E0038]: the trait `SomeTrait` cannot be made into an object
   --> $DIR/E0033.rs:6:20
    |
 LL |     let trait_obj: &dyn SomeTrait = SomeTrait;
-   |                    ^^^^^^^^^^^^^^ the trait `SomeTrait` cannot be made into an object
+   |                    ^^^^^^^^^^^^^^ `SomeTrait` cannot be made into an object
    |
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/E0033.rs:2:8

src/test/ui/error-codes/E0038.stderr

@@ -2,7 +2,7 @@ error[E0038]: the trait `Trait` cannot be made into an object
   --> $DIR/E0038.rs:5:16
    |
 LL | fn call_foo(x: Box<dyn Trait>) {
-   |                ^^^^^^^^^^^^^^ the trait `Trait` cannot be made into an object
+   |                ^^^^^^^^^^^^^^ `Trait` cannot be made into an object
    |
    = help: consider moving `foo` to another trait
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>