Rollup merge of rust-lang#88509 - m-ou-se:dyn-no-left-shift-right-shift-just-single-angle-brackets-please-thanks, r=petrochenkov

Don't suggest extra <> in dyn suggestion.

Fixes rust-lang#88508

Author: m-ou-se

Diff for: compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs

@@ -914,7 +914,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             });
 
         if result.is_ok() {
-            self.maybe_lint_bare_trait(qpath, hir_id);
+            self.maybe_lint_bare_trait(qpath, hir_id, span);
             self.register_wf_obligation(ty.into(), qself.span, traits::WellFormed(None));
         }
 
@@ -927,18 +927,23 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         )
     }
 
-    fn maybe_lint_bare_trait(&self, qpath: &QPath<'_>, hir_id: hir::HirId) {
+    fn maybe_lint_bare_trait(&self, qpath: &QPath<'_>, hir_id: hir::HirId, span: Span) {
         if let QPath::TypeRelative(self_ty, _) = qpath {
             if let TyKind::TraitObject([poly_trait_ref, ..], _, TraitObjectSyntax::None) =
                 self_ty.kind
             {
                 let msg = "trait objects without an explicit `dyn` are deprecated";
                 let (sugg, app) = match self.tcx.sess.source_map().span_to_snippet(self_ty.span) {
                     Ok(s) if poly_trait_ref.trait_ref.path.is_global() => {
-                        (format!("<dyn ({})>", s), Applicability::MachineApplicable)
+                        (format!("dyn ({})", s), Applicability::MachineApplicable)
                     }
-                    Ok(s) => (format!("<dyn {}>", s), Applicability::MachineApplicable),
-                    Err(_) => ("<dyn <type>>".to_string(), Applicability::HasPlaceholders),
+                    Ok(s) => (format!("dyn {}", s), Applicability::MachineApplicable),
+                    Err(_) => ("dyn <type>".to_string(), Applicability::HasPlaceholders),
+                };
+                // Wrap in `<..>` if it isn't already.
+                let sugg = match self.tcx.sess.source_map().span_to_snippet(span) {
+                    Ok(s) if s.starts_with('<') => sugg,
+                    _ => format!("<{}>", sugg),
                 };
                 let replace = String::from("use `dyn`");
                 if self.sess().edition() >= Edition::Edition2021 {

Diff for: src/test/ui/dyn-keyword/dyn-angle-brackets.fixed

@@ -0,0 +1,23 @@
+// See https://github.com/rust-lang/rust/issues/88508
+// run-rustfix
+// edition:2018
+#![deny(bare_trait_objects)]
+#![allow(dead_code)]
+#![allow(unused_imports)]
+
+use std::fmt;
+
+#[derive(Debug)]
+pub struct Foo;
+
+impl fmt::Display for Foo {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        <dyn fmt::Debug>::fmt(self, f)
+        //~^ ERROR trait objects without an explicit `dyn` are deprecated
+        //~| WARNING this is accepted in the current edition
+        //~| ERROR trait objects without an explicit `dyn` are deprecated
+        //~| WARNING this is accepted in the current edition
+    }
+}
+
+fn main() {}

Diff for: src/test/ui/dyn-keyword/dyn-angle-brackets.rs

@@ -0,0 +1,23 @@
+// See https://github.com/rust-lang/rust/issues/88508
+// run-rustfix
+// edition:2018
+#![deny(bare_trait_objects)]
+#![allow(dead_code)]
+#![allow(unused_imports)]
+
+use std::fmt;
+
+#[derive(Debug)]
+pub struct Foo;
+
+impl fmt::Display for Foo {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        <fmt::Debug>::fmt(self, f)
+        //~^ ERROR trait objects without an explicit `dyn` are deprecated
+        //~| WARNING this is accepted in the current edition
+        //~| ERROR trait objects without an explicit `dyn` are deprecated
+        //~| WARNING this is accepted in the current edition
+    }
+}
+
+fn main() {}

Diff for: src/test/ui/dyn-keyword/dyn-angle-brackets.stderr

@@ -0,0 +1,25 @@
+error: trait objects without an explicit `dyn` are deprecated
+  --> $DIR/dyn-angle-brackets.rs:15:10
+   |
+LL |         <fmt::Debug>::fmt(self, f)
+   |          ^^^^^^^^^^ help: use `dyn`: `dyn fmt::Debug`
+   |
+note: the lint level is defined here
+  --> $DIR/dyn-angle-brackets.rs:4:9
+   |
+LL | #![deny(bare_trait_objects)]
+   |         ^^^^^^^^^^^^^^^^^^
+   = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
+
+error: trait objects without an explicit `dyn` are deprecated
+  --> $DIR/dyn-angle-brackets.rs:15:10
+   |
+LL |         <fmt::Debug>::fmt(self, f)
+   |          ^^^^^^^^^^ help: use `dyn`: `dyn fmt::Debug`
+   |
+   = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
+
+error: aborting due to 2 previous errors
+