error parsing lifetime following by Sized and message + between them

detect the pattern at the general site parse_impl_ty()
this will fix #102598

2 files changed, 19 insertions, 1 deletions

diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index beb9d55d454..063421d62fe 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -2449,7 +2449,6 @@ impl<'a> Parser<'a> {
             };
             let (pat, ty) = if is_name_required || this.is_named_param() {
                 debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);
-
                 let (pat, colon) = this.parse_fn_param_pat_colon()?;
                 if !colon {
                     let mut err = this.unexpected::<()>().unwrap_err();
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index b7206b57642..fc26278909c 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -613,6 +613,25 @@ impl<'a> Parser<'a> {
     /// Parses an `impl B0 + ... + Bn` type.
     fn parse_impl_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
         // Always parse bounds greedily for better error recovery.
+        if self.token.is_lifetime() {
+            self.look_ahead(1, |t| {
+                if let token::Ident(symname, _) = t.kind {
+                    // parse pattern with "'a Sized" we're supposed to give suggestion like
+                    // "'a + Sized"
+                    self.struct_span_err(
+                        self.token.span,
+                        &format!("expected `+` between lifetime and {}", symname),
+                    )
+                    .span_suggestion_verbose(
+                        self.token.span.shrink_to_hi(),
+                        "add `+`",
+                        " +",
+                        Applicability::MaybeIncorrect,
+                    )
+                    .emit();
+                }
+            })
+        }
         let bounds = self.parse_generic_bounds(None)?;
         *impl_dyn_multi = bounds.len() > 1 || self.prev_token.kind == TokenKind::BinOp(token::Plus);
         Ok(TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds))