Detect bare blocks with type ascription that were meant to be a `struct` literal

Address part of #34255.

Potential improvement: silence the other knock down errors in
`issue-34255-1.rs`.

2 files changed, 16 insertions, 4 deletions

diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 273fbea3580..59e0feb67c5 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -446,11 +446,13 @@ impl<'a> Parser<'a> {
                         )
                         .emit();
                     *self = snapshot;
-                    Ok(self.mk_block(
+                    let mut tail = self.mk_block(
                         vec![self.mk_stmt_err(expr.span)],
                         s,
                         lo.to(self.prev_token.span),
-                    ))
+                    );
+                    tail.could_be_bare_literal = true;
+                    Ok(tail)
                 }
                 (Err(mut err), Ok(tail)) => {
                     // We have a block tail that contains a somehow valid type ascription expr.
@@ -463,7 +465,10 @@ impl<'a> Parser<'a> {
                     self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
                     Err(err)
                 }
-                (Ok(_), Ok(tail)) => Ok(tail),
+                (Ok(_), Ok(mut tail)) => {
+                    tail.could_be_bare_literal = true;
+                    Ok(tail)
+                }
             });
         }
         None
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index 068bd36af55..25dcb4a112d 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -574,7 +574,14 @@ impl<'a> Parser<'a> {
     }
 
     pub(super) fn mk_block(&self, stmts: Vec<Stmt>, rules: BlockCheckMode, span: Span) -> P<Block> {
-        P(Block { stmts, id: DUMMY_NODE_ID, rules, span, tokens: None })
+        P(Block {
+            stmts,
+            id: DUMMY_NODE_ID,
+            rules,
+            span,
+            tokens: None,
+            could_be_bare_literal: false,
+        })
     }
 
     pub(super) fn mk_stmt(&self, span: Span, kind: StmtKind) -> Stmt {