Auto merge of #88598 - estebank:type-ascription-can-die-in-a-fire, r=wesleywiser

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`.

compiler/rustc_ast/src/ast.rs

@@ -558,6 +558,14 @@ pub struct Block {
     pub rules: BlockCheckMode,
     pub span: Span,
     pub tokens: Option<LazyTokenStream>,
+    /// The following *isn't* a parse error, but will cause multiple errors in following stages.
+    /// ```
+    /// let x = {
+    ///     foo: var
+    /// };
+    /// ```
+    /// #34255
+    pub could_be_bare_literal: bool,
 }
 
 /// A match pattern.