Add suggestion for bad block fragment error

compiler/rustc_parse/src/parser/expr.rs

@@ -2186,6 +2186,10 @@ impl<'a> Parser<'a> {
             self.sess.emit_err(errors::InvalidBlockMacroSegment {
                 span: self.token.span,
                 context: lo.to(self.token.span),
+                wrap: errors::WrapInExplicitBlock {
+                    lo: self.token.span.shrink_to_lo(),
+                    hi: self.token.span.shrink_to_hi(),
+                },
             });
         }