let_chains: readd kw::let to ident_can_begin_expr.

src/libsyntax/ext/tt/macro_parser.rs

@@ -825,7 +825,7 @@ fn may_begin_with(token: &Token, name: Name) -> bool {
     }
 
     match name {
-        sym::expr => token.can_begin_expr(),
+        sym::expr => token.can_begin_expr() && !token.is_keyword(kw::Let),
         sym::ty => token.can_begin_type(),
         sym::ident => get_macro_name(token).is_some(),
         sym::literal => token.can_begin_literal_or_bool(),

src/libsyntax/parse/token.rs

@@ -135,8 +135,7 @@ pub(crate) fn ident_can_begin_expr(name: ast::Name, span: Span, is_raw: bool) ->
         kw::False,
         kw::For,
         kw::If,
-        // FIXME(53667): Consider whether `Let` can be added here.
-        // kw::Let,
+        kw::Let,
         kw::Loop,
         kw::Match,
         kw::Move,