let_chains: Comment out Let in ident_can_begin_expr.

src/libsyntax/parse/token.rs

@@ -122,7 +122,8 @@ pub(crate) fn ident_can_begin_expr(ident: ast::Ident, is_raw: bool) -> bool {
         keywords::Continue.name(),
         keywords::False.name(),
         keywords::For.name(),
-        keywords::Let.name(),
+        // FIXME(53667): Consider whether `Let` can be added here.
+        // keywords::Let.name(),
         keywords::If.name(),
         keywords::Loop.name(),
         keywords::Match.name(),

src/test/ui/rfc-2497-if-let-chains/feature-gate.rs

@@ -91,11 +91,12 @@ fn _macros() {
             while $e {}
         }
     }
-    use_expr!(let 0 = 1 && 0 == 0);
+    use_expr!((let 0 = 1 && 0 == 0));
     //~^ ERROR `let` expressions in this position are experimental [E0658]
     use_expr!((let 0 = 1));
     //~^ ERROR `let` expressions in this position are experimental [E0658]
-    use_expr!(let 0 = 1);
+    // use_expr!(let 0 = 1);
+    // ^--- FIXME(53667): Consider whether `Let` can be added to `ident_can_begin_expr`.
 }
 
 fn main() {}

src/test/ui/rfc-2497-if-let-chains/feature-gate.stderr

@@ -251,10 +251,10 @@ LL |     while let Range { start: _, end: _ } = (true..true) && false {}
    = help: add #![feature(let_chains)] to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are experimental
-  --> $DIR/feature-gate.rs:94:15
+  --> $DIR/feature-gate.rs:94:16
    |
-LL |     use_expr!(let 0 = 1 && 0 == 0);
-   |               ^^^^^^^^^
+LL |     use_expr!((let 0 = 1 && 0 == 0));
+   |                ^^^^^^^^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/53667
    = help: add #![feature(let_chains)] to the crate attributes to enable