Update qquote.rs test case and make unexpected let error fatal

src/libsyntax/parse/parser.rs

@@ -2134,12 +2134,6 @@ impl<'a> Parser<'a> {
                 }
                 hi = self.last_span.hi;
             }
-            _ if self.token.is_keyword(keywords::Let) => {
-                // Catch this syntax error here, instead of in `check_strict_keywords`, so that
-                // we can explicitly mention that let is not to be used as an expression
-                let msg = "`let` is not an expression, so it cannot be used in this way";
-                return Err(self.diagnostic().struct_span_err(self.span, &msg));
-            },
             _ => {
                 if self.eat_lt() {
                     let (qself, path) =
@@ -2162,6 +2156,12 @@ impl<'a> Parser<'a> {
                     let lo = self.last_span.lo;
                     return self.parse_while_expr(None, lo, attrs);
                 }
+                if self.token.is_keyword(keywords::Let) {
+                    // Catch this syntax error here, instead of in `check_strict_keywords`, so
+                    // that we can explicitly mention that let is not to be used as an expression
+                    let msg = "`let` is not an expression, so it cannot be used in this way";
+                    self.span_err(self.span, msg);
+                }
                 if self.token.is_lifetime() {
                     let lifetime = self.get_lifetime();
                     let lo = self.span.lo;

src/test/run-fail-fulldeps/qquote.rs

@@ -10,7 +10,7 @@
 
 // ignore-cross-compile
 
-// error-pattern:expected identifier, found keyword `let`
+// error-pattern:`let` is not an expression, so it cannot be used in this way
 
 #![feature(quote, rustc_private)]