Reduce the diagnostic span when multiple fields are missing in pattern

src/test/ui/missing-fields-in-struct-pattern.rs

@@ -0,0 +1,17 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+struct S(usize, usize, usize, usize);
+
+fn main() {
+    if let S { a, b, c, d } = S(1, 2, 3, 4) {
+        println!("hi");
+    }
+}