Revert "Remove rule requiring non-nil block-style statements to be semi-terminated"

This reverts commit 0f5eaef5fb.

src/libsyntax/print/pprust.rs

@@ -682,9 +682,11 @@ fn print_stmt(s: ps, st: ast::stmt) {
       ast::stmt_expr(expr, _) {
         space_if_not_bol(s);
         print_expr(s, expr);
-        if expr_requires_semi_to_be_stmt(expr) {
-            word(s.s, ";");
-        }
+      }
+      ast::stmt_semi(expr, _) {
+        space_if_not_bol(s);
+        print_expr(s, expr);
+        word(s.s, ";");
       }
     }
     if parse::classify::stmt_ends_with_semi(st) { word(s.s, ";"); }