Resolve type variables when checking casting to char

src/librustc/middle/typeck/check/mod.rs

@@ -3033,6 +3033,7 @@ pub fn check_expr_with_unifier(fcx: @FnCtxt,
                     if type_is_c_like_enum(fcx, expr.span, t_e) && t_1_is_trivial {
                         // casts from C-like enums are allowed
                     } else if t_1_is_char {
+                        let te = fcx.infcx().resolve_type_vars_if_possible(te);
                         if ty::get(te).sty != ty::ty_uint(ast::TyU8) {
                             fcx.type_error_message(expr.span, |actual| {
                                 format!("only `u8` can be cast as `char`, not `{}`", actual)

src/test/run-pass/issue-9918.rs

@@ -0,0 +1,13 @@
+// Copyright 2014 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.
+
+pub fn main() {
+    assert_eq!((0 + 0u8) as char, '\0');
+}