// Copyright 2012-2015 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.

use ty::{self, Ty, TyCtxt};

use syntax::symbol::Symbol;

pub(super) trait Value<'tcx>: Sized {
    fn from_cycle_error<'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Self;
}

impl<'tcx, T> Value<'tcx> for T {
    default fn from_cycle_error<'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> T {
        tcx.sess.abort_if_errors();
        bug!("Value::from_cycle_error called without errors");
    }
}

impl<'tcx, T: Default> Value<'tcx> for T {
    default fn from_cycle_error<'a>(_: TyCtxt<'a, 'tcx, 'tcx>) -> T {
        T::default()
    }
}

impl<'tcx> Value<'tcx> for Ty<'tcx> {
    fn from_cycle_error<'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Ty<'tcx> {
        tcx.types.err
    }
}

impl<'tcx> Value<'tcx> for ty::SymbolName {
    fn from_cycle_error<'a>(_: TyCtxt<'a, 'tcx, 'tcx>) -> Self {
        ty::SymbolName { name: Symbol::intern("<error>").as_interned_str() }
    }
}