src/librustc_typeck/check/demand.rs

   1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11
  12 use check::{coercion, FnCtxt};
  13 use middle::ty::{self, Ty};
  14 use middle::infer;
  15
  16 use std::result::Result::{Err, Ok};
  17 use syntax::ast;
  18 use syntax::codemap::Span;
  19
  20 // Requires that the two types unify, and prints an error message if
  21 // they don't.
  22 pub fn suptype<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, sp: Span,
  23                          ty_expected: Ty<'tcx>, ty_actual: Ty<'tcx>) {
  24     suptype_with_fn(fcx, sp, false, ty_expected, ty_actual,
  25         |sp, e, a, s| { fcx.report_mismatched_types(sp, e, a, s) })
  26 }
  27
  28 /// As `suptype`, but call `handle_err` if unification for subtyping fails.
  29 pub fn suptype_with_fn<'a, 'tcx, F>(fcx: &FnCtxt<'a, 'tcx>,
  30                                     sp: Span,
  31                                     b_is_expected: bool,
  32                                     ty_a: Ty<'tcx>,
  33                                     ty_b: Ty<'tcx>,
  34                                     handle_err: F) where
  35     F: FnOnce(Span, Ty<'tcx>, Ty<'tcx>, &ty::type_err<'tcx>),
  36 {
  37     // n.b.: order of actual, expected is reversed
  38     match infer::mk_subty(fcx.infcx(), b_is_expected, infer::Misc(sp),
  39                           ty_b, ty_a) {
  40       Ok(()) => { /* ok */ }
  41       Err(ref err) => {
  42           handle_err(sp, ty_a, ty_b, err);
  43       }
  44     }
  45 }
  46
  47 pub fn eqtype<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, sp: Span,
  48                         expected: Ty<'tcx>, actual: Ty<'tcx>) {
  49     match infer::mk_eqty(fcx.infcx(), false, infer::Misc(sp), actual, expected) {
  50         Ok(()) => { /* ok */ }
  51         Err(ref err) => { fcx.report_mismatched_types(sp, expected, actual, err); }
  52     }
  53 }
  54
  55 // Checks that the type of `expr` can be coerced to `expected`.
  56 pub fn coerce<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
  57                         sp: Span,
  58                         expected: Ty<'tcx>,
  59                         expr: &ast::Expr) {
  60     let expr_ty = fcx.expr_ty(expr);
  61     debug!("demand::coerce(expected = {:?}, expr_ty = {:?})",
  62            expected,
  63            expr_ty);
  64     let expr_ty = fcx.resolve_type_vars_if_possible(expr_ty);
  65     let expected = fcx.resolve_type_vars_if_possible(expected);
  66     match coercion::mk_assignty(fcx, expr, expr_ty, expected) {
  67       Ok(()) => { /* ok */ }
  68       Err(ref err) => {
  69         fcx.report_mismatched_types(sp, expected, expr_ty, err);
  70       }
  71     }
  72 }