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// Copyright 2012 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.
// Type substitutions.
use middle::ty;
use middle::ty_fold;
use middle::ty_fold::TypeFolder;
use syntax::opt_vec::OptVec;
use std::at_vec;
///////////////////////////////////////////////////////////////////////////
// Public trait `Subst`
//
// Just call `foo.subst(tcx, substs)` to perform a substitution across
// `foo`.
pub trait Subst {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> Self;
}
///////////////////////////////////////////////////////////////////////////
// Substitution over types
//
// Because this is so common, we make a special optimization to avoid
// doing anything if `substs` is a no-op. I tried to generalize these
// to all subst methods but ran into trouble due to the limitations of
// our current method/trait matching algorithm. - Niko
impl Subst for ty::t {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> ty::t {
if ty::substs_is_noop(substs) {
*self
} else {
let mut folder = SubstFolder {tcx: tcx, substs: substs};
folder.fold_ty(*self)
}
}
}
struct SubstFolder<'a> {
tcx: ty::ctxt,
substs: &'a ty::substs
}
impl<'a> TypeFolder for SubstFolder<'a> {
fn tcx(&self) -> ty::ctxt { self.tcx }
fn fold_region(&mut self, r: ty::Region) -> ty::Region {
r.subst(self.tcx, self.substs)
}
fn fold_ty(&mut self, t: ty::t) -> ty::t {
if !ty::type_needs_subst(t) {
return t;
}
match ty::get(t).sty {
ty::ty_param(p) => {
self.substs.tps[p.idx]
}
ty::ty_self(_) => {
self.substs.self_ty.expect("ty_self not found in substs")
}
_ => {
ty_fold::super_fold_ty(self, t)
}
}
}
}
///////////////////////////////////////////////////////////////////////////
// Other types
impl<T:Subst> Subst for ~[T] {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> ~[T] {
self.map(|t| t.subst(tcx, substs))
}
}
impl<T:Subst> Subst for @[T] {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> @[T] {
at_vec::map(*self, |t| t.subst(tcx, substs))
}
}
impl<T:Subst> Subst for OptVec<T> {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> OptVec<T> {
self.map(|t| t.subst(tcx, substs))
}
}
impl<T:Subst + 'static> Subst for @T {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> @T {
match self {
&@ref t => @t.subst(tcx, substs)
}
}
}
impl<T:Subst> Subst for Option<T> {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> Option<T> {
self.as_ref().map(|t| t.subst(tcx, substs))
}
}
impl Subst for ty::TraitRef {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> ty::TraitRef {
ty::TraitRef {
def_id: self.def_id,
substs: self.substs.subst(tcx, substs)
}
}
}
impl Subst for ty::substs {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> ty::substs {
ty::substs {
regions: self.regions.subst(tcx, substs),
self_ty: self.self_ty.map(|typ| typ.subst(tcx, substs)),
tps: self.tps.map(|typ| typ.subst(tcx, substs))
}
}
}
impl Subst for ty::RegionSubsts {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> ty::RegionSubsts {
match *self {
ty::ErasedRegions => {
ty::ErasedRegions
}
ty::NonerasedRegions(ref regions) => {
ty::NonerasedRegions(regions.subst(tcx, substs))
}
}
}
}
impl Subst for ty::BareFnTy {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> ty::BareFnTy {
let mut folder = SubstFolder {tcx: tcx, substs: substs};
folder.fold_bare_fn_ty(self)
}
}
impl Subst for ty::ParamBounds {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> ty::ParamBounds {
ty::ParamBounds {
builtin_bounds: self.builtin_bounds,
trait_bounds: self.trait_bounds.subst(tcx, substs)
}
}
}
impl Subst for ty::TypeParameterDef {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> ty::TypeParameterDef {
ty::TypeParameterDef {
ident: self.ident,
def_id: self.def_id,
bounds: self.bounds.subst(tcx, substs)
}
}
}
impl Subst for ty::Generics {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> ty::Generics {
ty::Generics {
type_param_defs: self.type_param_defs.subst(tcx, substs),
region_param_defs: self.region_param_defs.subst(tcx, substs),
}
}
}
impl Subst for ty::RegionParameterDef {
fn subst(&self, _: ty::ctxt, _: &ty::substs) -> ty::RegionParameterDef {
*self
}
}
impl Subst for ty::Region {
fn subst(&self, _tcx: ty::ctxt, substs: &ty::substs) -> ty::Region {
// Note: This routine only handles regions that are bound on
// type declarationss and other outer declarations, not those
// bound in *fn types*. Region substitution of the bound
// regions that appear in a function signature is done using
// the specialized routine
// `middle::typeck::check::regionmanip::replace_bound_regions_in_fn_sig()`.
match self {
&ty::ReEarlyBound(_, i, _) => {
match substs.regions {
ty::ErasedRegions => ty::ReStatic,
ty::NonerasedRegions(ref regions) => *regions.get(i),
}
}
_ => *self
}
}
}
impl Subst for ty::ty_param_bounds_and_ty {
fn subst(&self, tcx: ty::ctxt, substs: &ty::substs) -> ty::ty_param_bounds_and_ty {
ty::ty_param_bounds_and_ty {
generics: self.generics.subst(tcx, substs),
ty: self.ty.subst(tcx, substs)
}
}
}
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