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Introduce new inference scheme: variables are now instantiated with at most one type, and region variables are introduced as needed

This commit is contained in:
Niko Matsakis 2014-07-22 07:46:36 -04:00
parent d6e5797e41
commit 4c01251416
36 changed files with 845 additions and 709 deletions
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214
src/librustc/middle/typeck/infer/combine.rs
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@ -8,43 +8,29 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// ______________________________________________________________________
// Type combining
///////////////////////////////////////////////////////////////////////////
// # Type combining
//
// There are three type combiners: sub, lub, and glb. Each implements
// the trait `Combine` and contains methods for combining two
// instances of various things and yielding a new instance. These
// combiner methods always yield a `result<T>`---failure is propagated
// upward using `and_then()` methods. There is a lot of common code for
// these operations, implemented as default methods on the `Combine`
// trait.
// There are four type combiners: equate, sub, lub, and glb. Each
// implements the trait `Combine` and contains methods for combining
// two instances of various things and yielding a new instance. These
// combiner methods always yield a `Result<T>`. There is a lot of
// common code for these operations, implemented as default methods on
// the `Combine` trait.
//
// In reality, the sub operation is rather different from lub/glb, but
// they are combined into one trait to avoid duplication (they used to
// be separate but there were many bugs because there were two copies
// of most routines).
// Each operation may have side-effects on the inference context,
// though these can be unrolled using snapshots. On success, the
// LUB/GLB operations return the appropriate bound. The Eq and Sub
// operations generally return the first operand.
//
// The differences are:
//
// - when making two things have a sub relationship, the order of the
// arguments is significant (a <: b) and the return value of the
// combine functions is largely irrelevant. The important thing is
// whether the action succeeds or fails. If it succeeds, then side
// effects have been committed into the type variables.
//
// - for GLB/LUB, the order of arguments is not significant (GLB(a,b) ==
// GLB(b,a)) and the return value is important (it is the GLB). Of
// course GLB/LUB may also have side effects.
//
// Contravariance
// ## Contravariance
//
// When you are relating two things which have a contravariant
// relationship, you should use `contratys()` or `contraregions()`,
// rather than inversing the order of arguments! This is necessary
// because the order of arguments is not relevant for LUB and GLB. It
// is also useful to track which value is the "expected" value in
// terms of error reporting, although we do not do that properly right
// now.
// terms of error reporting.
use middle::subst;
@ -53,14 +39,16 @@ use middle::ty::{FloatVar, FnSig, IntVar, TyVar};
use middle::ty::{IntType, UintType};
use middle::ty::{BuiltinBounds};
use middle::ty;
use middle::typeck::infer::{ToUres};
use middle::typeck::infer::equate::Equate;
use middle::typeck::infer::glb::Glb;
use middle::typeck::infer::lub::Lub;
use middle::typeck::infer::sub::Sub;
use middle::typeck::infer::unify::InferCtxtMethodsForSimplyUnifiableTypes;
use middle::typeck::infer::{InferCtxt, cres, ures};
use middle::typeck::infer::{TypeTrace};
use util::common::indent;
use middle::typeck::infer::{InferCtxt, cres};
use middle::typeck::infer::{MiscVariable, TypeTrace};
use middle::typeck::infer::type_variable::{RelationDir, EqTo,
SubtypeOf, SupertypeOf};
use middle::ty_fold::{RegionFolder, TypeFoldable};
use util::ppaux::Repr;
use std::result;
@ -75,6 +63,7 @@ pub trait Combine {
fn a_is_expected(&self) -> bool;
fn trace(&self) -> TypeTrace;
fn equate<'a>(&'a self) -> Equate<'a>;
fn sub<'a>(&'a self) -> Sub<'a>;
fn lub<'a>(&'a self) -> Lub<'a>;
fn glb<'a>(&'a self) -> Glb<'a>;
@ -101,7 +90,7 @@ pub trait Combine {
try!(result::fold_(as_
.iter()
.zip(bs.iter())
.map(|(a, b)| eq_tys(self, *a, *b))));
.map(|(a, b)| self.equate().tys(*a, *b))));
Ok(Vec::from_slice(as_))
}
@ -177,10 +166,7 @@ pub trait Combine {
let b_r = b_rs[i];
let variance = variances[i];
let r = match variance {
ty::Invariant => {
eq_regions(this, a_r, b_r)
.and_then(|()| Ok(a_r))
}
ty::Invariant => this.equate().regions(a_r, b_r),
ty::Covariant => this.regions(a_r, b_r),
ty::Contravariant => this.contraregions(a_r, b_r),
ty::Bivariant => Ok(a_r),
@ -334,34 +320,6 @@ pub fn expected_found<C:Combine,T>(
}
}
pub fn eq_tys<C:Combine>(this: &C, a: ty::t, b: ty::t) -> ures {
let suber = this.sub();
this.infcx().try(|| {
suber.tys(a, b).and_then(|_ok| suber.contratys(a, b)).to_ures()
})
}
pub fn eq_regions<C:Combine>(this: &C, a: ty::Region, b: ty::Region)
-> ures {
debug!("eq_regions({}, {})",
a.repr(this.infcx().tcx),
b.repr(this.infcx().tcx));
let sub = this.sub();
indent(|| {
this.infcx().try(|| {
sub.regions(a, b).and_then(|_r| sub.contraregions(a, b))
}).or_else(|e| {
// substitute a better error, but use the regions
// found in the original error
match e {
ty::terr_regions_does_not_outlive(a1, b1) =>
Err(ty::terr_regions_not_same(a1, b1)),
_ => Err(e)
}
}).to_ures()
})
}
pub fn super_fn_sigs<C:Combine>(this: &C, a: &ty::FnSig, b: &ty::FnSig) -> cres<ty::FnSig> {
fn argvecs<C:Combine>(this: &C, a_args: &[ty::t], b_args: &[ty::t]) -> cres<Vec<ty::t> > {
@ -453,8 +411,7 @@ pub fn super_tys<C:Combine>(this: &C, a: ty::t, b: ty::t) -> cres<ty::t> {
// Relate floating-point variables to other types
(&ty::ty_infer(FloatVar(a_id)), &ty::ty_infer(FloatVar(b_id))) => {
try!(this.infcx().simple_vars(this.a_is_expected(),
a_id, b_id));
try!(this.infcx().simple_vars(this.a_is_expected(), a_id, b_id));
Ok(a)
}
(&ty::ty_infer(FloatVar(v_id)), &ty::ty_float(v)) => {
@ -469,7 +426,8 @@ pub fn super_tys<C:Combine>(this: &C, a: ty::t, b: ty::t) -> cres<ty::t> {
(&ty::ty_bool, _) |
(&ty::ty_int(_), _) |
(&ty::ty_uint(_), _) |
(&ty::ty_float(_), _) => {
(&ty::ty_float(_), _) |
(&ty::ty_err, _) => {
if ty::get(a).sty == ty::get(b).sty {
Ok(a)
} else {
@ -512,7 +470,10 @@ pub fn super_tys<C:Combine>(this: &C, a: ty::t, b: ty::t) -> cres<ty::t> {
(&ty::ty_unboxed_closure(a_id, a_region),
&ty::ty_unboxed_closure(b_id, b_region))
if a_id == b_id => {
let region = if_ok!(this.regions(a_region, b_region));
// All ty_unboxed_closure types with the same id represent
// the (anonymous) type of the same closure expression. So
// all of their regions should be equated.
let region = try!(this.equate().regions(a_region, b_region));
Ok(ty::mk_unboxed_closure(tcx, a_id, region))
}
@ -609,3 +570,118 @@ pub fn super_tys<C:Combine>(this: &C, a: ty::t, b: ty::t) -> cres<ty::t> {
Ok(ty::mk_mach_float(val))
}
}
impl<'f> CombineFields<'f> {
pub fn switch_expected(&self) -> CombineFields<'f> {
CombineFields {
a_is_expected: !self.a_is_expected,
..(*self).clone()
}
}
fn equate(&self) -> Equate<'f> {
Equate((*self).clone())
}
fn sub(&self) -> Sub<'f> {
Sub((*self).clone())
}
pub fn instantiate(&self,
a_ty: ty::t,
dir: RelationDir,
b_vid: ty::TyVid)
-> cres<()>
{
let tcx = self.infcx.tcx;
let mut stack = Vec::new();
stack.push((a_ty, dir, b_vid));
loop {
// For each turn of the loop, we extract a tuple
//
// (a_ty, dir, b_vid)
//
// to relate. Here dir is either SubtypeOf or
// SupertypeOf. The idea is that we should ensure that
// the type `a_ty` is a subtype or supertype (respectively) of the
// type to which `b_vid` is bound.
//
// If `b_vid` has not yet been instantiated with a type
// (which is always true on the first iteration, but not
// necessarily true on later iterations), we will first
// instantiate `b_vid` with a *generalized* version of
// `a_ty`. Generalization introduces other inference
// variables wherever subtyping could occur (at time of
// this writing, this means replacing free regions with
// region variables).
let (a_ty, dir, b_vid) = match stack.pop() {
None => break,
Some(e) => e,
};
debug!("instantiate(a_ty={} dir={} b_vid={})",
a_ty.repr(tcx),
dir,
b_vid.repr(tcx));
// Check whether `vid` has been instantiated yet. If not,
// make a generalized form of `ty` and instantiate with
// that.
let b_ty = self.infcx.type_variables.borrow().probe(b_vid);
let b_ty = match b_ty {
Some(t) => t, // ...already instantiated.
None => { // ...not yet instantiated:
// Generalize type if necessary.
let generalized_ty = match dir {
EqTo => a_ty,
SupertypeOf | SubtypeOf => self.generalize(a_ty)
};
debug!("instantiate(a_ty={}, dir={}, \
b_vid={}, generalized_ty={})",
a_ty.repr(tcx), dir, b_vid.repr(tcx),
generalized_ty.repr(tcx));
self.infcx.type_variables
.borrow_mut()
.instantiate_and_push(
b_vid, generalized_ty, &mut stack);
generalized_ty
}
};
// The original triple was `(a_ty, dir, b_vid)` -- now we have
// resolved `b_vid` to `b_ty`, so apply `(a_ty, dir, b_ty)`:
//
// FIXME: This code is non-ideal because all these subtype
// relations wind up attributed to the same spans. We need
// to associate causes/spans with each of the relations in
// the stack to get this right.
match dir {
EqTo => {
try!(self.equate().tys(a_ty, b_ty));
}
SubtypeOf => {
try!(self.sub().tys(a_ty, b_ty));
}
SupertypeOf => {
try!(self.sub().contratys(a_ty, b_ty));
}
}
}
Ok(())
}
fn generalize(&self, t: ty::t) -> ty::t {
// FIXME: This is non-ideal because we don't give a very descriptive
// origin for this region variable.
let infcx = self.infcx;
let span = self.trace.origin.span();
t.fold_with(
&mut RegionFolder::regions(
self.infcx.tcx,
|_| infcx.next_region_var(MiscVariable(span))))
}
}

149
src/librustc/middle/typeck/infer/equate.rs Normal file
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@ -0,0 +1,149 @@
// 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.
use middle::ty::{BuiltinBounds};
use middle::ty;
use middle::ty::TyVar;
use middle::typeck::infer::combine::*;
use middle::typeck::infer::{cres};
use middle::typeck::infer::glb::Glb;
use middle::typeck::infer::InferCtxt;
use middle::typeck::infer::lub::Lub;
use middle::typeck::infer::sub::Sub;
use middle::typeck::infer::{TypeTrace, Subtype};
use middle::typeck::infer::type_variable::{EqTo};
use util::ppaux::{Repr};
use syntax::ast::{Onceness, FnStyle};
pub struct Equate<'f> {
fields: CombineFields<'f>
}
#[allow(non_snake_case_functions)]
pub fn Equate<'f>(cf: CombineFields<'f>) -> Equate<'f> {
Equate { fields: cf }
}
impl<'f> Combine for Equate<'f> {
fn infcx<'a>(&'a self) -> &'a InferCtxt<'a> { self.fields.infcx }
fn tag(&self) -> String { "eq".to_string() }
fn a_is_expected(&self) -> bool { self.fields.a_is_expected }
fn trace(&self) -> TypeTrace { self.fields.trace.clone() }
fn equate<'a>(&'a self) -> Equate<'a> { Equate(self.fields.clone()) }
fn sub<'a>(&'a self) -> Sub<'a> { Sub(self.fields.clone()) }
fn lub<'a>(&'a self) -> Lub<'a> { Lub(self.fields.clone()) }
fn glb<'a>(&'a self) -> Glb<'a> { Glb(self.fields.clone()) }
fn contratys(&self, a: ty::t, b: ty::t) -> cres<ty::t> {
self.tys(a, b)
}
fn contraregions(&self, a: ty::Region, b: ty::Region) -> cres<ty::Region> {
self.regions(a, b)
}
fn regions(&self, a: ty::Region, b: ty::Region) -> cres<ty::Region> {
debug!("{}.regions({}, {})",
self.tag(),
a.repr(self.fields.infcx.tcx),
b.repr(self.fields.infcx.tcx));
self.infcx().region_vars.make_eqregion(Subtype(self.trace()), a, b);
Ok(a)
}
fn mts(&self, a: &ty::mt, b: &ty::mt) -> cres<ty::mt> {
debug!("mts({} <: {})",
a.repr(self.fields.infcx.tcx),
b.repr(self.fields.infcx.tcx));
if a.mutbl != b.mutbl { return Err(ty::terr_mutability); }
let t = try!(self.tys(a.ty, b.ty));
Ok(ty::mt { mutbl: a.mutbl, ty: t })
}
fn fn_styles(&self, a: FnStyle, b: FnStyle) -> cres<FnStyle> {
if a != b {
Err(ty::terr_fn_style_mismatch(expected_found(self, a, b)))
} else {
Ok(a)
}
}
fn oncenesses(&self, a: Onceness, b: Onceness) -> cres<Onceness> {
if a != b {
Err(ty::terr_onceness_mismatch(expected_found(self, a, b)))
} else {
Ok(a)
}
}
fn builtin_bounds(&self,
a: BuiltinBounds,
b: BuiltinBounds)
-> cres<BuiltinBounds>
{
// More bounds is a subtype of fewer bounds.
//
// e.g., fn:Copy() <: fn(), because the former is a function
// that only closes over copyable things, but the latter is
// any function at all.
if a != b {
Err(ty::terr_builtin_bounds(expected_found(self, a, b)))
} else {
Ok(a)
}
}
fn tys(&self, a: ty::t, b: ty::t) -> cres<ty::t> {
debug!("{}.tys({}, {})", self.tag(),
a.repr(self.fields.infcx.tcx), b.repr(self.fields.infcx.tcx));
if a == b { return Ok(a); }
let infcx = self.fields.infcx;
let a = infcx.type_variables.borrow().replace_if_possible(a);
let b = infcx.type_variables.borrow().replace_if_possible(b);
match (&ty::get(a).sty, &ty::get(b).sty) {
(&ty::ty_bot, &ty::ty_bot) => {
Ok(a)
}
(&ty::ty_bot, _) |
(_, &ty::ty_bot) => {
Err(ty::terr_sorts(expected_found(self, a, b)))
}
(&ty::ty_infer(TyVar(a_id)), &ty::ty_infer(TyVar(b_id))) => {
infcx.type_variables.borrow_mut().relate_vars(a_id, EqTo, b_id);
Ok(a)
}
(&ty::ty_infer(TyVar(a_id)), _) => {
try!(self.fields.instantiate(b, EqTo, a_id));
Ok(a)
}
(_, &ty::ty_infer(TyVar(b_id))) => {
try!(self.fields.instantiate(a, EqTo, b_id));
Ok(a)
}
_ => {
super_tys(self, a, b)
}
}
}
fn fn_sigs(&self, a: &ty::FnSig, b: &ty::FnSig) -> cres<ty::FnSig> {
try!(self.sub().fn_sigs(a, b));
self.sub().fn_sigs(b, a)
}
}

39
src/librustc/middle/typeck/infer/glb.rs
View File

@ -12,9 +12,9 @@
use middle::ty::{BuiltinBounds};
use middle::ty::RegionVid;
use middle::ty;
use middle::typeck::infer::then;
use middle::typeck::infer::combine::*;
use middle::typeck::infer::lattice::*;
use middle::typeck::infer::equate::Equate;
use middle::typeck::infer::lub::Lub;
use middle::typeck::infer::sub::Sub;
use middle::typeck::infer::{cres, InferCtxt};
@ -31,7 +31,7 @@ use util::ppaux::Repr;
/// "Greatest lower bound" (common subtype)
pub struct Glb<'f> {
pub fields: CombineFields<'f>
fields: CombineFields<'f>
}
#[allow(non_snake_case_functions)]
@ -45,6 +45,7 @@ impl<'f> Combine for Glb<'f> {
fn a_is_expected(&self) -> bool { self.fields.a_is_expected }
fn trace(&self) -> TypeTrace { self.fields.trace.clone() }
fn equate<'a>(&'a self) -> Equate<'a> { Equate(self.fields.clone()) }
fn sub<'a>(&'a self) -> Sub<'a> { Sub(self.fields.clone()) }
fn lub<'a>(&'a self) -> Lub<'a> { Lub(self.fields.clone()) }
fn glb<'a>(&'a self) -> Glb<'a> { Glb(self.fields.clone()) }
@ -58,27 +59,25 @@ impl<'f> Combine for Glb<'f> {
mt_to_string(tcx, b));
match (a.mutbl, b.mutbl) {
// If one side or both is mut, then the GLB must use
// the precise type from the mut side.
(MutMutable, MutMutable) => {
eq_tys(self, a.ty, b.ty).then(|| {
Ok(ty::mt {ty: a.ty, mutbl: MutMutable})
})
}
// If one side or both is mut, then the GLB must use
// the precise type from the mut side.
(MutMutable, MutMutable) => {
let t = try!(self.equate().tys(a.ty, b.ty));
Ok(ty::mt {ty: t, mutbl: MutMutable})
}
// If one side or both is immutable, we can use the GLB of
// both sides but mutbl must be `MutImmutable`.
(MutImmutable, MutImmutable) => {
self.tys(a.ty, b.ty).and_then(|t| {
// If one side or both is immutable, we can use the GLB of
// both sides but mutbl must be `MutImmutable`.
(MutImmutable, MutImmutable) => {
let t = try!(self.tys(a.ty, b.ty));
Ok(ty::mt {ty: t, mutbl: MutImmutable})
})
}
}
// There is no mutual subtype of these combinations.
(MutMutable, MutImmutable) |
(MutImmutable, MutMutable) => {
Err(ty::terr_mutability)
}
// There is no mutual subtype of these combinations.
(MutMutable, MutImmutable) |
(MutImmutable, MutMutable) => {
Err(ty::terr_mutability)
}
}
}

502
src/librustc/middle/typeck/infer/lattice.rs
View File

@ -33,346 +33,55 @@
use middle::ty::{RegionVid, TyVar};
use middle::ty;
use middle::typeck::infer::{ToUres};
use middle::typeck::infer::*;
use middle::typeck::infer::combine::*;
use middle::typeck::infer::glb::Glb;
use middle::typeck::infer::lub::Lub;
use middle::typeck::infer::unify::*;
use middle::typeck::infer::sub::Sub;
use util::ppaux::Repr;
use std::collections::HashMap;
trait LatticeValue : Clone + Repr + PartialEq {
fn sub(cf: CombineFields, a: &Self, b: &Self) -> ures;
fn lub(cf: CombineFields, a: &Self, b: &Self) -> cres<Self>;
fn glb(cf: CombineFields, a: &Self, b: &Self) -> cres<Self>;
pub trait LatticeDir {
// Relates the bottom type to `t` and returns LUB(t, _|_) or
// GLB(t, _|_) as appropriate.
fn ty_bot(&self, t: ty::t) -> cres<ty::t>;
// Relates the type `v` to `a` and `b` such that `v` represents
// the LUB/GLB of `a` and `b` as appropriate.
fn relate_bound<'a>(&'a self, v: ty::t, a: ty::t, b: ty::t) -> cres<()>;
}
pub type LatticeOp<'a, T> =
|cf: CombineFields, a: &T, b: &T|: 'a -> cres<T>;
impl LatticeValue for ty::t {
fn sub(cf: CombineFields, a: &ty::t, b: &ty::t) -> ures {
Sub(cf).tys(*a, *b).to_ures()
impl<'a> LatticeDir for Lub<'a> {
fn ty_bot(&self, t: ty::t) -> cres<ty::t> {
Ok(t)
}
fn lub(cf: CombineFields, a: &ty::t, b: &ty::t) -> cres<ty::t> {
Lub(cf).tys(*a, *b)
}
fn glb(cf: CombineFields, a: &ty::t, b: &ty::t) -> cres<ty::t> {
Glb(cf).tys(*a, *b)
}
}
pub trait CombineFieldsLatticeMethods<T:LatticeValue, K:UnifyKey<Bounds<T>>> {
/// make variable a subtype of variable
fn var_sub_var(&self,
a_id: K,
b_id: K)
-> ures;
/// make variable a subtype of T
fn var_sub_t(&self,
a_id: K,
b: T)
-> ures;
/// make T a subtype of variable
fn t_sub_var(&self,
a: T,
b_id: K)
-> ures;
fn set_var_to_merged_bounds(&self,
v_id: K,
a: &Bounds<T>,
b: &Bounds<T>,
rank: uint)
-> ures;
}
pub trait CombineFieldsLatticeMethods2<T:LatticeValue> {
fn merge_bnd(&self,
a: &Bound<T>,
b: &Bound<T>,
lattice_op: LatticeOp<T>)
-> cres<Bound<T>>;
fn bnds(&self, a: &Bound<T>, b: &Bound<T>) -> ures;
}
impl<'f,T:LatticeValue, K:UnifyKey<Bounds<T>>>
CombineFieldsLatticeMethods<T,K> for CombineFields<'f>
{
fn var_sub_var(&self,
a_id: K,
b_id: K)
-> ures
{
/*!
* Make one variable a subtype of another variable. This is a
* subtle and tricky process, as described in detail at the
* top of infer.rs.
*/
let tcx = self.infcx.tcx;
let table = UnifyKey::unification_table(self.infcx);
// Need to make sub_id a subtype of sup_id.
let node_a = table.borrow_mut().get(tcx, a_id);
let node_b = table.borrow_mut().get(tcx, b_id);
let a_id = node_a.key.clone();
let b_id = node_b.key.clone();
let a_bounds = node_a.value.clone();
let b_bounds = node_b.value.clone();
debug!("vars({}={} <: {}={})",
a_id, a_bounds.repr(tcx),
b_id, b_bounds.repr(tcx));
if a_id == b_id { return Ok(()); }
// If both A's UB and B's LB have already been bound to types,
// see if we can make those types subtypes.
match (&a_bounds.ub, &b_bounds.lb) {
(&Some(ref a_ub), &Some(ref b_lb)) => {
let r = self.infcx.try(
|| LatticeValue::sub(self.clone(), a_ub, b_lb));
match r {
Ok(()) => {
return Ok(());
}
Err(_) => { /*fallthrough */ }
}
}
_ => { /*fallthrough*/ }
}
// Otherwise, we need to merge A and B so as to guarantee that
// A remains a subtype of B. Actually, there are other options,
// but that's the route we choose to take.
let (new_root, new_rank) =
table.borrow_mut().unify(tcx, &node_a, &node_b);
self.set_var_to_merged_bounds(new_root,
&a_bounds, &b_bounds,
new_rank)
}
/// make variable a subtype of T
fn var_sub_t(&self,
a_id: K,
b: T)
-> ures
{
/*!
* Make a variable (`a_id`) a subtype of the concrete type `b`.
*/
let tcx = self.infcx.tcx;
let table = UnifyKey::unification_table(self.infcx);
let node_a = table.borrow_mut().get(tcx, a_id);
let a_id = node_a.key.clone();
let a_bounds = &node_a.value;
let b_bounds = &Bounds { lb: None, ub: Some(b.clone()) };
debug!("var_sub_t({}={} <: {})",
a_id,
a_bounds.repr(self.infcx.tcx),
b.repr(self.infcx.tcx));
self.set_var_to_merged_bounds(
a_id, a_bounds, b_bounds, node_a.rank)
}
fn t_sub_var(&self,
a: T,
b_id: K)
-> ures
{
/*!
* Make a concrete type (`a`) a subtype of the variable `b_id`
*/
let tcx = self.infcx.tcx;
let table = UnifyKey::unification_table(self.infcx);
let a_bounds = &Bounds { lb: Some(a.clone()), ub: None };
let node_b = table.borrow_mut().get(tcx, b_id);
let b_id = node_b.key.clone();
let b_bounds = &node_b.value;
debug!("t_sub_var({} <: {}={})",
a.repr(self.infcx.tcx),
b_id,
b_bounds.repr(self.infcx.tcx));
self.set_var_to_merged_bounds(
b_id, a_bounds, b_bounds, node_b.rank)
}
fn set_var_to_merged_bounds(&self,
v_id: K,
a: &Bounds<T>,
b: &Bounds<T>,
rank: uint)
-> ures
{
/*!
* Updates the bounds for the variable `v_id` to be the intersection
* of `a` and `b`. That is, the new bounds for `v_id` will be
* a bounds c such that:
* c.ub <: a.ub
* c.ub <: b.ub
* a.lb <: c.lb
* b.lb <: c.lb
* If this cannot be achieved, the result is failure.
*/
// Think of the two diamonds, we want to find the
// intersection. There are basically four possibilities (you
// can swap A/B in these pictures):
//
// A A
// / \ / \
// / B \ / B \
// / / \ \ / / \ \
// * * * * * / * *
// \ \ / / \ / /
// \ B / / \ / /
// \ / * \ /
// A \ / A
// B
let tcx = self.infcx.tcx;
let table = UnifyKey::unification_table(self.infcx);
debug!("merge({},{},{})",
v_id,
a.repr(self.infcx.tcx),
b.repr(self.infcx.tcx));
// First, relate the lower/upper bounds of A and B.
// Note that these relations *must* hold for us
// to be able to merge A and B at all, and relating
// them explicitly gives the type inferencer more
// information and helps to produce tighter bounds
// when necessary.
let () = if_ok!(self.bnds(&a.lb, &b.ub));
let () = if_ok!(self.bnds(&b.lb, &a.ub));
let ub = if_ok!(self.merge_bnd(&a.ub, &b.ub, LatticeValue::glb));
let lb = if_ok!(self.merge_bnd(&a.lb, &b.lb, LatticeValue::lub));
let bounds = Bounds { lb: lb, ub: ub };
debug!("merge({}): bounds={}",
v_id,
bounds.repr(self.infcx.tcx));
// the new bounds must themselves
// be relatable:
let () = if_ok!(self.bnds(&bounds.lb, &bounds.ub));
table.borrow_mut().set(tcx, v_id, Root(bounds, rank));
fn relate_bound<'a>(&'a self, v: ty::t, a: ty::t, b: ty::t) -> cres<()> {
let sub = self.sub();
try!(sub.tys(a, v));
try!(sub.tys(b, v));
Ok(())
}
}
impl<'f,T:LatticeValue>
CombineFieldsLatticeMethods2<T> for CombineFields<'f>
{
fn merge_bnd(&self,
a: &Bound<T>,
b: &Bound<T>,
lattice_op: LatticeOp<T>)
-> cres<Bound<T>>
{
/*!
* Combines two bounds into a more general bound.
*/
debug!("merge_bnd({},{})",
a.repr(self.infcx.tcx),
b.repr(self.infcx.tcx));
match (a, b) {
(&None, &None) => Ok(None),
(&Some(_), &None) => Ok((*a).clone()),
(&None, &Some(_)) => Ok((*b).clone()),
(&Some(ref v_a), &Some(ref v_b)) => {
lattice_op(self.clone(), v_a, v_b).and_then(|v| Ok(Some(v)))
}
}
}
fn bnds(&self,
a: &Bound<T>,
b: &Bound<T>)
-> ures
{
debug!("bnds({} <: {})",
a.repr(self.infcx.tcx),
b.repr(self.infcx.tcx));
match (a, b) {
(&None, &None) |
(&Some(_), &None) |
(&None, &Some(_)) => {
Ok(())
}
(&Some(ref t_a), &Some(ref t_b)) => {
LatticeValue::sub(self.clone(), t_a, t_b)
}
}
}
}
// ______________________________________________________________________
// Lattice operations on variables
//
// This is common code used by both LUB and GLB to compute the LUB/GLB
// for pairs of variables or for variables and values.
pub trait LatticeDir {
fn combine_fields<'a>(&'a self) -> CombineFields<'a>;
fn bnd<T:Clone>(&self, b: &Bounds<T>) -> Option<T>;
fn with_bnd<T:Clone>(&self, b: &Bounds<T>, t: T) -> Bounds<T>;
}
pub trait TyLatticeDir {
fn ty_bot(&self, t: ty::t) -> cres<ty::t>;
}
impl<'f> LatticeDir for Lub<'f> {
fn combine_fields<'a>(&'a self) -> CombineFields<'a> { self.fields.clone() }
fn bnd<T:Clone>(&self, b: &Bounds<T>) -> Option<T> { b.ub.clone() }
fn with_bnd<T:Clone>(&self, b: &Bounds<T>, t: T) -> Bounds<T> {
Bounds { ub: Some(t), ..(*b).clone() }
}
}
impl<'f> TyLatticeDir for Lub<'f> {
fn ty_bot(&self, t: ty::t) -> cres<ty::t> {
Ok(t)
}
}
impl<'f> LatticeDir for Glb<'f> {
fn combine_fields<'a>(&'a self) -> CombineFields<'a> { self.fields.clone() }
fn bnd<T:Clone>(&self, b: &Bounds<T>) -> Option<T> { b.lb.clone() }
fn with_bnd<T:Clone>(&self, b: &Bounds<T>, t: T) -> Bounds<T> {
Bounds { lb: Some(t), ..(*b).clone() }
}
}
impl<'f> TyLatticeDir for Glb<'f> {
fn ty_bot(&self, _t: ty::t) -> cres<ty::t> {
impl<'a> LatticeDir for Glb<'a> {
fn ty_bot(&self, _: ty::t) -> cres<ty::t> {
Ok(ty::mk_bot())
}
fn relate_bound<'a>(&'a self, v: ty::t, a: ty::t, b: ty::t) -> cres<()> {
let sub = self.sub();
try!(sub.tys(v, a));
try!(sub.tys(v, b));
Ok(())
}
}
pub fn super_lattice_tys<L:LatticeDir+TyLatticeDir+Combine>(this: &L,
a: ty::t,
b: ty::t)
-> cres<ty::t> {
pub fn super_lattice_tys<L:LatticeDir+Combine>(this: &L,
a: ty::t,
b: ty::t)
-> cres<ty::t>
{
debug!("{}.lattice_tys({}, {})",
this.tag(),
a.repr(this.infcx().tcx),
@ -382,156 +91,27 @@ pub fn super_lattice_tys<L:LatticeDir+TyLatticeDir+Combine>(this: &L,
return Ok(a);
}
let tcx = this.infcx().tcx;
let infcx = this.infcx();
let a = infcx.type_variables.borrow().replace_if_possible(a);
let b = infcx.type_variables.borrow().replace_if_possible(b);
match (&ty::get(a).sty, &ty::get(b).sty) {
(&ty::ty_bot, _) => { return this.ty_bot(b); }
(_, &ty::ty_bot) => { return this.ty_bot(a); }
(&ty::ty_bot, _) => { this.ty_bot(b) }
(_, &ty::ty_bot) => { this.ty_bot(a) }
(&ty::ty_infer(TyVar(a_id)), &ty::ty_infer(TyVar(b_id))) => {
let r = if_ok!(lattice_vars(this, a_id, b_id,
|x, y| this.tys(*x, *y)));
return match r {
VarResult(v) => Ok(ty::mk_var(tcx, v)),
ValueResult(t) => Ok(t)
};
}
(&ty::ty_infer(TyVar(a_id)), _) => {
return lattice_var_and_t(this, a_id, &b,
|x, y| this.tys(*x, *y));
}
(_, &ty::ty_infer(TyVar(b_id))) => {
return lattice_var_and_t(this, b_id, &a,
|x, y| this.tys(*x, *y));
(&ty::ty_infer(TyVar(..)), _) |
(_, &ty::ty_infer(TyVar(..))) => {
let v = infcx.next_ty_var();
try!(this.relate_bound(v, a, b));
Ok(v)
}
_ => {
return super_tys(this, a, b);
super_tys(this, a, b)
}
}
}
pub type LatticeDirOp<'a, T> = |a: &T, b: &T|: 'a -> cres<T>;
#[deriving(Clone)]
pub enum LatticeVarResult<K,T> {
VarResult(K),
ValueResult(T)
}
/**
* Computes the LUB or GLB of two bounded variables. These could be any
* sort of variables, but in the comments on this function I'll assume
* we are doing an LUB on two type variables.
*
* This computation can be done in one of two ways:
*
* - If both variables have an upper bound, we may just compute the
* LUB of those bounds and return that, in which case we are
* returning a type. This is indicated with a `ValueResult` return.
*
* - If the variables do not both have an upper bound, we will unify
* the variables and return the unified variable, in which case the
* result is a variable. This is indicated with a `VarResult`
* return. */
pub fn lattice_vars<L:LatticeDir+Combine,
T:LatticeValue,
K:UnifyKey<Bounds<T>>>(
this: &L, // defines whether we want LUB or GLB
a_vid: K, // first variable
b_vid: K, // second variable
lattice_dir_op: LatticeDirOp<T>) // LUB or GLB operation on types
-> cres<LatticeVarResult<K,T>>
{
let tcx = this.infcx().tcx;
let table = UnifyKey::unification_table(this.infcx());
let node_a = table.borrow_mut().get(tcx, a_vid);
let node_b = table.borrow_mut().get(tcx, b_vid);
let a_vid = node_a.key.clone();
let b_vid = node_b.key.clone();
let a_bounds = &node_a.value;
let b_bounds = &node_b.value;
debug!("{}.lattice_vars({}={} <: {}={})",
this.tag(),
a_vid, a_bounds.repr(tcx),
b_vid, b_bounds.repr(tcx));
// Same variable: the easy case.
if a_vid == b_vid {
return Ok(VarResult(a_vid));
}
// If both A and B have an UB type, then we can just compute the
// LUB of those types:
let (a_bnd, b_bnd) = (this.bnd(a_bounds), this.bnd(b_bounds));
match (a_bnd, b_bnd) {
(Some(ref a_ty), Some(ref b_ty)) => {
match this.infcx().try(|| lattice_dir_op(a_ty, b_ty) ) {
Ok(t) => return Ok(ValueResult(t)),
Err(_) => { /*fallthrough */ }
}
}
_ => {/*fallthrough*/}
}
// Otherwise, we need to merge A and B into one variable. We can
// then use either variable as an upper bound:
let cf = this.combine_fields();
let () = try!(cf.var_sub_var(a_vid.clone(), b_vid.clone()));
Ok(VarResult(a_vid.clone()))
}
pub fn lattice_var_and_t<L:LatticeDir+Combine,
T:LatticeValue,
K:UnifyKey<Bounds<T>>>(
this: &L,
a_id: K,
b: &T,
lattice_dir_op: LatticeDirOp<T>)
-> cres<T>
{
let tcx = this.infcx().tcx;
let table = UnifyKey::unification_table(this.infcx());
let node_a = table.borrow_mut().get(tcx, a_id);
let a_id = node_a.key.clone();
let a_bounds = &node_a.value;
// The comments in this function are written for LUB, but they
// apply equally well to GLB if you inverse upper/lower/sub/super/etc.
debug!("{}.lattice_var_and_t({}={} <: {})",
this.tag(),
a_id,
a_bounds.repr(this.infcx().tcx),
b.repr(this.infcx().tcx));
match this.bnd(a_bounds) {
Some(ref a_bnd) => {
// If a has an upper bound, return the LUB(a.ub, b)
debug!("bnd=Some({})", a_bnd.repr(this.infcx().tcx));
lattice_dir_op(a_bnd, b)
}
None => {
// If a does not have an upper bound, make b the upper bound of a
// and then return b.
debug!("bnd=None");
let a_bounds = this.with_bnd(a_bounds, (*b).clone());
let () = try!(this.combine_fields().bnds(&a_bounds.lb,
&a_bounds.ub));
table.borrow_mut().set(tcx,
a_id.clone(),
Root(a_bounds.clone(), node_a.rank));
Ok((*b).clone())
}
}
}
// ___________________________________________________________________________
///////////////////////////////////////////////////////////////////////////
// Random utility functions used by LUB/GLB when computing LUB/GLB of
// fn types

23
src/librustc/middle/typeck/infer/lub.rs
View File

@ -11,8 +11,8 @@
use middle::ty::{BuiltinBounds};
use middle::ty::RegionVid;
use middle::ty;
use middle::typeck::infer::then;
use middle::typeck::infer::combine::*;
use middle::typeck::infer::equate::Equate;
use middle::typeck::infer::glb::Glb;
use middle::typeck::infer::lattice::*;
use middle::typeck::infer::sub::Sub;
@ -30,7 +30,7 @@ use util::ppaux::Repr;
/// "Least upper bound" (common supertype)
pub struct Lub<'f> {
pub fields: CombineFields<'f>
fields: CombineFields<'f>
}
#[allow(non_snake_case_functions)]
@ -44,6 +44,7 @@ impl<'f> Combine for Lub<'f> {
fn a_is_expected(&self) -> bool { self.fields.a_is_expected }
fn trace(&self) -> TypeTrace { self.fields.trace.clone() }
fn equate<'a>(&'a self) -> Equate<'a> { Equate(self.fields.clone()) }
fn sub<'a>(&'a self) -> Sub<'a> { Sub(self.fields.clone()) }
fn lub<'a>(&'a self) -> Lub<'a> { Lub(self.fields.clone()) }
fn glb<'a>(&'a self) -> Glb<'a> { Glb(self.fields.clone()) }
@ -62,17 +63,15 @@ impl<'f> Combine for Lub<'f> {
let m = a.mutbl;
match m {
MutImmutable => {
self.tys(a.ty, b.ty).and_then(|t| Ok(ty::mt {ty: t, mutbl: m}) )
}
MutImmutable => {
let t = try!(self.tys(a.ty, b.ty));
Ok(ty::mt {ty: t, mutbl: m})
}
MutMutable => {
self.fields.infcx.try(|| {
eq_tys(self, a.ty, b.ty).then(|| {
Ok(ty::mt {ty: a.ty, mutbl: m})
})
}).or_else(|e| Err(e))
}
MutMutable => {
let t = try!(self.equate().tys(a.ty, b.ty));
Ok(ty::mt {ty: t, mutbl: m})
}
}
}

53
src/librustc/middle/typeck/infer/mod.rs
View File

@ -29,13 +29,14 @@ use middle::ty_fold;
use middle::ty_fold::TypeFolder;
use middle::typeck::check::regionmanip::replace_late_bound_regions_in_fn_sig;
use middle::typeck::infer::coercion::Coerce;
use middle::typeck::infer::combine::{Combine, CombineFields, eq_tys};
use middle::typeck::infer::region_inference::{RegionSnapshot};
use middle::typeck::infer::region_inference::{RegionVarBindings};
use middle::typeck::infer::combine::{Combine, CombineFields};
use middle::typeck::infer::region_inference::{RegionVarBindings,
RegionSnapshot};
use middle::typeck::infer::resolve::{resolver};
use middle::typeck::infer::equate::Equate;
use middle::typeck::infer::sub::Sub;
use middle::typeck::infer::lub::Lub;
use middle::typeck::infer::unify::{UnificationTable, Snapshot};
use middle::typeck::infer::unify::{UnificationTable};
use middle::typeck::infer::error_reporting::ErrorReporting;
use std::cell::{RefCell};
use std::collections::HashMap;
@ -46,19 +47,20 @@ use syntax::codemap::Span;
use util::common::indent;
use util::ppaux::{bound_region_to_string, ty_to_string, trait_ref_to_string, Repr};
pub mod doc;
pub mod macros;
pub mod coercion;
pub mod combine;
pub mod doc;
pub mod equate;
pub mod error_reporting;
pub mod glb;
pub mod lattice;
pub mod lub;
pub mod region_inference;
pub mod resolve;
pub mod sub;
pub mod unify;
pub mod coercion;
pub mod error_reporting;
pub mod test;
pub mod type_variable;
pub mod unify;
pub type Bound<T> = Option<T>;
@ -79,8 +81,7 @@ pub struct InferCtxt<'a> {
// We instantiate UnificationTable with bounds<ty::t> because the
// types that might instantiate a general type variable have an
// order, represented by its upper and lower bounds.
type_unification_table:
RefCell<UnificationTable<ty::TyVid, Bounds<ty::t>>>,
type_variables: RefCell<type_variable::TypeVariableTable>,
// Map from integral variable to the kind of integer it represents
int_unification_table:
@ -293,7 +294,7 @@ pub fn fixup_err_to_string(f: fixup_err) -> String {
pub fn new_infer_ctxt<'a>(tcx: &'a ty::ctxt) -> InferCtxt<'a> {
InferCtxt {
tcx: tcx,
type_unification_table: RefCell::new(UnificationTable::new()),
type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
int_unification_table: RefCell::new(UnificationTable::new()),
float_unification_table: RefCell::new(UnificationTable::new()),
region_vars: RegionVarBindings::new(tcx),
@ -395,8 +396,8 @@ pub fn mk_eqty(cx: &InferCtxt,
origin: origin,
values: Types(expected_found(a_is_expected, a, b))
};
let suber = cx.sub(a_is_expected, trace);
eq_tys(&suber, a, b)
try!(cx.equate(a_is_expected, trace).tys(a, b));
Ok(())
})
}
@ -511,9 +512,9 @@ pub fn uok() -> ures {
}
pub struct CombinedSnapshot {
type_snapshot: Snapshot<ty::TyVid>,
int_snapshot: Snapshot<ty::IntVid>,
float_snapshot: Snapshot<ty::FloatVid>,
type_snapshot: type_variable::Snapshot,
int_snapshot: unify::Snapshot<ty::IntVid>,
float_snapshot: unify::Snapshot<ty::FloatVid>,
region_vars_snapshot: RegionSnapshot,
}
@ -525,6 +526,10 @@ impl<'a> InferCtxt<'a> {
trace: trace}
}
pub fn equate<'a>(&'a self, a_is_expected: bool, trace: TypeTrace) -> Equate<'a> {
Equate(self.combine_fields(a_is_expected, trace))
}
pub fn sub<'a>(&'a self, a_is_expected: bool, trace: TypeTrace) -> Sub<'a> {
Sub(self.combine_fields(a_is_expected, trace))
}
@ -533,13 +538,9 @@ impl<'a> InferCtxt<'a> {
Lub(self.combine_fields(a_is_expected, trace))
}
pub fn in_snapshot(&self) -> bool {
self.region_vars.in_snapshot()
}
fn start_snapshot(&self) -> CombinedSnapshot {
CombinedSnapshot {
type_snapshot: self.type_unification_table.borrow_mut().snapshot(),
type_snapshot: self.type_variables.borrow_mut().snapshot(),
int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
region_vars_snapshot: self.region_vars.start_snapshot(),
@ -553,7 +554,7 @@ impl<'a> InferCtxt<'a> {
float_snapshot,
region_vars_snapshot } = snapshot;
self.type_unification_table
self.type_variables
.borrow_mut()
.rollback_to(type_snapshot);
self.int_unification_table
@ -573,7 +574,7 @@ impl<'a> InferCtxt<'a> {
float_snapshot,
region_vars_snapshot } = snapshot;
self.type_unification_table
self.type_variables
.borrow_mut()
.commit(type_snapshot);
self.int_unification_table
@ -636,9 +637,9 @@ impl<'a> InferCtxt<'a> {
impl<'a> InferCtxt<'a> {
pub fn next_ty_var_id(&self) -> TyVid {
self.type_unification_table
self.type_variables
.borrow_mut()
.new_key(Bounds { lb: None, ub: None })
.new_var()
}
pub fn next_ty_var(&self) -> ty::t {

14
src/librustc/middle/typeck/infer/region_inference/mod.rs
View File

@ -234,7 +234,7 @@ impl<'a> RegionVarBindings<'a> {
}
}
pub fn in_snapshot(&self) -> bool {
fn in_snapshot(&self) -> bool {
self.undo_log.borrow().len() > 0
}
@ -406,6 +406,18 @@ impl<'a> RegionVarBindings<'a> {
}
}
pub fn make_eqregion(&self,
origin: SubregionOrigin,
sub: Region,
sup: Region) {
if sub != sup {
// Eventually, it would be nice to add direct support for
// equating regions.
self.make_subregion(origin.clone(), sub, sup);
self.make_subregion(origin, sup, sub);
}
}
pub fn make_subregion(&self,
origin: SubregionOrigin,
sub: Region,

34
src/librustc/middle/typeck/infer/resolve.rs
View File

@ -48,12 +48,11 @@
use middle::ty::{FloatVar, FloatVid, IntVar, IntVid, RegionVid, TyVar, TyVid};
use middle::ty::{type_is_bot, IntType, UintType};
use middle::ty::{IntType, UintType};
use middle::ty;
use middle::ty_fold;
use middle::typeck::infer::{Bounds, cyclic_ty, fixup_err, fres, InferCtxt};
use middle::typeck::infer::{unresolved_float_ty, unresolved_int_ty};
use middle::typeck::infer::{unresolved_ty};
use middle::typeck::infer::{cyclic_ty, fixup_err, fres, InferCtxt};
use middle::typeck::infer::{unresolved_int_ty,unresolved_float_ty,unresolved_ty};
use syntax::codemap::Span;
use util::common::indent;
use util::ppaux::{Repr, ty_to_string};
@ -132,8 +131,8 @@ impl<'a> ResolveState<'a> {
assert!(self.v_seen.is_empty());
match self.err {
None => {
debug!("Resolved to {} + {} (modes={:x})",
ty_to_string(self.infcx.tcx, rty),
debug!("Resolved {} to {} (modes={:x})",
ty_to_string(self.infcx.tcx, typ),
ty_to_string(self.infcx.tcx, rty),
self.modes);
return Ok(rty);
@ -219,21 +218,16 @@ impl<'a> ResolveState<'a> {
// tend to carry more restrictions or higher
// perf. penalties, so it pays to know more.
let node =
self.infcx.type_unification_table.borrow_mut().get(tcx, vid);
let t1 = match node.value {
Bounds { ub:_, lb:Some(t) } if !type_is_bot(t) => {
self.resolve_type(t)
}
Bounds { ub:Some(t), lb:_ } | Bounds { ub:_, lb:Some(t) } => {
self.resolve_type(t)
}
Bounds { ub:None, lb:None } => {
if self.should(force_tvar) {
self.err = Some(unresolved_ty(vid));
let t1 = match self.infcx.type_variables.borrow().probe(vid) {
Some(t) => {
self.resolve_type(t)
}
None => {
if self.should(force_tvar) {
self.err = Some(unresolved_ty(vid));
}
ty::mk_var(tcx, vid)
}
ty::mk_var(tcx, vid)
}
};
self.v_seen.pop().unwrap();
return t1;

61
src/librustc/middle/typeck/infer/sub.rs
View File

@ -15,12 +15,12 @@ use middle::ty::TyVar;
use middle::typeck::check::regionmanip::replace_late_bound_regions_in_fn_sig;
use middle::typeck::infer::combine::*;
use middle::typeck::infer::{cres, CresCompare};
use middle::typeck::infer::equate::Equate;
use middle::typeck::infer::glb::Glb;
use middle::typeck::infer::InferCtxt;
use middle::typeck::infer::lattice::CombineFieldsLatticeMethods;
use middle::typeck::infer::lub::Lub;
use middle::typeck::infer::then;
use middle::typeck::infer::{TypeTrace, Subtype};
use middle::typeck::infer::type_variable::{SubtypeOf, SupertypeOf};
use util::common::{indenter};
use util::ppaux::{bound_region_to_string, Repr};
@ -43,27 +43,23 @@ impl<'f> Combine for Sub<'f> {
fn a_is_expected(&self) -> bool { self.fields.a_is_expected }
fn trace(&self) -> TypeTrace { self.fields.trace.clone() }
fn equate<'a>(&'a self) -> Equate<'a> { Equate(self.fields.clone()) }
fn sub<'a>(&'a self) -> Sub<'a> { Sub(self.fields.clone()) }
fn lub<'a>(&'a self) -> Lub<'a> { Lub(self.fields.clone()) }
fn glb<'a>(&'a self) -> Glb<'a> { Glb(self.fields.clone()) }
fn contratys(&self, a: ty::t, b: ty::t) -> cres<ty::t> {
let opp = CombineFields {
a_is_expected: !self.fields.a_is_expected,
..self.fields.clone()
};
Sub(opp).tys(b, a)
Sub(self.fields.switch_expected()).tys(b, a)
}
fn contraregions(&self, a: ty::Region, b: ty::Region)
-> cres<ty::Region>
{
let opp = CombineFields {
a_is_expected: !self.fields.a_is_expected,
..self.fields.clone()
};
Sub(opp).regions(b, a)
}
-> cres<ty::Region> {
let opp = CombineFields {
a_is_expected: !self.fields.a_is_expected,
..self.fields.clone()
};
Sub(opp).regions(b, a)
}
fn regions(&self, a: ty::Region, b: ty::Region) -> cres<ty::Region> {
debug!("{}.regions({}, {})",
@ -84,16 +80,18 @@ impl<'f> Combine for Sub<'f> {
}
match b.mutbl {
MutMutable => {
// If supertype is mut, subtype must match exactly
// (i.e., invariant if mut):
eq_tys(self, a.ty, b.ty).then(|| Ok(*a))
}
MutImmutable => {
// Otherwise we can be covariant:
self.tys(a.ty, b.ty).and_then(|_t| Ok(*a) )
}
MutMutable => {
// If supertype is mut, subtype must match exactly
// (i.e., invariant if mut):
try!(self.equate().tys(a.ty, b.ty));
}
MutImmutable => {
// Otherwise we can be covariant:
try!(self.tys(a.ty, b.ty));
}
}
Ok(*a) // return is meaningless in sub, just return *a
}
fn fn_styles(&self, a: FnStyle, b: FnStyle) -> cres<FnStyle> {
@ -126,14 +124,19 @@ impl<'f> Combine for Sub<'f> {
debug!("{}.tys({}, {})", self.tag(),
a.repr(self.fields.infcx.tcx), b.repr(self.fields.infcx.tcx));
if a == b { return Ok(a); }
let _indenter = indenter();
let infcx = self.fields.infcx;
let a = infcx.type_variables.borrow().replace_if_possible(a);
let b = infcx.type_variables.borrow().replace_if_possible(b);
match (&ty::get(a).sty, &ty::get(b).sty) {
(&ty::ty_bot, _) => {
Ok(a)
}
(&ty::ty_infer(TyVar(a_id)), &ty::ty_infer(TyVar(b_id))) => {
if_ok!(self.fields.var_sub_var(a_id, b_id));
infcx.type_variables
.borrow_mut()
.relate_vars(a_id, SubtypeOf, b_id);
Ok(a)
}
// The vec/str check here and below is so that we don't unify
@ -145,7 +148,9 @@ impl<'f> Combine for Sub<'f> {
Err(ty::terr_sorts(expected_found(self, a, b)))
}
(&ty::ty_infer(TyVar(a_id)), _) => {
if_ok!(self.fields.var_sub_t(a_id, b));
try!(self.fields
.switch_expected()
.instantiate(b, SupertypeOf, a_id));
Ok(a)
}
@ -154,7 +159,7 @@ impl<'f> Combine for Sub<'f> {
Err(ty::terr_sorts(expected_found(self, a, b)))
}
(_, &ty::ty_infer(TyVar(b_id))) => {
if_ok!(self.fields.t_sub_var(a, b_id));
try!(self.fields.instantiate(a, SubtypeOf, b_id));
Ok(a)
}

173
src/librustc/middle/typeck/infer/type_variable.rs Normal file
View File

@ -0,0 +1,173 @@
// 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.
use middle::ty;
use std::mem;
use util::snapshot_vec as sv;
pub struct TypeVariableTable {
values: sv::SnapshotVec<TypeVariableData,UndoEntry,Delegate>,
}
struct TypeVariableData {
value: TypeVariableValue
}
enum TypeVariableValue {
Known(ty::t),
Bounded(Vec<Relation>),
}
pub struct Snapshot {
snapshot: sv::Snapshot
}
enum UndoEntry {
// The type of the var was specified.
SpecifyVar(ty::TyVid, Vec<Relation>),
Relate(ty::TyVid, ty::TyVid),
}
struct Delegate;
type Relation = (RelationDir, ty::TyVid);
#[deriving(PartialEq,Show)]
pub enum RelationDir {
SubtypeOf, SupertypeOf, EqTo
}
impl RelationDir {
fn opposite(self) -> RelationDir {
match self {
SubtypeOf => SupertypeOf,
SupertypeOf => SubtypeOf,
EqTo => EqTo
}
}
}
impl TypeVariableTable {
pub fn new() -> TypeVariableTable {
TypeVariableTable { values: sv::SnapshotVec::new(Delegate) }
}
fn relations<'a>(&'a mut self, a: ty::TyVid) -> &'a mut Vec<Relation> {
relations(self.values.get_mut(a.index))
}
pub fn relate_vars(&mut self, a: ty::TyVid, dir: RelationDir, b: ty::TyVid) {
/*!
* Records that `a <: b`, `a :> b`, or `a == b`, depending on `dir`.
*
* Precondition: neither `a` nor `b` are known.
*/
if a != b {
self.relations(a).push((dir, b));
self.relations(b).push((dir.opposite(), a));
self.values.record(Relate(a, b));
}
}
pub fn instantiate_and_push(
&mut self,
vid: ty::TyVid,
ty: ty::t,
stack: &mut Vec<(ty::t, RelationDir, ty::TyVid)>)
{
/*!
* Instantiates `vid` with the type `ty` and then pushes an
* entry onto `stack` for each of the relations of `vid` to
* other variables. The relations will have the form `(ty,
* dir, vid1)` where `vid1` is some other variable id.
*/
let old_value = {
let value_ptr = &mut self.values.get_mut(vid.index).value;
mem::replace(value_ptr, Known(ty))
};
let relations = match old_value {
Bounded(b) => b,
Known(_) => fail!("Asked to instantiate variable that is \
already instantiated")
};
for &(dir, vid) in relations.iter() {
stack.push((ty, dir, vid));
}
self.values.record(SpecifyVar(vid, relations));
}
pub fn new_var(&mut self) -> ty::TyVid {
let index =
self.values.push(
TypeVariableData { value: Bounded(Vec::new()) });
ty::TyVid { index: index }
}
pub fn probe(&self, vid: ty::TyVid) -> Option<ty::t> {
match self.values.get(vid.index).value {
Bounded(..) => None,
Known(t) => Some(t)
}
}
pub fn replace_if_possible(&self, t: ty::t) -> ty::t {
match ty::get(t).sty {
ty::ty_infer(ty::TyVar(v)) => {
match self.probe(v) {
None => t,
Some(u) => u
}
}
_ => t,
}
}
pub fn snapshot(&mut self) -> Snapshot {
Snapshot { snapshot: self.values.start_snapshot() }
}
pub fn rollback_to(&mut self, s: Snapshot) {
self.values.rollback_to(s.snapshot);
}
pub fn commit(&mut self, s: Snapshot) {
self.values.commit(s.snapshot);
}
}
impl sv::SnapshotVecDelegate<TypeVariableData,UndoEntry> for Delegate {
fn reverse(&mut self,
values: &mut Vec<TypeVariableData>,
action: UndoEntry) {
match action {
SpecifyVar(vid, relations) => {
values.get_mut(vid.index).value = Bounded(relations);
}
Relate(a, b) => {
relations(values.get_mut(a.index)).pop();
relations(values.get_mut(b.index)).pop();
}
}
}
}
fn relations<'a>(v: &'a mut TypeVariableData) -> &'a mut Vec<Relation> {
match v.value {
Known(_) => fail!("var_sub_var: variable is known"),
Bounded(ref mut relations) => relations
}
}

45
src/librustc/middle/typeck/infer/unify.rs
View File

@ -12,7 +12,7 @@ use std::kinds::marker;
use middle::ty::{expected_found, IntVarValue};
use middle::ty;
use middle::typeck::infer::{Bounds, uok, ures};
use middle::typeck::infer::{uok, ures};
use middle::typeck::infer::InferCtxt;
use std::cell::RefCell;
use std::fmt::Show;
@ -23,12 +23,12 @@ use util::snapshot_vec as sv;
/**
* This trait is implemented by any type that can serve as a type
* variable. We call such variables *unification keys*. For example,
* this trait is implemented by `TyVid`, which represents normal
* type variables, and `IntVid`, which represents integral variables.
* this trait is implemented by `IntVid`, which represents integral
* variables.
*
* Each key type has an associated value type `V`. For example,
* for `TyVid`, this is `Bounds<ty::t>`, representing a pair of
* upper- and lower-bound types.
* Each key type has an associated value type `V`. For example, for
* `IntVid`, this is `Option<IntVarValue>`, representing some
* (possibly not yet known) sort of integer.
*
* Implementations of this trait are at the end of this file.
*/
@ -48,11 +48,10 @@ pub trait UnifyKey<V> : Clone + Show + PartialEq + Repr {
}
/**
* Trait for valid types that a type variable can be set to. Note
* that this is typically not the end type that the value will
* take on, but rather some wrapper: for example, for normal type
* variables, the associated type is not `ty::t` but rather
* `Bounds<ty::t>`.
* Trait for valid types that a type variable can be set to. Note that
* this is typically not the end type that the value will take on, but
* rather an `Option` wrapper (where `None` represents a variable
* whose value is not yet set).
*
* Implementations of this trait are at the end of this file.
*/
@ -109,9 +108,9 @@ pub struct Node<K,V> {
pub struct Delegate;
// We can't use V:LatticeValue, much as I would like to,
// because frequently the pattern is that V=Bounds<U> for some
// because frequently the pattern is that V=Option<U> for some
// other type parameter U, and we have no way to say
// Bounds<U>:
// Option<U>:LatticeValue.
impl<V:PartialEq+Clone+Repr,K:UnifyKey<V>> UnificationTable<K,V> {
pub fn new() -> UnificationTable<K,V> {
@ -375,26 +374,6 @@ impl<'tcx,V:SimplyUnifiable,K:UnifyKey<Option<V>>>
///////////////////////////////////////////////////////////////////////////
// General type keys
impl UnifyKey<Bounds<ty::t>> for ty::TyVid {
fn index(&self) -> uint { self.index }
fn from_index(i: uint) -> ty::TyVid { ty::TyVid { index: i } }
fn unification_table<'v>(infcx: &'v InferCtxt)
-> &'v RefCell<UnificationTable<ty::TyVid, Bounds<ty::t>>>
{
return &infcx.type_unification_table;
}
fn tag(_: Option<ty::TyVid>) -> &'static str {
"TyVid"
}
}
impl UnifyValue for Bounds<ty::t> { }
// Integral type keys
impl UnifyKey<Option<IntVarValue>> for ty::IntVid {

2
src/test/compile-fail/issue-10291.rs
View File

@ -9,7 +9,7 @@
// except according to those terms.
fn test<'x>(x: &'x int) {
drop::< <'z>|&'z int| -> &'z int>(|z| {
drop::< <'z>|&'z int| -> &'z int >(|z| {
x
//~^ ERROR cannot infer an appropriate lifetime
});

2
src/test/compile-fail/issue-13482.rs
View File

@ -12,7 +12,7 @@ fn main() {
let x = [1,2];
let y = match x {
[] => None,
//~^ ERROR expected `[<generic integer #1>, .. 2]`, found a fixed vector pattern of size 0
//~^ ERROR expected `[<generic integer #0>, .. 2]`, found a fixed vector pattern of size 0
[a,_] => Some(a)
};
}

2
src/test/compile-fail/issue-16338.rs
View File

@ -12,6 +12,6 @@ use std::raw::Slice;
fn main() {
let Slice { data: data, len: len } = "foo";
//~^ ERROR mismatched types: expected `&'static str`, found a structure pattern
//~^ ERROR mismatched types: expected `&str`, found a structure pattern
}

2
src/test/compile-fail/issue-2149.rs
View File

@ -22,5 +22,5 @@ impl<A> vec_monad<A> for Vec<A> {
}
fn main() {
["hi"].bind(|x| [x] );
//~^ ERROR type `[&'static str, .. 1]` does not implement any method in scope named `bind`
//~^ ERROR type `[&str, .. 1]` does not implement any method in scope named `bind`
}

44
src/test/compile-fail/kindck-send-object1.rs Normal file
View File

@ -0,0 +1,44 @@
// 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.
// Test which object types are considered sendable. This test
// is broken into two parts because some errors occur in distinct
// phases in the compiler. See kindck-send-object2.rs as well!
fn assert_send<T:Send>() { }
trait Dummy { }
// careful with object types, who knows what they close over...
fn test51<'a>() {
assert_send::<&'a Dummy>(); //~ ERROR does not fulfill the required lifetime
}
fn test52<'a>() {
assert_send::<&'a Dummy+Send>(); //~ ERROR does not fulfill the required lifetime
}
// ...unless they are properly bounded
fn test60() {
assert_send::<&'static Dummy+Send>();
}
fn test61() {
assert_send::<Box<Dummy+Send>>();
}
// closure and object types can have lifetime bounds which make
// them not ok
fn test_70<'a>() {
assert_send::<proc():'a>(); //~ ERROR does not fulfill the required lifetime
}
fn test_71<'a>() {
assert_send::<Box<Dummy+'a>>(); //~ ERROR does not fulfill the required lifetime
}
fn main() { }

32
src/test/compile-fail/kindck-send-object2.rs Normal file
View File

@ -0,0 +1,32 @@
// 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.
// Continue kindck-send-object1.rs.
fn assert_send<T:Send>() { }
trait Dummy { }
fn test50() {
assert_send::<&'static Dummy>(); //~ ERROR does not fulfill `Send`
}
fn test53() {
assert_send::<Box<Dummy>>(); //~ ERROR does not fulfill `Send`
}
// ...unless they are properly bounded
fn test60() {
assert_send::<&'static Dummy+Send>();
}
fn test61() {
assert_send::<Box<Dummy+Send>>();
}
fn main() { }

25
src/test/compile-fail/kindck-send-owned.rs Normal file
View File

@ -0,0 +1,25 @@
// 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.
// Test which of the builtin types are considered sendable.
fn assert_send<T:Send>() { }
// owned content are ok
fn test30() { assert_send::<Box<int>>(); }
fn test31() { assert_send::<String>(); }
fn test32() { assert_send::<Vec<int> >(); }
// but not if they own a bad thing
fn test40<'a>(_: &'a int) {
assert_send::<Box<&'a int>>(); //~ ERROR does not fulfill the required lifetime
}
fn main() { }

34
src/test/compile-fail/kindck-send-region-pointers.rs Normal file
View File

@ -0,0 +1,34 @@
// 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.
// Test that borrowed pointers are not sendable unless 'static.
fn assert_send<T:Send>() { }
// lifetime pointers with 'static lifetime are ok
fn test01() { assert_send::<&'static int>(); }
fn test02() { assert_send::<&'static str>(); }
fn test03() { assert_send::<&'static [int]>(); }
// whether or not they are mutable
fn test10() { assert_send::<&'static mut int>(); }
// otherwise lifetime pointers are not ok
fn test20<'a>(_: &'a int) {
assert_send::<&'a int>(); //~ ERROR does not fulfill the required lifetime
}
fn test21<'a>(_: &'a int) {
assert_send::<&'a str>(); //~ ERROR does not fulfill the required lifetime
}
fn test22<'a>(_: &'a int) {
assert_send::<&'a [int]>(); //~ ERROR does not fulfill the required lifetime
}
fn main() { }

22
src/librustc/middle/typeck/infer/macros.rs → src/test/compile-fail/kindck-send-unsafe.rs
View File

@ -1,4 +1,4 @@
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// 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.
//
@ -8,13 +8,15 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![macro_escape]
fn assert_send<T:Send>() { }
macro_rules! if_ok(
($inp: expr) => (
match $inp {
Ok(v) => { v }
Err(e) => { return Err(e); }
}
)
)
// unsafe ptrs are ok unless they point at unsendable things
fn test70() {
assert_send::<*mut int>();
}
fn test71<'a>() {
assert_send::<*mut &'a int>(); //~ ERROR does not fulfill the required lifetime
}
fn main() {
}

2
src/test/compile-fail/regions-bounds.rs
View File

@ -17,12 +17,10 @@ struct a_class<'a> { x:&'a int }
fn a_fn1<'a,'b>(e: an_enum<'a>) -> an_enum<'b> {
return e; //~ ERROR mismatched types: expected `an_enum<'b>`, found `an_enum<'a>`
//~^ ERROR cannot infer
}
fn a_fn3<'a,'b>(e: a_class<'a>) -> a_class<'b> {
return e; //~ ERROR mismatched types: expected `a_class<'b>`, found `a_class<'a>`
//~^ ERROR cannot infer
}
fn main() { }

3
src/test/compile-fail/regions-escape-bound-fn-2.rs
View File

@ -15,7 +15,6 @@ fn with_int(f: |x: &int|) {
fn main() {
let mut x = None;
//~^ ERROR lifetime of variable does not enclose its declaration
//~^^ ERROR type of expression contains references that are not valid during the expression
with_int(|y| x = Some(y));
//~^ ERROR cannot infer
}

4
src/test/compile-fail/regions-escape-bound-fn.rs
View File

@ -14,6 +14,6 @@ fn with_int(f: |x: &int|) {
}
fn main() {
let mut x: Option<&int> = None; //~ ERROR cannot infer
with_int(|y| x = Some(y));
let mut x: Option<&int> = None;
with_int(|y| x = Some(y)); //~ ERROR cannot infer
}

2
src/test/compile-fail/regions-escape-via-trait-or-not.rs
View File

@ -27,7 +27,7 @@ fn with<R:Deref>(f: |x: &int| -> R) -> int {
}
fn return_it() -> int {
with(|o| o) //~ ERROR cannot infer an appropriate lifetime
with(|o| o) //~ ERROR cannot infer
}
fn main() {

1
src/test/compile-fail/regions-infer-at-fn-not-param.rs
View File

@ -22,7 +22,6 @@ struct not_parameterized2 {
fn take1<'a>(p: parameterized1) -> parameterized1<'a> { p }
//~^ ERROR mismatched types
//~^^ ERROR cannot infer
fn take3(p: not_parameterized1) -> not_parameterized1 { p }
fn take4(p: not_parameterized2) -> not_parameterized2 { p }

1
src/test/compile-fail/regions-infer-contravariance-due-to-decl.rs
View File

@ -33,7 +33,6 @@ fn use_<'short,'long>(c: Contravariant<'short>,
// covariant with respect to its parameter 'a.
let _: Contravariant<'long> = c; //~ ERROR mismatched types
//~^ ERROR cannot infer an appropriate lifetime
}
fn main() {}

1
src/test/compile-fail/regions-infer-covariance-due-to-decl.rs
View File

@ -30,7 +30,6 @@ fn use_<'short,'long>(c: Covariant<'long>,
// contravariant with respect to its parameter 'a.
let _: Covariant<'short> = c; //~ ERROR mismatched types
//~^ ERROR cannot infer an appropriate lifetime
}
fn main() {}

2
src/test/compile-fail/regions-infer-not-param.rs
View File

@ -23,11 +23,9 @@ struct indirect2<'a> {
}
fn take_direct<'a,'b>(p: direct<'a>) -> direct<'b> { p } //~ ERROR mismatched types
//~^ ERROR cannot infer
fn take_indirect1(p: indirect1) -> indirect1 { p }
fn take_indirect2<'a,'b>(p: indirect2<'a>) -> indirect2<'b> { p } //~ ERROR mismatched types
//~^ ERROR cannot infer
fn main() {}

9
src/test/compile-fail/regions-infer-paramd-indirect.rs
View File

@ -22,18 +22,17 @@ struct c<'a> {
}
trait set_f<'a> {
fn set_f_ok(&self, b: Gc<b<'a>>);
fn set_f_bad(&self, b: Gc<b>);
fn set_f_ok(&mut self, b: Gc<b<'a>>);
fn set_f_bad(&mut self, b: Gc<b>);
}
impl<'a> set_f<'a> for c<'a> {
fn set_f_ok(&self, b: Gc<b<'a>>) {
fn set_f_ok(&mut self, b: Gc<b<'a>>) {
self.f = b;
}
fn set_f_bad(&self, b: Gc<b>) {
fn set_f_bad(&mut self, b: Gc<b>) {
self.f = b; //~ ERROR mismatched types: expected `Gc<Gc<&'a int>>`, found `Gc<Gc<&int>>`
//~^ ERROR cannot infer
}
}

2
src/test/compile-fail/regions-reborrow-from-shorter-mut-ref-mut-ref.rs
View File

@ -11,7 +11,7 @@
// Issue #8624. Test for reborrowing with 3 levels, not just two.
fn copy_borrowed_ptr<'a, 'b, 'c>(p: &'a mut &'b mut &'c mut int) -> &'b mut int {
&mut ***p //~ ERROR lifetime of `p` is too short to guarantee its contents
&mut ***p //~ ERROR cannot infer
}
fn main() {

2
src/test/compile-fail/regions-ret-borrowed-1.rs
View File

@ -19,8 +19,6 @@ fn with<R>(f: <'a>|x: &'a int| -> R) -> R {
fn return_it<'a>() -> &'a int {
with(|o| o)
//~^ ERROR cannot infer
//~^^ ERROR not valid during the expression
//~^^^ ERROR not valid at this point
}
fn main() {

2
src/test/compile-fail/regions-ret-borrowed.rs
View File

@ -22,8 +22,6 @@ fn with<R>(f: |x: &int| -> R) -> R {
fn return_it<'a>() -> &'a int {
with(|o| o)
//~^ ERROR cannot infer
//~^^ ERROR not valid during the expression
//~^^^ ERROR not valid at this point
}
fn main() {

1
src/test/compile-fail/regions-variance-contravariant-use-covariant-in-second-position.rs
View File

@ -33,7 +33,6 @@ fn use_<'short,'long>(c: S<'long, 'short>,
// covariant with respect to its parameter 'a.
let _: S<'long, 'long> = c; //~ ERROR mismatched types
//~^ ERROR cannot infer an appropriate lifetime
}
fn main() {}

1
src/test/compile-fail/regions-variance-contravariant-use-covariant.rs
View File

@ -31,7 +31,6 @@ fn use_<'short,'long>(c: Contravariant<'short>,
// covariant with respect to its parameter 'a.
let _: Contravariant<'long> = c; //~ ERROR mismatched types
//~^ ERROR cannot infer an appropriate lifetime
}
fn main() {}

1
src/test/compile-fail/regions-variance-covariant-use-contravariant.rs
View File

@ -31,7 +31,6 @@ fn use_<'short,'long>(c: Covariant<'long>,
// contravariant with respect to its parameter 'a.
let _: Covariant<'short> = c; //~ ERROR mismatched types
//~^ ERROR cannot infer an appropriate lifetime
}
fn main() {}

48
src/test/run-pass/regions-scope-chain-example.rs Normal file
View File

@ -0,0 +1,48 @@
// 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.
// This is an example where the older inference algorithm failed. The
// specifics of why it failed are somewhat, but not entirely, tailed
// to the algorithm. Ultimately the problem is that when computing the
// mutual supertype of both sides of the `if` it would be faced with a
// choice of tightening bounds or unifying variables and it took the
// wrong path. The new algorithm avoids this problem and hence this
// example typechecks correctly.
enum ScopeChain<'a> {
Link(Scope<'a>),
End
}
type Scope<'a> = &'a ScopeChain<'a>;
struct OuterContext;
struct Context<'a> {
foo: &'a OuterContext
}
impl<'a> Context<'a> {
fn foo(&mut self, scope: Scope) {
let link = if 1i < 2 {
let l = Link(scope);
self.take_scope(&l);
l
} else {
Link(scope)
};
self.take_scope(&link);
}
fn take_scope(&mut self, x: Scope) {
}
}
fn main() { }