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auto merge of #18388 : nikomatsakis/rust/fn-trait-hierarchy, r=acrichto

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Add blanket impls to allow the various `Fn` traits to be interconverted.

Fixes #18387.
This commit is contained in:
bors 2014-11-06 04:21:49 +00:00
commit 0e2f9b9485
15 changed files with 313 additions and 94 deletions
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70
src/libcore/ops.rs
View File

@ -866,13 +866,45 @@ pub trait FnOnce<Args,Result> {
extern "rust-call" fn call_once(self, args: Args) -> Result;
}
macro_rules! def_fn_mut(
impl<F,A,R> FnMut<A,R> for F
where F : Fn<A,R>
{
extern "rust-call" fn call_mut(&mut self, args: A) -> R {
self.call(args)
}
}
impl<F,A,R> FnOnce<A,R> for F
where F : FnMut<A,R>
{
extern "rust-call" fn call_once(mut self, args: A) -> R {
self.call_mut(args)
}
}
impl<Result> Fn<(),Result> for extern "Rust" fn() -> Result {
#[allow(non_snake_case)]
extern "rust-call" fn call(&self, _args: ()) -> Result {
(*self)()
}
}
impl<Result,A0> Fn<(A0,),Result> for extern "Rust" fn(A0) -> Result {
#[allow(non_snake_case)]
extern "rust-call" fn call(&self, args: (A0,)) -> Result {
let (a0,) = args;
(*self)(a0)
}
}
macro_rules! def_fn(
($($args:ident)*) => (
impl<Result$(,$args)*>
FnMut<($($args,)*),Result>
Fn<($($args,)*),Result>
for extern "Rust" fn($($args: $args,)*) -> Result {
#[allow(non_snake_case)]
extern "rust-call" fn call_mut(&mut self, args: ($($args,)*)) -> Result {
extern "rust-call" fn call(&self, args: ($($args,)*)) -> Result {
let ($($args,)*) = args;
(*self)($($args,)*)
}
@ -880,20 +912,18 @@ macro_rules! def_fn_mut(
)
)
def_fn_mut!()
def_fn_mut!(A0)
def_fn_mut!(A0 A1)
def_fn_mut!(A0 A1 A2)
def_fn_mut!(A0 A1 A2 A3)
def_fn_mut!(A0 A1 A2 A3 A4)
def_fn_mut!(A0 A1 A2 A3 A4 A5)
def_fn_mut!(A0 A1 A2 A3 A4 A5 A6)
def_fn_mut!(A0 A1 A2 A3 A4 A5 A6 A7)
def_fn_mut!(A0 A1 A2 A3 A4 A5 A6 A7 A8)
def_fn_mut!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9)
def_fn_mut!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10)
def_fn_mut!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11)
def_fn_mut!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12)
def_fn_mut!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13)
def_fn_mut!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14)
def_fn_mut!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15)
def_fn!(A0 A1)
def_fn!(A0 A1 A2)
def_fn!(A0 A1 A2 A3)
def_fn!(A0 A1 A2 A3 A4)
def_fn!(A0 A1 A2 A3 A4 A5)
def_fn!(A0 A1 A2 A3 A4 A5 A6)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15)

2
src/librustc/middle/traits/coherence.rs
View File

@ -43,7 +43,7 @@ pub fn impl_can_satisfy(infcx: &InferCtxt,
// Determine whether `impl2` can provide an implementation for those
// same types.
let param_env = ty::empty_parameter_environment();
let mut selcx = SelectionContext::new(infcx, &param_env, infcx.tcx);
let mut selcx = SelectionContext::intercrate(infcx, &param_env, infcx.tcx);
let obligation = Obligation::misc(DUMMY_SP, impl1_trait_ref);
debug!("impl_can_satisfy obligation={}", obligation.repr(infcx.tcx));
selcx.evaluate_impl(impl2_def_id, &obligation)

148
src/librustc/middle/traits/select.rs
View File

@ -45,6 +45,22 @@ pub struct SelectionContext<'cx, 'tcx:'cx> {
/// which is important for checking for trait bounds that
/// recursively require themselves.
skolemizer: TypeSkolemizer<'cx, 'tcx>,
/// If true, indicates that the evaluation should be conservative
/// and consider the possibility of types outside this crate.
/// This comes up primarily when resolving ambiguity. Imagine
/// there is some trait reference `$0 : Bar` where `$0` is an
/// inference variable. If `intercrate` is true, then we can never
/// say for sure that this reference is not implemented, even if
/// there are *no impls at all for `Bar`*, because `$0` could be
/// bound to some type that in a downstream crate that implements
/// `Bar`. This is the suitable mode for coherence. Elsewhere,
/// though, we set this to false, because we are only interested
/// in types that the user could actually have written --- in
/// other words, we consider `$0 : Bar` to be unimplemented if
/// there is no type that the user could *actually name* that
/// would satisfy it. This avoids crippling inference, basically.
intercrate: bool,
}
// A stack that walks back up the stack frame.
@ -142,6 +158,20 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
param_env: param_env,
typer: typer,
skolemizer: infcx.skolemizer(),
intercrate: false,
}
}
pub fn intercrate(infcx: &'cx InferCtxt<'cx, 'tcx>,
param_env: &'cx ty::ParameterEnvironment,
typer: &'cx Typer<'tcx>)
-> SelectionContext<'cx, 'tcx> {
SelectionContext {
infcx: infcx,
param_env: param_env,
typer: typer,
skolemizer: infcx.skolemizer(),
intercrate: true,
}
}
@ -214,44 +244,20 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// The result is "true" if the obligation *may* hold and "false" if
// we can be sure it does not.
pub fn evaluate_obligation_intercrate(&mut self,
obligation: &Obligation)
-> bool
pub fn evaluate_obligation(&mut self,
obligation: &Obligation)
-> bool
{
/*!
* Evaluates whether the obligation `obligation` can be
* satisfied (by any means). This "intercrate" version allows
* for the possibility that unbound type variables may be
* instantiated with types from another crate. This is
* important for coherence. In practice this means that
* unbound type variables must always be considered ambiguous.
* satisfied (by any means).
*/
debug!("evaluate_obligation_intercrate({})",
debug!("evaluate_obligation({})",
obligation.repr(self.tcx()));
let stack = self.push_stack(None, obligation);
self.evaluate_stack_intercrate(&stack).may_apply()
}
pub fn evaluate_obligation_intracrate(&mut self,
obligation: &Obligation)
-> bool
{
/*!
* Evaluates whether the obligation `obligation` can be
* satisfied (by any means). This "intracrate" version does
* not allow for the possibility that unbound type variables
* may be instantiated with types from another crate; hence,
* if there are unbound inputs but no crates locally visible,
* it considers the result to be unimplemented.
*/
debug!("evaluate_obligation_intracrate({})",
obligation.repr(self.tcx()));
let stack = self.push_stack(None, obligation);
self.evaluate_stack_intracrate(&stack).may_apply()
self.evaluate_stack(&stack).may_apply()
}
fn evaluate_builtin_bound_recursively(&mut self,
@ -288,46 +294,53 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let stack = self.push_stack(previous_stack.map(|x| x), obligation);
// FIXME(#17901) -- Intercrate vs intracrate resolution is a
// tricky question here. For coherence, we want
// intercrate. Also, there was a nasty cycle around impls like
// `impl<T:Eq> Eq for Vec<T>` (which would wind up checking
// whether `$0:Eq`, where $0 was the value substituted for
// `T`, which could then be checked against the very same
// impl). This problem is avoided by the stricter rules around
// unbound type variables by intercrate. I suspect that in the
// latter case a more fine-grained rule would suffice (i.e.,
// consider it ambiguous if even 1 impl matches, no need to
// figure out which one, but call it unimplemented if 0 impls
// match).
let result = self.evaluate_stack_intercrate(&stack);
let result = self.evaluate_stack(&stack);
debug!("result: {}", result);
result
}
fn evaluate_stack_intercrate(&mut self,
fn evaluate_stack(&mut self,
stack: &ObligationStack)
-> EvaluationResult
{
// Whenever any of the types are unbound, there can always be
// an impl. Even if there are no impls in this crate, perhaps
// the type would be unified with something from another crate
// that does provide an impl.
// In intercrate mode, whenever any of the types are unbound,
// there can always be an impl. Even if there are no impls in
// this crate, perhaps the type would be unified with
// something from another crate that does provide an impl.
//
// In intracrate mode, we must still be conservative. The reason is
// that we want to avoid cycles. Imagine an impl like:
//
// impl<T:Eq> Eq for Vec<T>
//
// and a trait reference like `$0 : Eq` where `$0` is an
// unbound variable. When we evaluate this trait-reference, we
// will unify `$0` with `Vec<$1>` (for some fresh variable
// `$1`), on the condition that `$1 : Eq`. We will then wind
// up with many candidates (since that are other `Eq` impls
// that apply) and try to winnow things down. This results in
// a recurssive evaluation that `$1 : Eq` -- as you can
// imagine, this is just where we started. To avoid that, we
// check for unbound variables and return an ambiguous (hence possible)
// match if we've seen this trait before.
//
// This suffices to allow chains like `FnMut` implemented in
// terms of `Fn` etc, but we could probably make this more
// precise still.
let input_types = stack.skol_trait_ref.input_types();
if input_types.iter().any(|&t| ty::type_is_skolemized(t)) {
debug!("evaluate_stack_intercrate({}) --> unbound argument, must be ambiguous",
let unbound_input_types = input_types.iter().any(|&t| ty::type_is_skolemized(t));
if
unbound_input_types &&
(self.intercrate ||
stack.iter().skip(1).any(
|prev| stack.skol_trait_ref.def_id == prev.skol_trait_ref.def_id))
{
debug!("evaluate_stack_intracrate({}) --> unbound argument, recursion --> ambiguous",
stack.skol_trait_ref.repr(self.tcx()));
return EvaluatedToAmbig;
}
self.evaluate_stack_intracrate(stack)
}
fn evaluate_stack_intracrate(&mut self,
stack: &ObligationStack)
-> EvaluationResult
{
// If there is any previous entry on the stack that precisely
// matches this obligation, then we can assume that the
// obligation is satisfied for now (still all other conditions
@ -592,7 +605,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
Err(_) => { return Err(()); }
}
if self.evaluate_obligation_intracrate(obligation) {
if self.evaluate_obligation(obligation) {
Ok(())
} else {
Err(())
@ -804,12 +817,12 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
&candidates[i],
&candidates[j]));
if is_dup {
debug!("Dropping candidate #{}/#{}: {}",
debug!("Dropping candidate #{}/{}: {}",
i, candidates.len(), candidates[i].repr(self.tcx()));
candidates.swap_remove(i);
} else {
debug!("Retaining candidate #{}/#{}",
i, candidates.len());
debug!("Retaining candidate #{}/{}: {}",
i, candidates.len(), candidates[i].repr(self.tcx()));
i += 1;
}
}
@ -828,7 +841,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// be the case that you could still satisfy the obligation
// from another crate by instantiating the type variables with
// a type from another crate that does have an impl. This case
// is checked for in `evaluate_obligation` (and hence users
// is checked for in `evaluate_stack` (and hence users
// who might care about this case, like coherence, should use
// that function).
if candidates.len() == 0 {
@ -849,6 +862,17 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// global cache. We want the cache that is specific to this
// scope whenever where clauses might affect the result.
// Avoid using the master cache during coherence and just rely
// on the local cache. This effectively disables caching
// during coherence. It is really just a simplification to
// avoid us having to fear that coherence results "pollute"
// the master cache. Since coherence executes pretty quickly,
// it's not worth going to more trouble to increase the
// hit-rate I don't think.
if self.intercrate {
return &self.param_env.selection_cache;
}
// If the trait refers to any parameters in scope, then use
// the cache of the param-environment.
if

2
src/librustc/middle/typeck/check/method.rs
View File

@ -235,7 +235,7 @@ pub fn lookup_in_trait_adjusted<'a, 'tcx>(
let mut selcx = traits::SelectionContext::new(fcx.infcx(),
&fcx.inh.param_env,
fcx);
if !selcx.evaluate_obligation_intracrate(&obligation) {
if !selcx.evaluate_obligation(&obligation) {
debug!("--> Cannot match obligation");
return None; // Cannot be matched, no such method resolution is possible.
}

11
src/librustc/middle/typeck/check/mod.rs
View File

@ -2147,11 +2147,11 @@ fn try_overloaded_call<'a>(fcx: &FnCtxt,
_ => {}
}
// Try `FnOnce`, then `FnMut`, then `Fn`.
// Try the options that are least restrictive on the caller first.
for &(maybe_function_trait, method_name) in [
(fcx.tcx().lang_items.fn_once_trait(), token::intern("call_once")),
(fcx.tcx().lang_items.fn_trait(), token::intern("call")),
(fcx.tcx().lang_items.fn_mut_trait(), token::intern("call_mut")),
(fcx.tcx().lang_items.fn_trait(), token::intern("call"))
(fcx.tcx().lang_items.fn_once_trait(), token::intern("call_once")),
].iter() {
let function_trait = match maybe_function_trait {
None => continue,
@ -3493,6 +3493,11 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
ast::FnOnceUnboxedClosureKind => ty::FnOnceUnboxedClosureKind,
};
debug!("unboxed_closure for {} --> sig={} kind={}",
local_def(expr.id).repr(fcx.tcx()),
fn_ty.sig.repr(fcx.tcx()),
kind);
let unboxed_closure = ty::UnboxedClosure {
closure_type: fn_ty,
kind: kind,

34
src/test/compile-fail/unboxed-closures-fnmut-as-fn.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.
// Checks that the Fn trait hierarchy rules do not permit
// Fn to be used where FnMut is implemented.
#![feature(unboxed_closure_sugar)]
#![feature(overloaded_calls)]
use std::ops::{Fn,FnMut,FnOnce};
struct S;
impl FnMut<(int,),int> for S {
extern "rust-call" fn call_mut(&mut self, (x,): (int,)) -> int {
x * x
}
}
fn call_it<F:Fn(int)->int>(f: &F, x: int) -> int {
f.call((x,))
}
fn main() {
let x = call_it(&S, 22); //~ ERROR not implemented
}

2
src/test/compile-fail/unboxed-closures-static-call-wrong-trait.rs
View File

@ -12,6 +12,6 @@
fn main() {
let mut_ = |&mut: x| x;
mut_.call_once((0i, )); //~ ERROR type `closure` does not implement
mut_.call((0i, )); //~ ERROR type `closure` does not implement
}

2
src/test/compile-fail/unboxed-closures-vtable-mismatch.rs
View File

@ -18,7 +18,7 @@ fn call_it<F:FnMut<(int,int),int>>(y: int, mut f: F) -> int {
pub fn main() {
let f = |&mut: x: uint, y: int| -> int { (x as int) + y };
let z = call_it(3, f); //~ ERROR type mismatch
let z = call_it(3, f); //~ ERROR not implemented
println!("{}", z);
}

4
src/test/compile-fail/unboxed-closures-wrong-trait.rs
View File

@ -10,13 +10,13 @@
#![feature(lang_items, overloaded_calls, unboxed_closures)]
fn c<F:FnOnce(int, int) -> int>(f: F) -> int {
fn c<F:Fn(int, int) -> int>(f: F) -> int {
f(5, 6)
}
fn main() {
let z: int = 7;
assert_eq!(c(|&: x: int, y| x + y + z), 10);
assert_eq!(c(|&mut: x: int, y| x + y + z), 10);
//~^ ERROR not implemented
}

4
src/test/run-pass/issue-16668.rs
View File

@ -20,8 +20,8 @@ impl<'a, I, O: 'a> Parser<'a, I, O> {
fn compose<K: 'a>(mut self, mut rhs: Parser<'a, O, K>) -> Parser<'a, I, K> {
Parser {
parse: box move |&mut: x: I| {
match self.parse.call_mut((x,)) {
Ok(r) => rhs.parse.call_mut((r,)),
match (*self.parse).call_mut((x,)) {
Ok(r) => (*rhs.parse).call_mut((r,)),
Err(e) => Err(e)
}
}

40
src/test/run-pass/unboxed-closures-extern-fn.rs Normal file
View File

@ -0,0 +1,40 @@
// 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.
// Checks that extern fn points implement the full range of Fn traits.
#![feature(unboxed_closure_sugar)]
#![feature(overloaded_calls)]
use std::ops::{Fn,FnMut,FnOnce};
fn square(x: int) -> int { x * x }
fn call_it<F:Fn(int)->int>(f: &F, x: int) -> int {
f.call((x,))
}
fn call_it_mut<F:FnMut(int)->int>(f: &mut F, x: int) -> int {
f.call_mut((x,))
}
fn call_it_once<F:FnOnce(int)->int>(f: F, x: int) -> int {
f.call_once((x,))
}
fn main() {
let x = call_it(&square, 22);
let y = call_it_mut(&mut square, 22);
let z = call_it_once(square, 22);
assert_eq!(x, square(22));
assert_eq!(y, square(22));
assert_eq!(z, square(22));
}

46
src/test/run-pass/unboxed-closures-fn-as-fnmut-and-fnonce.rs Normal file
View File

@ -0,0 +1,46 @@
// 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.
// Checks that the Fn trait hierarchy rules permit
// any Fn trait to be used where Fn is implemented.
#![feature(unboxed_closure_sugar)]
#![feature(overloaded_calls)]
use std::ops::{Fn,FnMut,FnOnce};
struct S;
impl Fn<(int,),int> for S {
extern "rust-call" fn call(&self, (x,): (int,)) -> int {
x * x
}
}
fn call_it<F:Fn(int)->int>(f: &F, x: int) -> int {
f.call((x,))
}
fn call_it_mut<F:FnMut(int)->int>(f: &mut F, x: int) -> int {
f.call_mut((x,))
}
fn call_it_once<F:FnOnce(int)->int>(f: F, x: int) -> int {
f.call_once((x,))
}
fn main() {
let x = call_it(&S, 22);
let y = call_it_mut(&mut S, 22);
let z = call_it_once(S, 22);
assert_eq!(x, y);
assert_eq!(y, z);
}

40
src/test/run-pass/unboxed-closures-fnmut-as-fnonce.rs Normal file
View File

@ -0,0 +1,40 @@
// 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.
// Checks that the Fn trait hierarchy rules permit
// FnMut or FnOnce to be used where FnMut is implemented.
#![feature(unboxed_closure_sugar)]
#![feature(overloaded_calls)]
use std::ops::{FnMut,FnOnce};
struct S;
impl FnMut<(int,),int> for S {
extern "rust-call" fn call_mut(&mut self, (x,): (int,)) -> int {
x * x
}
}
fn call_it_mut<F:FnMut(int)->int>(f: &mut F, x: int) -> int {
f.call_mut((x,))
}
fn call_it_once<F:FnOnce(int)->int>(f: F, x: int) -> int {
f.call_once((x,))
}
fn main() {
let y = call_it_mut(&mut S, 22);
let z = call_it_once(S, 22);
assert_eq!(y, z);
}

0
src/test/run-pass/fn-trait-sugar.rs → src/test/run-pass/unboxed-closures-manual-impl.rs
View File

2
src/test/run-pass/unboxed-closures-zero-args.rs
View File

@ -12,6 +12,6 @@
fn main() {
let mut zero = |&mut:| {};
zero.call_mut(());
let () = zero.call_mut(());
}