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simplify HR subtyping back to what we did before

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A lot of the refactors, however, seem helpful, so leave those in,
particularly since we may want to make this change in the future.
This commit is contained in:
Niko Matsakis 2016-05-16 19:59:58 -04:00
parent 52b2db1cca
commit 75543c08c7
8 changed files with 15 additions and 100 deletions
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3
src/librustc/diagnostics.rs
View File

@ -1647,6 +1647,5 @@ register_diagnostics! {
E0490, // a value of type `..` is borrowed for too long
E0491, // in type `..`, reference has a longer lifetime than the data it...
E0495, // cannot infer an appropriate lifetime due to conflicting requirements
E0525, // expected a closure that implements `..` but this closure only implements `..`
E0526, // skolemization subtype
E0525 // expected a closure that implements `..` but this closure only implements `..`
}

16
src/librustc/infer/error_reporting.rs
View File

@ -919,17 +919,6 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
"");
err
}
infer::SkolemizeSuccessor(span) => {
let mut err =
struct_span_err!(self.tcx.sess, span, E0526,
"to satisfy higher-ranked bounds, \
a static lifetime is required");
self.tcx.note_and_explain_region(&mut err,
"but the lifetime is only valid for ",
sub,
"");
err
}
}
}
@ -1817,11 +1806,6 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
"...so that references are valid when the destructor \
runs");
}
infer::SkolemizeSuccessor(span) => {
err.span_note(
span,
"...so that higher-ranked bounds are satisfied");
}
}
}
}

70
src/librustc/infer/higher_ranked/mod.rs
View File

@ -15,7 +15,6 @@ use super::{CombinedSnapshot,
InferCtxt,
LateBoundRegion,
HigherRankedType,
SubregionOrigin,
SkolemizationMap};
use super::combine::CombineFields;
use super::region_inference::{TaintDirections};
@ -527,7 +526,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
// be itself or other new variables.
let incoming_taints = self.tainted_regions(snapshot,
skol,
TaintDirections::incoming());
TaintDirections::both());
for &tainted_region in &incoming_taints {
// Each skolemized should only be relatable to itself
// or new variables:
@ -568,71 +567,6 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
self.issue_32330_warnings(span, &warnings);
for (_, &skol) in skol_map {
// The outputs from a skolemized variable must all be
// equatable with `'static`.
let outgoing_taints = self.tainted_regions(snapshot,
skol,
TaintDirections::outgoing());
for &tainted_region in &outgoing_taints {
match tainted_region {
ty::ReVar(vid) if new_vars.contains(&vid) => {
// There is a path from a skolemized variable
// to some region variable that doesn't escape
// this snapshot:
//
// [skol] -> [tainted_region]
//
// We can ignore this. The reasoning relies on
// the fact that the preivous loop
// completed. There are two possible cases
// here.
//
// - `tainted_region` eventually reaches a
// skolemized variable, which *must* be `skol`
// (because otherwise we would have already
// returned `Err`). In that case,
// `tainted_region` could be inferred to `skol`.
//
// - `tainted_region` never reaches a
// skolemized variable. In that case, we can
// safely choose `'static` as an upper bound
// incoming edges. This is a conservative
// choice -- the LUB might be one of the
// incoming skolemized variables, which we
// might know by ambient bounds. We can
// consider a more clever choice of upper
// bound later (modulo some theoretical
// breakage).
//
// We used to force such `tainted_region` to be
// `'static`, but that leads to problems when
// combined with `plug_leaks`. If you have a case
// where `[skol] -> [tainted_region] -> [skol]`,
// then `plug_leaks` concludes it should replace
// `'static` with a late-bound region, which is
// clearly wrong. (Well, what actually happens is
// you get assertion failures because it WOULD
// have to replace 'static with a late-bound
// region.)
}
ty::ReSkolemized(..) => {
// the only skolemized region we find in the
// successors of X can be X; if there was another
// region Y, then X would have been in the preds
// of Y, and we would have aborted above
assert_eq!(skol, tainted_region);
}
_ => {
self.region_vars.make_subregion(
SubregionOrigin::SkolemizeSuccessor(span),
ty::ReStatic,
tainted_region);
}
}
}
}
Ok(())
}
@ -682,7 +616,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
skol_map
.iter()
.flat_map(|(&skol_br, &skol)| {
self.tainted_regions(snapshot, skol, TaintDirections::incoming())
self.tainted_regions(snapshot, skol, TaintDirections::both())
.into_iter()
.map(move |tainted_region| (tainted_region, skol_br))
})

6
src/librustc/infer/mod.rs
View File

@ -340,11 +340,6 @@ pub enum SubregionOrigin<'tcx> {
// Region constraint arriving from destructor safety
SafeDestructor(Span),
// When doing a higher-ranked comparison, this region was a
// successor from a skolemized region, which means that it must be
// `'static` to be sound.
SkolemizeSuccessor(Span),
}
/// Places that type/region parameters can appear.
@ -1798,7 +1793,6 @@ impl<'tcx> SubregionOrigin<'tcx> {
AddrOf(a) => a,
AutoBorrow(a) => a,
SafeDestructor(a) => a,
SkolemizeSuccessor(a) => a,
}
}
}

2
src/libsyntax/ext/quote.rs
View File

@ -422,7 +422,7 @@ pub fn expand_quote_expr<'cx>(cx: &'cx mut ExtCtxt,
base::MacEager::expr(expanded)
}
pub fn expand_quote_item<'cx>(cx: &mut ExtCtxt,
pub fn expand_quote_item<'cx>(cx: &'cx mut ExtCtxt,
sp: Span,
tts: &[TokenTree])
-> Box<base::MacResult+'cx> {

2
src/libsyntax_ext/concat_idents.rs
View File

@ -17,7 +17,7 @@ use syntax::parse::token;
use syntax::parse::token::str_to_ident;
use syntax::ptr::P;
pub fn expand_syntax_ext<'cx>(cx: &mut ExtCtxt, sp: Span, tts: &[TokenTree])
pub fn expand_syntax_ext<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[TokenTree])
-> Box<base::MacResult+'cx> {
if !cx.ecfg.enable_concat_idents() {
feature_gate::emit_feature_err(&cx.parse_sess.span_diagnostic,

11
src/test/compile-fail/hr-subtype.rs
View File

@ -52,6 +52,10 @@ macro_rules! check {
//[bound_inv_a_b_vs_bound_inv_a]~^^^ ERROR mismatched types
//[bound_a_b_ret_a_vs_bound_a_ret_a]~^^^^ ERROR mismatched types
//[free_inv_x_vs_free_inv_y]~^^^^^ ERROR mismatched types
//[bound_a_b_vs_bound_a]~^^^^^^ ERROR mismatched types
//[bound_co_a_b_vs_bound_co_a]~^^^^^^^ ERROR mismatched types
//[bound_contra_a_contra_b_ret_co_a]~^^^^^^^^ ERROR mismatched types
//[bound_co_a_co_b_ret_contra_a]~^^^^^^^^^ ERROR mismatched types
}
}
}
@ -87,6 +91,9 @@ check! { free_inv_x_vs_free_inv_y: (fn(Inv<'x>),
// - if we are covariant, then 'a and 'b can be set to the call-site
// intersection;
// - if we are contravariant, then 'a can be inferred to 'static.
//
// FIXME(#32330) this is true, but we are not currently impl'ing this
// full semantics
check! { bound_a_b_vs_bound_a: (for<'a,'b> fn(&'a u32, &'b u32),
for<'a> fn(&'a u32, &'a u32)) }
check! { bound_co_a_b_vs_bound_co_a: (for<'a,'b> fn(Co<'a>, Co<'b>),
@ -109,8 +116,4 @@ fn main() {
//[bound_inv_a_vs_bound_inv_b]~^^^ ERROR compilation successful
//[bound_co_a_vs_bound_co_b]~^^^^ ERROR compilation successful
//[free_x_vs_free_x]~^^^^^ ERROR compilation successful
//[bound_a_b_vs_bound_a]~^^^^^^ ERROR compilation successful
//[bound_co_a_b_vs_bound_co_a]~^^^^^^^ ERROR compilation successful
//[bound_contra_a_contra_b_ret_co_a]~^^^^^^^^ ERROR compilation successful
//[bound_co_a_co_b_ret_contra_a]~^^^^^^^^^ ERROR compilation successful
}

5
src/test/compile-fail/regions-close-over-type-parameter-1.rs
View File

@ -19,7 +19,7 @@ trait SomeTrait { fn get(&self) -> isize; }
fn make_object1<A:SomeTrait>(v: A) -> Box<SomeTrait+'static> {
box v as Box<SomeTrait+'static>
//~^ ERROR the parameter type `A` may not live long enough
//~^^ ERROR the parameter type `A` may not live long enough
//~| ERROR the parameter type `A` may not live long enough
}
fn make_object2<'a,A:SomeTrait+'a>(v: A) -> Box<SomeTrait+'a> {
@ -28,7 +28,8 @@ fn make_object2<'a,A:SomeTrait+'a>(v: A) -> Box<SomeTrait+'a> {
fn make_object3<'a,'b,A:SomeTrait+'a>(v: A) -> Box<SomeTrait+'b> {
box v as Box<SomeTrait+'b>
//~^ ERROR E0478
//~^ ERROR the parameter type `A` may not live long enough
//~| ERROR the parameter type `A` may not live long enough
}
fn main() { }