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Auto merge of #47957 - bobtwinkles:fix_mir_consts, r=nikomatsakis
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[NLL] Improve DefiningTy::Const

Fixes #47590 by fixing the way DefiningTy represents constants. Previously, constants were represented using just the type of the variable. However, this will fail to capture early-bound regions as NLL inference vars, resulting in an ICE when we try to compute region VIDs a little bit later in the universal
region resolution process. (ref #47590)
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bors committed Feb 7, 2018
2 parents 4f93357 + e99f8fc commit fee39ba
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Showing 4 changed files with 128 additions and 38 deletions.
7 changes: 4 additions & 3 deletions src/librustc_mir/borrow_check/nll/region_infer/annotation.rs
Original file line number Diff line number Diff line change
Expand Up @@ -45,10 +45,11 @@ impl<'gcx, 'tcx> RegionInferenceContext<'tcx> {
&substs[..]
));
}
DefiningTy::Const(ty) => {
DefiningTy::Const(def_id, substs) => {
err.note(&format!(
"defining type: {:?}",
ty
"defining constant type: {:?} with substs {:#?}",
def_id,
&substs[..]
));
}
}
Expand Down
77 changes: 42 additions & 35 deletions src/librustc_mir/borrow_check/nll/universal_regions.rs
Original file line number Diff line number Diff line change
Expand Up @@ -125,7 +125,7 @@ pub enum DefiningTy<'tcx> {
/// The MIR represents some form of constant. The signature then
/// is that it has no inputs and a single return value, which is
/// the value of the constant.
Const(Ty<'tcx>),
Const(DefId, &'tcx Substs<'tcx>),
}

#[derive(Debug)]
Expand Down Expand Up @@ -534,34 +534,42 @@ impl<'cx, 'gcx, 'tcx> UniversalRegionsBuilder<'cx, 'gcx, 'tcx> {
/// see `DefiningTy` for details.
fn defining_ty(&self) -> DefiningTy<'tcx> {
let tcx = self.infcx.tcx;

let closure_base_def_id = tcx.closure_base_def_id(self.mir_def_id);

let defining_ty = if self.mir_def_id == closure_base_def_id {
tcx.type_of(closure_base_def_id)
} else {
let tables = tcx.typeck_tables_of(self.mir_def_id);
tables.node_id_to_type(self.mir_hir_id)
};

let defining_ty = self.infcx
.replace_free_regions_with_nll_infer_vars(FR, &defining_ty);

match tcx.hir.body_owner_kind(self.mir_node_id) {
BodyOwnerKind::Fn => match defining_ty.sty {
ty::TyClosure(def_id, substs) => DefiningTy::Closure(def_id, substs),
ty::TyGenerator(def_id, substs, interior) => {
DefiningTy::Generator(def_id, substs, interior)
BodyOwnerKind::Fn => {
let defining_ty = if self.mir_def_id == closure_base_def_id {
tcx.type_of(closure_base_def_id)
} else {
let tables = tcx.typeck_tables_of(self.mir_def_id);
tables.node_id_to_type(self.mir_hir_id)
};

let defining_ty = self.infcx
.replace_free_regions_with_nll_infer_vars(FR, &defining_ty);

match defining_ty.sty {
ty::TyClosure(def_id, substs) => DefiningTy::Closure(def_id, substs),
ty::TyGenerator(def_id, substs, interior) => {
DefiningTy::Generator(def_id, substs, interior)
}
ty::TyFnDef(def_id, substs) => DefiningTy::FnDef(def_id, substs),
_ => span_bug!(
tcx.def_span(self.mir_def_id),
"expected defining type for `{:?}`: `{:?}`",
self.mir_def_id,
defining_ty
),
}
ty::TyFnDef(def_id, substs) => DefiningTy::FnDef(def_id, substs),
_ => span_bug!(
tcx.def_span(self.mir_def_id),
"expected defining type for `{:?}`: `{:?}`",
self.mir_def_id,
defining_ty
),
},
BodyOwnerKind::Const | BodyOwnerKind::Static(..) => DefiningTy::Const(defining_ty),
}

BodyOwnerKind::Const | BodyOwnerKind::Static(..) => {
assert_eq!(closure_base_def_id, self.mir_def_id);
let identity_substs = Substs::identity_for_item(tcx, closure_base_def_id);
let substs = self.infcx
.replace_free_regions_with_nll_infer_vars(FR, &identity_substs);
DefiningTy::Const(self.mir_def_id, substs)
}
}
}

Expand Down Expand Up @@ -592,13 +600,7 @@ impl<'cx, 'gcx, 'tcx> UniversalRegionsBuilder<'cx, 'gcx, 'tcx> {
substs.substs
}

DefiningTy::FnDef(_, substs) => substs,

// When we encounter a constant body, just return whatever
// substitutions are in scope for that constant.
DefiningTy::Const(_) => {
identity_substs
}
DefiningTy::FnDef(_, substs) | DefiningTy::Const(_, substs) => substs,
};

let global_mapping = iter::once((gcx.types.re_static, fr_static));
Expand Down Expand Up @@ -660,9 +662,14 @@ impl<'cx, 'gcx, 'tcx> UniversalRegionsBuilder<'cx, 'gcx, 'tcx> {
sig.inputs_and_output()
}

// For a constant body, there are no inputs, and one
// "output" (the type of the constant).
DefiningTy::Const(ty) => ty::Binder::dummy(tcx.mk_type_list(iter::once(ty))),
DefiningTy::Const(def_id, _) => {
// For a constant body, there are no inputs, and one
// "output" (the type of the constant).
assert_eq!(self.mir_def_id, def_id);
let ty = tcx.type_of(def_id);
let ty = indices.fold_to_region_vids(tcx, &ty);
ty::Binder::dummy(tcx.mk_type_list(iter::once(ty)))
}
}
}

Expand Down
42 changes: 42 additions & 0 deletions src/test/ui/nll/trait-associated-constant.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,42 @@
// Copyright 2018 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 cases where we put various lifetime constraints on trait
// associated constants.

#![feature(rustc_attrs)]

use std::option::Option;

trait Anything<'a: 'b, 'b> {
const AC: Option<&'b str>;
}

struct OKStruct { }

impl<'a: 'b, 'b> Anything<'a, 'b> for OKStruct {
const AC: Option<&'b str> = None;
}

struct FailStruct1 { }

impl<'a: 'b, 'b, 'c> Anything<'a, 'b> for FailStruct1 {
const AC: Option<&'c str> = None;
//~^ ERROR: mismatched types
}

struct FailStruct2 { }

impl<'a: 'b, 'b> Anything<'a, 'b> for FailStruct2 {
const AC: Option<&'a str> = None;
//~^ ERROR: mismatched types
}

fn main() {}
40 changes: 40 additions & 0 deletions src/test/ui/nll/trait-associated-constant.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,40 @@
error[E0308]: mismatched types
--> $DIR/trait-associated-constant.rs:31:5
|
31 | const AC: Option<&'c str> = None;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ lifetime mismatch
|
= note: expected type `std::option::Option<&'b str>`
found type `std::option::Option<&'c str>`
note: the lifetime 'c as defined on the impl at 30:1...
--> $DIR/trait-associated-constant.rs:30:1
|
30 | impl<'a: 'b, 'b, 'c> Anything<'a, 'b> for FailStruct1 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...does not necessarily outlive the lifetime 'b as defined on the impl at 30:1
--> $DIR/trait-associated-constant.rs:30:1
|
30 | impl<'a: 'b, 'b, 'c> Anything<'a, 'b> for FailStruct1 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0308]: mismatched types
--> $DIR/trait-associated-constant.rs:38:5
|
38 | const AC: Option<&'a str> = None;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ lifetime mismatch
|
= note: expected type `std::option::Option<&'b str>`
found type `std::option::Option<&'a str>`
note: the lifetime 'a as defined on the impl at 37:1...
--> $DIR/trait-associated-constant.rs:37:1
|
37 | impl<'a: 'b, 'b> Anything<'a, 'b> for FailStruct2 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...does not necessarily outlive the lifetime 'b as defined on the impl at 37:1
--> $DIR/trait-associated-constant.rs:37:1
|
37 | impl<'a: 'b, 'b> Anything<'a, 'b> for FailStruct2 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 2 previous errors

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