diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs index e1d8839bb37..7a22ef3c81e 100644 --- a/src/librustc/ty/mod.rs +++ b/src/librustc/ty/mod.rs @@ -742,6 +742,14 @@ impl<'tcx> Generics<'tcx> { pub fn count(&self) -> usize { self.parent_count() + self.own_count() } + + pub fn region_param(&self, param: &EarlyBoundRegion) -> &RegionParameterDef<'tcx> { + &self.regions[param.index as usize - self.has_self as usize] + } + + pub fn type_param(&self, param: &ParamTy) -> &TypeParameterDef<'tcx> { + &self.types[param.idx as usize - self.has_self as usize - self.regions.len()] + } } /// Bounds on generics. diff --git a/src/librustc_typeck/check/dropck.rs b/src/librustc_typeck/check/dropck.rs index b48c37b2fc9..607b32fd140 100644 --- a/src/librustc_typeck/check/dropck.rs +++ b/src/librustc_typeck/check/dropck.rs @@ -556,20 +556,10 @@ fn has_dtor_of_interest<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>, } else { return DropckKind::BorrowedDataMustStrictlyOutliveSelf; }; + let method = tcx.impl_or_trait_item(dtor_method); - let substs = Substs::for_item(tcx, - method.container().id(), - |def, _| if def.pure_wrt_drop { - tcx.mk_region(ty::ReStatic) - } else { - substs.region_for_def(def) - }, - |def, _| if def.pure_wrt_drop { - tcx.mk_nil() - } else { - substs.type_for_def(def) - }); - let revised_ty = tcx.mk_adt(adt_def, &substs); + let impl_id: DefId = method.container().id(); + let revised_ty = revise_self_ty(tcx, adt_def, impl_id, substs); return DropckKind::RevisedSelf(revised_ty); } ty::TyTrait(..) | ty::TyProjection(..) | ty::TyAnon(..) => { @@ -581,3 +571,77 @@ fn has_dtor_of_interest<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>, } } } + +// Constructs new Ty just like the type defined by `adt_def` coupled +// with `substs`, except each type and lifetime parameter marked as +// `#[may_dangle]` in the Drop impl (identified by `impl_id`) is +// respectively mapped to `()` or `'static`. +// +// For example: If the `adt_def` maps to: +// +// enum Foo<'a, X, Y> { ... } +// +// and the `impl_id` maps to: +// +// impl<#[may_dangle] 'a, X, #[may_dangle] Y> Drop for Foo<'a, X, Y> { ... } +// +// then revises input: `Foo<'r,i64,&'r i64>` to: `Foo<'static,i64,()>` +fn revise_self_ty<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>, + adt_def: ty::AdtDef<'tcx>, + impl_id: DefId, + substs: &Substs<'tcx>) -> Ty<'tcx> { + // Get generics for `impl Drop` to query for `#[may_dangle]` attr. + let impl_bindings = tcx.lookup_generics(impl_id); + + // Get Substs attached to Self on `impl Drop`; process in parallel + // with `substs`, replacing dangling entries as appropriate. + let self_substs = { + let impl_self_ty: Ty<'tcx> = tcx.lookup_item_type(impl_id).ty; + if let ty::TyAdt(self_adt_def, self_substs) = impl_self_ty.sty { + assert_eq!(adt_def, self_adt_def); + self_substs + } else { + bug!("Self in `impl Drop for _` must be an Adt."); + } + }; + + // Walk `substs` + `self_substs`, build new substs appropriate for + // `adt_def`; each non-dangling param reuses entry from `substs`. + let substs = Substs::for_item( + tcx, + adt_def.did, + |def, _| { + let r_orig = substs.region_for_def(def); + let impl_self_orig = self_substs.region_for_def(def); + let r = if let ty::Region::ReEarlyBound(ref ebr) = *impl_self_orig { + if impl_bindings.region_param(ebr).pure_wrt_drop { + tcx.mk_region(ty::ReStatic) + } else { + r_orig + } + } else { + bug!("substs for an impl must map regions to ReEarlyBound"); + }; + debug!("has_dtor_of_interest mapping def {:?} orig {:?} to {:?}", + def, r_orig, r); + r + }, + |def, _| { + let t_orig = substs.type_for_def(def); + let impl_self_orig = self_substs.type_for_def(def); + let t = if let ty::TypeVariants::TyParam(ref pt) = impl_self_orig.sty { + if impl_bindings.type_param(pt).pure_wrt_drop { + tcx.mk_nil() + } else { + t_orig + } + } else { + bug!("substs for an impl must map types to TyParam"); + }; + debug!("has_dtor_of_interest mapping def {:?} orig {:?} {:?} to {:?} {:?}", + def, t_orig, t_orig.sty, t, t.sty); + t + }); + + return tcx.mk_adt(adt_def, &substs); +} diff --git a/src/test/compile-fail/dropck-eyepatch-reorder.rs b/src/test/compile-fail/dropck-eyepatch-reorder.rs new file mode 100644 index 00000000000..68b0ff3b5f0 --- /dev/null +++ b/src/test/compile-fail/dropck-eyepatch-reorder.rs @@ -0,0 +1,73 @@ +// Copyright 2016 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 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +#![feature(generic_param_attrs)] +#![feature(dropck_eyepatch)] + +// The point of this test is to test uses of `#[may_dangle]` attribute +// where the formal declaration order (in the impl generics) does not +// match the actual usage order (in the type instantiation). +// +// See also dropck-eyepatch.rs for more information about the general +// structure of the test. + +use std::fmt; + +struct Dt(&'static str, A); +struct Dr<'a, B:'a+fmt::Debug>(&'static str, &'a B); +struct Pt(&'static str, A, B); +struct Pr<'a, 'b, B:'a+'b+fmt::Debug>(&'static str, &'a B, &'b B); +struct St(&'static str, A); +struct Sr<'a, B:'a+fmt::Debug>(&'static str, &'a B); + +impl Drop for Dt { + fn drop(&mut self) { println!("drop {} {:?}", self.0, self.1); } +} +impl<'a, B: fmt::Debug> Drop for Dr<'a, B> { + fn drop(&mut self) { println!("drop {} {:?}", self.0, self.1); } +} +unsafe impl Drop for Pt { + // (unsafe to access self.1 due to #[may_dangle] on A) + fn drop(&mut self) { println!("drop {} {:?}", self.0, self.2); } +} +unsafe impl<'b, #[may_dangle] 'a, B: fmt::Debug> Drop for Pr<'a, 'b, B> { + // (unsafe to access self.1 due to #[may_dangle] on 'a) + fn drop(&mut self) { println!("drop {} {:?}", self.0, self.2); } +} + +fn main() { + use std::cell::Cell; + let c_long; + let (c, mut dt, mut dr, mut pt, mut pr, st, sr) + : (Cell<_>, Dt<_>, Dr<_>, Pt<_, _>, Pr<_>, St<_>, Sr<_>); + c_long = Cell::new(1); + c = Cell::new(1); + + // No error: sufficiently long-lived state can be referenced in dtors + dt = Dt("dt", &c_long); + dr = Dr("dr", &c_long); + // Error: destructor order imprecisely modelled + dt = Dt("dt", &c); //~ ERROR `c` does not live long enough + dr = Dr("dr", &c); //~ ERROR `c` does not live long enough + + // No error: Drop impl asserts .1 (A and &'a _) are not accessed + pt = Pt("pt", &c, &c_long); + pr = Pr("pr", &c, &c_long); + + // Error: Drop impl's assertion does not apply to `B` nor `&'b _` + pt = Pt("pt", &c_long, &c); //~ ERROR `c` does not live long enough + pr = Pr("pr", &c_long, &c); //~ ERROR `c` does not live long enough + + // No error: St and Sr have no destructor. + st = St("st", &c); + sr = Sr("sr", &c); + + println!("{:?}", (dt.0, dr.0, pt.0, pr.0, st.0, sr.0)); +} diff --git a/src/test/run-pass/dropck-eyepatch-reorder.rs b/src/test/run-pass/dropck-eyepatch-reorder.rs new file mode 100644 index 00000000000..bbf8bb8c352 --- /dev/null +++ b/src/test/run-pass/dropck-eyepatch-reorder.rs @@ -0,0 +1,89 @@ +// Copyright 2016 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 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +#![feature(generic_param_attrs)] +#![feature(dropck_eyepatch)] + +// The point of this test is to test uses of `#[may_dangle]` attribute +// where the formal declaration order (in the impl generics) does not +// match the actual usage order (in the type instantiation). +// +// See also dropck-eyepatch.rs for more information about the general +// structure of the test. + +trait Foo { fn foo(&self, _: &str); } + +struct Dt(&'static str, A); +struct Dr<'a, B:'a+Foo>(&'static str, &'a B); +struct Pt(&'static str, A, B); +struct Pr<'a, 'b, B:'a+'b+Foo>(&'static str, &'a B, &'b B); +struct St(&'static str, A); +struct Sr<'a, B:'a+Foo>(&'static str, &'a B); + +impl Drop for Dt { + fn drop(&mut self) { println!("drop {}", self.0); self.1.foo(self.0); } +} +impl<'a, B: Foo> Drop for Dr<'a, B> { + fn drop(&mut self) { println!("drop {}", self.0); self.1.foo(self.0); } +} +unsafe impl Drop for Pt { + // (unsafe to access self.1 due to #[may_dangle] on A) + fn drop(&mut self) { println!("drop {}", self.0); self.2.foo(self.0); } +} +unsafe impl<'b, #[may_dangle] 'a, B: Foo> Drop for Pr<'a, 'b, B> { + // (unsafe to access self.1 due to #[may_dangle] on 'a) + fn drop(&mut self) { println!("drop {}", self.0); self.2.foo(self.0); } +} + +fn main() { + use std::cell::RefCell; + + impl Foo for RefCell { + fn foo(&self, s: &str) { + let s2 = format!("{}|{}", *self.borrow(), s); + *self.borrow_mut() = s2; + } + } + + impl<'a, T:Foo> Foo for &'a T { + fn foo(&self, s: &str) { + (*self).foo(s); + } + } + + struct CheckOnDrop(RefCell, &'static str); + impl Drop for CheckOnDrop { + fn drop(&mut self) { assert_eq!(*self.0.borrow(), self.1); } + } + + let c_long; + let (c, dt, dr, pt, pr, st, sr) + : (CheckOnDrop, Dt<_>, Dr<_>, Pt<_, _>, Pr<_>, St<_>, Sr<_>); + c_long = CheckOnDrop(RefCell::new("c_long".to_string()), + "c_long|pr|pt|dr|dt"); + c = CheckOnDrop(RefCell::new("c".to_string()), + "c"); + + // No error: sufficiently long-lived state can be referenced in dtors + dt = Dt("dt", &c_long.0); + dr = Dr("dr", &c_long.0); + + // No error: Drop impl asserts .1 (A and &'a _) are not accessed + pt = Pt("pt", &c.0, &c_long.0); + pr = Pr("pr", &c.0, &c_long.0); + + // No error: St and Sr have no destructor. + st = St("st", &c.0); + sr = Sr("sr", &c.0); + + println!("{:?}", (dt.0, dr.0, pt.0, pr.0, st.0, sr.0)); + assert_eq!(*c_long.0.borrow(), "c_long"); + assert_eq!(*c.0.borrow(), "c"); +}