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Use global recursion limit when evaluating inhabitedness

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This commit is contained in:
Andrew Cann 2017-02-10 00:52:51 +08:00
parent 2bb9c5875d
commit 347bc77c2c
5 changed files with 55 additions and 47 deletions
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81
src/librustc/ty/inhabitedness/mod.rs
View File

@ -8,7 +8,7 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use util::nodemap::FxHashSet;
use util::nodemap::{FxHashMap, FxHashSet};
use ty::context::TyCtxt;
use ty::{AdtDef, VariantDef, FieldDef, TyS};
use ty::{DefId, Substs};
@ -62,26 +62,17 @@ mod def_id_forest;
// This code should only compile in modules where the uninhabitedness of Foo is
// visible.
const ARBITRARY_RECURSION_LIMIT: u32 = 24;
impl<'a, 'gcx, 'tcx> AdtDef {
/// Calculate the forest of DefIds from which this adt is visibly uninhabited.
pub fn uninhabited_from(
&self,
visited: &mut FxHashSet<(DefId, &'tcx Substs<'tcx>)>,
recursion_depth: u32,
visited: &mut FxHashMap<DefId, FxHashSet<&'tcx Substs<'tcx>>>,
tcx: TyCtxt<'a, 'gcx, 'tcx>,
substs: &'tcx Substs<'tcx>) -> DefIdForest
{
if !visited.insert((self.did, substs)) {
return DefIdForest::empty();
}
let ret = DefIdForest::intersection(tcx, self.variants.iter().map(|v| {
v.uninhabited_from(visited, recursion_depth, tcx, substs, self.adt_kind())
}));
visited.remove(&(self.did, substs));
ret
DefIdForest::intersection(tcx, self.variants.iter().map(|v| {
v.uninhabited_from(visited, tcx, substs, self.adt_kind())
}))
}
}
@ -89,8 +80,7 @@ impl<'a, 'gcx, 'tcx> VariantDef {
/// Calculate the forest of DefIds from which this variant is visibly uninhabited.
pub fn uninhabited_from(
&self,
visited: &mut FxHashSet<(DefId, &'tcx Substs<'tcx>)>,
recursion_depth: u32,
visited: &mut FxHashMap<DefId, FxHashSet<&'tcx Substs<'tcx>>>,
tcx: TyCtxt<'a, 'gcx, 'tcx>,
substs: &'tcx Substs<'tcx>,
adt_kind: AdtKind) -> DefIdForest
@ -98,17 +88,17 @@ impl<'a, 'gcx, 'tcx> VariantDef {
match adt_kind {
AdtKind::Union => {
DefIdForest::intersection(tcx, self.fields.iter().map(|f| {
f.uninhabited_from(visited, recursion_depth, tcx, substs, false)
f.uninhabited_from(visited, tcx, substs, false)
}))
},
AdtKind::Struct => {
DefIdForest::union(tcx, self.fields.iter().map(|f| {
f.uninhabited_from(visited, recursion_depth, tcx, substs, false)
f.uninhabited_from(visited, tcx, substs, false)
}))
},
AdtKind::Enum => {
DefIdForest::union(tcx, self.fields.iter().map(|f| {
f.uninhabited_from(visited, recursion_depth, tcx, substs, true)
f.uninhabited_from(visited, tcx, substs, true)
}))
},
}
@ -119,14 +109,13 @@ impl<'a, 'gcx, 'tcx> FieldDef {
/// Calculate the forest of DefIds from which this field is visibly uninhabited.
pub fn uninhabited_from(
&self,
visited: &mut FxHashSet<(DefId, &'tcx Substs<'tcx>)>,
recursion_depth: u32,
visited: &mut FxHashMap<DefId, FxHashSet<&'tcx Substs<'tcx>>>,
tcx: TyCtxt<'a, 'gcx, 'tcx>,
substs: &'tcx Substs<'tcx>,
is_enum: bool) -> DefIdForest
{
let mut data_uninhabitedness = move || {
self.ty(tcx, substs).uninhabited_from(visited, recursion_depth, tcx)
self.ty(tcx, substs).uninhabited_from(visited, tcx)
};
// FIXME(canndrew): Currently enum fields are (incorrectly) stored with
// Visibility::Invisible so we need to override self.vis if we're
@ -151,15 +140,9 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
/// Calculate the forest of DefIds from which this type is visibly uninhabited.
pub fn uninhabited_from(
&self,
visited: &mut FxHashSet<(DefId, &'tcx Substs<'tcx>)>,
mut recursion_depth: u32,
visited: &mut FxHashMap<DefId, FxHashSet<&'tcx Substs<'tcx>>>,
tcx: TyCtxt<'a, 'gcx, 'tcx>) -> DefIdForest
{
recursion_depth += 1;
if recursion_depth >= ARBITRARY_RECURSION_LIMIT {
return DefIdForest::empty();
}
match tcx.lift_to_global(&self) {
Some(global_ty) => {
{
@ -168,13 +151,13 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
return forest.clone();
}
}
let forest = global_ty.uninhabited_from_inner(visited, recursion_depth, tcx);
let forest = global_ty.uninhabited_from_inner(visited, tcx);
let mut cache = tcx.inhabitedness_cache.borrow_mut();
cache.insert(global_ty, forest.clone());
forest
},
None => {
let forest = self.uninhabited_from_inner(visited, recursion_depth, tcx);
let forest = self.uninhabited_from_inner(visited, tcx);
forest
},
}
@ -182,30 +165,54 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
fn uninhabited_from_inner(
&self,
visited: &mut FxHashSet<(DefId, &'tcx Substs<'tcx>)>,
recursion_depth: u32,
visited: &mut FxHashMap<DefId, FxHashSet<&'tcx Substs<'tcx>>>,
tcx: TyCtxt<'a, 'gcx, 'tcx>) -> DefIdForest
{
match self.sty {
TyAdt(def, substs) => {
def.uninhabited_from(visited, recursion_depth, tcx, substs)
{
let mut substs_set = visited.entry(def.did).or_insert(FxHashSet::default());
if !substs_set.insert(substs) {
// We are already calculating the inhabitedness of this type.
// The type must contain a reference to itself. Break the
// infinite loop.
return DefIdForest::empty();
}
if substs_set.len() >= tcx.sess.recursion_limit.get() / 4 {
// We have gone very deep, reinstantiating this ADT inside
// itself with different type arguments. We are probably
// hitting an infinite loop. For example, it's possible to write:
// a type Foo<T>
// which contains a Foo<(T, T)>
// which contains a Foo<((T, T), (T, T))>
// which contains a Foo<(((T, T), (T, T)), ((T, T), (T, T)))>
// etc.
let error = format!("reached recursion limit while checking
inhabitedness of `{}`", self);
tcx.sess.fatal(&error);
}
}
let ret = def.uninhabited_from(visited, tcx, substs);
let mut substs_set = visited.get_mut(&def.did).unwrap();
substs_set.remove(substs);
ret
},
TyNever => DefIdForest::full(tcx),
TyTuple(ref tys, _) => {
DefIdForest::union(tcx, tys.iter().map(|ty| {
ty.uninhabited_from(visited, recursion_depth, tcx)
ty.uninhabited_from(visited, tcx)
}))
},
TyArray(ty, len) => {
if len == 0 {
DefIdForest::empty()
} else {
ty.uninhabited_from(visited, recursion_depth, tcx)
ty.uninhabited_from(visited, tcx)
}
}
TyRef(_, ref tm) => {
tm.ty.uninhabited_from(visited, recursion_depth, tcx)
tm.ty.uninhabited_from(visited, tcx)
}
_ => DefIdForest::empty(),

6
src/librustc/ty/sty.rs
View File

@ -24,7 +24,7 @@ use std::cmp::Ordering;
use syntax::abi;
use syntax::ast::{self, Name};
use syntax::symbol::{keywords, InternedString};
use util::nodemap::FxHashSet;
use util::nodemap::FxHashMap;
use serialize;
@ -1018,8 +1018,8 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
/// This code should only compile in modules where the uninhabitedness of Foo is
/// visible.
pub fn is_uninhabited_from(&self, module: DefId, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> bool {
let mut visited = FxHashSet::default();
let forest = self.uninhabited_from(&mut visited, 0, tcx);
let mut visited = FxHashMap::default();
let forest = self.uninhabited_from(&mut visited, tcx);
// To check whether this type is uninhabited at all (not just from the
// given node) you could check whether the forest is empty.

6
src/librustc_const_eval/_match.rs
View File

@ -17,7 +17,7 @@ use eval::{compare_const_vals};
use rustc_const_math::ConstInt;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::indexed_vec::Idx;
use pattern::{FieldPattern, Pattern, PatternKind};
@ -404,8 +404,8 @@ fn all_constructors<'a, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
}
ty::TyAdt(def, substs) if def.is_enum() && def.variants.len() != 1 => {
def.variants.iter().filter_map(|v| {
let mut visited = FxHashSet::default();
let forest = v.uninhabited_from(&mut visited, 0,
let mut visited = FxHashMap::default();
let forest = v.uninhabited_from(&mut visited,
cx.tcx, substs,
AdtKind::Enum);
if forest.contains(cx.tcx, cx.module)

6
src/librustc_mir/build/matches/simplify.rs
View File

@ -26,7 +26,7 @@ use build::{BlockAnd, BlockAndExtension, Builder};
use build::matches::{Binding, MatchPair, Candidate};
use hair::*;
use rustc::mir::*;
use rustc_data_structures::fx::FxHashSet;
use rustc_data_structures::fx::FxHashMap;
use std::mem;
@ -102,8 +102,8 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
if self.hir.tcx().sess.features.borrow().never_type {
let irrefutable = adt_def.variants.iter().enumerate().all(|(i, v)| {
i == variant_index || {
let mut visited = FxHashSet::default();
let node_set = v.uninhabited_from(&mut visited, 0,
let mut visited = FxHashMap::default();
let node_set = v.uninhabited_from(&mut visited,
self.hir.tcx(),
substs,
adt_def.adt_kind());

3
src/test/compile-fail/inhabitedness-infinite-loop.rs
View File

@ -8,6 +8,8 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// error-pattern:reached recursion limit
#![feature(never_type)]
struct Foo<'a, T: 'a> {
@ -17,7 +19,6 @@ struct Foo<'a, T: 'a> {
fn wub(f: Foo<!>) {
match f {}
//~^ ERROR non-exhaustive
}
fn main() {}