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un-break the `construct_witness` logic 

Fixes #35609.
This commit is contained in:
Ariel Ben-Yehuda 2016-09-24 20:45:59 +03:00
parent abae5e7e25
commit 04a92a1f56
4 changed files with 290 additions and 150 deletions
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333
src/librustc_const_eval/_match.rs
View File

@ -171,7 +171,7 @@ impl Constructor {
#[derive(Clone, PartialEq)]
pub enum Usefulness {
Useful,
UsefulWithWitness(Vec<P<Pat>>),
UsefulWithWitness(Vec<Witness>),
NotUseful
}
@ -181,6 +181,13 @@ pub enum WitnessPreference {
LeaveOutWitness
}
#[derive(Copy, Clone, Debug)]
struct PatternContext<'tcx> {
ty: Ty<'tcx>,
max_slice_length: usize,
}
fn const_val_to_expr(value: &ConstVal) -> P<hir::Expr> {
let node = match value {
&ConstVal::Bool(b) => ast::LitKind::Bool(b),
@ -194,93 +201,126 @@ fn const_val_to_expr(value: &ConstVal) -> P<hir::Expr> {
})
}
/// Constructs a partial witness for a pattern given a list of
/// patterns expanded by the specialization step.
///
/// When a pattern P is discovered to be useful, this function is used bottom-up
/// to reconstruct a complete witness, e.g. a pattern P' that covers a subset
/// of values, V, where each value in that set is not covered by any previously
/// used patterns and is covered by the pattern P'. Examples:
///
/// left_ty: tuple of 3 elements
/// pats: [10, 20, _] => (10, 20, _)
///
/// left_ty: struct X { a: (bool, &'static str), b: usize}
/// pats: [(false, "foo"), 42] => X { a: (false, "foo"), b: 42 }
fn construct_witness<'a,'tcx>(cx: &MatchCheckCtxt<'a,'tcx>, ctor: &Constructor,
pats: Vec<&Pat>, left_ty: Ty<'tcx>) -> P<Pat> {
let pats_len = pats.len();
let mut pats = pats.into_iter().map(|p| P((*p).clone()));
let pat = match left_ty.sty {
ty::TyTuple(..) => PatKind::Tuple(pats.collect(), None),
/// A stack of patterns in reverse order of construction
#[derive(Clone, PartialEq, Eq)]
pub struct Witness(Vec<P<Pat>>);
ty::TyAdt(adt, _) => {
let v = ctor.variant_for_adt(adt);
match v.ctor_kind {
CtorKind::Fictive => {
let field_pats: hir::HirVec<_> = v.fields.iter()
.zip(pats)
.filter(|&(_, ref pat)| pat.node != PatKind::Wild)
.map(|(field, pat)| Spanned {
span: DUMMY_SP,
node: hir::FieldPat {
name: field.name,
pat: pat,
is_shorthand: false,
}
}).collect();
let has_more_fields = field_pats.len() < pats_len;
PatKind::Struct(def_to_path(cx.tcx, v.did), field_pats, has_more_fields)
impl Witness {
pub fn single_pattern(&self) -> &Pat {
assert_eq!(self.0.len(), 1);
&self.0[0]
}
fn push_wild_constructor<'a, 'tcx>(
mut self,
cx: &MatchCheckCtxt<'a, 'tcx>,
ctor: &Constructor,
ty: Ty<'tcx>)
-> Self
{
let arity = constructor_arity(cx, ctor, ty);
self.0.extend(repeat(DUMMY_WILD_PAT).take(arity).map(|p| P(p.clone())));
self.apply_constructor(cx, ctor, ty)
}
/// Constructs a partial witness for a pattern given a list of
/// patterns expanded by the specialization step.
///
/// When a pattern P is discovered to be useful, this function is used bottom-up
/// to reconstruct a complete witness, e.g. a pattern P' that covers a subset
/// of values, V, where each value in that set is not covered by any previously
/// used patterns and is covered by the pattern P'. Examples:
///
/// left_ty: tuple of 3 elements
/// pats: [10, 20, _] => (10, 20, _)
///
/// left_ty: struct X { a: (bool, &'static str), b: usize}
/// pats: [(false, "foo"), 42] => X { a: (false, "foo"), b: 42 }
fn apply_constructor<'a, 'tcx>(
mut self,
cx: &MatchCheckCtxt<'a,'tcx>,
ctor: &Constructor,
ty: Ty<'tcx>)
-> Self
{
let arity = constructor_arity(cx, ctor, ty);
let pat = {
let len = self.0.len();
let mut pats = self.0.drain(len-arity..).rev();
match ty.sty {
ty::TyTuple(..) => PatKind::Tuple(pats.collect(), None),
ty::TyAdt(adt, _) => {
let v = ctor.variant_for_adt(adt);
match v.ctor_kind {
CtorKind::Fictive => {
let field_pats: hir::HirVec<_> = v.fields.iter()
.zip(pats)
.filter(|&(_, ref pat)| pat.node != PatKind::Wild)
.map(|(field, pat)| Spanned {
span: DUMMY_SP,
node: hir::FieldPat {
name: field.name,
pat: pat,
is_shorthand: false,
}
}).collect();
let has_more_fields = field_pats.len() < arity;
PatKind::Struct(
def_to_path(cx.tcx, v.did), field_pats, has_more_fields)
}
CtorKind::Fn => {
PatKind::TupleStruct(
def_to_path(cx.tcx, v.did), pats.collect(), None)
}
CtorKind::Const => {
PatKind::Path(None, def_to_path(cx.tcx, v.did))
}
}
}
CtorKind::Fn => {
PatKind::TupleStruct(def_to_path(cx.tcx, v.did), pats.collect(), None)
ty::TyRef(_, ty::TypeAndMut { mutbl, .. }) => {
PatKind::Ref(pats.nth(0).unwrap(), mutbl)
}
CtorKind::Const => {
PatKind::Path(None, def_to_path(cx.tcx, v.did))
ty::TySlice(_) | ty::TyArray(..) => {
PatKind::Slice(pats.collect(), None, hir::HirVec::new())
}
_ => {
match *ctor {
ConstantValue(ref v) => PatKind::Lit(const_val_to_expr(v)),
_ => PatKind::Wild,
}
}
}
}
};
ty::TyRef(_, ty::TypeAndMut { mutbl, .. }) => {
assert_eq!(pats_len, 1);
PatKind::Ref(pats.nth(0).unwrap(), mutbl)
}
self.0.push(P(hir::Pat {
id: DUMMY_NODE_ID,
node: pat,
span: DUMMY_SP
}));
ty::TySlice(_) => match ctor {
&Slice(n) => {
assert_eq!(pats_len, n);
PatKind::Slice(pats.collect(), None, hir::HirVec::new())
},
_ => unreachable!()
},
ty::TyArray(_, len) => {
assert_eq!(pats_len, len);
PatKind::Slice(pats.collect(), None, hir::HirVec::new())
}
_ => {
match *ctor {
ConstantValue(ref v) => PatKind::Lit(const_val_to_expr(v)),
_ => PatKind::Wild,
}
}
};
P(hir::Pat {
id: DUMMY_NODE_ID,
node: pat,
span: DUMMY_SP
})
self
}
}
fn missing_constructors(cx: &MatchCheckCtxt, &Matrix(ref rows): &Matrix,
left_ty: Ty, max_slice_length: usize) -> Vec<Constructor> {
let used_constructors: Vec<Constructor> = rows.iter()
.flat_map(|row| pat_constructors(cx, row[0], left_ty, max_slice_length))
/// Return the set of constructors from the same type as the first column of `matrix`,
/// that are matched only by wildcard patterns from that first column.
///
/// Therefore, if there is some pattern that is unmatched by `matrix`, it will
/// still be unmatched if the first constructor is replaced by any of the constructors
/// in the return value.
fn missing_constructors(cx: &MatchCheckCtxt, matrix: &Matrix,
pcx: PatternContext) -> Vec<Constructor> {
let used_constructors: Vec<Constructor> =
matrix.0.iter()
.flat_map(|row| pat_constructors(cx, row[0], pcx).unwrap_or(vec![]))
.collect();
all_constructors(cx, left_ty, max_slice_length)
.into_iter()
all_constructors(cx, pcx).into_iter()
.filter(|c| !used_constructors.contains(c))
.collect()
}
@ -289,13 +329,12 @@ fn missing_constructors(cx: &MatchCheckCtxt, &Matrix(ref rows): &Matrix,
/// values of type `left_ty`. For vectors, this would normally be an infinite set
/// but is instead bounded by the maximum fixed length of slice patterns in
/// the column of patterns being analyzed.
fn all_constructors(_cx: &MatchCheckCtxt, left_ty: Ty,
max_slice_length: usize) -> Vec<Constructor> {
match left_ty.sty {
fn all_constructors(_cx: &MatchCheckCtxt, pcx: PatternContext) -> Vec<Constructor> {
match pcx.ty.sty {
ty::TyBool =>
[true, false].iter().map(|b| ConstantValue(ConstVal::Bool(*b))).collect(),
ty::TySlice(_) =>
(0..max_slice_length+1).map(|length| Slice(length)).collect(),
(0..pcx.max_slice_length+1).map(|length| Slice(length)).collect(),
ty::TyAdt(def, _) if def.is_enum() =>
def.variants.iter().map(|v| Variant(v.did)).collect(),
_ => vec![Single]
@ -324,7 +363,9 @@ pub fn is_useful<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>,
debug!("is_useful({:?}, {:?})", matrix, v);
if rows.is_empty() {
return match witness {
ConstructWitness => UsefulWithWitness(vec!()),
ConstructWitness => UsefulWithWitness(vec![Witness(
repeat(DUMMY_WILD_PAT).take(v.len()).map(|p| P(p.clone())).collect()
)]),
LeaveOutWitness => Useful
};
}
@ -332,44 +373,37 @@ pub fn is_useful<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>,
return NotUseful;
}
assert!(rows.iter().all(|r| r.len() == v.len()));
let left_ty = match rows.iter().filter_map(|r| r[0].pattern_ty).next()
.or_else(|| v[0].pattern_ty)
{
Some(ty) => ty,
None => {
// all patterns are wildcards - we can pick any type we want
cx.tcx.types.bool
}
let pcx = PatternContext {
ty: match rows.iter().filter_map(|r| r[0].pattern_ty).next()
.or_else(|| v[0].pattern_ty)
{
Some(ty) => ty,
None => {
// all patterns are wildcards - we can pick any type we want
cx.tcx.types.bool
}
},
max_slice_length: rows.iter().filter_map(|row| match row[0].pat.node {
PatKind::Slice(ref before, _, ref after) => Some(before.len() + after.len()),
_ => None
}).max().map_or(0, |v| v + 1)
};
let max_slice_length = rows.iter().filter_map(|row| match row[0].pat.node {
PatKind::Slice(ref before, _, ref after) => Some(before.len() + after.len()),
_ => None
}).max().map_or(0, |v| v + 1);
debug!("is_useful: pcx={:?}, expanding {:?}", pcx, v[0]);
let constructors = pat_constructors(cx, v[0], left_ty, max_slice_length);
debug!("is_useful - pat_constructors = {:?} left_ty = {:?}", constructors,
left_ty);
if constructors.is_empty() {
let constructors = missing_constructors(cx, matrix, left_ty, max_slice_length);
if let Some(constructors) = pat_constructors(cx, v[0], pcx) {
debug!("is_useful - expanding constructors: {:?}", constructors);
constructors.into_iter().map(|c|
is_useful_specialized(cx, matrix, v, c.clone(), pcx.ty, witness)
).find(|result| result != &NotUseful).unwrap_or(NotUseful)
} else {
debug!("is_useful - expanding wildcard");
let constructors = missing_constructors(cx, matrix, pcx);
debug!("is_useful - missing_constructors = {:?}", constructors);
if constructors.is_empty() {
all_constructors(cx, left_ty, max_slice_length).into_iter().map(|c| {
match is_useful_specialized(cx, matrix, v, c.clone(), left_ty, witness) {
UsefulWithWitness(pats) => UsefulWithWitness({
let arity = constructor_arity(cx, &c, left_ty);
let mut result = {
let pat_slice = &pats[..];
let subpats: Vec<_> = (0..arity).map(|i| {
pat_slice.get(i).map_or(DUMMY_WILD_PAT, |p| &**p)
}).collect();
vec![construct_witness(cx, &c, subpats, left_ty)]
};
result.extend(pats.into_iter().skip(arity));
result
}),
result => result
}
all_constructors(cx, pcx).into_iter().map(|c| {
is_useful_specialized(cx, matrix, v, c.clone(), pcx.ty, witness)
}).find(|result| result != &NotUseful).unwrap_or(NotUseful)
} else {
let matrix = rows.iter().filter_map(|r| {
@ -380,21 +414,15 @@ pub fn is_useful<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>,
}).collect();
match is_useful(cx, &matrix, &v[1..], witness) {
UsefulWithWitness(pats) => {
let mut new_pats: Vec<_> = constructors.into_iter().map(|constructor| {
let arity = constructor_arity(cx, &constructor, left_ty);
let wild_pats = vec![DUMMY_WILD_PAT; arity];
construct_witness(cx, &constructor, wild_pats, left_ty)
}).collect();
new_pats.extend(pats);
UsefulWithWitness(new_pats)
},
UsefulWithWitness(pats.into_iter().flat_map(|witness| {
constructors.iter().map(move |ctor| {
witness.clone().push_wild_constructor(cx, ctor, pcx.ty)
})
}).collect())
}
result => result
}
}
} else {
constructors.into_iter().map(|c|
is_useful_specialized(cx, matrix, v, c.clone(), left_ty, witness)
).find(|result| result != &NotUseful).unwrap_or(NotUseful)
}
}
@ -411,7 +439,14 @@ fn is_useful_specialized<'a, 'tcx>(
specialize(cx, &r[..], &ctor, 0, arity)
}).collect());
match specialize(cx, v, &ctor, 0, arity) {
Some(v) => is_useful(cx, &matrix, &v[..], witness),
Some(v) => match is_useful(cx, &matrix, &v[..], witness) {
UsefulWithWitness(witnesses) => UsefulWithWitness(
witnesses.into_iter()
.map(|witness| witness.apply_constructor(cx, &ctor, lty))
.collect()
),
result => result
},
None => NotUseful
}
}
@ -423,41 +458,43 @@ fn is_useful_specialized<'a, 'tcx>(
/// Slice patterns, however, can match slices of different lengths. For instance,
/// `[a, b, ..tail]` can match a slice of length 2, 3, 4 and so on.
///
/// On the other hand, a wild pattern and an identifier pattern cannot be
/// specialized in any way.
fn pat_constructors(cx: &MatchCheckCtxt, p: Pattern,
left_ty: Ty, max_slice_length: usize) -> Vec<Constructor> {
/// Returns None in case of a catch-all, which can't be specialized.
fn pat_constructors(cx: &MatchCheckCtxt,
p: Pattern,
pcx: PatternContext)
-> Option<Vec<Constructor>>
{
let pat = p.as_raw();
match pat.node {
PatKind::Struct(..) | PatKind::TupleStruct(..) | PatKind::Path(..) =>
match cx.tcx.expect_def(pat.id) {
Def::Variant(id) | Def::VariantCtor(id, _) => vec![Variant(id)],
Def::Variant(id) | Def::VariantCtor(id, _) => Some(vec![Variant(id)]),
Def::Struct(..) | Def::StructCtor(..) | Def::Union(..) |
Def::TyAlias(..) | Def::AssociatedTy(..) => vec![Single],
Def::TyAlias(..) | Def::AssociatedTy(..) => Some(vec![Single]),
Def::Const(..) | Def::AssociatedConst(..) =>
span_bug!(p.span(), "const pattern should've been rewritten"),
def => span_bug!(p.span(), "pat_constructors: unexpected definition {:?}", def),
},
PatKind::Lit(ref expr) =>
vec![ConstantValue(eval_const_expr(cx.tcx, &expr))],
Some(vec![ConstantValue(eval_const_expr(cx.tcx, &expr))]),
PatKind::Range(ref lo, ref hi) =>
vec![ConstantRange(eval_const_expr(cx.tcx, &lo), eval_const_expr(cx.tcx, &hi))],
Some(vec![ConstantRange(eval_const_expr(cx.tcx, &lo), eval_const_expr(cx.tcx, &hi))]),
PatKind::Slice(ref before, ref slice, ref after) =>
match left_ty.sty {
ty::TyArray(..) => vec![Single],
match pcx.ty.sty {
ty::TyArray(..) => Some(vec![Single]),
ty::TySlice(_) if slice.is_some() => {
(before.len() + after.len()..max_slice_length+1)
.map(|length| Slice(length))
.collect()
Some((before.len() + after.len()..pcx.max_slice_length+1)
.map(|length| Slice(length))
.collect())
}
ty::TySlice(_) => vec!(Slice(before.len() + after.len())),
ty::TySlice(_) => Some(vec!(Slice(before.len() + after.len()))),
_ => span_bug!(pat.span, "pat_constructors: unexpected \
slice pattern type {:?}", left_ty)
slice pattern type {:?}", pcx.ty)
},
PatKind::Box(..) | PatKind::Tuple(..) | PatKind::Ref(..) =>
vec![Single],
Some(vec![Single]),
PatKind::Binding(..) | PatKind::Wild =>
vec![],
None,
}
}
@ -466,7 +503,7 @@ fn pat_constructors(cx: &MatchCheckCtxt, p: Pattern,
///
/// For instance, a tuple pattern (_, 42, Some([])) has the arity of 3.
/// A struct pattern's arity is the number of fields it contains, etc.
pub fn constructor_arity(_cx: &MatchCheckCtxt, ctor: &Constructor, ty: Ty) -> usize {
fn constructor_arity(_cx: &MatchCheckCtxt, ctor: &Constructor, ty: Ty) -> usize {
debug!("constructor_arity({:?}, {:?})", ctor, ty);
match ty.sty {
ty::TyTuple(ref fs) => fs.len(),
@ -685,7 +722,7 @@ fn specialize<'a, 'b, 'tcx>(
pub fn is_refutable<A, F>(cx: &MatchCheckCtxt, pat: &Pat, refutable: F)
-> Option<A> where
F: FnOnce(&Pat) -> A,
F: FnOnce(&Witness) -> A,
{
let pats = Matrix(vec!(vec!(wrap_pat(cx, pat))));
match is_useful(cx, &pats, &[DUMMY_WILD_PATTERN], ConstructWitness) {

4
src/librustc_const_eval/check_match.rs
View File

@ -297,7 +297,7 @@ fn check_exhaustive<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>,
let witnesses = if pats.is_empty() {
vec![DUMMY_WILD_PAT]
} else {
pats.iter().map(|w| &**w).collect()
pats.iter().map(|w| w.single_pattern()).collect()
};
match source {
hir::MatchSource::ForLoopDesugar => {
@ -484,7 +484,7 @@ fn check_irrefutable(cx: &MatchCheckCtxt, pat: &Pat, is_fn_arg: bool) {
};
is_refutable(cx, pat, |uncovered_pat| {
let pattern_string = pat_to_string(uncovered_pat);
let pattern_string = pat_to_string(uncovered_pat.single_pattern());
struct_span_err!(cx.tcx.sess, pat.span, E0005,
"refutable pattern in {}: `{}` not covered",
origin,

53
src/test/ui/check_match/issue-35609.rs Normal file
View File

@ -0,0 +1,53 @@
// 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 <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.
enum Enum {
A, B, C, D, E, F
}
use Enum::*;
struct S(Enum, ());
struct Sd { x: Enum, y: () }
fn main() {
match (A, ()) {
(A, _) => {}
}
match (A, A) {
(_, A) => {}
}
match ((A, ()), ()) {
((A, ()), _) => {}
}
match ((A, ()), A) {
((A, ()), _) => {}
}
match ((A, ()), ()) {
((A, _), _) => {}
}
match S(A, ()) {
S(A, _) => {}
}
match (Sd { x: A, y: () }) {
Sd { x: A, y: _ } => {}
}
match Some(A) {
Some(A) => (),
None => ()
}
}

50
src/test/ui/check_match/issue-35609.stderr Normal file
View File

@ -0,0 +1,50 @@
error[E0004]: non-exhaustive patterns: `(B, _)`, `(C, _)`, `(D, _)` and 2 more not covered
--> $DIR/issue-35609.rs:20:11
|
20 | match (A, ()) {
| ^^^^^^^ patterns `(B, _)`, `(C, _)`, `(D, _)` and 2 more not covered
error[E0004]: non-exhaustive patterns: `(A, B)`, `(B, B)`, `(C, B)` and 27 more not covered
--> $DIR/issue-35609.rs:24:11
|
24 | match (A, A) {
| ^^^^^^ patterns `(A, B)`, `(B, B)`, `(C, B)` and 27 more not covered
error[E0004]: non-exhaustive patterns: `((B, _), _)`, `((C, _), _)`, `((D, _), _)` and 2 more not covered
--> $DIR/issue-35609.rs:28:11
|
28 | match ((A, ()), ()) {
| ^^^^^^^^^^^^^ patterns `((B, _), _)`, `((C, _), _)`, `((D, _), _)` and 2 more not covered
error[E0004]: non-exhaustive patterns: `((B, _), _)`, `((C, _), _)`, `((D, _), _)` and 2 more not covered
--> $DIR/issue-35609.rs:32:11
|
32 | match ((A, ()), A) {
| ^^^^^^^^^^^^ patterns `((B, _), _)`, `((C, _), _)`, `((D, _), _)` and 2 more not covered
error[E0004]: non-exhaustive patterns: `((B, _), _)`, `((C, _), _)`, `((D, _), _)` and 2 more not covered
--> $DIR/issue-35609.rs:36:11
|
36 | match ((A, ()), ()) {
| ^^^^^^^^^^^^^ patterns `((B, _), _)`, `((C, _), _)`, `((D, _), _)` and 2 more not covered
error[E0004]: non-exhaustive patterns: `S(B, _)`, `S(C, _)`, `S(D, _)` and 2 more not covered
--> $DIR/issue-35609.rs:41:11
|
41 | match S(A, ()) {
| ^^^^^^^^ patterns `S(B, _)`, `S(C, _)`, `S(D, _)` and 2 more not covered
error[E0004]: non-exhaustive patterns: `Sd { x: B, .. }`, `Sd { x: C, .. }`, `Sd { x: D, .. }` and 2 more not covered
--> $DIR/issue-35609.rs:45:11
|
45 | match (Sd { x: A, y: () }) {
| ^^^^^^^^^^^^^^^^^^^^ patterns `Sd { x: B, .. }`, `Sd { x: C, .. }`, `Sd { x: D, .. }` and 2 more not covered
error[E0004]: non-exhaustive patterns: `Some(B)`, `Some(C)`, `Some(D)` and 2 more not covered
--> $DIR/issue-35609.rs:49:11
|
49 | match Some(A) {
| ^^^^^^^ patterns `Some(B)`, `Some(C)`, `Some(D)` and 2 more not covered
error: aborting due to 8 previous errors