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use a struct abstraction in check_match

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This commit is contained in:
Ariel Ben-Yehuda 2016-09-24 16:49:51 +03:00
parent b69cca6da4
commit bb5afb4121
1 changed files with 94 additions and 60 deletions
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154
src/librustc_const_eval/check_match.rs
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@ -52,7 +52,55 @@ pub const DUMMY_WILD_PAT: &'static Pat = &Pat {
span: DUMMY_SP
};
struct Matrix<'a, 'tcx>(Vec<Vec<(&'a Pat, Option<Ty<'tcx>>)>>);
pub const DUMMY_WILD_PATTERN : Pattern<'static, 'static> = Pattern {
pat: DUMMY_WILD_PAT,
pattern_ty: None
};
#[derive(Copy, Clone)]
pub struct Pattern<'a, 'tcx> {
pat: &'a Pat,
pattern_ty: Option<Ty<'tcx>>
}
impl<'a, 'tcx> Pattern<'a, 'tcx> {
fn as_raw(self) -> &'a Pat {
let mut pat = self.pat;
while let PatKind::Binding(.., Some(ref s)) = pat.node {
pat = s;
}
return pat;
}
/// Checks for common cases of "catchall" patterns that may not be intended as such.
fn is_catchall(self, dm: &DefMap) -> bool {
fn is_catchall(dm: &DefMap, pat: &Pat) -> bool {
match pat.node {
PatKind::Binding(.., None) => true,
PatKind::Binding(.., Some(ref s)) => is_catchall(dm, s),
PatKind::Ref(ref s, _) => is_catchall(dm, s),
PatKind::Tuple(ref v, _) => v.iter().all(|p|is_catchall(dm, &p)),
_ => false
}
}
is_catchall(dm, self.pat)
}
fn span(self) -> Span {
self.pat.span
}
}
struct Matrix<'a, 'tcx>(Vec<Vec<Pattern<'a, 'tcx>>>);
impl<'a, 'tcx> fmt::Debug for Pattern<'a, 'tcx> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "{}: {:?}", pat_to_string(self.pat), self.pattern_ty)
}
}
/// Pretty-printer for matrices of patterns, example:
/// ++++++++++++++++++++++++++
@ -72,9 +120,7 @@ impl<'a, 'tcx> fmt::Debug for Matrix<'a, 'tcx> {
let &Matrix(ref m) = self;
let pretty_printed_matrix: Vec<Vec<String>> = m.iter().map(|row| {
row.iter()
.map(|&(pat,ty)| format!("{}: {:?}", pat_to_string(&pat), ty))
.collect::<Vec<String>>()
row.iter().map(|pat| format!("{:?}", pat)).collect()
}).collect();
let column_count = m.iter().map(|row| row.len()).max().unwrap_or(0);
@ -100,9 +146,8 @@ impl<'a, 'tcx> fmt::Debug for Matrix<'a, 'tcx> {
}
}
impl<'a, 'tcx> FromIterator<Vec<(&'a Pat, Option<Ty<'tcx>>)>> for Matrix<'a, 'tcx> {
fn from_iter<T: IntoIterator<Item=Vec<(&'a Pat, Option<Ty<'tcx>>)>>>(iter: T)
-> Self
impl<'a, 'tcx> FromIterator<Vec<Pattern<'a, 'tcx>>> for Matrix<'a, 'tcx> {
fn from_iter<T: IntoIterator<Item=Vec<Pattern<'a, 'tcx>>>>(iter: T) -> Self
{
Matrix(iter.into_iter().collect())
}
@ -349,8 +394,8 @@ fn check_arms(cx: &MatchCheckCtxt,
err.span_label(pat.span, &format!("this is an unreachable pattern"));
// if we had a catchall pattern, hint at that
for row in &seen.0 {
if pat_is_catchall(&cx.tcx.def_map.borrow(), row[0].0) {
span_note!(err, row[0].0.span,
if row[0].is_catchall(&cx.tcx.def_map.borrow()) {
span_note!(err, row[0].span(),
"this pattern matches any value");
}
}
@ -374,29 +419,11 @@ fn check_arms(cx: &MatchCheckCtxt,
}
}
/// Checks for common cases of "catchall" patterns that may not be intended as such.
fn pat_is_catchall(dm: &DefMap, p: &Pat) -> bool {
match p.node {
PatKind::Binding(.., None) => true,
PatKind::Binding(.., Some(ref s)) => pat_is_catchall(dm, &s),
PatKind::Ref(ref s, _) => pat_is_catchall(dm, &s),
PatKind::Tuple(ref v, _) => v.iter().all(|p| pat_is_catchall(dm, &p)),
_ => false
}
}
fn raw_pat(p: &Pat) -> &Pat {
match p.node {
PatKind::Binding(.., Some(ref s)) => raw_pat(&s),
_ => p
}
}
fn check_exhaustive<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>,
sp: Span,
matrix: &Matrix<'a, 'tcx>,
source: hir::MatchSource) {
match is_useful(cx, matrix, &[(DUMMY_WILD_PAT, None)], ConstructWitness) {
match is_useful(cx, matrix, &[DUMMY_WILD_PATTERN], ConstructWitness) {
UsefulWithWitness(pats) => {
let witnesses = if pats.is_empty() {
vec![DUMMY_WILD_PAT]
@ -655,7 +682,7 @@ impl Constructor {
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].0, left_ty, max_slice_length))
.flat_map(|row| pat_constructors(cx, row[0], left_ty, max_slice_length))
.collect();
all_constructors(cx, left_ty, max_slice_length)
.into_iter()
@ -695,7 +722,7 @@ fn all_constructors(_cx: &MatchCheckCtxt, left_ty: Ty,
// So it assumes that v is non-empty.
fn is_useful<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>,
matrix: &Matrix<'a, 'tcx>,
v: &[(&Pat, Option<Ty<'tcx>>)],
v: &[Pattern<'a, 'tcx>],
witness: WitnessPreference)
-> Usefulness {
let &Matrix(ref rows) = matrix;
@ -710,7 +737,9 @@ 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].1).next().or_else(|| v[0].1) {
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
@ -718,12 +747,12 @@ fn is_useful<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>,
}
};
let max_slice_length = rows.iter().filter_map(|row| match row[0].0.node {
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);
let constructors = pat_constructors(cx, v[0].0, left_ty, max_slice_length);
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() {
@ -749,7 +778,7 @@ fn is_useful<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>,
}).find(|result| result != &NotUseful).unwrap_or(NotUseful)
} else {
let matrix = rows.iter().filter_map(|r| {
match raw_pat(r[0].0).node {
match r[0].as_raw().node {
PatKind::Binding(..) | PatKind::Wild => Some(r[1..].to_vec()),
_ => None,
}
@ -777,7 +806,7 @@ fn is_useful<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>,
fn is_useful_specialized<'a, 'tcx>(
cx: &MatchCheckCtxt<'a, 'tcx>,
&Matrix(ref m): &Matrix<'a, 'tcx>,
v: &[(&Pat, Option<Ty<'tcx>>)],
v: &[Pattern<'a, 'tcx>],
ctor: Constructor,
lty: Ty<'tcx>,
witness: WitnessPreference) -> Usefulness
@ -801,9 +830,9 @@ fn is_useful_specialized<'a, 'tcx>(
///
/// On the other hand, a wild pattern and an identifier pattern cannot be
/// specialized in any way.
fn pat_constructors(cx: &MatchCheckCtxt, p: &Pat,
fn pat_constructors(cx: &MatchCheckCtxt, p: Pattern,
left_ty: Ty, max_slice_length: usize) -> Vec<Constructor> {
let pat = raw_pat(p);
let pat = p.as_raw();
match pat.node {
PatKind::Struct(..) | PatKind::TupleStruct(..) | PatKind::Path(..) =>
match cx.tcx.expect_def(pat.id) {
@ -811,8 +840,8 @@ fn pat_constructors(cx: &MatchCheckCtxt, p: &Pat,
Def::Struct(..) | Def::StructCtor(..) | Def::Union(..) |
Def::TyAlias(..) | Def::AssociatedTy(..) => vec![Single],
Def::Const(..) | Def::AssociatedConst(..) =>
span_bug!(pat.span, "const pattern should've been rewritten"),
def => span_bug!(pat.span, "pat_constructors: unexpected definition {:?}", def),
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))],
@ -881,15 +910,18 @@ fn range_covered_by_constructor(tcx: TyCtxt, span: Span,
fn wrap_pat<'a, 'b, 'tcx>(cx: &MatchCheckCtxt<'b, 'tcx>,
pat: &'a Pat)
-> (&'a Pat, Option<Ty<'tcx>>)
-> Pattern<'a, 'tcx>
{
let pat_ty = cx.tcx.pat_ty(pat);
(pat, Some(match pat.node {
PatKind::Binding(hir::BindByRef(..), ..) => {
pat_ty.builtin_deref(false, ty::NoPreference).unwrap().ty
}
_ => pat_ty
}))
Pattern {
pat: pat,
pattern_ty: Some(match pat.node {
PatKind::Binding(hir::BindByRef(..), ..) => {
pat_ty.builtin_deref(false, ty::NoPreference).unwrap().ty
}
_ => pat_ty
})
}
}
/// This is the main specialization step. It expands the first pattern in the given row
@ -902,20 +934,19 @@ fn wrap_pat<'a, 'b, 'tcx>(cx: &MatchCheckCtxt<'b, 'tcx>,
/// fields filled with wild patterns.
pub fn specialize<'a, 'b, 'tcx>(
cx: &MatchCheckCtxt<'b, 'tcx>,
r: &[(&'a Pat, Option<Ty<'tcx>>)],
r: &[Pattern<'a, 'tcx>],
constructor: &Constructor, col: usize, arity: usize)
-> Option<Vec<(&'a Pat, Option<Ty<'tcx>>)>>
-> Option<Vec<Pattern<'a, 'tcx>>>
{
let pat = raw_pat(r[col].0);
let pat = r[col].as_raw();
let &Pat {
id: pat_id, ref node, span: pat_span
} = pat;
let wpat = |pat: &'a Pat| wrap_pat(cx, pat);
let dummy_pat = (DUMMY_WILD_PAT, None);
let head: Option<Vec<(&Pat, Option<Ty>)>> = match *node {
let head: Option<Vec<Pattern>> = match *node {
PatKind::Binding(..) | PatKind::Wild =>
Some(vec![dummy_pat; arity]),
Some(vec![DUMMY_WILD_PATTERN; arity]),
PatKind::Path(..) => {
match cx.tcx.expect_def(pat_id) {
@ -942,7 +973,7 @@ pub fn specialize<'a, 'b, 'tcx>(
let mut pats: Vec<_> = args[..ddpos].iter().map(|p| {
wpat(p)
}).collect();
pats.extend(repeat((DUMMY_WILD_PAT, None)).take(arity - args.len()));
pats.extend(repeat(DUMMY_WILD_PATTERN).take(arity - args.len()));
pats.extend(args[ddpos..].iter().map(|p| wpat(p)));
Some(pats)
}
@ -961,7 +992,7 @@ pub fn specialize<'a, 'b, 'tcx>(
Some(variant.fields.iter().map(|sf| {
match pattern_fields.iter().find(|f| f.node.name == sf.name) {
Some(ref f) => wpat(&f.node.pat),
_ => dummy_pat
_ => DUMMY_WILD_PATTERN
}
}).collect())
} else {
@ -971,7 +1002,7 @@ pub fn specialize<'a, 'b, 'tcx>(
PatKind::Tuple(ref args, Some(ddpos)) => {
let mut pats: Vec<_> = args[..ddpos].iter().map(|p| wpat(p)).collect();
pats.extend(repeat(dummy_pat).take(arity - args.len()));
pats.extend(repeat(DUMMY_WILD_PATTERN).take(arity - args.len()));
pats.extend(args[ddpos..].iter().map(|p| wpat(p)));
Some(pats)
}
@ -982,12 +1013,15 @@ pub fn specialize<'a, 'b, 'tcx>(
Some(vec![wpat(&**inner)]),
PatKind::Lit(ref expr) => {
match r[col].1 {
match r[col].pattern_ty {
Some(&ty::TyS { sty: ty::TyRef(_, mt), .. }) => {
// HACK: handle string literals. A string literal pattern
// serves both as an unary reference pattern and as a
// nullary value pattern, depending on the type.
Some(vec![(pat, Some(mt.ty))])
Some(vec![Pattern {
pat: pat,
pattern_ty: Some(mt.ty)
}])
}
Some(ty) => {
assert_eq!(constructor_arity(cx, constructor, ty), 0);
@ -1023,14 +1057,14 @@ pub fn specialize<'a, 'b, 'tcx>(
// Fixed-length vectors.
Some(
before.iter().map(|p| wpat(p)).chain(
repeat(dummy_pat).take(arity - pat_len).chain(
repeat(DUMMY_WILD_PATTERN).take(arity - pat_len).chain(
after.iter().map(|p| wpat(p))
)).collect())
},
Slice(length) if pat_len <= length && slice.is_some() => {
Some(
before.iter().map(|p| wpat(p)).chain(
repeat(dummy_pat).take(arity - pat_len).chain(
repeat(DUMMY_WILD_PATTERN).take(arity - pat_len).chain(
after.iter().map(|p| wpat(p))
)).collect())
}
@ -1105,7 +1139,7 @@ fn is_refutable<A, F>(cx: &MatchCheckCtxt, pat: &Pat, refutable: F) -> Option<A>
F: FnOnce(&Pat) -> A,
{
let pats = Matrix(vec!(vec!(wrap_pat(cx, pat))));
match is_useful(cx, &pats, &[(DUMMY_WILD_PAT, None)], ConstructWitness) {
match is_useful(cx, &pats, &[DUMMY_WILD_PATTERN], ConstructWitness) {
UsefulWithWitness(pats) => Some(refutable(&pats[0])),
NotUseful => None,
Useful => bug!()