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Auto merge of #50912 - varkor:exhaustive-integer-matching, r=arielb1

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Exhaustive integer matching

This adds a new feature flag `exhaustive_integer_patterns` that enables exhaustive matching of integer types by their values. For example, the following is now accepted:
```rust
#![feature(exhaustive_integer_patterns)]
#![feature(exclusive_range_pattern)]

fn matcher(x: u8) {
  match x { // ok
    0 .. 32 => { /* foo */ }
    32 => { /* bar */ }
    33 ..= 255 => { /* baz */ }
  }
}
```
This matching is permitted on all integer (signed/unsigned and char) types. Sensible error messages are also provided. For example:
```rust
fn matcher(x: u8) {
  match x { //~ ERROR
    0 .. 32 => { /* foo */ }
  }
}
```
results in:
```
error[E0004]: non-exhaustive patterns: `32u8...255u8` not covered
 --> matches.rs:3:9
  |
6 |   match x {
  |         ^ pattern `32u8...255u8` not covered
```

This implements https://github.com/rust-lang/rfcs/issues/1550 for https://github.com/rust-lang/rust/issues/50907. While there hasn't been a full RFC for this feature, it was suggested that this might be a feature that obviously complements the existing exhaustiveness checks (e.g. for `bool`) and so a feature gate would be sufficient for now.
This commit is contained in:
bors 2018-08-22 00:57:00 +00:00
commit a79cffb8b8
10 changed files with 927 additions and 84 deletions
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2
src/librustc/mir/mod.rs
View file

@ -2228,7 +2228,7 @@ pub fn fmt_const_val<W: Write>(fmt: &mut W, const_val: &ty::Const) -> fmt::Resul
}
}
pub fn print_miri_value<W: Write>(value: Value, ty: Ty, f: &mut W) -> fmt::Result {
pub fn print_miri_value<'tcx, W: Write>(value: Value, ty: Ty<'tcx>, f: &mut W) -> fmt::Result {
use ty::TypeVariants::*;
// print some primitives
if let Value::Scalar(ScalarMaybeUndef::Scalar(Scalar::Bits { bits, .. })) = value {

694
src/librustc_mir/hair/pattern/_match.rs
View file

@ -8,6 +8,164 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
/// This file includes the logic for exhaustiveness and usefulness checking for
/// pattern-matching. Specifically, given a list of patterns for a type, we can
/// tell whether:
/// (a) the patterns cover every possible constructor for the type [exhaustiveness]
/// (b) each pattern is necessary [usefulness]
///
/// The algorithm implemented here is a modified version of the one described in:
/// http://moscova.inria.fr/~maranget/papers/warn/index.html
/// However, to save future implementors from reading the original paper, I'm going
/// to summarise the algorithm here to hopefully save time and be a little clearer
/// (without being so rigorous).
///
/// The core of the algorithm revolves about a "usefulness" check. In particular, we
/// are trying to compute a predicate `U(P, p_{m + 1})` where `P` is a list of patterns
/// of length `m` for a compound (product) type with `n` components (we refer to this as
/// a matrix). `U(P, p_{m + 1})` represents whether, given an existing list of patterns
/// `p_1 ..= p_m`, adding a new pattern will be "useful" (that is, cover previously-
/// uncovered values of the type).
///
/// If we have this predicate, then we can easily compute both exhaustiveness of an
/// entire set of patterns and the individual usefulness of each one.
/// (a) the set of patterns is exhaustive iff `U(P, _)` is false (i.e. adding a wildcard
/// match doesn't increase the number of values we're matching)
/// (b) a pattern `p_i` is not useful if `U(P[0..=(i-1), p_i)` is false (i.e. adding a
/// pattern to those that have come before it doesn't increase the number of values
/// we're matching).
///
/// For example, say we have the following:
/// ```
/// // x: (Option<bool>, Result<()>)
/// match x {
/// (Some(true), _) => {}
/// (None, Err(())) => {}
/// (None, Err(_)) => {}
/// }
/// ```
/// Here, the matrix `P` is 3 x 2 (rows x columns).
/// [
/// [Some(true), _],
/// [None, Err(())],
/// [None, Err(_)],
/// ]
/// We can tell it's not exhaustive, because `U(P, _)` is true (we're not covering
/// `[Some(false), _]`, for instance). In addition, row 3 is not useful, because
/// all the values it covers are already covered by row 2.
///
/// To compute `U`, we must have two other concepts.
/// 1. `S(c, P)` is a "specialised matrix", where `c` is a constructor (like `Some` or
/// `None`). You can think of it as filtering `P` to just the rows whose *first* pattern
/// can cover `c` (and expanding OR-patterns into distinct patterns), and then expanding
/// the constructor into all of its components.
/// The specialisation of a row vector is computed by `specialize`.
///
/// It is computed as follows. For each row `p_i` of P, we have four cases:
/// 1.1. `p_(i,1) = c(r_1, .., r_a)`. Then `S(c, P)` has a corresponding row:
/// r_1, .., r_a, p_(i,2), .., p_(i,n)
/// 1.2. `p_(i,1) = c'(r_1, .., r_a')` where `c ≠ c'`. Then `S(c, P)` has no
/// corresponding row.
/// 1.3. `p_(i,1) = _`. Then `S(c, P)` has a corresponding row:
/// _, .., _, p_(i,2), .., p_(i,n)
/// 1.4. `p_(i,1) = r_1 | r_2`. Then `S(c, P)` has corresponding rows inlined from:
/// S(c, (r_1, p_(i,2), .., p_(i,n)))
/// S(c, (r_2, p_(i,2), .., p_(i,n)))
///
/// 2. `D(P)` is a "default matrix". This is used when we know there are missing
/// constructor cases, but there might be existing wildcard patterns, so to check the
/// usefulness of the matrix, we have to check all its *other* components.
/// The default matrix is computed inline in `is_useful`.
///
/// It is computed as follows. For each row `p_i` of P, we have three cases:
/// 1.1. `p_(i,1) = c(r_1, .., r_a)`. Then `D(P)` has no corresponding row.
/// 1.2. `p_(i,1) = _`. Then `D(P)` has a corresponding row:
/// p_(i,2), .., p_(i,n)
/// 1.3. `p_(i,1) = r_1 | r_2`. Then `D(P)` has corresponding rows inlined from:
/// D((r_1, p_(i,2), .., p_(i,n)))
/// D((r_2, p_(i,2), .., p_(i,n)))
///
/// Note that the OR-patterns are not always used directly in Rust, but are used to derive
/// the exhaustive integer matching rules, so they're written here for posterity.
///
/// The algorithm for computing `U`
/// -------------------------------
/// The algorithm is inductive (on the number of columns: i.e. components of tuple patterns).
/// That means we're going to check the components from left-to-right, so the algorithm
/// operates principally on the first component of the matrix and new pattern `p_{m + 1}`.
/// This algorithm is realised in the `is_useful` function.
///
/// Base case. (`n = 0`, i.e. an empty tuple pattern)
/// - If `P` already contains an empty pattern (i.e. if the number of patterns `m > 0`),
/// then `U(P, p_{m + 1})` is false.
/// - Otherwise, `P` must be empty, so `U(P, p_{m + 1})` is true.
///
/// Inductive step. (`n > 0`, i.e. whether there's at least one column
/// [which may then be expanded into further columns later])
/// We're going to match on the new pattern, `p_{m + 1}`.
/// - If `p_{m + 1} == c(r_1, .., r_a)`, then we have a constructor pattern.
/// Thus, the usefulness of `p_{m + 1}` can be reduced to whether it is useful when
/// we ignore all the patterns in `P` that involve other constructors. This is where
/// `S(c, P)` comes in:
/// `U(P, p_{m + 1}) := U(S(c, P), S(c, p_{m + 1}))`
/// This special case is handled in `is_useful_specialized`.
/// - If `p_{m + 1} == _`, then we have two more cases:
/// + All the constructors of the first component of the type exist within
/// all the rows (after having expanded OR-patterns). In this case:
/// `U(P, p_{m + 1}) := ∨(k ϵ constructors) U(S(k, P), S(k, p_{m + 1}))`
/// I.e. the pattern `p_{m + 1}` is only useful when all the constructors are
/// present *if* its later components are useful for the respective constructors
/// covered by `p_{m + 1}` (usually a single constructor, but all in the case of `_`).
/// + Some constructors are not present in the existing rows (after having expanded
/// OR-patterns). However, there might be wildcard patterns (`_`) present. Thus, we
/// are only really concerned with the other patterns leading with wildcards. This is
/// where `D` comes in:
/// `U(P, p_{m + 1}) := U(D(P), p_({m + 1},2), .., p_({m + 1},n))`
/// - If `p_{m + 1} == r_1 | r_2`, then the usefulness depends on each separately:
/// `U(P, p_{m + 1}) := U(P, (r_1, p_({m + 1},2), .., p_({m + 1},n)))
/// || U(P, (r_2, p_({m + 1},2), .., p_({m + 1},n)))`
///
/// Modifications to the algorithm
/// ------------------------------
/// The algorithm in the paper doesn't cover some of the special cases that arise in Rust, for
/// example uninhabited types and variable-length slice patterns. These are drawn attention to
/// throughout the code below. I'll make a quick note here about how exhaustive integer matching
/// is accounted for, though.
///
/// Exhaustive integer matching
/// ---------------------------
/// An integer type can be thought of as a (huge) sum type: 1 | 2 | 3 | ...
/// So to support exhaustive integer matching, we can make use of the logic in the paper for
/// OR-patterns. However, we obviously can't just treat ranges x..=y as individual sums, because
/// they are likely gigantic. So we instead treat ranges as constructors of the integers. This means
/// that we have a constructor *of* constructors (the integers themselves). We then need to work
/// through all the inductive step rules above, deriving how the ranges would be treated as
/// OR-patterns, and making sure that they're treated in the same way even when they're ranges.
/// There are really only four special cases here:
/// - When we match on a constructor that's actually a range, we have to treat it as if we would
/// an OR-pattern.
/// + It turns out that we can simply extend the case for single-value patterns in
/// `specialize` to either be *equal* to a value constructor, or *contained within* a range
/// constructor.
/// + When the pattern itself is a range, you just want to tell whether any of the values in
/// the pattern range coincide with values in the constructor range, which is precisely
/// intersection.
/// Since when encountering a range pattern for a value constructor, we also use inclusion, it
/// means that whenever the constructor is a value/range and the pattern is also a value/range,
/// we can simply use intersection to test usefulness.
/// - When we're testing for usefulness of a pattern and the pattern's first component is a
/// wildcard.
/// + If all the constructors appear in the matrix, we have a slight complication. By default,
/// the behaviour (i.e. a disjunction over specialised matrices for each constructor) is
/// invalid, because we want a disjunction over every *integer* in each range, not just a
/// disjunction over every range. This is a bit more tricky to deal with: essentially we need
/// to form equivalence classes of subranges of the constructor range for which the behaviour
/// of the matrix `P` and new pattern `p_{m + 1}` are the same. This is described in more
/// detail in `split_grouped_constructors`.
/// + If some constructors are missing from the matrix, it turns out we don't need to do
/// anything special (because we know none of the integers are actually wildcards: i.e. we
/// can't span wildcards using ranges).
use self::Constructor::*;
use self::Usefulness::*;
use self::WitnessPreference::*;
@ -21,18 +179,22 @@ use super::{PatternFoldable, PatternFolder, compare_const_vals};
use rustc::hir::def_id::DefId;
use rustc::hir::RangeEnd;
use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
use rustc::ty::layout::{Integer, IntegerExt};
use rustc::mir::Field;
use rustc::mir::interpret::ConstValue;
use rustc::util::common::ErrorReported;
use syntax::attr::{SignedInt, UnsignedInt};
use syntax_pos::{Span, DUMMY_SP};
use arena::TypedArena;
use std::cmp::{self, Ordering};
use std::cmp::{self, Ordering, min, max};
use std::fmt;
use std::iter::{FromIterator, IntoIterator};
use std::ops::RangeInclusive;
use std::u128;
pub fn expand_pattern<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>, pat: Pattern<'tcx>)
-> &'a Pattern<'tcx>
@ -138,7 +300,6 @@ impl<'a, 'tcx> FromIterator<Vec<&'a Pattern<'tcx>>> for Matrix<'a, 'tcx> {
}
}
//NOTE: appears to be the only place other then InferCtxt to contain a ParamEnv
pub struct MatchCheckCtxt<'a, 'tcx: 'a> {
pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
/// The module in which the match occurs. This is necessary for
@ -165,7 +326,7 @@ impl<'a, 'tcx> MatchCheckCtxt<'a, 'tcx> {
tcx,
module,
pattern_arena: &pattern_arena,
byte_array_map: FxHashMap(),
byte_array_map: FxHashMap::default(),
})
}
@ -273,7 +434,7 @@ impl<'tcx> Constructor<'tcx> {
}
}
#[derive(Clone)]
#[derive(Clone, Debug)]
pub enum Usefulness<'tcx> {
Useful,
UsefulWithWitness(Vec<Witness<'tcx>>),
@ -289,7 +450,7 @@ impl<'tcx> Usefulness<'tcx> {
}
}
#[derive(Copy, Clone)]
#[derive(Copy, Clone, Debug)]
pub enum WitnessPreference {
ConstructWitness,
LeaveOutWitness
@ -301,8 +462,39 @@ struct PatternContext<'tcx> {
max_slice_length: u64,
}
/// A stack of patterns in reverse order of construction
#[derive(Clone)]
/// A witness of non-exhaustiveness for error reporting, represented
/// as a list of patterns (in reverse order of construction) with
/// wildcards inside to represent elements that can take any inhabitant
/// of the type as a value.
///
/// A witness against a list of patterns should have the same types
/// and length as the pattern matched against. Because Rust `match`
/// is always against a single pattern, at the end the witness will
/// have length 1, but in the middle of the algorithm, it can contain
/// multiple patterns.
///
/// For example, if we are constructing a witness for the match against
/// ```
/// struct Pair(Option<(u32, u32)>, bool);
///
/// match (p: Pair) {
/// Pair(None, _) => {}
/// Pair(_, false) => {}
/// }
/// ```
///
/// We'll perform the following steps:
/// 1. Start with an empty witness
/// `Witness(vec![])`
/// 2. Push a witness `Some(_)` against the `None`
/// `Witness(vec![Some(_)])`
/// 3. Push a witness `true` against the `false`
/// `Witness(vec![Some(_), true])`
/// 4. Apply the `Pair` constructor to the witnesses
/// `Witness(vec![Pair(Some(_), true)])`
///
/// The final `Pair(Some(_), true)` is then the resulting witness.
#[derive(Clone, Debug)]
pub struct Witness<'tcx>(Vec<Pattern<'tcx>>);
impl<'tcx> Witness<'tcx> {
@ -353,7 +545,7 @@ impl<'tcx> Witness<'tcx> {
let arity = constructor_arity(cx, ctor, ty);
let pat = {
let len = self.0.len() as u64;
let mut pats = self.0.drain((len-arity) as usize..).rev();
let mut pats = self.0.drain((len - arity) as usize..).rev();
match ty.sty {
ty::TyAdt(..) |
@ -396,6 +588,7 @@ impl<'tcx> Witness<'tcx> {
_ => {
match *ctor {
ConstantValue(value) => PatternKind::Constant { value },
ConstantRange(lo, hi, end) => PatternKind::Range { lo, hi, end },
_ => PatternKind::Wild,
}
}
@ -417,10 +610,6 @@ impl<'tcx> Witness<'tcx> {
/// but is instead bounded by the maximum fixed length of slice patterns in
/// the column of patterns being analyzed.
///
/// This intentionally does not list ConstantValue specializations for
/// non-booleans, because we currently assume that there is always a
/// "non-standard constant" that matches. See issue #12483.
///
/// We make sure to omit constructors that are statically impossible. eg for
/// Option<!> we do not include Some(_) in the returned list of constructors.
fn all_constructors<'a, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
@ -428,7 +617,8 @@ fn all_constructors<'a, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
-> Vec<Constructor<'tcx>>
{
debug!("all_constructors({:?})", pcx.ty);
match pcx.ty.sty {
let exhaustive_integer_patterns = cx.tcx.features().exhaustive_integer_patterns;
let ctors = match pcx.ty.sty {
ty::TyBool => {
[true, false].iter().map(|&b| {
ConstantValue(ty::Const::from_bool(cx.tcx, b))
@ -457,6 +647,36 @@ fn all_constructors<'a, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
.map(|v| Variant(v.did))
.collect()
}
ty::TyChar if exhaustive_integer_patterns => {
let endpoint = |c: char| {
let ty = ty::ParamEnv::empty().and(cx.tcx.types.char);
ty::Const::from_bits(cx.tcx, c as u128, ty)
};
vec![
// The valid Unicode Scalar Value ranges.
ConstantRange(endpoint('\u{0000}'), endpoint('\u{D7FF}'), RangeEnd::Included),
ConstantRange(endpoint('\u{E000}'), endpoint('\u{10FFFF}'), RangeEnd::Included),
]
}
ty::TyInt(ity) if exhaustive_integer_patterns => {
// FIXME(49937): refactor these bit manipulations into interpret.
let bits = Integer::from_attr(cx.tcx, SignedInt(ity)).size().bits() as u128;
let min = 1u128 << (bits - 1);
let max = (1u128 << (bits - 1)) - 1;
let ty = ty::ParamEnv::empty().and(pcx.ty);
vec![ConstantRange(ty::Const::from_bits(cx.tcx, min as u128, ty),
ty::Const::from_bits(cx.tcx, max as u128, ty),
RangeEnd::Included)]
}
ty::TyUint(uty) if exhaustive_integer_patterns => {
// FIXME(49937): refactor these bit manipulations into interpret.
let bits = Integer::from_attr(cx.tcx, UnsignedInt(uty)).size().bits() as u128;
let max = !0u128 >> (128 - bits);
let ty = ty::ParamEnv::empty().and(pcx.ty);
vec![ConstantRange(ty::Const::from_bits(cx.tcx, 0, ty),
ty::Const::from_bits(cx.tcx, max, ty),
RangeEnd::Included)]
}
_ => {
if cx.is_uninhabited(pcx.ty) {
vec![]
@ -464,7 +684,8 @@ fn all_constructors<'a, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
vec![Single]
}
}
}
};
ctors
}
fn max_slice_length<'p, 'a: 'p, 'tcx: 'a, I>(
@ -497,7 +718,7 @@ fn max_slice_length<'p, 'a: 'p, 'tcx: 'a, I>(
// `[true, ..]`
// `[.., false]`
// Then any slice of length ≥1 that matches one of these two
// patterns can be be trivially turned to a slice of any
// patterns can be trivially turned to a slice of any
// other length ≥1 that matches them and vice-versa - for
// but the slice from length 2 `[false, true]` that matches neither
// of these patterns can't be turned to a slice from length 1 that
@ -569,6 +790,189 @@ fn max_slice_length<'p, 'a: 'p, 'tcx: 'a, I>(
cmp::max(max_fixed_len + 1, max_prefix_len + max_suffix_len)
}
/// An inclusive interval, used for precise integer exhaustiveness checking.
/// `IntRange`s always store a contiguous range. This means that values are
/// encoded such that `0` encodes the minimum value for the integer,
/// regardless of the signedness.
/// For example, the pattern `-128...127i8` is encoded as `0..=255`.
/// This makes comparisons and arithmetic on interval endpoints much more
/// straightforward. See `signed_bias` for details.
///
/// `IntRange` is never used to encode an empty range or a "range" that wraps
/// around the (offset) space: i.e. `range.lo <= range.hi`.
#[derive(Clone)]
struct IntRange<'tcx> {
pub range: RangeInclusive<u128>,
pub ty: Ty<'tcx>,
}
impl<'tcx> IntRange<'tcx> {
fn from_ctor(tcx: TyCtxt<'_, 'tcx, 'tcx>,
ctor: &Constructor<'tcx>)
-> Option<IntRange<'tcx>> {
match ctor {
ConstantRange(lo, hi, end) => {
assert_eq!(lo.ty, hi.ty);
let ty = lo.ty;
let env_ty = ty::ParamEnv::empty().and(ty);
if let Some(lo) = lo.assert_bits(tcx, env_ty) {
if let Some(hi) = hi.assert_bits(tcx, env_ty) {
// Perform a shift if the underlying types are signed,
// which makes the interval arithmetic simpler.
let bias = IntRange::signed_bias(tcx, ty);
let (lo, hi) = (lo ^ bias, hi ^ bias);
// Make sure the interval is well-formed.
return if lo > hi || lo == hi && *end == RangeEnd::Excluded {
None
} else {
let offset = (*end == RangeEnd::Excluded) as u128;
Some(IntRange { range: lo..=(hi - offset), ty })
};
}
}
None
}
ConstantValue(val) => {
let ty = val.ty;
if let Some(val) = val.assert_bits(tcx, ty::ParamEnv::empty().and(ty)) {
let bias = IntRange::signed_bias(tcx, ty);
let val = val ^ bias;
Some(IntRange { range: val..=val, ty })
} else {
None
}
}
Single | Variant(_) | Slice(_) => {
None
}
}
}
fn from_pat(tcx: TyCtxt<'_, 'tcx, 'tcx>,
pat: &Pattern<'tcx>)
-> Option<IntRange<'tcx>> {
Self::from_ctor(tcx, &match pat.kind {
box PatternKind::Constant { value } => ConstantValue(value),
box PatternKind::Range { lo, hi, end } => ConstantRange(lo, hi, end),
_ => return None,
})
}
// The return value of `signed_bias` should be XORed with an endpoint to encode/decode it.
fn signed_bias(tcx: TyCtxt<'_, 'tcx, 'tcx>, ty: Ty<'tcx>) -> u128 {
match ty.sty {
ty::TyInt(ity) => {
let bits = Integer::from_attr(tcx, SignedInt(ity)).size().bits() as u128;
1u128 << (bits - 1)
}
_ => 0
}
}
/// Convert a `RangeInclusive` to a `ConstantValue` or inclusive `ConstantRange`.
fn range_to_ctor(
tcx: TyCtxt<'_, 'tcx, 'tcx>,
ty: Ty<'tcx>,
r: RangeInclusive<u128>,
) -> Constructor<'tcx> {
let bias = IntRange::signed_bias(tcx, ty);
let ty = ty::ParamEnv::empty().and(ty);
let (lo, hi) = r.into_inner();
if lo == hi {
ConstantValue(ty::Const::from_bits(tcx, lo ^ bias, ty))
} else {
ConstantRange(ty::Const::from_bits(tcx, lo ^ bias, ty),
ty::Const::from_bits(tcx, hi ^ bias, ty),
RangeEnd::Included)
}
}
/// Return a collection of ranges that spans the values covered by `ranges`, subtracted
/// by the values covered by `self`: i.e. `ranges \ self` (in set notation).
fn subtract_from(self,
tcx: TyCtxt<'_, 'tcx, 'tcx>,
ranges: Vec<Constructor<'tcx>>)
-> Vec<Constructor<'tcx>> {
let ranges = ranges.into_iter().filter_map(|r| {
IntRange::from_ctor(tcx, &r).map(|i| i.range)
});
let mut remaining_ranges = vec![];
let ty = self.ty;
let (lo, hi) = self.range.into_inner();
for subrange in ranges {
let (subrange_lo, subrange_hi) = subrange.into_inner();
if lo > subrange_hi || subrange_lo > hi {
// The pattern doesn't intersect with the subrange at all,
// so the subrange remains untouched.
remaining_ranges.push(Self::range_to_ctor(tcx, ty, subrange_lo..=subrange_hi));
} else {
if lo > subrange_lo {
// The pattern intersects an upper section of the
// subrange, so a lower section will remain.
remaining_ranges.push(Self::range_to_ctor(tcx, ty, subrange_lo..=(lo - 1)));
}
if hi < subrange_hi {
// The pattern intersects a lower section of the
// subrange, so an upper section will remain.
remaining_ranges.push(Self::range_to_ctor(tcx, ty, (hi + 1)..=subrange_hi));
}
}
}
remaining_ranges
}
fn intersection(&self, other: &Self) -> Option<Self> {
let ty = self.ty;
let (lo, hi) = (*self.range.start(), *self.range.end());
let (other_lo, other_hi) = (*other.range.start(), *other.range.end());
if lo <= other_hi && other_lo <= hi {
Some(IntRange { range: max(lo, other_lo)..=min(hi, other_hi), ty })
} else {
None
}
}
}
// Return a set of constructors equivalent to `all_ctors \ used_ctors`.
fn compute_missing_ctors<'a, 'tcx: 'a>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
all_ctors: &Vec<Constructor<'tcx>>,
used_ctors: &Vec<Constructor<'tcx>>,
) -> Vec<Constructor<'tcx>> {
let mut missing_ctors = vec![];
for req_ctor in all_ctors {
let mut refined_ctors = vec![req_ctor.clone()];
for used_ctor in used_ctors {
if used_ctor == req_ctor {
// If a constructor appears in a `match` arm, we can
// eliminate it straight away.
refined_ctors = vec![]
} else if tcx.features().exhaustive_integer_patterns {
if let Some(interval) = IntRange::from_ctor(tcx, used_ctor) {
// Refine the required constructors for the type by subtracting
// the range defined by the current constructor pattern.
refined_ctors = interval.subtract_from(tcx, refined_ctors);
}
}
// If the constructor patterns that have been considered so far
// already cover the entire range of values, then we the
// constructor is not missing, and we can move on to the next one.
if refined_ctors.is_empty() {
break;
}
}
// If a constructor has not been matched, then it is missing.
// We add `refined_ctors` instead of `req_ctor`, because then we can
// provide more detailed error information about precisely which
// ranges have been omitted.
missing_ctors.extend(refined_ctors);
}
missing_ctors
}
/// Algorithm from http://moscova.inria.fr/~maranget/papers/warn/index.html
/// The algorithm from the paper has been modified to correctly handle empty
/// types. The changes are:
@ -637,8 +1041,7 @@ pub fn is_useful<'p, 'a: 'p, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
// FIXME: this might lead to "unstable" behavior with macro hygiene
// introducing uninhabited patterns for inaccessible fields. We
// need to figure out how to model that.
ty: rows.iter().map(|r| r[0].ty).find(|ty| !ty.references_error())
.unwrap_or(v[0].ty),
ty: rows.iter().map(|r| r[0].ty).find(|ty| !ty.references_error()).unwrap_or(v[0].ty),
max_slice_length: max_slice_length(cx, rows.iter().map(|r| r[0]).chain(Some(v[0])))
};
@ -646,7 +1049,7 @@ pub fn is_useful<'p, 'a: 'p, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
if let Some(constructors) = pat_constructors(cx, v[0], pcx) {
debug!("is_useful - expanding constructors: {:#?}", constructors);
constructors.into_iter().map(|c|
split_grouped_constructors(cx.tcx, constructors, matrix, pcx.ty).into_iter().map(|c|
is_useful_specialized(cx, matrix, v, c.clone(), pcx.ty, witness)
).find(|result| result.is_useful()).unwrap_or(NotUseful)
} else {
@ -656,11 +1059,10 @@ pub fn is_useful<'p, 'a: 'p, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
pat_constructors(cx, row[0], pcx).unwrap_or(vec![])
}).collect();
debug!("used_ctors = {:#?}", used_ctors);
// `all_ctors` are all the constructors for the given type, which
// should all be represented (or caught with the wild pattern `_`).
let all_ctors = all_constructors(cx, pcx);
debug!("all_ctors = {:#?}", all_ctors);
let missing_ctors: Vec<Constructor> = all_ctors.iter().filter(|c| {
!used_ctors.contains(*c)
}).cloned().collect();
// `missing_ctors` is the set of constructors from the same type as the
// first column of `matrix` that are matched only by wildcard patterns
@ -681,10 +1083,12 @@ pub fn is_useful<'p, 'a: 'p, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
// feature flag is not present, so this is only
// needed for that case.
let is_privately_empty =
all_ctors.is_empty() && !cx.is_uninhabited(pcx.ty);
let is_declared_nonexhaustive =
cx.is_non_exhaustive_enum(pcx.ty) && !cx.is_local(pcx.ty);
// Find those constructors that are not matched by any non-wildcard patterns in the
// current column.
let missing_ctors = compute_missing_ctors(cx.tcx, &all_ctors, &used_ctors);
let is_privately_empty = all_ctors.is_empty() && !cx.is_uninhabited(pcx.ty);
let is_declared_nonexhaustive = cx.is_non_exhaustive_enum(pcx.ty) && !cx.is_local(pcx.ty);
debug!("missing_ctors={:#?} is_privately_empty={:#?} is_declared_nonexhaustive={:#?}",
missing_ctors, is_privately_empty, is_declared_nonexhaustive);
@ -693,7 +1097,7 @@ pub fn is_useful<'p, 'a: 'p, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
let is_non_exhaustive = is_privately_empty || is_declared_nonexhaustive;
if missing_ctors.is_empty() && !is_non_exhaustive {
all_ctors.into_iter().map(|c| {
split_grouped_constructors(cx.tcx, all_ctors, matrix, pcx.ty).into_iter().map(|c| {
is_useful_specialized(cx, matrix, v, c.clone(), pcx.ty, witness)
}).find(|result| result.is_useful()).unwrap_or(NotUseful)
} else {
@ -753,7 +1157,7 @@ pub fn is_useful<'p, 'a: 'p, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
// `used_ctors` is empty.
let new_witnesses = if is_non_exhaustive || used_ctors.is_empty() {
// All constructors are unused. Add wild patterns
// rather than each individual constructor
// rather than each individual constructor.
pats.into_iter().map(|mut witness| {
witness.0.push(Pattern {
ty: pcx.ty,
@ -765,6 +1169,10 @@ pub fn is_useful<'p, 'a: 'p, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
} else {
pats.into_iter().flat_map(|witness| {
missing_ctors.iter().map(move |ctor| {
// Extends the witness with a "wild" version of this
// constructor, that matches everything that can be built with
// it. For example, if `ctor` is a `Constructor::Variant` for
// `Option::Some`, this pushes the witness for `Some(_)`.
witness.clone().push_wild_constructor(cx, ctor, pcx.ty)
})
}).collect()
@ -777,14 +1185,16 @@ pub fn is_useful<'p, 'a: 'p, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
}
}
/// A shorthand for the `U(S(c, P), S(c, q))` operation from the paper. I.e. `is_useful` applied
/// to the specialised version of both the pattern matrix `P` and the new pattern `q`.
fn is_useful_specialized<'p, 'a:'p, 'tcx: 'a>(
cx: &mut MatchCheckCtxt<'a, 'tcx>,
&Matrix(ref m): &Matrix<'p, 'tcx>,
v: &[&'p Pattern<'tcx>],
ctor: Constructor<'tcx>,
lty: Ty<'tcx>,
witness: WitnessPreference) -> Usefulness<'tcx>
{
witness: WitnessPreference,
) -> Usefulness<'tcx> {
debug!("is_useful_specialized({:#?}, {:#?}, {:?})", v, ctor, lty);
let sub_pat_tys = constructor_sub_pattern_tys(cx, &ctor, lty);
let wild_patterns_owned: Vec<_> = sub_pat_tys.iter().map(|ty| {
@ -806,7 +1216,7 @@ fn is_useful_specialized<'p, 'a:'p, 'tcx: 'a>(
.collect()
),
result => result
},
}
None => NotUseful
}
}
@ -818,23 +1228,20 @@ fn is_useful_specialized<'p, 'a:'p, 'tcx: 'a>(
/// 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.
///
/// Returns None in case of a catch-all, which can't be specialized.
/// Returns `None` in case of a catch-all, which can't be specialized.
fn pat_constructors<'tcx>(cx: &mut MatchCheckCtxt,
pat: &Pattern<'tcx>,
pcx: PatternContext)
-> Option<Vec<Constructor<'tcx>>>
{
match *pat.kind {
PatternKind::Binding { .. } | PatternKind::Wild =>
None,
PatternKind::Leaf { .. } | PatternKind::Deref { .. } =>
Some(vec![Single]),
PatternKind::Variant { adt_def, variant_index, .. } =>
Some(vec![Variant(adt_def.variants[variant_index].did)]),
PatternKind::Constant { value } =>
Some(vec![ConstantValue(value)]),
PatternKind::Range { lo, hi, end } =>
Some(vec![ConstantRange(lo, hi, end)]),
PatternKind::Binding { .. } | PatternKind::Wild => None,
PatternKind::Leaf { .. } | PatternKind::Deref { .. } => Some(vec![Single]),
PatternKind::Variant { adt_def, variant_index, .. } => {
Some(vec![Variant(adt_def.variants[variant_index].did)])
}
PatternKind::Constant { value } => Some(vec![ConstantValue(value)]),
PatternKind::Range { lo, hi, end } => Some(vec![ConstantRange(lo, hi, end)]),
PatternKind::Array { .. } => match pcx.ty.sty {
ty::TyArray(_, length) => Some(vec![
Slice(length.unwrap_usize(cx.tcx))
@ -970,13 +1377,167 @@ fn slice_pat_covered_by_constructor<'tcx>(
Ok(true)
}
// Whether to evaluate a constructor using exhaustive integer matching. This is true if the
// constructor is a range or constant with an integer type.
fn should_treat_range_exhaustively(tcx: TyCtxt<'_, 'tcx, 'tcx>, ctor: &Constructor<'tcx>) -> bool {
if tcx.features().exhaustive_integer_patterns {
if let ConstantValue(value) | ConstantRange(value, _, _) = ctor {
if let ty::TyChar | ty::TyInt(_) | ty::TyUint(_) = value.ty.sty {
return true;
}
}
}
false
}
/// For exhaustive integer matching, some constructors are grouped within other constructors
/// (namely integer typed values are grouped within ranges). However, when specialising these
/// constructors, we want to be specialising for the underlying constructors (the integers), not
/// the groups (the ranges). Thus we need to split the groups up. Splitting them up naïvely would
/// mean creating a separate constructor for every single value in the range, which is clearly
/// impractical. However, observe that for some ranges of integers, the specialisation will be
/// identical across all values in that range (i.e. there are equivalence classes of ranges of
/// constructors based on their `is_useful_specialised` outcome). These classes are grouped by
/// the patterns that apply to them (in the matrix `P`). We can split the range whenever the
/// patterns that apply to that range (specifically: the patterns that *intersect* with that range)
/// change.
/// Our solution, therefore, is to split the range constructor into subranges at every single point
/// the group of intersecting patterns changes (using the method described below).
/// And voilà! We're testing precisely those ranges that we need to, without any exhaustive matching
/// on actual integers. The nice thing about this is that the number of subranges is linear in the
/// number of rows in the matrix (i.e. the number of cases in the `match` statement), so we don't
/// need to be worried about matching over gargantuan ranges.
///
/// Essentially, given the first column of a matrix representing ranges, looking like the following:
///
/// |------| |----------| |-------| ||
/// |-------| |-------| |----| ||
/// |---------|
///
/// We split the ranges up into equivalence classes so the ranges are no longer overlapping:
///
/// |--|--|||-||||--||---|||-------| |-|||| ||
///
/// The logic for determining how to split the ranges is fairly straightforward: we calculate
/// boundaries for each interval range, sort them, then create constructors for each new interval
/// between every pair of boundary points. (This essentially sums up to performing the intuitive
/// merging operation depicted above.)
fn split_grouped_constructors<'p, 'a: 'p, 'tcx: 'a>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
ctors: Vec<Constructor<'tcx>>,
&Matrix(ref m): &Matrix<'p, 'tcx>,
ty: Ty<'tcx>,
) -> Vec<Constructor<'tcx>> {
let mut split_ctors = Vec::with_capacity(ctors.len());
for ctor in ctors.into_iter() {
match ctor {
// For now, only ranges may denote groups of "subconstructors", so we only need to
// special-case constant ranges.
ConstantRange(..) if should_treat_range_exhaustively(tcx, &ctor) => {
// We only care about finding all the subranges within the range of the constructor
// range. Anything else is irrelevant, because it is guaranteed to result in
// `NotUseful`, which is the default case anyway, and can be ignored.
let ctor_range = IntRange::from_ctor(tcx, &ctor).unwrap();
/// Represents a border between 2 integers. Because the intervals spanning borders
/// must be able to cover every integer, we need to be able to represent
/// 2^128 + 1 such borders.
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
enum Border {
JustBefore(u128),
AfterMax,
}
// A function for extracting the borders of an integer interval.
fn range_borders(r: IntRange<'_>) -> impl Iterator<Item = Border> {
let (lo, hi) = r.range.into_inner();
let from = Border::JustBefore(lo);
let to = match hi.checked_add(1) {
Some(m) => Border::JustBefore(m),
None => Border::AfterMax,
};
vec![from, to].into_iter()
}
// `borders` is the set of borders between equivalence classes: each equivalence
// class lies between 2 borders.
let row_borders = m.iter()
.flat_map(|row| IntRange::from_pat(tcx, row[0]))
.flat_map(|range| ctor_range.intersection(&range))
.flat_map(|range| range_borders(range));
let ctor_borders = range_borders(ctor_range.clone());
let mut borders: Vec<_> = row_borders.chain(ctor_borders).collect();
borders.sort_unstable();
// We're going to iterate through every pair of borders, making sure that each
// represents an interval of nonnegative length, and convert each such interval
// into a constructor.
for IntRange { range, .. } in borders.windows(2).filter_map(|window| {
match (window[0], window[1]) {
(Border::JustBefore(n), Border::JustBefore(m)) => {
if n < m {
Some(IntRange { range: n..=(m - 1), ty })
} else {
None
}
}
(Border::JustBefore(n), Border::AfterMax) => {
Some(IntRange { range: n..=u128::MAX, ty })
}
(Border::AfterMax, _) => None,
}
}) {
split_ctors.push(IntRange::range_to_ctor(tcx, ty, range));
}
}
// Any other constructor can be used unchanged.
_ => split_ctors.push(ctor),
}
}
split_ctors
}
/// Check whether there exists any shared value in either `ctor` or `pat` by intersecting them.
fn constructor_intersects_pattern<'p, 'a: 'p, 'tcx: 'a>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
ctor: &Constructor<'tcx>,
pat: &'p Pattern<'tcx>,
) -> Option<Vec<&'p Pattern<'tcx>>> {
if should_treat_range_exhaustively(tcx, ctor) {
match (IntRange::from_ctor(tcx, ctor), IntRange::from_pat(tcx, pat)) {
(Some(ctor), Some(pat)) => {
ctor.intersection(&pat).map(|_| {
let (pat_lo, pat_hi) = pat.range.into_inner();
let (ctor_lo, ctor_hi) = ctor.range.into_inner();
assert!(pat_lo <= ctor_lo && ctor_hi <= pat_hi);
vec![]
})
}
_ => None,
}
} else {
// Fallback for non-ranges and ranges that involve floating-point numbers, which are not
// conveniently handled by `IntRange`. For these cases, the constructor may not be a range
// so intersection actually devolves into being covered by the pattern.
match constructor_covered_by_range(tcx, ctor, pat) {
Ok(true) => Some(vec![]),
Ok(false) | Err(ErrorReported) => None,
}
}
}
fn constructor_covered_by_range<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
ctor: &Constructor<'tcx>,
from: &'tcx ty::Const<'tcx>, to: &'tcx ty::Const<'tcx>,
end: RangeEnd,
ty: Ty<'tcx>,
pat: &Pattern<'tcx>,
) -> Result<bool, ErrorReported> {
let (from, to, end, ty) = match pat.kind {
box PatternKind::Constant { value } => (value, value, RangeEnd::Included, value.ty),
box PatternKind::Range { lo, hi, end } => (lo, hi, end, lo.ty),
_ => bug!("`constructor_covered_by_range` called with {:?}", pat),
};
trace!("constructor_covered_by_range {:#?}, {:#?}, {:#?}, {}", ctor, from, to, ty);
let cmp_from = |c_from| compare_const_vals(tcx, c_from, from, ty::ParamEnv::empty().and(ty))
.map(|res| res != Ordering::Less);
@ -1040,15 +1601,14 @@ fn specialize<'p, 'a: 'p, 'tcx: 'a>(
cx: &mut MatchCheckCtxt<'a, 'tcx>,
r: &[&'p Pattern<'tcx>],
constructor: &Constructor<'tcx>,
wild_patterns: &[&'p Pattern<'tcx>])
-> Option<Vec<&'p Pattern<'tcx>>>
{
wild_patterns: &[&'p Pattern<'tcx>],
) -> Option<Vec<&'p Pattern<'tcx>>> {
let pat = &r[0];
let head: Option<Vec<&Pattern>> = match *pat.kind {
PatternKind::Binding { .. } | PatternKind::Wild => {
Some(wild_patterns.to_owned())
},
}
PatternKind::Variant { adt_def, variant_index, ref subpatterns, .. } => {
let ref variant = adt_def.variants[variant_index];
@ -1062,6 +1622,7 @@ fn specialize<'p, 'a: 'p, 'tcx: 'a>(
PatternKind::Leaf { ref subpatterns } => {
Some(patterns_for_variant(subpatterns, wild_patterns))
}
PatternKind::Deref { ref subpattern } => {
Some(vec![subpattern])
}
@ -1090,30 +1651,21 @@ fn specialize<'p, 'a: 'p, 'tcx: 'a>(
span_bug!(pat.span,
"unexpected const-val {:?} with ctor {:?}", value, constructor)
}
},
_ => {
match constructor_covered_by_range(
cx.tcx,
constructor, value, value, RangeEnd::Included,
value.ty,
) {
Ok(true) => Some(vec![]),
Ok(false) => None,
Err(ErrorReported) => None,
}
_ => {
// If the constructor is a:
// Single value: add a row if the constructor equals the pattern.
// Range: add a row if the constructor contains the pattern.
constructor_intersects_pattern(cx.tcx, constructor, pat)
}
}
}
PatternKind::Range { lo, hi, ref end } => {
match constructor_covered_by_range(
cx.tcx,
constructor, lo, hi, end.clone(), lo.ty,
) {
Ok(true) => Some(vec![]),
Ok(false) => None,
Err(ErrorReported) => None,
}
PatternKind::Range { .. } => {
// If the constructor is a:
// Single value: add a row if the pattern contains the constructor.
// Range: add a row if the constructor intersects the pattern.
constructor_intersects_pattern(cx.tcx, constructor, pat)
}
PatternKind::Array { ref prefix, ref slice, ref suffix } |
@ -1123,14 +1675,12 @@ fn specialize<'p, 'a: 'p, 'tcx: 'a>(
let pat_len = prefix.len() + suffix.len();
if let Some(slice_count) = wild_patterns.len().checked_sub(pat_len) {
if slice_count == 0 || slice.is_some() {
Some(
prefix.iter().chain(
Some(prefix.iter().chain(
wild_patterns.iter().map(|p| *p)
.skip(prefix.len())
.take(slice_count)
.chain(
suffix.iter()
)).collect())
.chain(suffix.iter())
).collect())
} else {
None
}

4
src/librustc_mir/hair/pattern/check_match.rs
View file

@ -272,7 +272,7 @@ impl<'a, 'tcx> MatchVisitor<'a, 'tcx> {
self.tables);
let pattern = patcx.lower_pattern(pat);
let pattern_ty = pattern.ty;
let pats : Matrix = vec![vec![
let pats: Matrix = vec![vec![
expand_pattern(cx, pattern)
]].into_iter().collect();
@ -391,7 +391,7 @@ fn check_arms<'a, 'tcx>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
printed_if_let_err = true;
}
}
},
}
hir::MatchSource::WhileLetDesugar => {
// check which arm we're on.

16
src/librustc_mir/hair/pattern/mod.rs
View file

@ -233,7 +233,7 @@ impl<'tcx> fmt::Display for Pattern<'tcx> {
PatternKind::Range { lo, hi, end } => {
fmt_const_val(f, lo)?;
match end {
RangeEnd::Included => write!(f, "...")?,
RangeEnd::Included => write!(f, "..=")?,
RangeEnd::Excluded => write!(f, "..")?,
}
fmt_const_val(f, hi)
@ -368,9 +368,14 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
"lower range bound must be less than upper",
);
PatternKind::Wild
},
(RangeEnd::Included, None) |
(RangeEnd::Included, Some(Ordering::Greater)) => {
}
(RangeEnd::Included, Some(Ordering::Equal)) => {
PatternKind::Constant { value: lo }
}
(RangeEnd::Included, Some(Ordering::Less)) => {
PatternKind::Range { lo, hi, end }
}
(RangeEnd::Included, _) => {
let mut err = struct_span_err!(
self.tcx.sess,
lo_expr.span,
@ -390,8 +395,7 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
}
err.emit();
PatternKind::Wild
},
(RangeEnd::Included, Some(_)) => PatternKind::Range { lo, hi, end },
}
}
}
_ => PatternKind::Wild

1
src/librustc_mir/lib.rs
View file

@ -36,6 +36,7 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
#![feature(unicode_internals)]
#![feature(step_trait)]
#![feature(slice_concat_ext)]
#![feature(if_while_or_patterns)]
#![recursion_limit="256"]

3
src/libsyntax/feature_gate.rs
View file

@ -471,6 +471,9 @@ declare_features! (
// 'a: { break 'a; }
(active, label_break_value, "1.28.0", Some(48594), None),
// Integer match exhaustiveness checking
(active, exhaustive_integer_patterns, "1.30.0", Some(50907), None),
// #[panic_implementation]
(active, panic_implementation, "1.28.0", Some(44489), None),

173
src/test/ui/exhaustive_integer_patterns.rs Normal file
View file

@ -0,0 +1,173 @@
// 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.
#![feature(exhaustive_integer_patterns)]
#![feature(exclusive_range_pattern)]
#![deny(unreachable_patterns)]
use std::{char, usize, u8, u16, u32, u64, u128, isize, i8, i16, i32, i64, i128};
fn main() {
let x: u8 = 0;
// A single range covering the entire domain.
match x {
0 ..= 255 => {} // ok
}
// A combination of ranges and values.
// These are currently allowed to be overlapping.
match x {
0 ..= 32 => {}
33 => {}
34 .. 128 => {}
100 ..= 200 => {}
200 => {} //~ ERROR unreachable pattern
201 ..= 255 => {}
}
// An incomplete set of values.
match x { //~ ERROR non-exhaustive patterns
0 .. 128 => {}
}
// A more incomplete set of values.
match x { //~ ERROR non-exhaustive patterns
0 ..= 10 => {}
20 ..= 30 => {}
35 => {}
70 .. 255 => {}
}
let x: i8 = 0;
match x { //~ ERROR non-exhaustive patterns
-7 => {}
-5..=120 => {}
-2..=20 => {} //~ ERROR unreachable pattern
125 => {}
}
// Let's test other types too!
let c: char = '\u{0}';
match c {
'\u{0}' ..= char::MAX => {} // ok
}
// We can actually get away with just covering the
// following two ranges, which correspond to all
// valid Unicode Scalar Values.
match c {
'\u{0000}' ..= '\u{D7FF}' => {}
'\u{E000}' ..= '\u{10_FFFF}' => {}
}
match 0usize {
0 ..= usize::MAX => {} // ok
}
match 0u16 {
0 ..= u16::MAX => {} // ok
}
match 0u32 {
0 ..= u32::MAX => {} // ok
}
match 0u64 {
0 ..= u64::MAX => {} // ok
}
match 0u128 {
0 ..= u128::MAX => {} // ok
}
match 0isize {
isize::MIN ..= isize::MAX => {} // ok
}
match 0i8 {
-128 ..= 127 => {} // ok
}
match 0i8 { //~ ERROR non-exhaustive patterns
-127 ..= 127 => {}
}
match 0i16 {
i16::MIN ..= i16::MAX => {} // ok
}
match 0i16 { //~ ERROR non-exhaustive patterns
i16::MIN ..= -1 => {}
1 ..= i16::MAX => {}
}
match 0i32 {
i32::MIN ..= i32::MAX => {} // ok
}
match 0i64 {
i64::MIN ..= i64::MAX => {} // ok
}
match 0i128 {
i128::MIN ..= i128::MAX => {} // ok
}
// Make sure that guards don't factor into the exhaustiveness checks.
match 0u8 { //~ ERROR non-exhaustive patterns
0 .. 128 => {}
128 ..= 255 if true => {}
}
match 0u8 {
0 .. 128 => {}
128 ..= 255 if false => {}
128 ..= 255 => {} // ok, because previous arm was guarded
}
// Now things start getting a bit more interesting. Testing products!
match (0u8, Some(())) { //~ ERROR non-exhaustive patterns
(1, _) => {}
(_, None) => {}
}
match (0u8, true) { //~ ERROR non-exhaustive patterns
(0 ..= 125, false) => {}
(128 ..= 255, false) => {}
(0 ..= 255, true) => {}
}
match (0u8, true) { // ok
(0 ..= 125, false) => {}
(128 ..= 255, false) => {}
(0 ..= 255, true) => {}
(125 .. 128, false) => {}
}
match 0u8 { // ok
0 .. 2 => {}
1 ..= 2 => {}
_ => {}
}
const LIM: u128 = u128::MAX - 1;
match 0u128 { //~ ERROR non-exhaustive patterns
0 ..= LIM => {}
}
match 0u128 { //~ ERROR non-exhaustive patterns
0 ..= 4 => {}
}
match 0u128 { //~ ERROR non-exhaustive patterns
4 ..= u128::MAX => {}
}
}

87
src/test/ui/exhaustive_integer_patterns.stderr Normal file
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error: unreachable pattern
--> $DIR/exhaustive_integer_patterns.rs:32:9
|
LL | 200 => {} //~ ERROR unreachable pattern
| ^^^
|
note: lint level defined here
--> $DIR/exhaustive_integer_patterns.rs:13:9
|
LL | #![deny(unreachable_patterns)]
| ^^^^^^^^^^^^^^^^^^^^
error[E0004]: non-exhaustive patterns: `128u8..=255u8` not covered
--> $DIR/exhaustive_integer_patterns.rs:37:11
|
LL | match x { //~ ERROR non-exhaustive patterns
| ^ pattern `128u8..=255u8` not covered
error[E0004]: non-exhaustive patterns: `11u8..=19u8`, `31u8..=34u8`, `36u8..=69u8` and 1 more not covered
--> $DIR/exhaustive_integer_patterns.rs:42:11
|
LL | match x { //~ ERROR non-exhaustive patterns
| ^ patterns `11u8..=19u8`, `31u8..=34u8`, `36u8..=69u8` and 1 more not covered
error: unreachable pattern
--> $DIR/exhaustive_integer_patterns.rs:53:9
|
LL | -2..=20 => {} //~ ERROR unreachable pattern
| ^^^^^^^
error[E0004]: non-exhaustive patterns: `-128i8..=-8i8`, `-6i8`, `121i8..=124i8` and 1 more not covered
--> $DIR/exhaustive_integer_patterns.rs:50:11
|
LL | match x { //~ ERROR non-exhaustive patterns
| ^ patterns `-128i8..=-8i8`, `-6i8`, `121i8..=124i8` and 1 more not covered
error[E0004]: non-exhaustive patterns: `-128i8` not covered
--> $DIR/exhaustive_integer_patterns.rs:99:11
|
LL | match 0i8 { //~ ERROR non-exhaustive patterns
| ^^^ pattern `-128i8` not covered
error[E0004]: non-exhaustive patterns: `0i16` not covered
--> $DIR/exhaustive_integer_patterns.rs:107:11
|
LL | match 0i16 { //~ ERROR non-exhaustive patterns
| ^^^^ pattern `0i16` not covered
error[E0004]: non-exhaustive patterns: `128u8..=255u8` not covered
--> $DIR/exhaustive_integer_patterns.rs:125:11
|
LL | match 0u8 { //~ ERROR non-exhaustive patterns
| ^^^ pattern `128u8..=255u8` not covered
error[E0004]: non-exhaustive patterns: `(0u8, Some(_))` and `(2u8..=255u8, Some(_))` not covered
--> $DIR/exhaustive_integer_patterns.rs:137:11
|
LL | match (0u8, Some(())) { //~ ERROR non-exhaustive patterns
| ^^^^^^^^^^^^^^^ patterns `(0u8, Some(_))` and `(2u8..=255u8, Some(_))` not covered
error[E0004]: non-exhaustive patterns: `(126u8..=127u8, false)` not covered
--> $DIR/exhaustive_integer_patterns.rs:142:11
|
LL | match (0u8, true) { //~ ERROR non-exhaustive patterns
| ^^^^^^^^^^^ pattern `(126u8..=127u8, false)` not covered
error[E0004]: non-exhaustive patterns: `340282366920938463463374607431768211455u128` not covered
--> $DIR/exhaustive_integer_patterns.rs:162:11
|
LL | match 0u128 { //~ ERROR non-exhaustive patterns
| ^^^^^ pattern `340282366920938463463374607431768211455u128` not covered
error[E0004]: non-exhaustive patterns: `5u128..=340282366920938463463374607431768211455u128` not covered
--> $DIR/exhaustive_integer_patterns.rs:166:11
|
LL | match 0u128 { //~ ERROR non-exhaustive patterns
| ^^^^^ pattern `5u128..=340282366920938463463374607431768211455u128` not covered
error[E0004]: non-exhaustive patterns: `0u128..=3u128` not covered
--> $DIR/exhaustive_integer_patterns.rs:170:11
|
LL | match 0u128 { //~ ERROR non-exhaustive patterns
| ^^^^^ pattern `0u128..=3u128` not covered
error: aborting due to 13 previous errors
For more information about this error, try `rustc --explain E0004`.

16
src/test/ui/feature-gate-exhaustive_integer_patterns.rs Normal file
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// 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.
fn main() {
let x: u8 = 0;
match x { //~ ERROR non-exhaustive patterns: `_` not covered
0 ..= 255 => {}
}
}

9
src/test/ui/feature-gate-exhaustive_integer_patterns.stderr Normal file
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error[E0004]: non-exhaustive patterns: `_` not covered
--> $DIR/feature-gate-exhaustive_integer_patterns.rs:13:11
|
LL | match x { //~ ERROR non-exhaustive patterns: `_` not covered
| ^ pattern `_` not covered
error: aborting due to previous error
For more information about this error, try `rustc --explain E0004`.