diff options
5 files changed, 40 insertions, 25 deletions
diff --git a/src/librustc_mir/hair/pattern/_match.rs b/src/librustc_mir/hair/pattern/_match.rs index 15f88334e8d..8d7e605f7c9 100644 --- a/src/librustc_mir/hair/pattern/_match.rs +++ b/src/librustc_mir/hair/pattern/_match.rs @@ -2042,7 +2042,7 @@ fn split_grouped_constructors<'p, 'tcx>( // // Of course, if fixed-length patterns exist, we must be sure // that our length is large enough to miss them all, so - // we can pick `L = max(FIXED_LEN+1 ∪ {max(PREFIX_LEN) + max(SUFFIX_LEN)})` + // we can pick `L = max(max(FIXED_LEN)+1, max(PREFIX_LEN) + max(SUFFIX_LEN))` // // for example, with the above pair of patterns, all elements // but the first and last can be added/removed, so any @@ -2080,9 +2080,24 @@ fn split_grouped_constructors<'p, 'tcx>( } } - let max_slice_length = cmp::max(max_fixed_len + 1, max_prefix_len + max_suffix_len); - split_ctors - .extend((self_prefix + self_suffix..=max_slice_length).map(FixedLenSlice)) + // For diagnostics, we keep the prefix and suffix lengths separate, so in the case + // where `max_fixed_len+1` is the largest, we adapt `max_prefix_len` accordingly, + // so that `L = max_prefix_len + max_suffix_len`. + if max_fixed_len + 1 >= max_prefix_len + max_suffix_len { + // The subtraction can't overflow thanks to the above check. + // The new `max_prefix_len` is also guaranteed to be larger than its previous + // value. + max_prefix_len = max_fixed_len + 1 - max_suffix_len; + } + + // `ctor` originally covered the range `(self_prefix + self_suffix..infinity)`. We + // now split it into two: lengths smaller than `max_prefix_len + max_suffix_len` + // are treated independently as fixed-lengths slices, and lengths above are + // captured by a final VarLenSlice constructor. + split_ctors.extend( + (self_prefix + self_suffix..max_prefix_len + max_suffix_len).map(FixedLenSlice), + ); + split_ctors.push(VarLenSlice(max_prefix_len, max_suffix_len)); } // Any other constructor can be used unchanged. _ => split_ctors.push(ctor), diff --git a/src/test/ui/pattern/usefulness/match-slice-patterns.rs b/src/test/ui/pattern/usefulness/match-slice-patterns.rs index afbeb61e441..af7fd53a1f1 100644 --- a/src/test/ui/pattern/usefulness/match-slice-patterns.rs +++ b/src/test/ui/pattern/usefulness/match-slice-patterns.rs @@ -2,7 +2,7 @@ fn check(list: &[Option<()>]) { match list { - //~^ ERROR `&[_, Some(_), None, _]` not covered + //~^ ERROR `&[_, Some(_), .., None, _]` not covered &[] => {}, &[_] => {}, &[_, _] => {}, diff --git a/src/test/ui/pattern/usefulness/match-slice-patterns.stderr b/src/test/ui/pattern/usefulness/match-slice-patterns.stderr index 24769db34c9..72ae5d5fe3b 100644 --- a/src/test/ui/pattern/usefulness/match-slice-patterns.stderr +++ b/src/test/ui/pattern/usefulness/match-slice-patterns.stderr @@ -1,8 +1,8 @@ -error[E0004]: non-exhaustive patterns: `&[_, Some(_), None, _]` not covered +error[E0004]: non-exhaustive patterns: `&[_, Some(_), .., None, _]` not covered --> $DIR/match-slice-patterns.rs:4:11 | LL | match list { - | ^^^^ pattern `&[_, Some(_), None, _]` not covered + | ^^^^ pattern `&[_, Some(_), .., None, _]` not covered | = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms diff --git a/src/test/ui/pattern/usefulness/slice-patterns.rs b/src/test/ui/pattern/usefulness/slice-patterns.rs index e11f11ba752..da2d40caf1a 100644 --- a/src/test/ui/pattern/usefulness/slice-patterns.rs +++ b/src/test/ui/pattern/usefulness/slice-patterns.rs @@ -37,7 +37,7 @@ fn main() { [.., false] => {} } match s { - //~^ ERROR `&[false, true]` not covered + //~^ ERROR `&[false, .., true]` not covered [] => {} [true, ..] => {} [.., false] => {} @@ -57,18 +57,18 @@ fn main() { [_] => {} } match s { - //~^ ERROR `&[false]` not covered + //~^ ERROR `&[false, ..]` not covered [] => {} [true, ..] => {} } match s { - //~^ ERROR `&[false, _]` not covered + //~^ ERROR `&[false, _, ..]` not covered [] => {} [_] => {} [true, ..] => {} } match s { - //~^ ERROR `&[_, false]` not covered + //~^ ERROR `&[_, .., false]` not covered [] => {} [_] => {} [.., true] => {} @@ -94,14 +94,14 @@ fn main() { [..] => {} } match s { - //~^ ERROR `&[_, _, true]` not covered + //~^ ERROR `&[_, _, .., true]` not covered [] => {} [_] => {} [_, _] => {} [.., false] => {} } match s { - //~^ ERROR `&[true, _, _]` not covered + //~^ ERROR `&[true, _, .., _]` not covered [] => {} [_] => {} [_, _] => {} diff --git a/src/test/ui/pattern/usefulness/slice-patterns.stderr b/src/test/ui/pattern/usefulness/slice-patterns.stderr index 666e16627c5..6afe4705b0e 100644 --- a/src/test/ui/pattern/usefulness/slice-patterns.stderr +++ b/src/test/ui/pattern/usefulness/slice-patterns.stderr @@ -14,11 +14,11 @@ LL | match s3 { | = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms -error[E0004]: non-exhaustive patterns: `&[false, true]` not covered +error[E0004]: non-exhaustive patterns: `&[false, .., true]` not covered --> $DIR/slice-patterns.rs:39:11 | LL | match s { - | ^ pattern `&[false, true]` not covered + | ^ pattern `&[false, .., true]` not covered | = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms @@ -46,27 +46,27 @@ LL | match s { | = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms -error[E0004]: non-exhaustive patterns: `&[false]` not covered +error[E0004]: non-exhaustive patterns: `&[false, ..]` not covered --> $DIR/slice-patterns.rs:59:11 | LL | match s { - | ^ pattern `&[false]` not covered + | ^ pattern `&[false, ..]` not covered | = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms -error[E0004]: non-exhaustive patterns: `&[false, _]` not covered +error[E0004]: non-exhaustive patterns: `&[false, _, ..]` not covered --> $DIR/slice-patterns.rs:64:11 | LL | match s { - | ^ pattern `&[false, _]` not covered + | ^ pattern `&[false, _, ..]` not covered | = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms -error[E0004]: non-exhaustive patterns: `&[_, false]` not covered +error[E0004]: non-exhaustive patterns: `&[_, .., false]` not covered --> $DIR/slice-patterns.rs:70:11 | LL | match s { - | ^ pattern `&[_, false]` not covered + | ^ pattern `&[_, .., false]` not covered | = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms @@ -112,19 +112,19 @@ error: unreachable pattern LL | [false, true] => {} | ^^^^^^^^^^^^^ -error[E0004]: non-exhaustive patterns: `&[_, _, true]` not covered +error[E0004]: non-exhaustive patterns: `&[_, _, .., true]` not covered --> $DIR/slice-patterns.rs:96:11 | LL | match s { - | ^ pattern `&[_, _, true]` not covered + | ^ pattern `&[_, _, .., true]` not covered | = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms -error[E0004]: non-exhaustive patterns: `&[true, _, _]` not covered +error[E0004]: non-exhaustive patterns: `&[true, _, .., _]` not covered --> $DIR/slice-patterns.rs:103:11 | LL | match s { - | ^ pattern `&[true, _, _]` not covered + | ^ pattern `&[true, _, .., _]` not covered | = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms |