diff --git a/src/librustc_const_eval/_match.rs b/src/librustc_const_eval/_match.rs index 7f5eb31612cb..e7d3af87bdaa 100644 --- a/src/librustc_const_eval/_match.rs +++ b/src/librustc_const_eval/_match.rs @@ -39,7 +39,7 @@ use syntax_pos::{Span, DUMMY_SP}; use arena::TypedArena; -use std::cmp::Ordering; +use std::cmp::{self, Ordering}; use std::fmt; use std::iter::{FromIterator, IntoIterator, repeat}; @@ -419,6 +419,52 @@ fn all_constructors(_cx: &mut MatchCheckCtxt, pcx: PatternContext) -> Vec( + _cx: &mut MatchCheckCtxt<'a, 'tcx>, + patterns: I) -> usize + where I: Iterator]> +{ + // The exhaustiveness-checking paper does not include any details on + // checking variable-length slice patterns. However, they are matched + // by an infinite collection of fixed-length array patterns. + // + // To check that infinite set, we notice that for every length + // larger than the length of the maximum fixed-length pattern, + // only variable-length patterns apply. + // + // For variable length patterns, all elements after the first + // `prefix_len` but before the last `suffix_len` are matched by + // the wildcard "middle" pattern, and therefore can be added/removed + // without affecting the match result. + // + // This means that all patterns with length at least + // `max(max_fixed+1,max_prefix+max_suffix)` are equivalent, so we + // only need to check patterns from that length and below. + + let mut max_prefix_len = 0; + let mut max_suffix_len = 0; + let mut max_fixed_len = 0; + + for row in patterns { + match *row[0].kind { + PatternKind::Constant { value: ConstVal::ByteStr(ref data) } => { + max_fixed_len = cmp::max(max_fixed_len, data.len()); + } + PatternKind::Slice { ref prefix, slice: None, ref suffix } => { + let fixed_len = prefix.len() + suffix.len(); + max_fixed_len = cmp::max(max_fixed_len, fixed_len); + } + PatternKind::Slice { ref prefix, slice: Some(_), ref suffix } => { + max_prefix_len = cmp::max(max_prefix_len, prefix.len()); + max_suffix_len = cmp::max(max_suffix_len, suffix.len()); + } + _ => {} + } + } + + cmp::max(max_fixed_len + 1, max_prefix_len + max_suffix_len) +} + /// Algorithm from http://moscova.inria.fr/~maranget/papers/warn/index.html /// /// Whether a vector `v` of patterns is 'useful' in relation to a set of such @@ -453,16 +499,12 @@ pub fn is_useful<'a, 'tcx>(cx: &mut MatchCheckCtxt<'a, 'tcx>, let &Matrix(ref rows) = matrix; assert!(rows.iter().all(|r| r.len() == v.len())); + + let pcx = PatternContext { ty: rows.iter().map(|r| r[0].ty).find(|ty| !ty.references_error()) .unwrap_or(v[0].ty), - max_slice_length: rows.iter().filter_map(|row| match *row[0].kind { - PatternKind::Slice { ref prefix, slice: _, ref suffix } => - Some(prefix.len() + suffix.len()), - PatternKind::Constant { value: ConstVal::ByteStr(ref data) } => - Some(data.len()), - _ => None - }).max().map_or(0, |v| v + 1) + max_slice_length: max_slice_length(cx, rows.iter().map(|r| &**r).chain(Some(v))) }; debug!("is_useful_expand_first_col: pcx={:?}, expanding {:?}", pcx, v[0]); diff --git a/src/test/compile-fail/match-slice-patterns.rs b/src/test/compile-fail/match-slice-patterns.rs new file mode 100644 index 000000000000..c0fc75f9713a --- /dev/null +++ b/src/test/compile-fail/match-slice-patterns.rs @@ -0,0 +1,24 @@ +// 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 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +#![feature(advanced_slice_patterns, slice_patterns)] + +fn check(list: &[Option<()>]) { + match list { + //~^ ERROR `&[None, Some(_), None, _]` and `&[Some(_), Some(_), None, _]` not covered + &[] => {}, + &[_] => {}, + &[_, _] => {}, + &[_, None, ..] => {}, + &[.., Some(_), _] => {}, + } +} + +fn main() {} diff --git a/src/test/run-pass/issue-37598.rs b/src/test/run-pass/issue-37598.rs new file mode 100644 index 000000000000..d32d2fc29544 --- /dev/null +++ b/src/test/run-pass/issue-37598.rs @@ -0,0 +1,21 @@ +// 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 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +#![feature(advanced_slice_patterns, slice_patterns)] + +fn check(list: &[u8]) { + match list { + &[] => {}, + &[_u1, _u2, ref _next..] => {}, + &[_u1] => {}, + } +} + +fn main() {}