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Allow constants of byte slice type as patterns

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This commit is contained in:
Oliver Scherer 2018-11-13 14:10:47 +01:00
parent a49316ddc9
commit 7df1d9f656
2 changed files with 68 additions and 59 deletions
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116
src/librustc_mir/hair/pattern/_match.rs
View file

@ -330,47 +330,6 @@ impl<'a, 'tcx> MatchCheckCtxt<'a, 'tcx> {
})
}
// convert a byte-string pattern to a list of u8 patterns.
fn lower_byte_str_pattern<'p>(&mut self, pat: &'p Pattern<'tcx>) -> Vec<&'p Pattern<'tcx>>
where 'a: 'p
{
let pattern_arena = &*self.pattern_arena;
let tcx = self.tcx;
self.byte_array_map.entry(pat).or_insert_with(|| {
match pat.kind {
box PatternKind::Constant {
value: const_val
} => {
if let Some(ptr) = const_val.to_ptr() {
let is_array_ptr = const_val.ty
.builtin_deref(true)
.and_then(|t| t.ty.builtin_index())
.map_or(false, |t| t == tcx.types.u8);
assert!(is_array_ptr);
let alloc = tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id);
assert_eq!(ptr.offset.bytes(), 0);
// FIXME: check length
alloc.bytes.iter().map(|b| {
&*pattern_arena.alloc(Pattern {
ty: tcx.types.u8,
span: pat.span,
kind: box PatternKind::Constant {
value: ty::Const::from_bits(
tcx,
*b as u128,
ty::ParamEnv::empty().and(tcx.types.u8))
}
})
}).collect()
} else {
bug!("not a byte str: {:?}", const_val)
}
}
_ => span_bug!(pat.span, "unexpected byte array pattern {:?}", pat)
}
}).clone()
}
fn is_uninhabited(&self, ty: Ty<'tcx>) -> bool {
if self.tcx.features().exhaustive_patterns {
self.tcx.is_ty_uninhabited_from(self.module, ty)
@ -1705,26 +1664,65 @@ fn specialize<'p, 'a: 'p, 'tcx: 'a>(
PatternKind::Constant { value } => {
match *constructor {
Slice(..) => {
if let Some(ptr) = value.to_ptr() {
let is_array_ptr = value.ty
.builtin_deref(true)
.and_then(|t| t.ty.builtin_index())
.map_or(false, |t| t == cx.tcx.types.u8);
assert!(is_array_ptr);
let data_len = cx.tcx
.alloc_map
.lock()
.unwrap_memory(ptr.alloc_id)
.bytes
.len();
if wild_patterns.len() == data_len {
Some(cx.lower_byte_str_pattern(pat))
} else {
None
// we extract an `Option` for the pointer because slices of zero elements don't
// necessarily point to memory, they are usually just integers. The only time
// they should be pointing to memory is when they are subslices of nonzero
// slices
let (opt_ptr, data_len) = match value.ty.builtin_deref(false).unwrap().ty.sty {
ty::TyKind::Array(t, n) => {
assert!(t == cx.tcx.types.u8);
(value.to_ptr(), n.unwrap_usize(cx.tcx))
},
ty::TyKind::Slice(t) => {
assert!(t == cx.tcx.types.u8);
match value.val {
ConstValue::ScalarPair(ptr, n) => (
ptr.to_ptr().ok(),
n.to_bits(cx.tcx.data_layout.pointer_size).unwrap() as u64
),
_ => span_bug!(
pat.span,
"slice pattern constant must be scalar pair but is {:?}",
value,
),
}
},
_ => span_bug!(
pat.span,
"unexpected const-val {:?} with ctor {:?}",
value,
constructor,
),
};
if wild_patterns.len() as u64 == data_len {
// convert a byte-string pattern to a list of u8 patterns.
match (data_len, opt_ptr) {
(0, _) => Some(Vec::new()),
(_, Some(ptr)) => {
let alloc = cx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id);
// FIXME: use `Allocation::read_bytes` once available
assert_eq!(ptr.offset.bytes(), 0);
Some(alloc.bytes.iter().map(|b| {
&*cx.pattern_arena.alloc(Pattern {
ty: cx.tcx.types.u8,
span: pat.span,
kind: box PatternKind::Constant {
value: ty::Const::from_bits(
cx.tcx,
*b as u128,
ty::ParamEnv::empty().and(cx.tcx.types.u8))
},
})
}).collect())
},
(_, None) => span_bug!(
pat.span,
"non zero length slice with const-val {:?}",
value,
),
}
} else {
span_bug!(pat.span,
"unexpected const-val {:?} with ctor {:?}", value, constructor)
None
}
}
_ => {

11
src/test/ui/pattern/slice-pattern-const.rs Normal file
View file

@ -0,0 +1,11 @@
// compile-pass
fn main() {
let s = &[0x00; 4][..]; //Slice of any value
const MAGIC_TEST: &[u8] = b"TEST"; //Const slice to pattern match with
match s {
MAGIC_TEST => (),
[0x00, 0x00, 0x00, 0x00] => (),
_ => ()
}
}