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提交 3141f2d7 编写于 作者: N Nadrieril
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Inline `all_constructors`

上级 bbb4ac06
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Showing with 115 addition and 121 deletion
compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
浏览文件 @ 3141f2d7
......@@ -791,124 +791,6 @@ fn is_covered_by_any<'p>(
}
}
/// This determines the set of all possible constructors of a pattern matching
/// values of type `left_ty`. For vectors, this would normally be an infinite set
/// but is instead bounded by the maximum fixed length of slice patterns in
/// the column of patterns being analyzed.
///
/// We make sure to omit constructors that are statically impossible. E.g., for
/// `Option<!>`, we do not include `Some(_)` in the returned list of constructors.
/// Invariant: this returns an empty `Vec` if and only if the type is uninhabited (as determined by
/// `cx.is_uninhabited()`).
fn all_constructors<'p, 'tcx>(pcx: PatCtxt<'_, 'p, 'tcx>) -> SmallVec<[Constructor<'tcx>; 1]> {
debug!("all_constructors({:?})", pcx.ty);
let cx = pcx.cx;
let make_range = |start, end| {
IntRange(
// `unwrap()` is ok because we know the type is an integer.
IntRange::from_range(cx.tcx, start, end, pcx.ty, &RangeEnd::Included).unwrap(),
)
};
match pcx.ty.kind() {
ty::Bool => smallvec![make_range(0, 1)],
ty::Array(sub_ty, len) if len.try_eval_usize(cx.tcx, cx.param_env).is_some() => {
let len = len.eval_usize(cx.tcx, cx.param_env);
if len != 0 && cx.is_uninhabited(sub_ty) {
smallvec![]
} else {
smallvec![Slice(Slice::new(Some(len), VarLen(0, 0)))]
}
}
// Treat arrays of a constant but unknown length like slices.
ty::Array(sub_ty, _) | ty::Slice(sub_ty) => {
let kind = if cx.is_uninhabited(sub_ty) { FixedLen(0) } else { VarLen(0, 0) };
smallvec![Slice(Slice::new(None, kind))]
}
ty::Adt(def, substs) if def.is_enum() => {
// If the enum is declared as `#[non_exhaustive]`, we treat it as if it had an
// additional "unknown" constructor.
// There is no point in enumerating all possible variants, because the user can't
// actually match against them all themselves. So we always return only the fictitious
// constructor.
// E.g., in an example like:
//
// ```
// let err: io::ErrorKind = ...;
// match err {
// io::ErrorKind::NotFound => {},
// }
// ```
//
// we don't want to show every possible IO error, but instead have only `_` as the
// witness.
let is_declared_nonexhaustive = cx.is_foreign_non_exhaustive_enum(pcx.ty);
// If `exhaustive_patterns` is disabled and our scrutinee is an empty enum, we treat it
// as though it had an "unknown" constructor to avoid exposing its emptiness. The
// exception is if the pattern is at the top level, because we want empty matches to be
// considered exhaustive.
let is_secretly_empty = def.variants.is_empty()
&& !cx.tcx.features().exhaustive_patterns
&& !pcx.is_top_level;
if is_secretly_empty || is_declared_nonexhaustive {
smallvec![NonExhaustive]
} else if cx.tcx.features().exhaustive_patterns {
// If `exhaustive_patterns` is enabled, we exclude variants known to be
// uninhabited.
def.variants
.iter()
.filter(|v| {
!v.uninhabited_from(cx.tcx, substs, def.adt_kind(), cx.param_env)
.contains(cx.tcx, cx.module)
})
.map(|v| Variant(v.def_id))
.collect()
} else {
def.variants.iter().map(|v| Variant(v.def_id)).collect()
}
}
ty::Char => {
smallvec![
// The valid Unicode Scalar Value ranges.
make_range('\u{0000}' as u128, '\u{D7FF}' as u128),
make_range('\u{E000}' as u128, '\u{10FFFF}' as u128),
]
}
ty::Int(_) | ty::Uint(_)
if pcx.ty.is_ptr_sized_integral()
&& !cx.tcx.features().precise_pointer_size_matching =>
{
// `usize`/`isize` are not allowed to be matched exhaustively unless the
// `precise_pointer_size_matching` feature is enabled. So we treat those types like
// `#[non_exhaustive]` enums by returning a special unmatcheable constructor.
smallvec![NonExhaustive]
}
&ty::Int(ity) => {
let bits = Integer::from_attr(&cx.tcx, SignedInt(ity)).size().bits() as u128;
let min = 1u128 << (bits - 1);
let max = min - 1;
smallvec![make_range(min, max)]
}
&ty::Uint(uty) => {
let size = Integer::from_attr(&cx.tcx, UnsignedInt(uty)).size();
let max = size.truncate(u128::MAX);
smallvec![make_range(0, max)]
}
// If `exhaustive_patterns` is disabled and our scrutinee is the never type, we cannot
// expose its emptiness. The exception is if the pattern is at the top level, because we
// want empty matches to be considered exhaustive.
ty::Never if !cx.tcx.features().exhaustive_patterns && !pcx.is_top_level => {
smallvec![NonExhaustive]
}
ty::Never => smallvec![],
_ if cx.is_uninhabited(pcx.ty) => smallvec![],
ty::Adt(..) | ty::Tuple(..) | ty::Ref(..) => smallvec![Single],
// This type is one for which we cannot list constructors, like `str` or `f64`.
_ => smallvec![NonExhaustive],
}
}
/// A wildcard constructor that we split relative to the constructors in the matrix, as explained
/// at the top of the file.
/// For splitting wildcards, there are two groups of constructors: there are the constructors
......@@ -926,9 +808,121 @@ pub(super) struct SplitWildcard<'tcx> {
impl<'tcx> SplitWildcard<'tcx> {
pub(super) fn new<'p>(pcx: PatCtxt<'_, 'p, 'tcx>) -> Self {
let matrix_ctors = Vec::new();
let all_ctors = all_constructors(pcx);
SplitWildcard { matrix_ctors, all_ctors }
debug!("SplitWildcard::new({:?})", pcx.ty);
let cx = pcx.cx;
let make_range = |start, end| {
IntRange(
// `unwrap()` is ok because we know the type is an integer.
IntRange::from_range(cx.tcx, start, end, pcx.ty, &RangeEnd::Included).unwrap(),
)
};
// This determines the set of all possible constructors for the type `pcx.ty`. For numbers,
// arrays and slices we use ranges and variable-length slices when appropriate.
//
// If the `exhaustive_patterns` feature is enabled, we make sure to omit constructors that
// are statically impossible. E.g., for `Option<!>`, we do not include `Some(_)` in the
// returned list of constructors.
// Invariant: this is empty if and only if the type is uninhabited (as determined by
// `cx.is_uninhabited()`).
let all_ctors = match pcx.ty.kind() {
ty::Bool => smallvec![make_range(0, 1)],
ty::Array(sub_ty, len) if len.try_eval_usize(cx.tcx, cx.param_env).is_some() => {
let len = len.eval_usize(cx.tcx, cx.param_env);
if len != 0 && cx.is_uninhabited(sub_ty) {
smallvec![]
} else {
smallvec![Slice(Slice::new(Some(len), VarLen(0, 0)))]
}
}
// Treat arrays of a constant but unknown length like slices.
ty::Array(sub_ty, _) | ty::Slice(sub_ty) => {
let kind = if cx.is_uninhabited(sub_ty) { FixedLen(0) } else { VarLen(0, 0) };
smallvec![Slice(Slice::new(None, kind))]
}
ty::Adt(def, substs) if def.is_enum() => {
// If the enum is declared as `#[non_exhaustive]`, we treat it as if it had an
// additional "unknown" constructor.
// There is no point in enumerating all possible variants, because the user can't
// actually match against them all themselves. So we always return only the fictitious
// constructor.
// E.g., in an example like:
//
// ```
// let err: io::ErrorKind = ...;
// match err {
// io::ErrorKind::NotFound => {},
// }
// ```
//
// we don't want to show every possible IO error, but instead have only `_` as the
// witness.
let is_declared_nonexhaustive = cx.is_foreign_non_exhaustive_enum(pcx.ty);
// If `exhaustive_patterns` is disabled and our scrutinee is an empty enum, we treat it
// as though it had an "unknown" constructor to avoid exposing its emptiness. The
// exception is if the pattern is at the top level, because we want empty matches to be
// considered exhaustive.
let is_secretly_empty = def.variants.is_empty()
&& !cx.tcx.features().exhaustive_patterns
&& !pcx.is_top_level;
if is_secretly_empty || is_declared_nonexhaustive {
smallvec![NonExhaustive]
} else if cx.tcx.features().exhaustive_patterns {
// If `exhaustive_patterns` is enabled, we exclude variants known to be
// uninhabited.
def.variants
.iter()
.filter(|v| {
!v.uninhabited_from(cx.tcx, substs, def.adt_kind(), cx.param_env)
.contains(cx.tcx, cx.module)
})
.map(|v| Variant(v.def_id))
.collect()
} else {
def.variants.iter().map(|v| Variant(v.def_id)).collect()
}
}
ty::Char => {
smallvec![
// The valid Unicode Scalar Value ranges.
make_range('\u{0000}' as u128, '\u{D7FF}' as u128),
make_range('\u{E000}' as u128, '\u{10FFFF}' as u128),
]
}
ty::Int(_) | ty::Uint(_)
if pcx.ty.is_ptr_sized_integral()
&& !cx.tcx.features().precise_pointer_size_matching =>
{
// `usize`/`isize` are not allowed to be matched exhaustively unless the
// `precise_pointer_size_matching` feature is enabled. So we treat those types like
// `#[non_exhaustive]` enums by returning a special unmatcheable constructor.
smallvec![NonExhaustive]
}
&ty::Int(ity) => {
let bits = Integer::from_attr(&cx.tcx, SignedInt(ity)).size().bits() as u128;
let min = 1u128 << (bits - 1);
let max = min - 1;
smallvec![make_range(min, max)]
}
&ty::Uint(uty) => {
let size = Integer::from_attr(&cx.tcx, UnsignedInt(uty)).size();
let max = size.truncate(u128::MAX);
smallvec![make_range(0, max)]
}
// If `exhaustive_patterns` is disabled and our scrutinee is the never type, we cannot
// expose its emptiness. The exception is if the pattern is at the top level, because we
// want empty matches to be considered exhaustive.
ty::Never if !cx.tcx.features().exhaustive_patterns && !pcx.is_top_level => {
smallvec![NonExhaustive]
}
ty::Never => smallvec![],
_ if cx.is_uninhabited(pcx.ty) => smallvec![],
ty::Adt(..) | ty::Tuple(..) | ty::Ref(..) => smallvec![Single],
// This type is one for which we cannot list constructors, like `str` or `f64`.
_ => smallvec![NonExhaustive],
};
SplitWildcard { matrix_ctors: Vec::new(), all_ctors }
}
/// Pass a set of constructors relative to which to split this one. Don't call twice, it won't
......
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