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// Testing candidates
//
// After candidates have been simplified, the only match pairs that
// remain are those that require some sort of test. The functions here
// identify what tests are needed, perform the tests, and then filter
// the candidates based on the result.
use crate::build::expr::as_place::PlaceBuilder;
use crate::build::matches::{Candidate, MatchPair, Test, TestKind};
use crate::build::Builder;
use crate::thir::pattern::compare_const_vals;
use rustc_data_structures::fx::FxIndexMap;
use rustc_hir::{LangItem, RangeEnd};
use rustc_index::bit_set::BitSet;
use rustc_middle::mir::*;
use rustc_middle::thir::*;
use rustc_middle::ty::util::IntTypeExt;
use rustc_middle::ty::GenericArg;
use rustc_middle::ty::{self, adjustment::PointerCoercion, Ty, TyCtxt};
use rustc_span::def_id::DefId;
use rustc_span::symbol::{sym, Symbol};
use rustc_span::Span;
use rustc_target::abi::VariantIdx;
use std::cmp::Ordering;
impl<'a, 'tcx> Builder<'a, 'tcx> {
/// Identifies what test is needed to decide if `match_pair` is applicable.
///
/// It is a bug to call this with a not-fully-simplified pattern.
pub(super) fn test<'pat>(&mut self, match_pair: &MatchPair<'pat, 'tcx>) -> Test<'tcx> {
match match_pair.pattern.kind {
PatKind::Variant { adt_def, args: _, variant_index: _, subpatterns: _ } => Test {
span: match_pair.pattern.span,
kind: TestKind::Switch {
adt_def,
variants: BitSet::new_empty(adt_def.variants().len()),
},
},
PatKind::Constant { .. } if is_switch_ty(match_pair.pattern.ty) => {
// For integers, we use a `SwitchInt` match, which allows
// us to handle more cases.
Test {
span: match_pair.pattern.span,
kind: TestKind::SwitchInt {
switch_ty: match_pair.pattern.ty,
// these maps are empty to start; cases are
// added below in add_cases_to_switch
options: Default::default(),
},
}
}
PatKind::Constant { value } => Test {
span: match_pair.pattern.span,
kind: TestKind::Eq { value, ty: match_pair.pattern.ty },
},
PatKind::Range(ref range) => {
assert_eq!(range.lo.ty(), match_pair.pattern.ty);
assert_eq!(range.hi.ty(), match_pair.pattern.ty);
Test { span: match_pair.pattern.span, kind: TestKind::Range(range.clone()) }
}
PatKind::Slice { ref prefix, ref slice, ref suffix } => {
let len = prefix.len() + suffix.len();
let op = if slice.is_some() { BinOp::Ge } else { BinOp::Eq };
Test { span: match_pair.pattern.span, kind: TestKind::Len { len: len as u64, op } }
}
PatKind::Or { .. } => bug!("or-patterns should have already been handled"),
PatKind::AscribeUserType { .. }
| PatKind::Array { .. }
| PatKind::Wild
| PatKind::Binding { .. }
| PatKind::Leaf { .. }
| PatKind::Deref { .. } => self.error_simplifiable(match_pair),
}
}
pub(super) fn add_cases_to_switch<'pat>(
&mut self,
test_place: &PlaceBuilder<'tcx>,
candidate: &Candidate<'pat, 'tcx>,
options: &mut FxIndexMap<Const<'tcx>, u128>,
) -> bool {
let Some(match_pair) = candidate.match_pairs.iter().find(|mp| mp.place == *test_place)
else {
return false;
};
match match_pair.pattern.kind {
PatKind::Constant { value } => {
options.entry(value).or_insert_with(|| value.eval_bits(self.tcx, self.param_env));
true
}
PatKind::Variant { .. } => {
panic!("you should have called add_variants_to_switch instead!");
}
PatKind::Range(ref range) => {
// Check that none of the switch values are in the range.
self.values_not_contained_in_range(&*range, options).unwrap_or(false)
}
PatKind::Slice { .. }
| PatKind::Array { .. }
| PatKind::Wild
| PatKind::Or { .. }
| PatKind::Binding { .. }
| PatKind::AscribeUserType { .. }
| PatKind::Leaf { .. }
| PatKind::Deref { .. } => {
// don't know how to add these patterns to a switch
false
}
}
}
pub(super) fn add_variants_to_switch<'pat>(
&mut self,
test_place: &PlaceBuilder<'tcx>,
candidate: &Candidate<'pat, 'tcx>,
variants: &mut BitSet<VariantIdx>,
) -> bool {
let Some(match_pair) = candidate.match_pairs.iter().find(|mp| mp.place == *test_place)
else {
return false;
};
match match_pair.pattern.kind {
PatKind::Variant { adt_def: _, variant_index, .. } => {
// We have a pattern testing for variant `variant_index`
// set the corresponding index to true
variants.insert(variant_index);
true
}
_ => {
// don't know how to add these patterns to a switch
false
}
}
}
#[instrument(skip(self, make_target_blocks, place_builder), level = "debug")]
pub(super) fn perform_test(
&mut self,
match_start_span: Span,
scrutinee_span: Span,
block: BasicBlock,
place_builder: &PlaceBuilder<'tcx>,
test: &Test<'tcx>,
make_target_blocks: impl FnOnce(&mut Self) -> Vec<BasicBlock>,
) {
let place = place_builder.to_place(self);
let place_ty = place.ty(&self.local_decls, self.tcx);
debug!(?place, ?place_ty,);
let source_info = self.source_info(test.span);
match test.kind {
TestKind::Switch { adt_def, ref variants } => {
let target_blocks = make_target_blocks(self);
// Variants is a BitVec of indexes into adt_def.variants.
let num_enum_variants = adt_def.variants().len();
debug_assert_eq!(target_blocks.len(), num_enum_variants + 1);
let otherwise_block = *target_blocks.last().unwrap();
let tcx = self.tcx;
let switch_targets = SwitchTargets::new(
adt_def.discriminants(tcx).filter_map(|(idx, discr)| {
if variants.contains(idx) {
debug_assert_ne!(
target_blocks[idx.index()],
otherwise_block,
"no candidates for tested discriminant: {discr:?}",
);
Some((discr.val, target_blocks[idx.index()]))
} else {
debug_assert_eq!(
target_blocks[idx.index()],
otherwise_block,
"found candidates for untested discriminant: {discr:?}",
);
None
}
}),
otherwise_block,
);
debug!("num_enum_variants: {}, variants: {:?}", num_enum_variants, variants);
let discr_ty = adt_def.repr().discr_type().to_ty(tcx);
let discr = self.temp(discr_ty, test.span);
self.cfg.push_assign(
block,
self.source_info(scrutinee_span),
discr,
Rvalue::Discriminant(place),
);
self.cfg.terminate(
block,
self.source_info(match_start_span),
TerminatorKind::SwitchInt {
discr: Operand::Move(discr),
targets: switch_targets,
},
);
}
TestKind::SwitchInt { switch_ty, ref options } => {
let target_blocks = make_target_blocks(self);
let terminator = if *switch_ty.kind() == ty::Bool {
assert!(!options.is_empty() && options.len() <= 2);
let [first_bb, second_bb] = *target_blocks else {
bug!("`TestKind::SwitchInt` on `bool` should have two targets")
};
let (true_bb, false_bb) = match options[0] {
1 => (first_bb, second_bb),
0 => (second_bb, first_bb),
v => span_bug!(test.span, "expected boolean value but got {:?}", v),
};
TerminatorKind::if_(Operand::Copy(place), true_bb, false_bb)
} else {
// The switch may be inexhaustive so we have a catch all block
debug_assert_eq!(options.len() + 1, target_blocks.len());
let otherwise_block = *target_blocks.last().unwrap();
let switch_targets = SwitchTargets::new(
options.values().copied().zip(target_blocks),
otherwise_block,
);
TerminatorKind::SwitchInt {
discr: Operand::Copy(place),
targets: switch_targets,
}
};
self.cfg.terminate(block, self.source_info(match_start_span), terminator);
}
TestKind::Eq { value, ty } => {
let tcx = self.tcx;
if let ty::Adt(def, _) = ty.kind() && Some(def.did()) == tcx.lang_items().string() {
if !tcx.features().string_deref_patterns {
bug!("matching on `String` went through without enabling string_deref_patterns");
}
let re_erased = tcx.lifetimes.re_erased;
let ref_string = self.temp(Ty::new_imm_ref(tcx,re_erased, ty), test.span);
let ref_str_ty = Ty::new_imm_ref(tcx,re_erased, tcx.types.str_);
let ref_str = self.temp(ref_str_ty, test.span);
let deref = tcx.require_lang_item(LangItem::Deref, None);
let method = trait_method(tcx, deref, sym::deref, [ty]);
let eq_block = self.cfg.start_new_block();
self.cfg.push_assign(block, source_info, ref_string, Rvalue::Ref(re_erased, BorrowKind::Shared, place));
self.cfg.terminate(
block,
source_info,
TerminatorKind::Call {
func: Operand::Constant(Box::new(ConstOperand {
span: test.span,
user_ty: None,
const_: method,
})),
args: vec![Operand::Move(ref_string)],
destination: ref_str,
target: Some(eq_block),
unwind: UnwindAction::Continue,
call_source: CallSource::Misc,
fn_span: source_info.span
}
);
self.non_scalar_compare(eq_block, make_target_blocks, source_info, value, ref_str, ref_str_ty);
return;
}
if !ty.is_scalar() {
// Use `PartialEq::eq` instead of `BinOp::Eq`
// (the binop can only handle primitives)
self.non_scalar_compare(
block,
make_target_blocks,
source_info,
value,
place,
ty,
);
} else if let [success, fail] = *make_target_blocks(self) {
assert_eq!(value.ty(), ty);
let expect = self.literal_operand(test.span, value);
let val = Operand::Copy(place);
self.compare(block, success, fail, source_info, BinOp::Eq, expect, val);
} else {
bug!("`TestKind::Eq` should have two target blocks");
}
}
TestKind::Range(box PatRange { lo, hi, ref end }) => {
let lower_bound_success = self.cfg.start_new_block();
let target_blocks = make_target_blocks(self);
// Test `val` by computing `lo <= val && val <= hi`, using primitive comparisons.
let lo = self.literal_operand(test.span, lo);
let hi = self.literal_operand(test.span, hi);
let val = Operand::Copy(place);
let [success, fail] = *target_blocks else {
bug!("`TestKind::Range` should have two target blocks");
};
self.compare(
block,
lower_bound_success,
fail,
source_info,
BinOp::Le,
lo,
val.clone(),
);
let op = match *end {
RangeEnd::Included => BinOp::Le,
RangeEnd::Excluded => BinOp::Lt,
};
self.compare(lower_bound_success, success, fail, source_info, op, val, hi);
}
TestKind::Len { len, op } => {
let target_blocks = make_target_blocks(self);
let usize_ty = self.tcx.types.usize;
let actual = self.temp(usize_ty, test.span);
// actual = len(place)
self.cfg.push_assign(block, source_info, actual, Rvalue::Len(place));
// expected = <N>
let expected = self.push_usize(block, source_info, len);
let [true_bb, false_bb] = *target_blocks else {
bug!("`TestKind::Len` should have two target blocks");
};
// result = actual == expected OR result = actual < expected
// branch based on result
self.compare(
block,
true_bb,
false_bb,
source_info,
op,
Operand::Move(actual),
Operand::Move(expected),
);
}
}
}
/// Compare using the provided built-in comparison operator
fn compare(
&mut self,
block: BasicBlock,
success_block: BasicBlock,
fail_block: BasicBlock,
source_info: SourceInfo,
op: BinOp,
left: Operand<'tcx>,
right: Operand<'tcx>,
) {
let bool_ty = self.tcx.types.bool;
let result = self.temp(bool_ty, source_info.span);
// result = op(left, right)
self.cfg.push_assign(
block,
source_info,
result,
Rvalue::BinaryOp(op, Box::new((left, right))),
);
// branch based on result
self.cfg.terminate(
block,
source_info,
TerminatorKind::if_(Operand::Move(result), success_block, fail_block),
);
}
/// Compare two values using `<T as std::compare::PartialEq>::eq`.
/// If the values are already references, just call it directly, otherwise
/// take a reference to the values first and then call it.
fn non_scalar_compare(
&mut self,
block: BasicBlock,
make_target_blocks: impl FnOnce(&mut Self) -> Vec<BasicBlock>,
source_info: SourceInfo,
value: Const<'tcx>,
mut val: Place<'tcx>,
mut ty: Ty<'tcx>,
) {
let mut expect = self.literal_operand(source_info.span, value);
// If we're using `b"..."` as a pattern, we need to insert an
// unsizing coercion, as the byte string has the type `&[u8; N]`.
//
// We want to do this even when the scrutinee is a reference to an
// array, so we can call `<[u8]>::eq` rather than having to find an
// `<[u8; N]>::eq`.
let unsize = |ty: Ty<'tcx>| match ty.kind() {
ty::Ref(region, rty, _) => match rty.kind() {
ty::Array(inner_ty, n) => Some((region, inner_ty, n)),
_ => None,
},
_ => None,
};
let opt_ref_ty = unsize(ty);
let opt_ref_test_ty = unsize(value.ty());
match (opt_ref_ty, opt_ref_test_ty) {
// nothing to do, neither is an array
(None, None) => {}
(Some((region, elem_ty, _)), _) | (None, Some((region, elem_ty, _))) => {
let tcx = self.tcx;
// make both a slice
ty = Ty::new_imm_ref(tcx, *region, Ty::new_slice(tcx, *elem_ty));
if opt_ref_ty.is_some() {
let temp = self.temp(ty, source_info.span);
self.cfg.push_assign(
block,
source_info,
temp,
Rvalue::Cast(
CastKind::PointerCoercion(PointerCoercion::Unsize),
Operand::Copy(val),
ty,
),
);
val = temp;
}
if opt_ref_test_ty.is_some() {
let slice = self.temp(ty, source_info.span);
self.cfg.push_assign(
block,
source_info,
slice,
Rvalue::Cast(
CastKind::PointerCoercion(PointerCoercion::Unsize),
expect,
ty,
),
);
expect = Operand::Move(slice);
}
}
}
match *ty.kind() {
ty::Ref(_, deref_ty, _) => ty = deref_ty,
_ => {
// non_scalar_compare called on non-reference type
let temp = self.temp(ty, source_info.span);
self.cfg.push_assign(block, source_info, temp, Rvalue::Use(expect));
let ref_ty = Ty::new_imm_ref(self.tcx, self.tcx.lifetimes.re_erased, ty);
let ref_temp = self.temp(ref_ty, source_info.span);
self.cfg.push_assign(
block,
source_info,
ref_temp,
Rvalue::Ref(self.tcx.lifetimes.re_erased, BorrowKind::Shared, temp),
);
expect = Operand::Move(ref_temp);
let ref_temp = self.temp(ref_ty, source_info.span);
self.cfg.push_assign(
block,
source_info,
ref_temp,
Rvalue::Ref(self.tcx.lifetimes.re_erased, BorrowKind::Shared, val),
);
val = ref_temp;
}
}
let eq_def_id = self.tcx.require_lang_item(LangItem::PartialEq, Some(source_info.span));
let method = trait_method(self.tcx, eq_def_id, sym::eq, [ty, ty]);
let bool_ty = self.tcx.types.bool;
let eq_result = self.temp(bool_ty, source_info.span);
let eq_block = self.cfg.start_new_block();
self.cfg.terminate(
block,
source_info,
TerminatorKind::Call {
func: Operand::Constant(Box::new(ConstOperand {
span: source_info.span,
// FIXME(#54571): This constant comes from user input (a
// constant in a pattern). Are there forms where users can add
// type annotations here? For example, an associated constant?
// Need to experiment.
user_ty: None,
const_: method,
})),
args: vec![Operand::Copy(val), expect],
destination: eq_result,
target: Some(eq_block),
unwind: UnwindAction::Continue,
call_source: CallSource::MatchCmp,
fn_span: source_info.span,
},
);
self.diverge_from(block);
let [success_block, fail_block] = *make_target_blocks(self) else {
bug!("`TestKind::Eq` should have two target blocks")
};
// check the result
self.cfg.terminate(
eq_block,
source_info,
TerminatorKind::if_(Operand::Move(eq_result), success_block, fail_block),
);
}
/// Given that we are performing `test` against `test_place`, this job
/// sorts out what the status of `candidate` will be after the test. See
/// `test_candidates` for the usage of this function. The returned index is
/// the index that this candidate should be placed in the
/// `target_candidates` vec. The candidate may be modified to update its
/// `match_pairs`.
///
/// So, for example, if this candidate is `x @ Some(P0)` and the `Test` is
/// a variant test, then we would modify the candidate to be `(x as
/// Option).0 @ P0` and return the index corresponding to the variant
/// `Some`.
///
/// However, in some cases, the test may just not be relevant to candidate.
/// For example, suppose we are testing whether `foo.x == 22`, but in one
/// match arm we have `Foo { x: _, ... }`... in that case, the test for
/// the value of `x` has no particular relevance to this candidate. In
/// such cases, this function just returns None without doing anything.
/// This is used by the overall `match_candidates` algorithm to structure
/// the match as a whole. See `match_candidates` for more details.
///
/// FIXME(#29623). In some cases, we have some tricky choices to make. for
/// example, if we are testing that `x == 22`, but the candidate is `x @
/// 13..55`, what should we do? In the event that the test is true, we know
/// that the candidate applies, but in the event of false, we don't know
/// that it *doesn't* apply. For now, we return false, indicate that the
/// test does not apply to this candidate, but it might be we can get
/// tighter match code if we do something a bit different.
pub(super) fn sort_candidate<'pat>(
&mut self,
test_place: &PlaceBuilder<'tcx>,
test: &Test<'tcx>,
candidate: &mut Candidate<'pat, 'tcx>,
) -> Option<usize> {
// Find the match_pair for this place (if any). At present,
// afaik, there can be at most one. (In the future, if we
// adopted a more general `@` operator, there might be more
// than one, but it'd be very unusual to have two sides that
// both require tests; you'd expect one side to be simplified
// away.)
let (match_pair_index, match_pair) =
candidate.match_pairs.iter().enumerate().find(|&(_, mp)| mp.place == *test_place)?;
match (&test.kind, &match_pair.pattern.kind) {
// If we are performing a variant switch, then this
// informs variant patterns, but nothing else.
(
&TestKind::Switch { adt_def: tested_adt_def, .. },
&PatKind::Variant { adt_def, variant_index, ref subpatterns, .. },
) => {
assert_eq!(adt_def, tested_adt_def);
self.candidate_after_variant_switch(
match_pair_index,
adt_def,
variant_index,
subpatterns,
candidate,
);
Some(variant_index.as_usize())
}
(&TestKind::Switch { .. }, _) => None,
// If we are performing a switch over integers, then this informs integer
// equality, but nothing else.
//
// FIXME(#29623) we could use PatKind::Range to rule
// things out here, in some cases.
(TestKind::SwitchInt { switch_ty: _, options }, PatKind::Constant { value })
if is_switch_ty(match_pair.pattern.ty) =>
{
let index = options.get_index_of(value).unwrap();
self.candidate_without_match_pair(match_pair_index, candidate);
Some(index)
}
(TestKind::SwitchInt { switch_ty: _, options }, PatKind::Range(range)) => {
let not_contained =
self.values_not_contained_in_range(&*range, options).unwrap_or(false);
not_contained.then(|| {
// No switch values are contained in the pattern range,
// so the pattern can be matched only if this test fails.
options.len()
})
}
(&TestKind::SwitchInt { .. }, _) => None,
(
&TestKind::Len { len: test_len, op: BinOp::Eq },
PatKind::Slice { prefix, slice, suffix },
) => {
let pat_len = (prefix.len() + suffix.len()) as u64;
match (test_len.cmp(&pat_len), slice) {
(Ordering::Equal, &None) => {
// on true, min_len = len = $actual_length,
// on false, len != $actual_length
self.candidate_after_slice_test(
match_pair_index,
candidate,
prefix,
slice,
suffix,
);
Some(0)
}
(Ordering::Less, _) => {
// test_len < pat_len. If $actual_len = test_len,
// then $actual_len < pat_len and we don't have
// enough elements.
Some(1)
}
(Ordering::Equal | Ordering::Greater, &Some(_)) => {
// This can match both if $actual_len = test_len >= pat_len,
// and if $actual_len > test_len. We can't advance.
None
}
(Ordering::Greater, &None) => {
// test_len != pat_len, so if $actual_len = test_len, then
// $actual_len != pat_len.
Some(1)
}
}
}
(
&TestKind::Len { len: test_len, op: BinOp::Ge },
PatKind::Slice { prefix, slice, suffix },
) => {
// the test is `$actual_len >= test_len`
let pat_len = (prefix.len() + suffix.len()) as u64;
match (test_len.cmp(&pat_len), slice) {
(Ordering::Equal, &Some(_)) => {
// $actual_len >= test_len = pat_len,
// so we can match.
self.candidate_after_slice_test(
match_pair_index,
candidate,
prefix,
slice,
suffix,
);
Some(0)
}
(Ordering::Less, _) | (Ordering::Equal, &None) => {
// test_len <= pat_len. If $actual_len < test_len,
// then it is also < pat_len, so the test passing is
// necessary (but insufficient).
Some(0)
}
(Ordering::Greater, &None) => {
// test_len > pat_len. If $actual_len >= test_len > pat_len,
// then we know we won't have a match.
Some(1)
}
(Ordering::Greater, &Some(_)) => {
// test_len < pat_len, and is therefore less
// strict. This can still go both ways.
None
}
}
}
(TestKind::Range(test), PatKind::Range(pat)) => {
use std::cmp::Ordering::*;
if test == pat {
self.candidate_without_match_pair(match_pair_index, candidate);
return Some(0);
}
// For performance, it's important to only do the second
// `compare_const_vals` if necessary.
let no_overlap = if matches!(
(compare_const_vals(self.tcx, test.hi, pat.lo, self.param_env)?, test.end),
(Less, _) | (Equal, RangeEnd::Excluded) // test < pat
) || matches!(
(compare_const_vals(self.tcx, test.lo, pat.hi, self.param_env)?, pat.end),
(Greater, _) | (Equal, RangeEnd::Excluded) // test > pat
) {
Some(1)
} else {
None
};
// If the testing range does not overlap with pattern range,
// the pattern can be matched only if this test fails.
no_overlap
}
(TestKind::Range(range), &PatKind::Constant { value }) => {
if let Some(false) = self.const_range_contains(&*range, value) {
// `value` is not contained in the testing range,
// so `value` can be matched only if this test fails.
Some(1)
} else {
None
}
}
(&TestKind::Range { .. }, _) => None,
(&TestKind::Eq { .. } | &TestKind::Len { .. }, _) => {
// The call to `self.test(&match_pair)` below is not actually used to generate any
// MIR. Instead, we just want to compare with `test` (the parameter of the method)
// to see if it is the same.
//
// However, at this point we can still encounter or-patterns that were extracted
// from previous calls to `sort_candidate`, so we need to manually address that
// case to avoid panicking in `self.test()`.
if let PatKind::Or { .. } = &match_pair.pattern.kind {
return None;
}
// These are all binary tests.
//
// FIXME(#29623) we can be more clever here
let pattern_test = self.test(&match_pair);
if pattern_test.kind == test.kind {
self.candidate_without_match_pair(match_pair_index, candidate);
Some(0)
} else {
None
}
}
}
}
fn candidate_without_match_pair(
&mut self,
match_pair_index: usize,
candidate: &mut Candidate<'_, 'tcx>,
) {
candidate.match_pairs.remove(match_pair_index);
}
fn candidate_after_slice_test<'pat>(
&mut self,
match_pair_index: usize,
candidate: &mut Candidate<'pat, 'tcx>,
prefix: &'pat [Box<Pat<'tcx>>],
opt_slice: &'pat Option<Box<Pat<'tcx>>>,
suffix: &'pat [Box<Pat<'tcx>>],
) {
let removed_place = candidate.match_pairs.remove(match_pair_index).place;
self.prefix_slice_suffix(
&mut candidate.match_pairs,
&removed_place,
prefix,
opt_slice,
suffix,
);
}
fn candidate_after_variant_switch<'pat>(
&mut self,
match_pair_index: usize,
adt_def: ty::AdtDef<'tcx>,
variant_index: VariantIdx,
subpatterns: &'pat [FieldPat<'tcx>],
candidate: &mut Candidate<'pat, 'tcx>,
) {
let match_pair = candidate.match_pairs.remove(match_pair_index);
// So, if we have a match-pattern like `x @ Enum::Variant(P1, P2)`,
// we want to create a set of derived match-patterns like
// `(x as Variant).0 @ P1` and `(x as Variant).1 @ P1`.
let downcast_place = match_pair.place.downcast(adt_def, variant_index); // `(x as Variant)`
let consequent_match_pairs = subpatterns.iter().map(|subpattern| {
// e.g., `(x as Variant).0`
let place = downcast_place
.clone_project(PlaceElem::Field(subpattern.field, subpattern.pattern.ty));
// e.g., `(x as Variant).0 @ P1`
MatchPair::new(place, &subpattern.pattern, self)
});
candidate.match_pairs.extend(consequent_match_pairs);
}
fn error_simplifiable<'pat>(&mut self, match_pair: &MatchPair<'pat, 'tcx>) -> ! {
span_bug!(match_pair.pattern.span, "simplifiable pattern found: {:?}", match_pair.pattern)
}
fn const_range_contains(&self, range: &PatRange<'tcx>, value: Const<'tcx>) -> Option<bool> {
use std::cmp::Ordering::*;
// For performance, it's important to only do the second
// `compare_const_vals` if necessary.
Some(
matches!(compare_const_vals(self.tcx, range.lo, value, self.param_env)?, Less | Equal)
&& matches!(
(compare_const_vals(self.tcx, value, range.hi, self.param_env)?, range.end),
(Less, _) | (Equal, RangeEnd::Included)
),
)
}
fn values_not_contained_in_range(
&self,
range: &PatRange<'tcx>,
options: &FxIndexMap<Const<'tcx>, u128>,
) -> Option<bool> {
for &val in options.keys() {
if self.const_range_contains(range, val)? {
return Some(false);
}
}
Some(true)
}
}
impl Test<'_> {
pub(super) fn targets(&self) -> usize {
match self.kind {
TestKind::Eq { .. } | TestKind::Range(_) | TestKind::Len { .. } => 2,
TestKind::Switch { adt_def, .. } => {
// While the switch that we generate doesn't test for all
// variants, we have a target for each variant and the
// otherwise case, and we make sure that all of the cases not
// specified have the same block.
adt_def.variants().len() + 1
}
TestKind::SwitchInt { switch_ty, ref options, .. } => {
if switch_ty.is_bool() {
// `bool` is special cased in `perform_test` to always
// branch to two blocks.
2
} else {
options.len() + 1
}
}
}
}
}
fn is_switch_ty(ty: Ty<'_>) -> bool {
ty.is_integral() || ty.is_char() || ty.is_bool()
}
fn trait_method<'tcx>(
tcx: TyCtxt<'tcx>,
trait_def_id: DefId,
method_name: Symbol,
args: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
) -> Const<'tcx> {
// The unhygienic comparison here is acceptable because this is only
// used on known traits.
let item = tcx
.associated_items(trait_def_id)
.filter_by_name_unhygienic(method_name)
.find(|item| item.kind == ty::AssocKind::Fn)
.expect("trait method not found");
let method_ty = Ty::new_fn_def(tcx, item.def_id, args);
Const::zero_sized(method_ty)
}