| // 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::Builder; |
| use crate::build::matches::{Candidate, MatchPair, Test, TestKind}; |
| use crate::hair::*; |
| use crate::hair::pattern::compare_const_vals; |
| use rustc_index::bit_set::BitSet; |
| use rustc_data_structures::fx::FxHashMap; |
| use rustc::ty::{self, Ty, adjustment::PointerCast}; |
| use rustc::ty::util::IntTypeExt; |
| use rustc::ty::layout::VariantIdx; |
| use rustc::mir::*; |
| use rustc::hir::RangeEnd; |
| use syntax_pos::symbol::sym; |
| |
| 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 simplifiable pattern. |
| pub fn test<'pat>(&mut self, match_pair: &MatchPair<'pat, 'tcx>) -> Test<'tcx> { |
| match *match_pair.pattern.kind { |
| PatKind::Variant { ref adt_def, substs: _, variant_index: _, subpatterns: _ } => { |
| Test { |
| span: match_pair.pattern.span, |
| kind: TestKind::Switch { |
| adt_def: adt_def.clone(), |
| 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: vec![], |
| indices: Default::default(), |
| } |
| } |
| } |
| |
| PatKind::Constant { value } => { |
| Test { |
| span: match_pair.pattern.span, |
| kind: TestKind::Eq { |
| value, |
| ty: match_pair.pattern.ty.clone() |
| } |
| } |
| } |
| |
| PatKind::Range(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), |
| } |
| } |
| |
| 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: op }, |
| } |
| } |
| |
| PatKind::Or { .. } => { |
| self.hir.tcx().sess.span_fatal( |
| match_pair.pattern.span, |
| "or-patterns are not fully implemented yet" |
| ) |
| } |
| |
| PatKind::AscribeUserType { .. } | |
| PatKind::Array { .. } | |
| PatKind::Wild | |
| PatKind::Binding { .. } | |
| PatKind::Leaf { .. } | |
| PatKind::Deref { .. } => { |
| self.error_simplifyable(match_pair) |
| } |
| } |
| } |
| |
| pub fn add_cases_to_switch<'pat>(&mut self, |
| test_place: &Place<'tcx>, |
| candidate: &Candidate<'pat, 'tcx>, |
| switch_ty: Ty<'tcx>, |
| options: &mut Vec<u128>, |
| indices: &mut FxHashMap<&'tcx ty::Const<'tcx>, usize>) |
| -> bool |
| { |
| let match_pair = match candidate.match_pairs.iter().find(|mp| mp.place == *test_place) { |
| Some(match_pair) => match_pair, |
| _ => { return false; } |
| }; |
| |
| match *match_pair.pattern.kind { |
| PatKind::Constant { value } => { |
| indices.entry(value) |
| .or_insert_with(|| { |
| options.push(value.eval_bits( |
| self.hir.tcx(), self.hir.param_env, switch_ty, |
| )); |
| options.len() - 1 |
| }); |
| true |
| } |
| PatKind::Variant { .. } => { |
| panic!("you should have called add_variants_to_switch instead!"); |
| } |
| PatKind::Range(range) => { |
| // Check that none of the switch values are in the range. |
| self.values_not_contained_in_range(range, indices) |
| .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 fn add_variants_to_switch<'pat>(&mut self, |
| test_place: &Place<'tcx>, |
| candidate: &Candidate<'pat, 'tcx>, |
| variants: &mut BitSet<VariantIdx>) |
| -> bool |
| { |
| let match_pair = match candidate.match_pairs.iter().find(|mp| mp.place == *test_place) { |
| Some(match_pair) => match_pair, |
| _ => { 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 |
| } |
| } |
| } |
| |
| pub fn perform_test( |
| &mut self, |
| block: BasicBlock, |
| place: &Place<'tcx>, |
| test: &Test<'tcx>, |
| make_target_blocks: impl FnOnce(&mut Self) -> Vec<BasicBlock>, |
| ) { |
| debug!("perform_test({:?}, {:?}: {:?}, {:?})", |
| block, |
| place, |
| place.ty(&self.local_decls, self.hir.tcx()), |
| test); |
| |
| 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(); |
| let used_variants = variants.count(); |
| debug_assert_eq!(target_blocks.len(), num_enum_variants + 1); |
| let otherwise_block = *target_blocks.last().unwrap(); |
| let mut targets = Vec::with_capacity(used_variants + 1); |
| let mut values = Vec::with_capacity(used_variants); |
| let tcx = self.hir.tcx(); |
| for (idx, discr) in adt_def.discriminants(tcx) { |
| if variants.contains(idx) { |
| debug_assert_ne!( |
| target_blocks[idx.index()], |
| otherwise_block, |
| "no canididates for tested discriminant: {:?}", |
| discr, |
| ); |
| values.push(discr.val); |
| targets.push(target_blocks[idx.index()]); |
| } else { |
| debug_assert_eq!( |
| target_blocks[idx.index()], |
| otherwise_block, |
| "found canididates for untested discriminant: {:?}", |
| discr, |
| ); |
| } |
| } |
| targets.push(otherwise_block); |
| debug!("num_enum_variants: {}, tested variants: {:?}, variants: {:?}", |
| num_enum_variants, values, 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, source_info, &discr, |
| Rvalue::Discriminant(place.clone())); |
| assert_eq!(values.len() + 1, targets.len()); |
| self.cfg.terminate(block, source_info, TerminatorKind::SwitchInt { |
| discr: Operand::Move(discr), |
| switch_ty: discr_ty, |
| values: From::from(values), |
| targets, |
| }); |
| } |
| |
| TestKind::SwitchInt { switch_ty, ref options, indices: _ } => { |
| let target_blocks = make_target_blocks(self); |
| let terminator = if switch_ty.kind == ty::Bool { |
| assert!(options.len() > 0 && options.len() <= 2); |
| if let [first_bb, second_bb] = *target_blocks { |
| 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_( |
| self.hir.tcx(), |
| Operand::Copy(place.clone()), |
| true_bb, |
| false_bb, |
| ) |
| } else { |
| bug!("`TestKind::SwitchInt` on `bool` should have two targets") |
| } |
| } else { |
| // The switch may be inexhaustive so we have a catch all block |
| debug_assert_eq!(options.len() + 1, target_blocks.len()); |
| TerminatorKind::SwitchInt { |
| discr: Operand::Copy(place.clone()), |
| switch_ty, |
| values: options.clone().into(), |
| targets: target_blocks, |
| } |
| }; |
| self.cfg.terminate(block, source_info, terminator); |
| } |
| |
| TestKind::Eq { value, ty } => { |
| 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.clone()); |
| self.compare(block, success, fail, source_info, BinOp::Eq, expect, val); |
| } else { |
| bug!("`TestKind::Eq` should have two target blocks"); |
| } |
| } |
| } |
| |
| TestKind::Range(PatRange { ref lo, ref 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.clone()); |
| |
| if let [success, fail] = *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); |
| } else { |
| bug!("`TestKind::Range` should have two target blocks"); |
| } |
| } |
| |
| TestKind::Len { len, op } => { |
| let target_blocks = make_target_blocks(self); |
| |
| let usize_ty = self.hir.usize_ty(); |
| let actual = self.temp(usize_ty, test.span); |
| |
| // actual = len(place) |
| self.cfg.push_assign(block, source_info, |
| &actual, Rvalue::Len(place.clone())); |
| |
| // expected = <N> |
| let expected = self.push_usize(block, source_info, len); |
| |
| if let [true_bb, false_bb] = *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), |
| ); |
| } else { |
| bug!("`TestKind::Len` should have two target blocks"); |
| } |
| } |
| } |
| } |
| |
| /// 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.hir.bool_ty(); |
| let result = self.temp(bool_ty, source_info.span); |
| |
| // result = op(left, right) |
| self.cfg.push_assign( |
| block, |
| source_info, |
| &result, |
| Rvalue::BinaryOp(op, left, right), |
| ); |
| |
| // branch based on result |
| self.cfg.terminate( |
| block, |
| source_info, |
| TerminatorKind::if_( |
| self.hir.tcx(), |
| Operand::Move(result), |
| success_block, |
| fail_block, |
| ), |
| ); |
| } |
| |
| /// Compare two `&T` values using `<T as std::compare::PartialEq>::eq` |
| fn non_scalar_compare( |
| &mut self, |
| block: BasicBlock, |
| make_target_blocks: impl FnOnce(&mut Self) -> Vec<BasicBlock>, |
| source_info: SourceInfo, |
| value: &'tcx ty::Const<'tcx>, |
| place: &Place<'tcx>, |
| mut ty: Ty<'tcx>, |
| ) { |
| use rustc::middle::lang_items::EqTraitLangItem; |
| |
| let mut expect = self.literal_operand(source_info.span, value); |
| let mut val = Operand::Copy(place.clone()); |
| |
| // 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.hir.tcx(); |
| // make both a slice |
| ty = tcx.mk_imm_ref(region, tcx.mk_slice(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::Pointer(PointerCast::Unsize), val, ty |
| ) |
| ); |
| val = Operand::Move(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::Pointer(PointerCast::Unsize), expect, ty |
| ) |
| ); |
| expect = Operand::Move(slice); |
| } |
| }, |
| } |
| |
| let deref_ty = match ty.kind { |
| ty::Ref(_, deref_ty, _) => deref_ty, |
| _ => bug!("non_scalar_compare called on non-reference type: {}", ty), |
| }; |
| |
| let eq_def_id = self.hir.tcx().require_lang_item(EqTraitLangItem, None); |
| let method = self.hir.trait_method(eq_def_id, sym::eq, deref_ty, &[deref_ty.into()]); |
| |
| let bool_ty = self.hir.bool_ty(); |
| let eq_result = self.temp(bool_ty, source_info.span); |
| let eq_block = self.cfg.start_new_block(); |
| let cleanup = self.diverge_cleanup(); |
| self.cfg.terminate(block, source_info, TerminatorKind::Call { |
| func: Operand::Constant(box Constant { |
| 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, |
| |
| literal: method, |
| }), |
| args: vec![val, expect], |
| destination: Some((eq_result.clone(), eq_block)), |
| cleanup: Some(cleanup), |
| from_hir_call: false, |
| }); |
| |
| if let [success_block, fail_block] = *make_target_blocks(self) { |
| // check the result |
| self.cfg.terminate( |
| eq_block, |
| source_info, |
| TerminatorKind::if_( |
| self.hir.tcx(), |
| Operand::Move(eq_result), |
| success_block, |
| fail_block, |
| ), |
| ); |
| } else { |
| bug!("`TestKind::Eq` should have two target blocks") |
| } |
| } |
| |
| /// 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 |
| /// what value `x` has 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 fn sort_candidate<'pat>( |
| &mut self, |
| test_place: &Place<'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: _, ref indices }, |
| &PatKind::Constant { ref value }) |
| if is_switch_ty(match_pair.pattern.ty) => { |
| let index = indices[value]; |
| self.candidate_without_match_pair(match_pair_index, candidate); |
| Some(index) |
| } |
| |
| (&TestKind::SwitchInt { switch_ty: _, ref options, ref indices }, |
| &PatKind::Range(range)) => { |
| let not_contained = self |
| .values_not_contained_in_range(range, indices) |
| .unwrap_or(false); |
| |
| if not_contained { |
| // No switch values are contained in the pattern range, |
| // so the pattern can be matched only if this test fails. |
| let otherwise = options.len(); |
| Some(otherwise) |
| } else { |
| None |
| } |
| } |
| |
| (&TestKind::SwitchInt { .. }, _) => None, |
| |
| (&TestKind::Len { len: test_len, op: BinOp::Eq }, |
| &PatKind::Slice { ref prefix, ref slice, ref 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.as_ref(), |
| 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, &Some(_)) | (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 |
| // $actual_len != pat_len. |
| Some(1) |
| } |
| } |
| } |
| |
| (&TestKind::Len { len: test_len, op: BinOp::Ge }, |
| &PatKind::Slice { ref prefix, ref slice, ref suffix }) => { |
| // the test is `$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.as_ref(), |
| 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)) => { |
| if test == pat { |
| self.candidate_without_match_pair( |
| match_pair_index, |
| candidate, |
| ); |
| return Some(0); |
| } |
| |
| let no_overlap = (|| { |
| use std::cmp::Ordering::*; |
| use rustc::hir::RangeEnd::*; |
| |
| let tcx = self.hir.tcx(); |
| |
| let test_ty = test.lo.ty; |
| let lo = compare_const_vals(tcx, test.lo, pat.hi, self.hir.param_env, test_ty)?; |
| let hi = compare_const_vals(tcx, test.hi, pat.lo, self.hir.param_env, test_ty)?; |
| |
| match (test.end, pat.end, lo, hi) { |
| // pat < test |
| (_, _, Greater, _) | |
| (_, Excluded, Equal, _) | |
| // pat > test |
| (_, _, _, Less) | |
| (Excluded, _, _, Equal) => Some(true), |
| _ => Some(false), |
| } |
| })(); |
| |
| if let Some(true) = no_overlap { |
| // Testing range does not overlap with pattern range, |
| // so the pattern can be matched only if this test fails. |
| Some(1) |
| } else { |
| None |
| } |
| } |
| |
| (&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 { .. }, _) => { |
| // 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 [Pat<'tcx>], |
| opt_slice: Option<&'pat Pat<'tcx>>, |
| suffix: &'pat [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: &'tcx ty::AdtDef, |
| variant_index: VariantIdx, |
| subpatterns: &'pat [FieldPat<'tcx>], |
| candidate: &mut Candidate<'pat, 'tcx>, |
| ) { |
| let match_pair = candidate.match_pairs.remove(match_pair_index); |
| let tcx = self.hir.tcx(); |
| |
| // 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 elem = ProjectionElem::Downcast( |
| Some(adt_def.variants[variant_index].ident.name), variant_index); |
| let downcast_place = tcx.mk_place_elem(match_pair.place, elem); // `(x as Variant)` |
| let consequent_match_pairs = subpatterns.iter().map(|subpattern| { |
| // e.g., `(x as Variant).0` |
| let place = |
| tcx.mk_place_field(downcast_place.clone(), subpattern.field, subpattern.pattern.ty); |
| // e.g., `(x as Variant).0 @ P1` |
| MatchPair::new(place, &subpattern.pattern) |
| }); |
| |
| candidate.match_pairs.extend(consequent_match_pairs); |
| } |
| |
| fn error_simplifyable<'pat>(&mut self, match_pair: &MatchPair<'pat, 'tcx>) -> ! { |
| span_bug!(match_pair.pattern.span, |
| "simplifyable pattern found: {:?}", |
| match_pair.pattern) |
| } |
| |
| fn const_range_contains( |
| &self, |
| range: PatRange<'tcx>, |
| value: &'tcx ty::Const<'tcx>, |
| ) -> Option<bool> { |
| use std::cmp::Ordering::*; |
| |
| let tcx = self.hir.tcx(); |
| |
| let a = compare_const_vals(tcx, range.lo, value, self.hir.param_env, range.lo.ty)?; |
| let b = compare_const_vals(tcx, value, range.hi, self.hir.param_env, range.lo.ty)?; |
| |
| match (b, range.end) { |
| (Less, _) | |
| (Equal, RangeEnd::Included) if a != Greater => Some(true), |
| _ => Some(false), |
| } |
| } |
| |
| fn values_not_contained_in_range( |
| &self, |
| range: PatRange<'tcx>, |
| indices: &FxHashMap<&'tcx ty::Const<'tcx>, usize>, |
| ) -> Option<bool> { |
| for &val in indices.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() |
| } |
