Unnamed repository; edit this file 'description' to name the repository.
| -rw-r--r-- | Cargo.lock | 100 | ||||
| -rw-r--r-- | Cargo.toml | 1 | ||||
| -rw-r--r-- | crates/hir-def/src/lib.rs | 9 | ||||
| -rw-r--r-- | crates/hir-ty/Cargo.toml | 1 | ||||
| -rw-r--r-- | crates/hir-ty/src/diagnostics/expr.rs | 38 | ||||
| -rw-r--r-- | crates/hir-ty/src/diagnostics/match_check.rs | 5 | ||||
| -rw-r--r-- | crates/hir-ty/src/diagnostics/match_check/deconstruct_pat.rs | 1098 | ||||
| -rw-r--r-- | crates/hir-ty/src/diagnostics/match_check/pat_analysis.rs | 475 | ||||
| -rw-r--r-- | crates/hir-ty/src/diagnostics/match_check/usefulness.rs | 824 | ||||
| -rw-r--r-- | crates/hir-ty/src/lib.rs | 3 | ||||
| -rw-r--r-- | crates/rust-analyzer/tests/slow-tests/tidy.rs | 1 |
11 files changed, 603 insertions, 1952 deletions
diff --git a/Cargo.lock b/Cargo.lock index a743d1c870..bdb9feee5f 100644 --- a/Cargo.lock +++ b/Cargo.lock @@ -166,7 +166,7 @@ checksum = "5676cea088c32290fe65c82895be9d06dd21e0fa49bb97ca840529e9417ab71a" dependencies = [ "proc-macro2", "quote", - "syn", + "syn 2.0.39", "synstructure", ] @@ -313,6 +313,17 @@ dependencies = [ ] [[package]] +name = "derivative" +version = "2.2.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fcc3dd5e9e9c0b295d6e1e4d811fb6f157d5ffd784b8d202fc62eac8035a770b" +dependencies = [ + "proc-macro2", + "quote", + "syn 1.0.109", +] + +[[package]] name = "derive_arbitrary" version = "1.3.2" source = "registry+https://github.com/rust-lang/crates.io-index" @@ -320,7 +331,7 @@ checksum = "67e77553c4162a157adbf834ebae5b415acbecbeafc7a74b0e886657506a7611" dependencies = [ "proc-macro2", "quote", - "syn", + "syn 2.0.39", ] [[package]] @@ -581,7 +592,8 @@ dependencies = [ "profile", "project-model", "ra-ap-rustc_abi", - "ra-ap-rustc_index", + "ra-ap-rustc_index 0.21.0", + "ra-ap-rustc_pattern_analysis", "rustc-hash", "scoped-tls", "smallvec", @@ -1412,7 +1424,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "7816f980fab89e878ff2e916e2077d484e3aa1c619a3cc982c8a417c3dfe45fa" dependencies = [ "bitflags 1.3.2", - "ra-ap-rustc_index", + "ra-ap-rustc_index 0.21.0", "tracing", ] @@ -1423,7 +1435,18 @@ source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "8352918d61aa4afab9f2ed7314cf638976b20949b3d61d2f468c975b0d251f24" dependencies = [ "arrayvec", - "ra-ap-rustc_index_macros", + "ra-ap-rustc_index_macros 0.21.0", + "smallvec", +] + +[[package]] +name = "ra-ap-rustc_index" +version = "0.33.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "5e5313d7f243b63ef9e58d94355b11aa8499f1328055f1f58adf0a5ea7d2faca" +dependencies = [ + "arrayvec", + "ra-ap-rustc_index_macros 0.33.0", "smallvec", ] @@ -1435,7 +1458,19 @@ checksum = "66a9424018828155a3e3596515598f90e68427d8f35eff6df7f0856c73fc58a8" dependencies = [ "proc-macro2", "quote", - "syn", + "syn 2.0.39", + "synstructure", +] + +[[package]] +name = "ra-ap-rustc_index_macros" +version = "0.33.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "a83108ebf3e73dde205b9c25706209bcd7736480820f90ded28eabaf8b469f25" +dependencies = [ + "proc-macro2", + "quote", + "syn 2.0.39", "synstructure", ] @@ -1455,11 +1490,25 @@ version = "0.21.0" source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "d557201d71792487bd2bab637ab5be9aa6fff59b88e25e12de180b0f9d2df60f" dependencies = [ - "ra-ap-rustc_index", + "ra-ap-rustc_index 0.21.0", "ra-ap-rustc_lexer", ] [[package]] +name = "ra-ap-rustc_pattern_analysis" +version = "0.33.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "6c4085e0c771fd4b883930b599ef42966b855762bbe4052c17673b3253421a6d" +dependencies = [ + "derivative", + "ra-ap-rustc_index 0.33.0", + "rustc-hash", + "rustc_apfloat", + "smallvec", + "tracing", +] + +[[package]] name = "rayon" version = "1.8.0" source = "registry+https://github.com/rust-lang/crates.io-index" @@ -1593,7 +1642,7 @@ dependencies = [ "heck", "proc-macro2", "quote", - "syn", + "syn 2.0.39", ] [[package]] @@ -1609,6 +1658,16 @@ source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "08d43f7aa6b08d49f382cde6a7982047c3426db949b1424bc4b7ec9ae12c6ce2" [[package]] +name = "rustc_apfloat" +version = "0.2.0+llvm-462a31f5a5ab" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "465187772033a5ee566f69fe008df03628fce549a0899aae76f0a0c2e34696be" +dependencies = [ + "bitflags 1.3.2", + "smallvec", +] + +[[package]] name = "ryu" version = "1.0.13" source = "registry+https://github.com/rust-lang/crates.io-index" @@ -1670,7 +1729,7 @@ checksum = "43576ca501357b9b071ac53cdc7da8ef0cbd9493d8df094cd821777ea6e894d3" dependencies = [ "proc-macro2", "quote", - "syn", + "syn 2.0.39", ] [[package]] @@ -1693,7 +1752,7 @@ checksum = "bcec881020c684085e55a25f7fd888954d56609ef363479dc5a1305eb0d40cab" dependencies = [ "proc-macro2", "quote", - "syn", + "syn 2.0.39", ] [[package]] @@ -1707,9 +1766,9 @@ dependencies = [ [[package]] name = "smallvec" -version = "1.10.0" +version = "1.12.0" source = "registry+https://github.com/rust-lang/crates.io-index" -checksum = "a507befe795404456341dfab10cef66ead4c041f62b8b11bbb92bffe5d0953e0" +checksum = "2593d31f82ead8df961d8bd23a64c2ccf2eb5dd34b0a34bfb4dd54011c72009e" [[package]] name = "smol_str" @@ -1772,6 +1831,17 @@ dependencies = [ [[package]] name = "syn" +version = "1.0.109" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "72b64191b275b66ffe2469e8af2c1cfe3bafa67b529ead792a6d0160888b4237" +dependencies = [ + "proc-macro2", + "quote", + "unicode-ident", +] + +[[package]] +name = "syn" version = "2.0.39" source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "23e78b90f2fcf45d3e842032ce32e3f2d1545ba6636271dcbf24fa306d87be7a" @@ -1789,7 +1859,7 @@ checksum = "285ba80e733fac80aa4270fbcdf83772a79b80aa35c97075320abfee4a915b06" dependencies = [ "proc-macro2", "quote", - "syn", + "syn 2.0.39", "unicode-xid", ] @@ -1876,7 +1946,7 @@ checksum = "f9456a42c5b0d803c8cd86e73dd7cc9edd429499f37a3550d286d5e86720569f" dependencies = [ "proc-macro2", "quote", - "syn", + "syn 2.0.39", ] [[package]] @@ -1977,7 +2047,7 @@ checksum = "34704c8d6ebcbc939824180af020566b01a7c01f80641264eba0999f6c2b6be7" dependencies = [ "proc-macro2", "quote", - "syn", + "syn 2.0.39", ] [[package]] diff --git a/Cargo.toml b/Cargo.toml index 2547f1ccb9..ed5b2eb9b2 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -83,6 +83,7 @@ ra-ap-rustc_lexer = { version = "0.21.0", default-features = false } ra-ap-rustc_parse_format = { version = "0.21.0", default-features = false } ra-ap-rustc_index = { version = "0.21.0", default-features = false } ra-ap-rustc_abi = { version = "0.21.0", default-features = false } +ra-ap-rustc_pattern_analysis = { version = "0.33.0", default-features = false } # local crates that aren't published to crates.io. These should not have versions. sourcegen = { path = "./crates/sourcegen" } diff --git a/crates/hir-def/src/lib.rs b/crates/hir-def/src/lib.rs index adf070fe7d..790e3b414b 100644 --- a/crates/hir-def/src/lib.rs +++ b/crates/hir-def/src/lib.rs @@ -939,6 +939,15 @@ impl From<AssocItemId> for AttrDefId { } } } +impl From<VariantId> for AttrDefId { + fn from(vid: VariantId) -> Self { + match vid { + VariantId::EnumVariantId(id) => id.into(), + VariantId::StructId(id) => id.into(), + VariantId::UnionId(id) => id.into(), + } + } +} #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)] pub enum VariantId { diff --git a/crates/hir-ty/Cargo.toml b/crates/hir-ty/Cargo.toml index 822a7d3e91..1f8f8744f9 100644 --- a/crates/hir-ty/Cargo.toml +++ b/crates/hir-ty/Cargo.toml @@ -36,6 +36,7 @@ indexmap.workspace = true ra-ap-rustc_abi.workspace = true ra-ap-rustc_index.workspace = true +ra-ap-rustc_pattern_analysis.workspace = true # local deps diff --git a/crates/hir-ty/src/diagnostics/expr.rs b/crates/hir-ty/src/diagnostics/expr.rs index f1bf162bc6..530608292e 100644 --- a/crates/hir-ty/src/diagnostics/expr.rs +++ b/crates/hir-ty/src/diagnostics/expr.rs @@ -11,6 +11,7 @@ use hir_def::{ItemContainerId, Lookup}; use hir_expand::name; use itertools::Itertools; use rustc_hash::FxHashSet; +use rustc_pattern_analysis::usefulness::{compute_match_usefulness, ValidityConstraint}; use triomphe::Arc; use typed_arena::Arena; @@ -18,8 +19,7 @@ use crate::{ db::HirDatabase, diagnostics::match_check::{ self, - deconstruct_pat::DeconstructedPat, - usefulness::{compute_match_usefulness, MatchCheckCtx}, + pat_analysis::{self, DeconstructedPat, MatchCheckCtx, WitnessPat}, }, display::HirDisplay, InferenceResult, Ty, TyExt, @@ -152,7 +152,14 @@ impl ExprValidator { } let pattern_arena = Arena::new(); - let cx = MatchCheckCtx::new(self.owner.module(db.upcast()), self.owner, db, &pattern_arena); + let ty_arena = Arena::new(); + let cx = MatchCheckCtx::new( + self.owner.module(db.upcast()), + self.owner, + db, + &pattern_arena, + &ty_arena, + ); let mut m_arms = Vec::with_capacity(arms.len()); let mut has_lowering_errors = false; @@ -178,9 +185,10 @@ impl ExprValidator { // If we had a NotUsefulMatchArm diagnostic, we could // check the usefulness of each pattern as we added it // to the matrix here. - let m_arm = match_check::MatchArm { + let m_arm = pat_analysis::MatchArm { pat: self.lower_pattern(&cx, arm.pat, db, &body, &mut has_lowering_errors), has_guard: arm.guard.is_some(), + arm_data: (), }; m_arms.push(m_arm); if !has_lowering_errors { @@ -197,7 +205,15 @@ impl ExprValidator { return; } - let report = compute_match_usefulness(&cx, &m_arms, scrut_ty); + let report = match compute_match_usefulness( + rustc_pattern_analysis::MatchCtxt { tycx: &cx }, + m_arms.as_slice(), + scrut_ty.clone(), + ValidityConstraint::ValidOnly, + ) { + Ok(report) => report, + Err(void) => match void {}, + }; // FIXME Report unreachable arms // https://github.com/rust-lang/rust/blob/f31622a50/compiler/rustc_mir_build/src/thir/pattern/check_match.rs#L200 @@ -213,7 +229,7 @@ impl ExprValidator { fn lower_pattern<'p>( &self, - cx: &MatchCheckCtx<'_, 'p>, + cx: &MatchCheckCtx<'p>, pat: PatId, db: &dyn HirDatabase, body: &Body, @@ -221,7 +237,7 @@ impl ExprValidator { ) -> &'p DeconstructedPat<'p> { let mut patcx = match_check::PatCtxt::new(db, &self.infer, body); let pattern = patcx.lower_pattern(pat); - let pattern = cx.pattern_arena.alloc(DeconstructedPat::from_pat(cx, &pattern)); + let pattern = cx.pattern_arena.alloc(cx.lower_pat(&pattern)); if !patcx.errors.is_empty() { *have_errors = true; } @@ -364,16 +380,16 @@ fn types_of_subpatterns_do_match(pat: PatId, body: &Body, infer: &InferenceResul } fn missing_match_arms<'p>( - cx: &MatchCheckCtx<'_, 'p>, + cx: &MatchCheckCtx<'p>, scrut_ty: &Ty, - witnesses: Vec<DeconstructedPat<'p>>, + witnesses: Vec<WitnessPat<'p>>, arms: &[MatchArm], ) -> String { - struct DisplayWitness<'a, 'p>(&'a DeconstructedPat<'p>, &'a MatchCheckCtx<'a, 'p>); + struct DisplayWitness<'a, 'p>(&'a WitnessPat<'p>, &'a MatchCheckCtx<'p>); impl fmt::Display for DisplayWitness<'_, '_> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { let DisplayWitness(witness, cx) = *self; - let pat = witness.to_pat(cx); + let pat = cx.hoist_witness_pat(witness); write!(f, "{}", pat.display(cx.db)) } } diff --git a/crates/hir-ty/src/diagnostics/match_check.rs b/crates/hir-ty/src/diagnostics/match_check.rs index 9e84cd0184..8d6e502c6a 100644 --- a/crates/hir-ty/src/diagnostics/match_check.rs +++ b/crates/hir-ty/src/diagnostics/match_check.rs @@ -7,8 +7,7 @@ mod pat_util; -pub(crate) mod deconstruct_pat; -pub(crate) mod usefulness; +pub(crate) mod pat_analysis; use chalk_ir::Mutability; use hir_def::{ @@ -27,8 +26,6 @@ use crate::{ use self::pat_util::EnumerateAndAdjustIterator; -pub(crate) use self::usefulness::MatchArm; - #[derive(Clone, Debug)] pub(crate) enum PatternError { Unimplemented, diff --git a/crates/hir-ty/src/diagnostics/match_check/deconstruct_pat.rs b/crates/hir-ty/src/diagnostics/match_check/deconstruct_pat.rs deleted file mode 100644 index f066f8b798..0000000000 --- a/crates/hir-ty/src/diagnostics/match_check/deconstruct_pat.rs +++ /dev/null @@ -1,1098 +0,0 @@ -//! [`super::usefulness`] explains most of what is happening in this file. As explained there, -//! values and patterns are made from constructors applied to fields. This file defines a -//! `Constructor` enum, a `Fields` struct, and various operations to manipulate them and convert -//! them from/to patterns. -//! -//! There's one idea that is not detailed in [`super::usefulness`] because the details are not -//! needed there: _constructor splitting_. -//! -//! # Constructor splitting -//! -//! The idea is as follows: given a constructor `c` and a matrix, we want to specialize in turn -//! with all the value constructors that are covered by `c`, and compute usefulness for each. -//! Instead of listing all those constructors (which is intractable), we group those value -//! constructors together as much as possible. Example: -//! -//! ``` -//! match (0, false) { -//! (0 ..=100, true) => {} // `p_1` -//! (50..=150, false) => {} // `p_2` -//! (0 ..=200, _) => {} // `q` -//! } -//! ``` -//! -//! The naive approach would try all numbers in the range `0..=200`. But we can be a lot more -//! clever: `0` and `1` for example will match the exact same rows, and return equivalent -//! witnesses. In fact all of `0..50` would. We can thus restrict our exploration to 4 -//! constructors: `0..50`, `50..=100`, `101..=150` and `151..=200`. That is enough and infinitely -//! more tractable. -//! -//! We capture this idea in a function `split(p_1 ... p_n, c)` which returns a list of constructors -//! `c'` covered by `c`. Given such a `c'`, we require that all value ctors `c''` covered by `c'` -//! return an equivalent set of witnesses after specializing and computing usefulness. -//! In the example above, witnesses for specializing by `c''` covered by `0..50` will only differ -//! in their first element. -//! -//! We usually also ask that the `c'` together cover all of the original `c`. However we allow -//! skipping some constructors as long as it doesn't change whether the resulting list of witnesses -//! is empty of not. We use this in the wildcard `_` case. -//! -//! Splitting is implemented in the [`Constructor::split`] function. We don't do splitting for -//! or-patterns; instead we just try the alternatives one-by-one. For details on splitting -//! wildcards, see [`SplitWildcard`]; for integer ranges, see [`SplitIntRange`]. - -use std::{ - cell::Cell, - cmp::{max, min}, - iter::once, - ops::RangeInclusive, -}; - -use hir_def::{EnumVariantId, HasModule, LocalFieldId, VariantId}; -use smallvec::{smallvec, SmallVec}; -use stdx::never; - -use crate::{ - infer::normalize, inhabitedness::is_enum_variant_uninhabited_from, AdtId, Interner, Scalar, Ty, - TyExt, TyKind, -}; - -use super::{ - is_box, - usefulness::{helper::Captures, MatchCheckCtx, PatCtxt}, - FieldPat, Pat, PatKind, -}; - -use self::Constructor::*; - -/// Recursively expand this pattern into its subpatterns. Only useful for or-patterns. -fn expand_or_pat(pat: &Pat) -> Vec<&Pat> { - fn expand<'p>(pat: &'p Pat, vec: &mut Vec<&'p Pat>) { - if let PatKind::Or { pats } = pat.kind.as_ref() { - for pat in pats { - expand(pat, vec); - } - } else { - vec.push(pat) - } - } - - let mut pats = Vec::new(); - expand(pat, &mut pats); - pats -} - -/// [Constructor] uses this in unimplemented variants. -/// It allows porting match expressions from upstream algorithm without losing semantics. -#[derive(Copy, Clone, Debug, PartialEq, Eq)] -pub(super) enum Void {} - -/// An inclusive interval, used for precise integer exhaustiveness checking. -/// `IntRange`s always store a contiguous range. This means that values are -/// encoded such that `0` encodes the minimum value for the integer, -/// regardless of the signedness. -/// For example, the pattern `-128..=127i8` is encoded as `0..=255`. -/// This makes comparisons and arithmetic on interval endpoints much more -/// straightforward. See `signed_bias` for details. -/// -/// `IntRange` is never used to encode an empty range or a "range" that wraps -/// around the (offset) space: i.e., `range.lo <= range.hi`. -#[derive(Clone, Debug, PartialEq, Eq)] -pub(super) struct IntRange { - range: RangeInclusive<u128>, -} - -impl IntRange { - #[inline] - fn is_integral(ty: &Ty) -> bool { - matches!( - ty.kind(Interner), - TyKind::Scalar(Scalar::Char | Scalar::Int(_) | Scalar::Uint(_) | Scalar::Bool) - ) - } - - fn is_singleton(&self) -> bool { - self.range.start() == self.range.end() - } - - fn boundaries(&self) -> (u128, u128) { - (*self.range.start(), *self.range.end()) - } - - #[inline] - fn from_bool(value: bool) -> IntRange { - let val = value as u128; - IntRange { range: val..=val } - } - - #[inline] - fn from_range(lo: u128, hi: u128, scalar_ty: Scalar) -> IntRange { - match scalar_ty { - Scalar::Bool => IntRange { range: lo..=hi }, - _ => unimplemented!(), - } - } - - fn is_subrange(&self, other: &Self) -> bool { - other.range.start() <= self.range.start() && self.range.end() <= other.range.end() - } - - fn intersection(&self, other: &Self) -> Option<Self> { - let (lo, hi) = self.boundaries(); - let (other_lo, other_hi) = other.boundaries(); - if lo <= other_hi && other_lo <= hi { - Some(IntRange { range: max(lo, other_lo)..=min(hi, other_hi) }) - } else { - None - } - } - - fn to_pat(&self, _cx: &MatchCheckCtx<'_, '_>, ty: Ty) -> Pat { - match ty.kind(Interner) { - TyKind::Scalar(Scalar::Bool) => { - let kind = match self.boundaries() { - (0, 0) => PatKind::LiteralBool { value: false }, - (1, 1) => PatKind::LiteralBool { value: true }, - (0, 1) => PatKind::Wild, - (lo, hi) => { - never!("bad range for bool pattern: {}..={}", lo, hi); - PatKind::Wild - } - }; - Pat { ty, kind: kind.into() } - } - _ => unimplemented!(), - } - } - - /// See `Constructor::is_covered_by` - fn is_covered_by(&self, other: &Self) -> bool { - if self.intersection(other).is_some() { - // Constructor splitting should ensure that all intersections we encounter are actually - // inclusions. - assert!(self.is_subrange(other)); - true - } else { - false - } - } -} - -/// Represents a border between 2 integers. Because the intervals spanning borders must be able to -/// cover every integer, we need to be able to represent 2^128 + 1 such borders. -#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)] -enum IntBorder { - JustBefore(u128), - AfterMax, -} - -/// A range of integers that is partitioned into disjoint subranges. This does constructor -/// splitting for integer ranges as explained at the top of the file. -/// -/// This is fed multiple ranges, and returns an output that covers the input, but is split so that -/// the only intersections between an output range and a seen range are inclusions. No output range -/// straddles the boundary of one of the inputs. -/// -/// The following input: -/// ``` -/// |-------------------------| // `self` -/// |------| |----------| |----| -/// |-------| |-------| -/// ``` -/// would be iterated over as follows: -/// ``` -/// ||---|--||-|---|---|---|--| -/// ``` -#[derive(Debug, Clone)] -struct SplitIntRange { - /// The range we are splitting - range: IntRange, - /// The borders of ranges we have seen. They are all contained within `range`. This is kept - /// sorted. - borders: Vec<IntBorder>, -} - -impl SplitIntRange { - fn new(range: IntRange) -> Self { - SplitIntRange { range, borders: Vec::new() } - } - - /// Internal use - fn to_borders(r: IntRange) -> [IntBorder; 2] { - use IntBorder::*; - let (lo, hi) = r.boundaries(); - let lo = JustBefore(lo); - let hi = match hi.checked_add(1) { - Some(m) => JustBefore(m), - None => AfterMax, - }; - [lo, hi] - } - - /// Add ranges relative to which we split. - fn split(&mut self, ranges: impl Iterator<Item = IntRange>) { - let this_range = &self.range; - let included_ranges = ranges.filter_map(|r| this_range.intersection(&r)); - let included_borders = included_ranges.flat_map(|r| { - let borders = Self::to_borders(r); - once(borders[0]).chain(once(borders[1])) - }); - self.borders.extend(included_borders); - self.borders.sort_unstable(); - } - - /// Iterate over the contained ranges. - fn iter(&self) -> impl Iterator<Item = IntRange> + '_ { - use IntBorder::*; - - let self_range = Self::to_borders(self.range.clone()); - // Start with the start of the range. - let mut prev_border = self_range[0]; - self.borders - .iter() - .copied() - // End with the end of the range. - .chain(once(self_range[1])) - // List pairs of adjacent borders. - .map(move |border| { - let ret = (prev_border, border); - prev_border = border; - ret - }) - // Skip duplicates. - .filter(|(prev_border, border)| prev_border != border) - // Finally, convert to ranges. - .map(|(prev_border, border)| { - let range = match (prev_border, border) { - (JustBefore(n), JustBefore(m)) if n < m => n..=(m - 1), - (JustBefore(n), AfterMax) => n..=u128::MAX, - _ => unreachable!(), // Ruled out by the sorting and filtering we did - }; - IntRange { range } - }) - } -} - -/// A constructor for array and slice patterns. -#[derive(Copy, Clone, Debug, PartialEq, Eq)] -pub(super) struct Slice { - _unimplemented: Void, -} - -impl Slice { - fn arity(self) -> usize { - match self._unimplemented {} - } - - /// See `Constructor::is_covered_by` - fn is_covered_by(self, _other: Self) -> bool { - match self._unimplemented {} - } -} - -/// A value can be decomposed into a constructor applied to some fields. This struct represents -/// the constructor. See also `Fields`. -/// -/// `pat_constructor` retrieves the constructor corresponding to a pattern. -/// `specialize_constructor` returns the list of fields corresponding to a pattern, given a -/// constructor. `Constructor::apply` reconstructs the pattern from a pair of `Constructor` and -/// `Fields`. -#[allow(dead_code)] -#[derive(Clone, Debug, PartialEq)] -pub(super) enum Constructor { - /// The constructor for patterns that have a single constructor, like tuples, struct patterns - /// and fixed-length arrays. - Single, - /// Enum variants. - Variant(EnumVariantId), - /// Ranges of integer literal values (`2`, `2..=5` or `2..5`). - IntRange(IntRange), - /// Ranges of floating-point literal values (`2.0..=5.2`). - FloatRange(Void), - /// String literals. Strings are not quite the same as `&[u8]` so we treat them separately. - Str(Void), - /// Array and slice patterns. - Slice(Slice), - /// Constants that must not be matched structurally. They are treated as black - /// boxes for the purposes of exhaustiveness: we must not inspect them, and they - /// don't count towards making a match exhaustive. - Opaque, - /// Fake extra constructor for enums that aren't allowed to be matched exhaustively. Also used - /// for those types for which we cannot list constructors explicitly, like `f64` and `str`. - NonExhaustive, - /// Stands for constructors that are not seen in the matrix, as explained in the documentation - /// for [`SplitWildcard`]. The carried `bool` is used for the `non_exhaustive_omitted_patterns` - /// lint. - Missing { nonexhaustive_enum_missing_real_variants: bool }, - /// Wildcard pattern. - Wildcard, - /// Or-pattern. - Or, -} - -impl Constructor { - pub(super) fn is_wildcard(&self) -> bool { - matches!(self, Wildcard) - } - - pub(super) fn is_non_exhaustive(&self) -> bool { - matches!(self, NonExhaustive) - } - - fn as_int_range(&self) -> Option<&IntRange> { - match self { - IntRange(range) => Some(range), - _ => None, - } - } - - fn as_slice(&self) -> Option<Slice> { - match self { - Slice(slice) => Some(*slice), - _ => None, - } - } - - pub(super) fn is_unstable_variant(&self, _pcx: PatCtxt<'_, '_>) -> bool { - false //FIXME: implement this - } - - pub(super) fn is_doc_hidden_variant(&self, _pcx: PatCtxt<'_, '_>) -> bool { - false //FIXME: implement this - } - - fn variant_id_for_adt(&self, adt: hir_def::AdtId) -> VariantId { - match *self { - Variant(id) => id.into(), - Single => { - assert!(!matches!(adt, hir_def::AdtId::EnumId(_))); - match adt { - hir_def::AdtId::EnumId(_) => unreachable!(), - hir_def::AdtId::StructId(id) => id.into(), - hir_def::AdtId::UnionId(id) => id.into(), - } - } - _ => panic!("bad constructor {self:?} for adt {adt:?}"), - } - } - - /// The number of fields for this constructor. This must be kept in sync with - /// `Fields::wildcards`. - pub(super) fn arity(&self, pcx: PatCtxt<'_, '_>) -> usize { - match self { - Single | Variant(_) => match *pcx.ty.kind(Interner) { - TyKind::Tuple(arity, ..) => arity, - TyKind::Ref(..) => 1, - TyKind::Adt(adt, ..) => { - if is_box(pcx.cx.db, adt.0) { - // The only legal patterns of type `Box` (outside `std`) are `_` and box - // patterns. If we're here we can assume this is a box pattern. - 1 - } else { - let variant = self.variant_id_for_adt(adt.0); - Fields::list_variant_nonhidden_fields(pcx.cx, pcx.ty, variant).count() - } - } - _ => { - never!("Unexpected type for `Single` constructor: {:?}", pcx.ty); - 0 - } - }, - Slice(slice) => slice.arity(), - Str(..) - | FloatRange(..) - | IntRange(..) - | NonExhaustive - | Opaque - | Missing { .. } - | Wildcard => 0, - Or => { - never!("The `Or` constructor doesn't have a fixed arity"); - 0 - } - } - } - - /// Some constructors (namely `Wildcard`, `IntRange` and `Slice`) actually stand for a set of actual - /// constructors (like variants, integers or fixed-sized slices). When specializing for these - /// constructors, we want to be specialising for the actual underlying constructors. - /// Naively, we would simply return the list of constructors they correspond to. We instead are - /// more clever: if there are constructors that we know will behave the same wrt the current - /// matrix, we keep them grouped. For example, all slices of a sufficiently large length - /// will either be all useful or all non-useful with a given matrix. - /// - /// See the branches for details on how the splitting is done. - /// - /// This function may discard some irrelevant constructors if this preserves behavior and - /// diagnostics. Eg. for the `_` case, we ignore the constructors already present in the - /// matrix, unless all of them are. - pub(super) fn split<'a>( - &self, - pcx: PatCtxt<'_, '_>, - ctors: impl Iterator<Item = &'a Constructor> + Clone, - ) -> SmallVec<[Self; 1]> { - match self { - Wildcard => { - let mut split_wildcard = SplitWildcard::new(pcx); - split_wildcard.split(pcx, ctors); - split_wildcard.into_ctors(pcx) - } - // Fast-track if the range is trivial. In particular, we don't do the overlapping - // ranges check. - IntRange(ctor_range) if !ctor_range.is_singleton() => { - let mut split_range = SplitIntRange::new(ctor_range.clone()); - let int_ranges = ctors.filter_map(|ctor| ctor.as_int_range()); - split_range.split(int_ranges.cloned()); - split_range.iter().map(IntRange).collect() - } - Slice(slice) => match slice._unimplemented {}, - // Any other constructor can be used unchanged. - _ => smallvec![self.clone()], - } - } - - /// Returns whether `self` is covered by `other`, i.e. whether `self` is a subset of `other`. - /// For the simple cases, this is simply checking for equality. For the "grouped" constructors, - /// this checks for inclusion. - // We inline because this has a single call site in `Matrix::specialize_constructor`. - #[inline] - pub(super) fn is_covered_by(&self, _pcx: PatCtxt<'_, '_>, other: &Self) -> bool { - // This must be kept in sync with `is_covered_by_any`. - match (self, other) { - // Wildcards cover anything - (_, Wildcard) => true, - // The missing ctors are not covered by anything in the matrix except wildcards. - (Missing { .. } | Wildcard, _) => false, - - (Single, Single) => true, - (Variant(self_id), Variant(other_id)) => self_id == other_id, - - (IntRange(self_range), IntRange(other_range)) => self_range.is_covered_by(other_range), - (FloatRange(void), FloatRange(..)) => match *void {}, - (Str(void), Str(..)) => match *void {}, - (Slice(self_slice), Slice(other_slice)) => self_slice.is_covered_by(*other_slice), - - // We are trying to inspect an opaque constant. Thus we skip the row. - (Opaque, _) | (_, Opaque) => false, - // Only a wildcard pattern can match the special extra constructor. - (NonExhaustive, _) => false, - - _ => { - never!("trying to compare incompatible constructors {:?} and {:?}", self, other); - // Continue with 'whatever is covered' supposed to result in false no-error diagnostic. - true - } - } - } - - /// Faster version of `is_covered_by` when applied to many constructors. `used_ctors` is - /// assumed to be built from `matrix.head_ctors()` with wildcards filtered out, and `self` is - /// assumed to have been split from a wildcard. - fn is_covered_by_any(&self, _pcx: PatCtxt<'_, '_>, used_ctors: &[Constructor]) -> bool { - if used_ctors.is_empty() { - return false; - } - - // This must be kept in sync with `is_covered_by`. - match self { - // If `self` is `Single`, `used_ctors` cannot contain anything else than `Single`s. - Single => !used_ctors.is_empty(), - Variant(_) => used_ctors.iter().any(|c| c == self), - IntRange(range) => used_ctors - .iter() - .filter_map(|c| c.as_int_range()) - .any(|other| range.is_covered_by(other)), - Slice(slice) => used_ctors - .iter() - .filter_map(|c| c.as_slice()) - .any(|other| slice.is_covered_by(other)), - // This constructor is never covered by anything else - NonExhaustive => false, - Str(..) | FloatRange(..) | Opaque | Missing { .. } | Wildcard | Or => { - never!("found unexpected ctor in all_ctors: {:?}", self); - true - } - } - } -} - -/// A wildcard constructor that we split relative to the constructors in the matrix, as explained -/// at the top of the file. -/// -/// A constructor that is not present in the matrix rows will only be covered by the rows that have -/// wildcards. Thus we can group all of those constructors together; we call them "missing -/// constructors". Splitting a wildcard would therefore list all present constructors individually -/// (or grouped if they are integers or slices), and then all missing constructors together as a -/// group. -/// -/// However we can go further: since any constructor will match the wildcard rows, and having more -/// rows can only reduce the amount of usefulness witnesses, we can skip the present constructors -/// and only try the missing ones. -/// This will not preserve the whole list of witnesses, but will preserve whether the list is empty -/// or not. In fact this is quite natural from the point of view of diagnostics too. This is done -/// in `to_ctors`: in some cases we only return `Missing`. -#[derive(Debug)] -pub(super) struct SplitWildcard { - /// Constructors seen in the matrix. - matrix_ctors: Vec<Constructor>, - /// All the constructors for this type - all_ctors: SmallVec<[Constructor; 1]>, -} - -impl SplitWildcard { - pub(super) fn new(pcx: PatCtxt<'_, '_>) -> Self { - let cx = pcx.cx; - let make_range = |start, end, scalar| IntRange(IntRange::from_range(start, end, scalar)); - - // Unhandled types are treated as non-exhaustive. Being explicit here instead of falling - // to catchall arm to ease further implementation. - let unhandled = || smallvec![NonExhaustive]; - - // 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(Interner) { - TyKind::Scalar(Scalar::Bool) => smallvec![make_range(0, 1, Scalar::Bool)], - // TyKind::Array(..) if ... => unhandled(), - TyKind::Array(..) | TyKind::Slice(..) => unhandled(), - TyKind::Adt(AdtId(hir_def::AdtId::EnumId(enum_id)), subst) => { - let enum_data = cx.db.enum_data(*enum_id); - - // 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); - - let is_exhaustive_pat_feature = cx.feature_exhaustive_patterns(); - - // 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 = enum_data.variants.is_empty() - && !is_exhaustive_pat_feature - && !pcx.is_top_level; - - let mut ctors: SmallVec<[_; 1]> = enum_data - .variants - .iter() - .map(|&(variant, _)| variant) - .filter(|&variant| { - // If `exhaustive_patterns` is enabled, we exclude variants known to be - // uninhabited. - let is_uninhabited = is_exhaustive_pat_feature - && is_enum_variant_uninhabited_from(variant, subst, cx.module, cx.db); - !is_uninhabited - }) - .map(Variant) - .collect(); - - if is_secretly_empty || is_declared_nonexhaustive { - ctors.push(NonExhaustive); - } - ctors - } - TyKind::Scalar(Scalar::Char) => unhandled(), - TyKind::Scalar(Scalar::Int(..) | Scalar::Uint(..)) => unhandled(), - TyKind::Never if !cx.feature_exhaustive_patterns() && !pcx.is_top_level => { - smallvec![NonExhaustive] - } - TyKind::Never => SmallVec::new(), - _ if cx.is_uninhabited(pcx.ty) => SmallVec::new(), - TyKind::Adt(..) | TyKind::Tuple(..) | TyKind::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 - /// do what you want. - pub(super) fn split<'a>( - &mut self, - pcx: PatCtxt<'_, '_>, - ctors: impl Iterator<Item = &'a Constructor> + Clone, - ) { - // Since `all_ctors` never contains wildcards, this won't recurse further. - self.all_ctors = - self.all_ctors.iter().flat_map(|ctor| ctor.split(pcx, ctors.clone())).collect(); - self.matrix_ctors = ctors.filter(|c| !c.is_wildcard()).cloned().collect(); - } - - /// Whether there are any value constructors for this type that are not present in the matrix. - fn any_missing(&self, pcx: PatCtxt<'_, '_>) -> bool { - self.iter_missing(pcx).next().is_some() - } - - /// Iterate over the constructors for this type that are not present in the matrix. - pub(super) fn iter_missing<'a, 'p>( - &'a self, - pcx: PatCtxt<'a, 'p>, - ) -> impl Iterator<Item = &'a Constructor> + Captures<'p> { - self.all_ctors.iter().filter(move |ctor| !ctor.is_covered_by_any(pcx, &self.matrix_ctors)) - } - - /// Return the set of constructors resulting from splitting the wildcard. As explained at the - /// top of the file, if any constructors are missing we can ignore the present ones. - fn into_ctors(self, pcx: PatCtxt<'_, '_>) -> SmallVec<[Constructor; 1]> { - if self.any_missing(pcx) { - // Some constructors are missing, thus we can specialize with the special `Missing` - // constructor, which stands for those constructors that are not seen in the matrix, - // and matches the same rows as any of them (namely the wildcard rows). See the top of - // the file for details. - // However, when all constructors are missing we can also specialize with the full - // `Wildcard` constructor. The difference will depend on what we want in diagnostics. - - // If some constructors are missing, we typically want to report those constructors, - // e.g.: - // ``` - // enum Direction { N, S, E, W } - // let Direction::N = ...; - // ``` - // we can report 3 witnesses: `S`, `E`, and `W`. - // - // However, if the user didn't actually specify a constructor - // in this arm, e.g., in - // ``` - // let x: (Direction, Direction, bool) = ...; - // let (_, _, false) = x; - // ``` - // we don't want to show all 16 possible witnesses `(<direction-1>, <direction-2>, - // true)` - we are satisfied with `(_, _, true)`. So if all constructors are missing we - // prefer to report just a wildcard `_`. - // - // The exception is: if we are at the top-level, for example in an empty match, we - // sometimes prefer reporting the list of constructors instead of just `_`. - let report_when_all_missing = pcx.is_top_level && !IntRange::is_integral(pcx.ty); - let ctor = if !self.matrix_ctors.is_empty() || report_when_all_missing { - if pcx.is_non_exhaustive { - Missing { - nonexhaustive_enum_missing_real_variants: self - .iter_missing(pcx) - .any(|c| !(c.is_non_exhaustive() || c.is_unstable_variant(pcx))), - } - } else { - Missing { nonexhaustive_enum_missing_real_variants: false } - } - } else { - Wildcard - }; - return smallvec![ctor]; - } - - // All the constructors are present in the matrix, so we just go through them all. - self.all_ctors - } -} - -/// A value can be decomposed into a constructor applied to some fields. This struct represents -/// those fields, generalized to allow patterns in each field. See also `Constructor`. -/// -/// This is constructed for a constructor using [`Fields::wildcards()`]. The idea is that -/// [`Fields::wildcards()`] constructs a list of fields where all entries are wildcards, and then -/// given a pattern we fill some of the fields with its subpatterns. -/// In the following example `Fields::wildcards` returns `[_, _, _, _]`. Then in -/// `extract_pattern_arguments` we fill some of the entries, and the result is -/// `[Some(0), _, _, _]`. -/// ```rust -/// let x: [Option<u8>; 4] = foo(); -/// match x { -/// [Some(0), ..] => {} -/// } -/// ``` -/// -/// Note that the number of fields of a constructor may not match the fields declared in the -/// original struct/variant. This happens if a private or `non_exhaustive` field is uninhabited, -/// because the code mustn't observe that it is uninhabited. In that case that field is not -/// included in `fields`. For that reason, when you have a `mir::Field` you must use -/// `index_with_declared_idx`. -#[derive(Clone, Copy)] -pub(super) struct Fields<'p> { - fields: &'p [DeconstructedPat<'p>], -} - -impl<'p> Fields<'p> { - fn empty() -> Self { - Fields { fields: &[] } - } - - fn singleton(cx: &MatchCheckCtx<'_, 'p>, field: DeconstructedPat<'p>) -> Self { - let field = cx.pattern_arena.alloc(field); - Fields { fields: std::slice::from_ref(field) } - } - - pub(super) fn from_iter( - cx: &MatchCheckCtx<'_, 'p>, - fields: impl IntoIterator<Item = DeconstructedPat<'p>>, - ) -> Self { - let fields: &[_] = cx.pattern_arena.alloc_extend(fields); - Fields { fields } - } - - fn wildcards_from_tys(cx: &MatchCheckCtx<'_, 'p>, tys: impl IntoIterator<Item = Ty>) -> Self { - Fields::from_iter(cx, tys.into_iter().map(DeconstructedPat::wildcard)) - } - - // In the cases of either a `#[non_exhaustive]` field list or a non-public field, we hide - // uninhabited fields in order not to reveal the uninhabitedness of the whole variant. - // This lists the fields we keep along with their types. - fn list_variant_nonhidden_fields<'a>( - cx: &'a MatchCheckCtx<'a, 'p>, - ty: &'a Ty, - variant: VariantId, - ) -> impl Iterator<Item = (LocalFieldId, Ty)> + Captures<'a> + Captures<'p> { - let (adt, substs) = ty.as_adt().unwrap(); - - let adt_is_local = variant.module(cx.db.upcast()).krate() == cx.module.krate(); - // Whether we must not match the fields of this variant exhaustively. - let is_non_exhaustive = is_field_list_non_exhaustive(variant, cx) && !adt_is_local; - - let visibility = cx.db.field_visibilities(variant); - let field_ty = cx.db.field_types(variant); - let fields_len = variant.variant_data(cx.db.upcast()).fields().len() as u32; - - (0..fields_len).map(|idx| LocalFieldId::from_raw(idx.into())).filter_map(move |fid| { - let ty = field_ty[fid].clone().substitute(Interner, substs); - let ty = normalize(cx.db, cx.db.trait_environment_for_body(cx.body), ty); - let is_visible = matches!(adt, hir_def::AdtId::EnumId(..)) - || visibility[fid].is_visible_from(cx.db.upcast(), cx.module); - let is_uninhabited = cx.is_uninhabited(&ty); - - if is_uninhabited && (!is_visible || is_non_exhaustive) { - None - } else { - Some((fid, ty)) - } - }) - } - - /// Creates a new list of wildcard fields for a given constructor. The result must have a - /// length of `constructor.arity()`. - pub(crate) fn wildcards( - cx: &MatchCheckCtx<'_, 'p>, - ty: &Ty, - constructor: &Constructor, - ) -> Self { - let ret = match constructor { - Single | Variant(_) => match ty.kind(Interner) { - TyKind::Tuple(_, substs) => { - let tys = substs.iter(Interner).map(|ty| ty.assert_ty_ref(Interner)); - Fields::wildcards_from_tys(cx, tys.cloned()) - } - TyKind::Ref(.., rty) => Fields::wildcards_from_tys(cx, once(rty.clone())), - &TyKind::Adt(AdtId(adt), ref substs) => { - if is_box(cx.db, adt) { - // The only legal patterns of type `Box` (outside `std`) are `_` and box - // patterns. If we're here we can assume this is a box pattern. - let subst_ty = substs.at(Interner, 0).assert_ty_ref(Interner).clone(); - Fields::wildcards_from_tys(cx, once(subst_ty)) - } else { - let variant = constructor.variant_id_for_adt(adt); - let tys = Fields::list_variant_nonhidden_fields(cx, ty, variant) - .map(|(_, ty)| ty); - Fields::wildcards_from_tys(cx, tys) - } - } - ty_kind => { - never!("Unexpected type for `Single` constructor: {:?}", ty_kind); - Fields::wildcards_from_tys(cx, once(ty.clone())) - } - }, - Slice(slice) => match slice._unimplemented {}, - Str(..) - | FloatRange(..) - | IntRange(..) - | NonExhaustive - | Opaque - | Missing { .. } - | Wildcard => Fields::empty(), - Or => { - never!("called `Fields::wildcards` on an `Or` ctor"); - Fields::empty() - } - }; - ret - } - - /// Returns the list of patterns. - pub(super) fn iter_patterns<'a>( - &'a self, - ) -> impl Iterator<Item = &'p DeconstructedPat<'p>> + Captures<'a> { - self.fields.iter() - } -} - -/// Values and patterns can be represented as a constructor applied to some fields. This represents -/// a pattern in this form. -/// This also keeps track of whether the pattern has been found reachable during analysis. For this -/// reason we should be careful not to clone patterns for which we care about that. Use -/// `clone_and_forget_reachability` if you're sure. -pub(crate) struct DeconstructedPat<'p> { - ctor: Constructor, - fields: Fields<'p>, - ty: Ty, - reachable: Cell<bool>, -} - -impl<'p> DeconstructedPat<'p> { - pub(super) fn wildcard(ty: Ty) -> Self { - Self::new(Wildcard, Fields::empty(), ty) - } - - pub(super) fn new(ctor: Constructor, fields: Fields<'p>, ty: Ty) -> Self { - DeconstructedPat { ctor, fields, ty, reachable: Cell::new(false) } - } - - /// Construct a pattern that matches everything that starts with this constructor. - /// For example, if `ctor` is a `Constructor::Variant` for `Option::Some`, we get the pattern - /// `Some(_)`. - pub(super) fn wild_from_ctor(pcx: PatCtxt<'_, 'p>, ctor: Constructor) -> Self { - let fields = Fields::wildcards(pcx.cx, pcx.ty, &ctor); - DeconstructedPat::new(ctor, fields, pcx.ty.clone()) - } - - /// Clone this value. This method emphasizes that cloning loses reachability information and - /// should be done carefully. - pub(super) fn clone_and_forget_reachability(&self) -> Self { - DeconstructedPat::new(self.ctor.clone(), self.fields, self.ty.clone()) - } - - pub(crate) fn from_pat(cx: &MatchCheckCtx<'_, 'p>, pat: &Pat) -> Self { - let mkpat = |pat| DeconstructedPat::from_pat(cx, pat); - let ctor; - let fields; - match pat.kind.as_ref() { - PatKind::Binding { subpattern: Some(subpat), .. } => return mkpat(subpat), - PatKind::Binding { subpattern: None, .. } | PatKind::Wild => { - ctor = Wildcard; - fields = Fields::empty(); - } - PatKind::Deref { subpattern } => { - ctor = Single; - fields = Fields::singleton(cx, mkpat(subpattern)); - } - PatKind::Leaf { subpatterns } | PatKind::Variant { subpatterns, .. } => { - match pat.ty.kind(Interner) { - TyKind::Tuple(_, substs) => { - ctor = Single; - let mut wilds: SmallVec<[_; 2]> = substs - .iter(Interner) - .map(|arg| arg.assert_ty_ref(Interner).clone()) - .map(DeconstructedPat::wildcard) - .collect(); - for pat in subpatterns { - let idx: u32 = pat.field.into_raw().into(); - wilds[idx as usize] = mkpat(&pat.pattern); - } - fields = Fields::from_iter(cx, wilds) - } - TyKind::Adt(adt, substs) if is_box(cx.db, adt.0) => { - // The only legal patterns of type `Box` (outside `std`) are `_` and box - // patterns. If we're here we can assume this is a box pattern. - // FIXME(Nadrieril): A `Box` can in theory be matched either with `Box(_, - // _)` or a box pattern. As a hack to avoid an ICE with the former, we - // ignore other fields than the first one. This will trigger an error later - // anyway. - // See https://github.com/rust-lang/rust/issues/82772 , - // explanation: https://github.com/rust-lang/rust/pull/82789#issuecomment-796921977 - // The problem is that we can't know from the type whether we'll match - // normally or through box-patterns. We'll have to figure out a proper - // solution when we introduce generalized deref patterns. Also need to - // prevent mixing of those two options. - let pat = - subpatterns.iter().find(|pat| pat.field.into_raw() == 0u32.into()); - let field = if let Some(pat) = pat { - mkpat(&pat.pattern) - } else { - let ty = substs.at(Interner, 0).assert_ty_ref(Interner).clone(); - DeconstructedPat::wildcard(ty) - }; - ctor = Single; - fields = Fields::singleton(cx, field) - } - &TyKind::Adt(adt, _) => { - ctor = match pat.kind.as_ref() { - PatKind::Leaf { .. } => Single, - PatKind::Variant { enum_variant, .. } => Variant(*enum_variant), - _ => { - never!(); - Wildcard - } - }; - let variant = ctor.variant_id_for_adt(adt.0); - let fields_len = variant.variant_data(cx.db.upcast()).fields().len(); - // For each field in the variant, we store the relevant index into `self.fields` if any. - let mut field_id_to_id: Vec<Option<usize>> = vec![None; fields_len]; - let tys = Fields::list_variant_nonhidden_fields(cx, &pat.ty, variant) - .enumerate() - .map(|(i, (fid, ty))| { - let field_idx: u32 = fid.into_raw().into(); - field_id_to_id[field_idx as usize] = Some(i); - ty - }); - let mut wilds: SmallVec<[_; 2]> = - tys.map(DeconstructedPat::wildcard).collect(); - for pat in subpatterns { - let field_idx: u32 = pat.field.into_raw().into(); - if let Some(i) = field_id_to_id[field_idx as usize] { - wilds[i] = mkpat(&pat.pattern); - } - } - fields = Fields::from_iter(cx, wilds); - } - _ => { - never!("pattern has unexpected type: pat: {:?}, ty: {:?}", pat, &pat.ty); - ctor = Wildcard; - fields = Fields::empty(); - } - } - } - &PatKind::LiteralBool { value } => { - ctor = IntRange(IntRange::from_bool(value)); - fields = Fields::empty(); - } - PatKind::Or { .. } => { - ctor = Or; - let pats: SmallVec<[_; 2]> = expand_or_pat(pat).into_iter().map(mkpat).collect(); - fields = Fields::from_iter(cx, pats) - } - } - DeconstructedPat::new(ctor, fields, pat.ty.clone()) - } - - pub(crate) fn to_pat(&self, cx: &MatchCheckCtx<'_, 'p>) -> Pat { - let mut subpatterns = self.iter_fields().map(|p| p.to_pat(cx)); - let pat = match &self.ctor { - Single | Variant(_) => match self.ty.kind(Interner) { - TyKind::Tuple(..) => PatKind::Leaf { - subpatterns: subpatterns - .zip(0u32..) - .map(|(p, i)| FieldPat { - field: LocalFieldId::from_raw(i.into()), - pattern: p, - }) - .collect(), - }, - TyKind::Adt(adt, _) if is_box(cx.db, adt.0) => { - // Without `box_patterns`, the only legal pattern of type `Box` is `_` (outside - // of `std`). So this branch is only reachable when the feature is enabled and - // the pattern is a box pattern. - PatKind::Deref { subpattern: subpatterns.next().unwrap() } - } - TyKind::Adt(adt, substs) => { - let variant = self.ctor.variant_id_for_adt(adt.0); - let subpatterns = Fields::list_variant_nonhidden_fields(cx, self.ty(), variant) - .zip(subpatterns) - .map(|((field, _ty), pattern)| FieldPat { field, pattern }) - .collect(); - - if let VariantId::EnumVariantId(enum_variant) = variant { - PatKind::Variant { substs: substs.clone(), enum_variant, subpatterns } - } else { - PatKind::Leaf { subpatterns } - } - } - // Note: given the expansion of `&str` patterns done in `expand_pattern`, we should - // be careful to reconstruct the correct constant pattern here. However a string - // literal pattern will never be reported as a non-exhaustiveness witness, so we - // ignore this issue. - TyKind::Ref(..) => PatKind::Deref { subpattern: subpatterns.next().unwrap() }, - _ => { - never!("unexpected ctor for type {:?} {:?}", self.ctor, self.ty); - PatKind::Wild - } - }, - &Slice(slice) => match slice._unimplemented {}, - &Str(void) => match void {}, - &FloatRange(void) => match void {}, - IntRange(range) => return range.to_pat(cx, self.ty.clone()), - Wildcard | NonExhaustive => PatKind::Wild, - Missing { .. } => { - never!( - "trying to convert a `Missing` constructor into a `Pat`; this is a bug, \ - `Missing` should have been processed in `apply_constructors`" - ); - PatKind::Wild - } - Opaque | Or => { - never!("can't convert to pattern: {:?}", self.ctor); - PatKind::Wild - } - }; - Pat { ty: self.ty.clone(), kind: Box::new(pat) } - } - - pub(super) fn is_or_pat(&self) -> bool { - matches!(self.ctor, Or) - } - - pub(super) fn ctor(&self) -> &Constructor { - &self.ctor - } - - pub(super) fn ty(&self) -> &Ty { - &self.ty - } - - pub(super) fn iter_fields<'a>(&'a self) -> impl Iterator<Item = &'p DeconstructedPat<'p>> + 'a { - self.fields.iter_patterns() - } - - /// Specialize this pattern with a constructor. - /// `other_ctor` can be different from `self.ctor`, but must be covered by it. - pub(super) fn specialize<'a>( - &'a self, - cx: &MatchCheckCtx<'_, 'p>, - other_ctor: &Constructor, - ) -> SmallVec<[&'p DeconstructedPat<'p>; 2]> { - match (&self.ctor, other_ctor) { - (Wildcard, _) => { - // We return a wildcard for each field of `other_ctor`. - Fields::wildcards(cx, &self.ty, other_ctor).iter_patterns().collect() - } - (Slice(self_slice), Slice(other_slice)) - if self_slice.arity() != other_slice.arity() => - { - match self_slice._unimplemented {} - } - _ => self.fields.iter_patterns().collect(), - } - } - - /// We keep track for each pattern if it was ever reachable during the analysis. This is used - /// with `unreachable_spans` to report unreachable subpatterns arising from or patterns. - pub(super) fn set_reachable(&self) { - self.reachable.set(true) - } - pub(super) fn is_reachable(&self) -> bool { - self.reachable.get() - } -} - -fn is_field_list_non_exhaustive(variant_id: VariantId, cx: &MatchCheckCtx<'_, '_>) -> bool { - let attr_def_id = match variant_id { - VariantId::EnumVariantId(id) => id.into(), - VariantId::StructId(id) => id.into(), - VariantId::UnionId(id) => id.into(), - }; - cx.db.attrs(attr_def_id).by_key("non_exhaustive").exists() -} diff --git a/crates/hir-ty/src/diagnostics/match_check/pat_analysis.rs b/crates/hir-ty/src/diagnostics/match_check/pat_analysis.rs new file mode 100644 index 0000000000..cd67ca5993 --- /dev/null +++ b/crates/hir-ty/src/diagnostics/match_check/pat_analysis.rs @@ -0,0 +1,475 @@ +//! Interface with `rustc_pattern_analysis`. + +use std::fmt; + +use hir_def::{DefWithBodyId, EnumVariantId, HasModule, LocalFieldId, ModuleId, VariantId}; +use rustc_hash::FxHashMap; +use rustc_pattern_analysis::{ + constructor::{Constructor, ConstructorSet, VariantVisibility}, + index::IdxContainer, + Captures, TypeCx, +}; +use smallvec::SmallVec; +use stdx::never; +use typed_arena::Arena; + +use crate::{ + db::HirDatabase, + infer::normalize, + inhabitedness::{is_enum_variant_uninhabited_from, is_ty_uninhabited_from}, + AdtId, Interner, Scalar, Ty, TyExt, TyKind, +}; + +use super::{is_box, FieldPat, Pat, PatKind}; + +use Constructor::*; + +// Re-export r-a-specific versions of all these types. +pub(crate) type DeconstructedPat<'p> = + rustc_pattern_analysis::pat::DeconstructedPat<'p, MatchCheckCtx<'p>>; +pub(crate) type MatchArm<'p> = rustc_pattern_analysis::MatchArm<'p, MatchCheckCtx<'p>>; +pub(crate) type WitnessPat<'p> = rustc_pattern_analysis::pat::WitnessPat<MatchCheckCtx<'p>>; + +/// [Constructor] uses this in unimplemented variants. +/// It allows porting match expressions from upstream algorithm without losing semantics. +#[derive(Copy, Clone, Debug, PartialEq, Eq)] +pub(crate) enum Void {} + +#[derive(Clone)] +pub(crate) struct MatchCheckCtx<'p> { + module: ModuleId, + body: DefWithBodyId, + pub(crate) db: &'p dyn HirDatabase, + pub(crate) pattern_arena: &'p Arena<DeconstructedPat<'p>>, + ty_arena: &'p Arena<Ty>, + exhaustive_patterns: bool, +} + +impl<'p> MatchCheckCtx<'p> { + pub(crate) fn new( + module: ModuleId, + body: DefWithBodyId, + db: &'p dyn HirDatabase, + pattern_arena: &'p Arena<DeconstructedPat<'p>>, + ty_arena: &'p Arena<Ty>, + ) -> Self { + let def_map = db.crate_def_map(module.krate()); + let exhaustive_patterns = def_map.is_unstable_feature_enabled("exhaustive_patterns"); + Self { module, body, db, pattern_arena, exhaustive_patterns, ty_arena } + } + + fn is_uninhabited(&self, ty: &Ty) -> bool { + is_ty_uninhabited_from(ty, self.module, self.db) + } + + /// Returns whether the given type is an enum from another crate declared `#[non_exhaustive]`. + fn is_foreign_non_exhaustive_enum(&self, ty: &Ty) -> bool { + match ty.as_adt() { + Some((adt @ hir_def::AdtId::EnumId(_), _)) => { + let has_non_exhaustive_attr = + self.db.attrs(adt.into()).by_key("non_exhaustive").exists(); + let is_local = adt.module(self.db.upcast()).krate() == self.module.krate(); + has_non_exhaustive_attr && !is_local + } + _ => false, + } + } + + fn variant_id_for_adt(&self, ctor: &Constructor<Self>, adt: hir_def::AdtId) -> VariantId { + match ctor { + &Variant(id) => id.into(), + Struct | UnionField => { + assert!(!matches!(adt, hir_def::AdtId::EnumId(_))); + match adt { + hir_def::AdtId::EnumId(_) => unreachable!(), + hir_def::AdtId::StructId(id) => id.into(), + hir_def::AdtId::UnionId(id) => id.into(), + } + } + _ => panic!("bad constructor {self:?} for adt {adt:?}"), + } + } + + // In the cases of either a `#[non_exhaustive]` field list or a non-public field, we hide + // uninhabited fields in order not to reveal the uninhabitedness of the whole variant. + // This lists the fields we keep along with their types. + fn list_variant_nonhidden_fields<'a>( + &'a self, + ty: &'a Ty, + variant: VariantId, + ) -> impl Iterator<Item = (LocalFieldId, Ty)> + Captures<'a> + Captures<'p> { + let cx = self; + let (adt, substs) = ty.as_adt().unwrap(); + + let adt_is_local = variant.module(cx.db.upcast()).krate() == cx.module.krate(); + + // Whether we must not match the fields of this variant exhaustively. + let is_non_exhaustive = + cx.db.attrs(variant.into()).by_key("non_exhaustive").exists() && !adt_is_local; + + let visibility = cx.db.field_visibilities(variant); + let field_ty = cx.db.field_types(variant); + let fields_len = variant.variant_data(cx.db.upcast()).fields().len() as u32; + + (0..fields_len).map(|idx| LocalFieldId::from_raw(idx.into())).filter_map(move |fid| { + let ty = field_ty[fid].clone().substitute(Interner, substs); + let ty = normalize(cx.db, cx.db.trait_environment_for_body(cx.body), ty); + let is_visible = matches!(adt, hir_def::AdtId::EnumId(..)) + || visibility[fid].is_visible_from(cx.db.upcast(), cx.module); + let is_uninhabited = cx.is_uninhabited(&ty); + + if is_uninhabited && (!is_visible || is_non_exhaustive) { + None + } else { + Some((fid, ty)) + } + }) + } + + pub(crate) fn lower_pat(&self, pat: &Pat) -> DeconstructedPat<'p> { + let singleton = |pat| std::slice::from_ref(self.pattern_arena.alloc(pat)); + let ctor; + let fields: &[_]; + + match pat.kind.as_ref() { + PatKind::Binding { subpattern: Some(subpat), .. } => return self.lower_pat(subpat), + PatKind::Binding { subpattern: None, .. } | PatKind::Wild => { + ctor = Wildcard; + fields = &[]; + } + PatKind::Deref { subpattern } => { + ctor = match pat.ty.kind(Interner) { + // This is a box pattern. + TyKind::Adt(adt, _) if is_box(self.db, adt.0) => Struct, + TyKind::Ref(..) => Ref, + _ => { + never!("pattern has unexpected type: pat: {:?}, ty: {:?}", pat, &pat.ty); + Wildcard + } + }; + fields = singleton(self.lower_pat(subpattern)); + } + PatKind::Leaf { subpatterns } | PatKind::Variant { subpatterns, .. } => { + match pat.ty.kind(Interner) { + TyKind::Tuple(_, substs) => { + ctor = Struct; + let mut wilds: SmallVec<[_; 2]> = substs + .iter(Interner) + .map(|arg| arg.assert_ty_ref(Interner).clone()) + .map(DeconstructedPat::wildcard) + .collect(); + for pat in subpatterns { + let idx: u32 = pat.field.into_raw().into(); + wilds[idx as usize] = self.lower_pat(&pat.pattern); + } + fields = self.pattern_arena.alloc_extend(wilds) + } + TyKind::Adt(adt, substs) if is_box(self.db, adt.0) => { + // The only legal patterns of type `Box` (outside `std`) are `_` and box + // patterns. If we're here we can assume this is a box pattern. + // FIXME(Nadrieril): A `Box` can in theory be matched either with `Box(_, + // _)` or a box pattern. As a hack to avoid an ICE with the former, we + // ignore other fields than the first one. This will trigger an error later + // anyway. + // See https://github.com/rust-lang/rust/issues/82772 , + // explanation: https://github.com/rust-lang/rust/pull/82789#issuecomment-796921977 + // The problem is that we can't know from the type whether we'll match + // normally or through box-patterns. We'll have to figure out a proper + // solution when we introduce generalized deref patterns. Also need to + // prevent mixing of those two options. + let pat = + subpatterns.iter().find(|pat| pat.field.into_raw() == 0u32.into()); + let field = if let Some(pat) = pat { + self.lower_pat(&pat.pattern) + } else { + let ty = substs.at(Interner, 0).assert_ty_ref(Interner).clone(); + DeconstructedPat::wildcard(ty) + }; + ctor = Struct; + fields = singleton(field); + } + &TyKind::Adt(adt, _) => { + ctor = match pat.kind.as_ref() { + PatKind::Leaf { .. } if matches!(adt.0, hir_def::AdtId::UnionId(_)) => { + UnionField + } + PatKind::Leaf { .. } => Struct, + PatKind::Variant { enum_variant, .. } => Variant(*enum_variant), + _ => { + never!(); + Wildcard + } + }; + let variant = self.variant_id_for_adt(&ctor, adt.0); + let fields_len = variant.variant_data(self.db.upcast()).fields().len(); + // For each field in the variant, we store the relevant index into `self.fields` if any. + let mut field_id_to_id: Vec<Option<usize>> = vec![None; fields_len]; + let tys = self + .list_variant_nonhidden_fields(&pat.ty, variant) + .enumerate() + .map(|(i, (fid, ty))| { + let field_idx: u32 = fid.into_raw().into(); + field_id_to_id[field_idx as usize] = Some(i); + ty + }); + let mut wilds: SmallVec<[_; 2]> = + tys.map(DeconstructedPat::wildcard).collect(); + for pat in subpatterns { + let field_idx: u32 = pat.field.into_raw().into(); + if let Some(i) = field_id_to_id[field_idx as usize] { + wilds[i] = self.lower_pat(&pat.pattern); + } + } + fields = self.pattern_arena.alloc_extend(wilds); + } + _ => { + never!("pattern has unexpected type: pat: {:?}, ty: {:?}", pat, &pat.ty); + ctor = Wildcard; + fields = &[]; + } + } + } + &PatKind::LiteralBool { value } => { + ctor = Bool(value); + fields = &[]; + } + PatKind::Or { pats } => { + ctor = Or; + // Collect here because `Arena::alloc_extend` panics on reentrancy. + let subpats: SmallVec<[_; 2]> = + pats.into_iter().map(|pat| self.lower_pat(pat)).collect(); + fields = self.pattern_arena.alloc_extend(subpats); + } + } + DeconstructedPat::new(ctor, fields, pat.ty.clone(), ()) + } + + pub(crate) fn hoist_witness_pat(&self, pat: &WitnessPat<'p>) -> Pat { + let mut subpatterns = pat.iter_fields().map(|p| self.hoist_witness_pat(p)); + let kind = match pat.ctor() { + &Bool(value) => PatKind::LiteralBool { value }, + IntRange(_) => unimplemented!(), + Struct | Variant(_) | UnionField => match pat.ty().kind(Interner) { + TyKind::Tuple(..) => PatKind::Leaf { + subpatterns: subpatterns + .zip(0u32..) + .map(|(p, i)| FieldPat { + field: LocalFieldId::from_raw(i.into()), + pattern: p, + }) + .collect(), + }, + TyKind::Adt(adt, _) if is_box(self.db, adt.0) => { + // Without `box_patterns`, the only legal pattern of type `Box` is `_` (outside + // of `std`). So this branch is only reachable when the feature is enabled and + // the pattern is a box pattern. + PatKind::Deref { subpattern: subpatterns.next().unwrap() } + } + TyKind::Adt(adt, substs) => { + let variant = self.variant_id_for_adt(pat.ctor(), adt.0); + let subpatterns = self + .list_variant_nonhidden_fields(pat.ty(), variant) + .zip(subpatterns) + .map(|((field, _ty), pattern)| FieldPat { field, pattern }) + .collect(); + + if let VariantId::EnumVariantId(enum_variant) = variant { + PatKind::Variant { substs: substs.clone(), enum_variant, subpatterns } + } else { + PatKind::Leaf { subpatterns } + } + } + _ => { + never!("unexpected ctor for type {:?} {:?}", pat.ctor(), pat.ty()); + PatKind::Wild + } + }, + // Note: given the expansion of `&str` patterns done in `expand_pattern`, we should + // be careful to reconstruct the correct constant pattern here. However a string + // literal pattern will never be reported as a non-exhaustiveness witness, so we + // ignore this issue. + Ref => PatKind::Deref { subpattern: subpatterns.next().unwrap() }, + Slice(_) => unimplemented!(), + &Str(void) => match void {}, + Wildcard | NonExhaustive | Hidden => PatKind::Wild, + Missing | F32Range(..) | F64Range(..) | Opaque(..) | Or => { + never!("can't convert to pattern: {:?}", pat.ctor()); + PatKind::Wild + } + }; + Pat { ty: pat.ty().clone(), kind: Box::new(kind) } + } +} + +impl<'p> TypeCx for MatchCheckCtx<'p> { + type Error = Void; + type Ty = Ty; + type VariantIdx = EnumVariantId; + type StrLit = Void; + type ArmData = (); + type PatData = (); + + fn is_exhaustive_patterns_feature_on(&self) -> bool { + self.exhaustive_patterns + } + + fn ctor_arity( + &self, + ctor: &rustc_pattern_analysis::constructor::Constructor<Self>, + ty: &Self::Ty, + ) -> usize { + match ctor { + Struct | Variant(_) | UnionField => match *ty.kind(Interner) { + TyKind::Tuple(arity, ..) => arity, + TyKind::Adt(AdtId(adt), ..) => { + if is_box(self.db, adt) { + // The only legal patterns of type `Box` (outside `std`) are `_` and box + // patterns. If we're here we can assume this is a box pattern. + 1 + } else { + let variant = self.variant_id_for_adt(ctor, adt); + self.list_variant_nonhidden_fields(ty, variant).count() + } + } + _ => { + never!("Unexpected type for `Single` constructor: {:?}", ty); + 0 + } + }, + Ref => 1, + Slice(..) => unimplemented!(), + Bool(..) | IntRange(..) | F32Range(..) | F64Range(..) | Str(..) | Opaque(..) + | NonExhaustive | Hidden | Missing | Wildcard => 0, + Or => { + never!("The `Or` constructor doesn't have a fixed arity"); + 0 + } + } + } + + fn ctor_sub_tys( + &self, + ctor: &rustc_pattern_analysis::constructor::Constructor<Self>, + ty: &Self::Ty, + ) -> &[Self::Ty] { + use std::iter::once; + fn alloc<'a>(cx: &'a MatchCheckCtx<'_>, iter: impl Iterator<Item = Ty>) -> &'a [Ty] { + cx.ty_arena.alloc_extend(iter) + } + match ctor { + Struct | Variant(_) | UnionField => match ty.kind(Interner) { + TyKind::Tuple(_, substs) => { + let tys = substs.iter(Interner).map(|ty| ty.assert_ty_ref(Interner)); + alloc(self, tys.cloned()) + } + TyKind::Ref(.., rty) => alloc(self, once(rty.clone())), + &TyKind::Adt(AdtId(adt), ref substs) => { + if is_box(self.db, adt) { + // The only legal patterns of type `Box` (outside `std`) are `_` and box + // patterns. If we're here we can assume this is a box pattern. + let subst_ty = substs.at(Interner, 0).assert_ty_ref(Interner).clone(); + alloc(self, once(subst_ty)) + } else { + let variant = self.variant_id_for_adt(ctor, adt); + let tys = self.list_variant_nonhidden_fields(ty, variant).map(|(_, ty)| ty); + alloc(self, tys) + } + } + ty_kind => { + never!("Unexpected type for `{:?}` constructor: {:?}", ctor, ty_kind); + alloc(self, once(ty.clone())) + } + }, + Ref => match ty.kind(Interner) { + TyKind::Ref(.., rty) => alloc(self, once(rty.clone())), + ty_kind => { + never!("Unexpected type for `{:?}` constructor: {:?}", ctor, ty_kind); + alloc(self, once(ty.clone())) + } + }, + Slice(_) => unreachable!("Found a `Slice` constructor in match checking"), + Bool(..) | IntRange(..) | F32Range(..) | F64Range(..) | Str(..) | Opaque(..) + | NonExhaustive | Hidden | Missing | Wildcard => &[], + Or => { + never!("called `Fields::wildcards` on an `Or` ctor"); + &[] + } + } + } + + fn ctors_for_ty( + &self, + ty: &Self::Ty, + ) -> Result<rustc_pattern_analysis::constructor::ConstructorSet<Self>, Self::Error> { + let cx = self; + + // Unhandled types are treated as non-exhaustive. Being explicit here instead of falling + // to catchall arm to ease further implementation. + let unhandled = || ConstructorSet::Unlistable; + + // This determines the set of all possible constructors for the type `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()`). + Ok(match ty.kind(Interner) { + TyKind::Scalar(Scalar::Bool) => ConstructorSet::Bool, + TyKind::Scalar(Scalar::Char) => unhandled(), + TyKind::Scalar(Scalar::Int(..) | Scalar::Uint(..)) => unhandled(), + TyKind::Array(..) | TyKind::Slice(..) => unhandled(), + TyKind::Adt(AdtId(hir_def::AdtId::EnumId(enum_id)), subst) => { + let enum_data = cx.db.enum_data(*enum_id); + let is_declared_nonexhaustive = cx.is_foreign_non_exhaustive_enum(ty); + + if enum_data.variants.is_empty() && !is_declared_nonexhaustive { + ConstructorSet::NoConstructors + } else { + let mut variants = FxHashMap::default(); + for &(variant, _) in enum_data.variants.iter() { + let is_uninhabited = + is_enum_variant_uninhabited_from(variant, subst, cx.module, cx.db); + let visibility = if is_uninhabited { + VariantVisibility::Empty + } else { + VariantVisibility::Visible + }; + variants.insert(variant, visibility); + } + + ConstructorSet::Variants { + variants: IdxContainer(variants), + non_exhaustive: is_declared_nonexhaustive, + } + } + } + TyKind::Adt(AdtId(hir_def::AdtId::UnionId(_)), _) => ConstructorSet::Union, + TyKind::Adt(..) | TyKind::Tuple(..) => { + ConstructorSet::Struct { empty: cx.is_uninhabited(ty) } + } + TyKind::Ref(..) => ConstructorSet::Ref, + TyKind::Never => ConstructorSet::NoConstructors, + // This type is one for which we cannot list constructors, like `str` or `f64`. + _ => ConstructorSet::Unlistable, + }) + } + + fn debug_pat( + _f: &mut fmt::Formatter<'_>, + _pat: &rustc_pattern_analysis::pat::DeconstructedPat<'_, Self>, + ) -> fmt::Result { + unimplemented!() + } + + fn bug(&self, fmt: fmt::Arguments<'_>) -> ! { + panic!("{}", fmt) + } +} + +impl<'p> fmt::Debug for MatchCheckCtx<'p> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("MatchCheckCtx").finish() + } +} diff --git a/crates/hir-ty/src/diagnostics/match_check/usefulness.rs b/crates/hir-ty/src/diagnostics/match_check/usefulness.rs deleted file mode 100644 index 1b1a5ff269..0000000000 --- a/crates/hir-ty/src/diagnostics/match_check/usefulness.rs +++ /dev/null @@ -1,824 +0,0 @@ -//! Based on rust-lang/rust (last sync f31622a50 2021-11-12) -//! <https://github.com/rust-lang/rust/blob/f31622a50/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs> -//! -//! ----- -//! -//! This file includes the logic for exhaustiveness and reachability checking for pattern-matching. -//! Specifically, given a list of patterns for a type, we can tell whether: -//! (a) each pattern is reachable (reachability) -//! (b) the patterns cover every possible value for the type (exhaustiveness) -//! -//! The algorithm implemented here is a modified version of the one described in [this -//! paper](http://moscova.inria.fr/~maranget/papers/warn/index.html). We have however generalized -//! it to accommodate the variety of patterns that Rust supports. We thus explain our version here, -//! without being as rigorous. -//! -//! -//! # Summary -//! -//! The core of the algorithm is the notion of "usefulness". A pattern `q` is said to be *useful* -//! relative to another pattern `p` of the same type if there is a value that is matched by `q` and -//! not matched by `p`. This generalizes to many `p`s: `q` is useful w.r.t. a list of patterns -//! `p_1 .. p_n` if there is a value that is matched by `q` and by none of the `p_i`. We write -//! `usefulness(p_1 .. p_n, q)` for a function that returns a list of such values. The aim of this -//! file is to compute it efficiently. -//! -//! This is enough to compute reachability: a pattern in a `match` expression is reachable iff it -//! is useful w.r.t. the patterns above it: -//! ```rust -//! match x { -//! Some(_) => ..., -//! None => ..., // reachable: `None` is matched by this but not the branch above -//! Some(0) => ..., // unreachable: all the values this matches are already matched by -//! // `Some(_)` above -//! } -//! ``` -//! -//! This is also enough to compute exhaustiveness: a match is exhaustive iff the wildcard `_` -//! pattern is _not_ useful w.r.t. the patterns in the match. The values returned by `usefulness` -//! are used to tell the user which values are missing. -//! ```rust -//! match x { -//! Some(0) => ..., -//! None => ..., -//! // not exhaustive: `_` is useful because it matches `Some(1)` -//! } -//! ``` -//! -//! The entrypoint of this file is the [`compute_match_usefulness`] function, which computes -//! reachability for each match branch and exhaustiveness for the whole match. -//! -//! -//! # Constructors and fields -//! -//! Note: we will often abbreviate "constructor" as "ctor". -//! -//! The idea that powers everything that is done in this file is the following: a (matcheable) -//! value is made from a constructor applied to a number of subvalues. Examples of constructors are -//! `Some`, `None`, `(,)` (the 2-tuple constructor), `Foo {..}` (the constructor for a struct -//! `Foo`), and `2` (the constructor for the number `2`). This is natural when we think of -//! pattern-matching, and this is the basis for what follows. -//! -//! Some of the ctors listed above might feel weird: `None` and `2` don't take any arguments. -//! That's ok: those are ctors that take a list of 0 arguments; they are the simplest case of -//! ctors. We treat `2` as a ctor because `u64` and other number types behave exactly like a huge -//! `enum`, with one variant for each number. This allows us to see any matcheable value as made up -//! from a tree of ctors, each having a set number of children. For example: `Foo { bar: None, -//! baz: Ok(0) }` is made from 4 different ctors, namely `Foo{..}`, `None`, `Ok` and `0`. -//! -//! This idea can be extended to patterns: they are also made from constructors applied to fields. -//! A pattern for a given type is allowed to use all the ctors for values of that type (which we -//! call "value constructors"), but there are also pattern-only ctors. The most important one is -//! the wildcard (`_`), and the others are integer ranges (`0..=10`), variable-length slices (`[x, -//! ..]`), and or-patterns (`Ok(0) | Err(_)`). Examples of valid patterns are `42`, `Some(_)`, `Foo -//! { bar: Some(0) | None, baz: _ }`. Note that a binder in a pattern (e.g. `Some(x)`) matches the -//! same values as a wildcard (e.g. `Some(_)`), so we treat both as wildcards. -//! -//! From this deconstruction we can compute whether a given value matches a given pattern; we -//! simply look at ctors one at a time. Given a pattern `p` and a value `v`, we want to compute -//! `matches!(v, p)`. It's mostly straightforward: we compare the head ctors and when they match -//! we compare their fields recursively. A few representative examples: -//! -//! - `matches!(v, _) := true` -//! - `matches!((v0, v1), (p0, p1)) := matches!(v0, p0) && matches!(v1, p1)` -//! - `matches!(Foo { bar: v0, baz: v1 }, Foo { bar: p0, baz: p1 }) := matches!(v0, p0) && matches!(v1, p1)` -//! - `matches!(Ok(v0), Ok(p0)) := matches!(v0, p0)` -//! - `matches!(Ok(v0), Err(p0)) := false` (incompatible variants) -//! - `matches!(v, 1..=100) := matches!(v, 1) || ... || matches!(v, 100)` -//! - `matches!([v0], [p0, .., p1]) := false` (incompatible lengths) -//! - `matches!([v0, v1, v2], [p0, .., p1]) := matches!(v0, p0) && matches!(v2, p1)` -//! - `matches!(v, p0 | p1) := matches!(v, p0) || matches!(v, p1)` -//! -//! Constructors, fields and relevant operations are defined in the [`super::deconstruct_pat`] module. -//! -//! Note: this constructors/fields distinction may not straightforwardly apply to every Rust type. -//! For example a value of type `Rc<u64>` can't be deconstructed that way, and `&str` has an -//! infinitude of constructors. There are also subtleties with visibility of fields and -//! uninhabitedness and various other things. The constructors idea can be extended to handle most -//! of these subtleties though; caveats are documented where relevant throughout the code. -//! -//! Whether constructors cover each other is computed by [`Constructor::is_covered_by`]. -//! -//! -//! # Specialization -//! -//! Recall that we wish to compute `usefulness(p_1 .. p_n, q)`: given a list of patterns `p_1 .. -//! p_n` and a pattern `q`, all of the same type, we want to find a list of values (called -//! "witnesses") that are matched by `q` and by none of the `p_i`. We obviously don't just -//! enumerate all possible values. From the discussion above we see that we can proceed -//! ctor-by-ctor: for each value ctor of the given type, we ask "is there a value that starts with -//! this constructor and matches `q` and none of the `p_i`?". As we saw above, there's a lot we can -//! say from knowing only the first constructor of our candidate value. -//! -//! Let's take the following example: -//! ``` -//! match x { -//! Enum::Variant1(_) => {} // `p1` -//! Enum::Variant2(None, 0) => {} // `p2` -//! Enum::Variant2(Some(_), 0) => {} // `q` -//! } -//! ``` -//! -//! We can easily see that if our candidate value `v` starts with `Variant1` it will not match `q`. -//! If `v = Variant2(v0, v1)` however, whether or not it matches `p2` and `q` will depend on `v0` -//! and `v1`. In fact, such a `v` will be a witness of usefulness of `q` exactly when the tuple -//! `(v0, v1)` is a witness of usefulness of `q'` in the following reduced match: -//! -//! ``` -//! match x { -//! (None, 0) => {} // `p2'` -//! (Some(_), 0) => {} // `q'` -//! } -//! ``` -//! -//! This motivates a new step in computing usefulness, that we call _specialization_. -//! Specialization consist of filtering a list of patterns for those that match a constructor, and -//! then looking into the constructor's fields. This enables usefulness to be computed recursively. -//! -//! Instead of acting on a single pattern in each row, we will consider a list of patterns for each -//! row, and we call such a list a _pattern-stack_. The idea is that we will specialize the -//! leftmost pattern, which amounts to popping the constructor and pushing its fields, which feels -//! like a stack. We note a pattern-stack simply with `[p_1 ... p_n]`. -//! Here's a sequence of specializations of a list of pattern-stacks, to illustrate what's -//! happening: -//! ``` -//! [Enum::Variant1(_)] -//! [Enum::Variant2(None, 0)] -//! [Enum::Variant2(Some(_), 0)] -//! //==>> specialize with `Variant2` -//! [None, 0] -//! [Some(_), 0] -//! //==>> specialize with `Some` -//! [_, 0] -//! //==>> specialize with `true` (say the type was `bool`) -//! [0] -//! //==>> specialize with `0` -//! [] -//! ``` -//! -//! The function `specialize(c, p)` takes a value constructor `c` and a pattern `p`, and returns 0 -//! or more pattern-stacks. If `c` does not match the head constructor of `p`, it returns nothing; -//! otherwise if returns the fields of the constructor. This only returns more than one -//! pattern-stack if `p` has a pattern-only constructor. -//! -//! - Specializing for the wrong constructor returns nothing -//! -//! `specialize(None, Some(p0)) := []` -//! -//! - Specializing for the correct constructor returns a single row with the fields -//! -//! `specialize(Variant1, Variant1(p0, p1, p2)) := [[p0, p1, p2]]` -//! -//! `specialize(Foo{..}, Foo { bar: p0, baz: p1 }) := [[p0, p1]]` -//! -//! - For or-patterns, we specialize each branch and concatenate the results -//! -//! `specialize(c, p0 | p1) := specialize(c, p0) ++ specialize(c, p1)` -//! -//! - We treat the other pattern constructors as if they were a large or-pattern of all the -//! possibilities: -//! -//! `specialize(c, _) := specialize(c, Variant1(_) | Variant2(_, _) | ...)` -//! -//! `specialize(c, 1..=100) := specialize(c, 1 | ... | 100)` -//! -//! `specialize(c, [p0, .., p1]) := specialize(c, [p0, p1] | [p0, _, p1] | [p0, _, _, p1] | ...)` -//! -//! - If `c` is a pattern-only constructor, `specialize` is defined on a case-by-case basis. See -//! the discussion about constructor splitting in [`super::deconstruct_pat`]. -//! -//! -//! We then extend this function to work with pattern-stacks as input, by acting on the first -//! column and keeping the other columns untouched. -//! -//! Specialization for the whole matrix is done in [`Matrix::specialize_constructor`]. Note that -//! or-patterns in the first column are expanded before being stored in the matrix. Specialization -//! for a single patstack is done from a combination of [`Constructor::is_covered_by`] and -//! [`PatStack::pop_head_constructor`]. The internals of how it's done mostly live in the -//! [`Fields`] struct. -//! -//! -//! # Computing usefulness -//! -//! We now have all we need to compute usefulness. The inputs to usefulness are a list of -//! pattern-stacks `p_1 ... p_n` (one per row), and a new pattern_stack `q`. The paper and this -//! file calls the list of patstacks a _matrix_. They must all have the same number of columns and -//! the patterns in a given column must all have the same type. `usefulness` returns a (possibly -//! empty) list of witnesses of usefulness. These witnesses will also be pattern-stacks. -//! -//! - base case: `n_columns == 0`. -//! Since a pattern-stack functions like a tuple of patterns, an empty one functions like the -//! unit type. Thus `q` is useful iff there are no rows above it, i.e. if `n == 0`. -//! -//! - inductive case: `n_columns > 0`. -//! We need a way to list the constructors we want to try. We will be more clever in the next -//! section but for now assume we list all value constructors for the type of the first column. -//! -//! - for each such ctor `c`: -//! -//! - for each `q'` returned by `specialize(c, q)`: -//! -//! - we compute `usefulness(specialize(c, p_1) ... specialize(c, p_n), q')` -//! -//! - for each witness found, we revert specialization by pushing the constructor `c` on top. -//! -//! - We return the concatenation of all the witnesses found, if any. -//! -//! Example: -//! ``` -//! [Some(true)] // p_1 -//! [None] // p_2 -//! [Some(_)] // q -//! //==>> try `None`: `specialize(None, q)` returns nothing -//! //==>> try `Some`: `specialize(Some, q)` returns a single row -//! [true] // p_1' -//! [_] // q' -//! //==>> try `true`: `specialize(true, q')` returns a single row -//! [] // p_1'' -//! [] // q'' -//! //==>> base case; `n != 0` so `q''` is not useful. -//! //==>> go back up a step -//! [true] // p_1' -//! [_] // q' -//! //==>> try `false`: `specialize(false, q')` returns a single row -//! [] // q'' -//! //==>> base case; `n == 0` so `q''` is useful. We return the single witness `[]` -//! witnesses: -//! [] -//! //==>> undo the specialization with `false` -//! witnesses: -//! [false] -//! //==>> undo the specialization with `Some` -//! witnesses: -//! [Some(false)] -//! //==>> we have tried all the constructors. The output is the single witness `[Some(false)]`. -//! ``` -//! -//! This computation is done in [`is_useful`]. In practice we don't care about the list of -//! witnesses when computing reachability; we only need to know whether any exist. We do keep the -//! witnesses when computing exhaustiveness to report them to the user. -//! -//! -//! # Making usefulness tractable: constructor splitting -//! -//! We're missing one last detail: which constructors do we list? Naively listing all value -//! constructors cannot work for types like `u64` or `&str`, so we need to be more clever. The -//! first obvious insight is that we only want to list constructors that are covered by the head -//! constructor of `q`. If it's a value constructor, we only try that one. If it's a pattern-only -//! constructor, we use the final clever idea for this algorithm: _constructor splitting_, where we -//! group together constructors that behave the same. -//! -//! The details are not necessary to understand this file, so we explain them in -//! [`super::deconstruct_pat`]. Splitting is done by the [`Constructor::split`] function. - -use std::iter::once; - -use hir_def::{AdtId, DefWithBodyId, HasModule, ModuleId}; -use smallvec::{smallvec, SmallVec}; -use typed_arena::Arena; - -use crate::{db::HirDatabase, inhabitedness::is_ty_uninhabited_from, Ty, TyExt}; - -use super::deconstruct_pat::{Constructor, DeconstructedPat, Fields, SplitWildcard}; - -use self::{helper::Captures, ArmType::*, Usefulness::*}; - -pub(crate) struct MatchCheckCtx<'a, 'p> { - pub(crate) module: ModuleId, - pub(crate) body: DefWithBodyId, - pub(crate) db: &'a dyn HirDatabase, - /// Lowered patterns from arms plus generated by the check. - pub(crate) pattern_arena: &'p Arena<DeconstructedPat<'p>>, - exhaustive_patterns: bool, -} - -impl<'a, 'p> MatchCheckCtx<'a, 'p> { - pub(crate) fn new( - module: ModuleId, - body: DefWithBodyId, - db: &'a dyn HirDatabase, - pattern_arena: &'p Arena<DeconstructedPat<'p>>, - ) -> Self { - let def_map = db.crate_def_map(module.krate()); - let exhaustive_patterns = def_map.is_unstable_feature_enabled("exhaustive_patterns"); - Self { module, body, db, pattern_arena, exhaustive_patterns } - } - - pub(super) fn is_uninhabited(&self, ty: &Ty) -> bool { - if self.feature_exhaustive_patterns() { - is_ty_uninhabited_from(ty, self.module, self.db) - } else { - false - } - } - - /// Returns whether the given type is an enum from another crate declared `#[non_exhaustive]`. - pub(super) fn is_foreign_non_exhaustive_enum(&self, ty: &Ty) -> bool { - match ty.as_adt() { - Some((adt @ AdtId::EnumId(_), _)) => { - let has_non_exhaustive_attr = - self.db.attrs(adt.into()).by_key("non_exhaustive").exists(); - let is_local = adt.module(self.db.upcast()).krate() == self.module.krate(); - has_non_exhaustive_attr && !is_local - } - _ => false, - } - } - - // Rust's unstable feature described as "Allows exhaustive pattern matching on types that contain uninhabited types." - pub(super) fn feature_exhaustive_patterns(&self) -> bool { - self.exhaustive_patterns - } -} - -#[derive(Copy, Clone)] -pub(super) struct PatCtxt<'a, 'p> { - pub(super) cx: &'a MatchCheckCtx<'a, 'p>, - /// Type of the current column under investigation. - pub(super) ty: &'a Ty, - /// Whether the current pattern is the whole pattern as found in a match arm, or if it's a - /// subpattern. - pub(super) is_top_level: bool, - /// Whether the current pattern is from a `non_exhaustive` enum. - pub(super) is_non_exhaustive: bool, -} - -/// A row of a matrix. Rows of len 1 are very common, which is why `SmallVec[_; 2]` -/// works well. -#[derive(Clone)] -pub(super) struct PatStack<'p> { - pats: SmallVec<[&'p DeconstructedPat<'p>; 2]>, -} - -impl<'p> PatStack<'p> { - fn from_pattern(pat: &'p DeconstructedPat<'p>) -> Self { - Self::from_vec(smallvec![pat]) - } - - fn from_vec(vec: SmallVec<[&'p DeconstructedPat<'p>; 2]>) -> Self { - PatStack { pats: vec } - } - - fn is_empty(&self) -> bool { - self.pats.is_empty() - } - - fn len(&self) -> usize { - self.pats.len() - } - - fn head(&self) -> &'p DeconstructedPat<'p> { - self.pats[0] - } - - // Recursively expand the first pattern into its subpatterns. Only useful if the pattern is an - // or-pattern. Panics if `self` is empty. - fn expand_or_pat(&self) -> impl Iterator<Item = PatStack<'p>> + Captures<'_> { - self.head().iter_fields().map(move |pat| { - let mut new_patstack = PatStack::from_pattern(pat); - new_patstack.pats.extend_from_slice(&self.pats[1..]); - new_patstack - }) - } - - /// This computes `S(self.head().ctor(), self)`. See top of the file for explanations. - /// - /// Structure patterns with a partial wild pattern (Foo { a: 42, .. }) have their missing - /// fields filled with wild patterns. - /// - /// This is roughly the inverse of `Constructor::apply`. - fn pop_head_constructor(&self, cx: &MatchCheckCtx<'_, 'p>, ctor: &Constructor) -> PatStack<'p> { - // We pop the head pattern and push the new fields extracted from the arguments of - // `self.head()`. - let mut new_fields: SmallVec<[_; 2]> = self.head().specialize(cx, ctor); - new_fields.extend_from_slice(&self.pats[1..]); - PatStack::from_vec(new_fields) - } -} - -/// A 2D matrix. -#[derive(Clone)] -pub(super) struct Matrix<'p> { - patterns: Vec<PatStack<'p>>, -} - -impl<'p> Matrix<'p> { - fn empty() -> Self { - Matrix { patterns: vec![] } - } - - /// Number of columns of this matrix. `None` is the matrix is empty. - pub(super) fn _column_count(&self) -> Option<usize> { - self.patterns.first().map(|r| r.len()) - } - - /// Pushes a new row to the matrix. If the row starts with an or-pattern, this recursively - /// expands it. - fn push(&mut self, row: PatStack<'p>) { - if !row.is_empty() && row.head().is_or_pat() { - self.patterns.extend(row.expand_or_pat()); - } else { - self.patterns.push(row); - } - } - - /// Iterate over the first component of each row - fn heads(&self) -> impl Iterator<Item = &'p DeconstructedPat<'p>> + Clone + Captures<'_> { - self.patterns.iter().map(|r| r.head()) - } - - /// This computes `S(constructor, self)`. See top of the file for explanations. - fn specialize_constructor(&self, pcx: PatCtxt<'_, 'p>, ctor: &Constructor) -> Matrix<'p> { - let mut matrix = Matrix::empty(); - for row in &self.patterns { - if ctor.is_covered_by(pcx, row.head().ctor()) { - let new_row = row.pop_head_constructor(pcx.cx, ctor); - matrix.push(new_row); - } - } - matrix - } -} - -/// This carries the results of computing usefulness, as described at the top of the file. When -/// checking usefulness of a match branch, we use the `NoWitnesses` variant, which also keeps track -/// of potential unreachable sub-patterns (in the presence of or-patterns). When checking -/// exhaustiveness of a whole match, we use the `WithWitnesses` variant, which carries a list of -/// witnesses of non-exhaustiveness when there are any. -/// Which variant to use is dictated by `ArmType`. -enum Usefulness<'p> { - /// If we don't care about witnesses, simply remember if the pattern was useful. - NoWitnesses { useful: bool }, - /// Carries a list of witnesses of non-exhaustiveness. If empty, indicates that the whole - /// pattern is unreachable. - WithWitnesses(Vec<Witness<'p>>), -} - -impl<'p> Usefulness<'p> { - fn new_useful(preference: ArmType) -> Self { - match preference { - // A single (empty) witness of reachability. - FakeExtraWildcard => WithWitnesses(vec![Witness(vec![])]), - RealArm => NoWitnesses { useful: true }, - } - } - fn new_not_useful(preference: ArmType) -> Self { - match preference { - FakeExtraWildcard => WithWitnesses(vec![]), - RealArm => NoWitnesses { useful: false }, - } - } - - fn is_useful(&self) -> bool { - match self { - Usefulness::NoWitnesses { useful } => *useful, - Usefulness::WithWitnesses(witnesses) => !witnesses.is_empty(), - } - } - - /// Combine usefulnesses from two branches. This is an associative operation. - fn extend(&mut self, other: Self) { - match (&mut *self, other) { - (WithWitnesses(_), WithWitnesses(o)) if o.is_empty() => {} - (WithWitnesses(s), WithWitnesses(o)) if s.is_empty() => *self = WithWitnesses(o), - (WithWitnesses(s), WithWitnesses(o)) => s.extend(o), - (NoWitnesses { useful: s_useful }, NoWitnesses { useful: o_useful }) => { - *s_useful = *s_useful || o_useful - } - _ => unreachable!(), - } - } - - /// After calculating usefulness after a specialization, call this to reconstruct a usefulness - /// that makes sense for the matrix pre-specialization. This new usefulness can then be merged - /// with the results of specializing with the other constructors. - fn apply_constructor( - self, - pcx: PatCtxt<'_, 'p>, - matrix: &Matrix<'p>, - ctor: &Constructor, - ) -> Self { - match self { - NoWitnesses { .. } => self, - WithWitnesses(ref witnesses) if witnesses.is_empty() => self, - WithWitnesses(witnesses) => { - let new_witnesses = if let Constructor::Missing { .. } = ctor { - // We got the special `Missing` constructor, so each of the missing constructors - // gives a new pattern that is not caught by the match. We list those patterns. - let new_patterns = if pcx.is_non_exhaustive { - // Here we don't want the user to try to list all variants, we want them to add - // a wildcard, so we only suggest that. - vec![DeconstructedPat::wildcard(pcx.ty.clone())] - } else { - let mut split_wildcard = SplitWildcard::new(pcx); - split_wildcard.split(pcx, matrix.heads().map(DeconstructedPat::ctor)); - - // This lets us know if we skipped any variants because they are marked - // `doc(hidden)` or they are unstable feature gate (only stdlib types). - let mut hide_variant_show_wild = false; - // Construct for each missing constructor a "wild" version of this - // constructor, that matches everything that can be built with - // it. For example, if `ctor` is a `Constructor::Variant` for - // `Option::Some`, we get the pattern `Some(_)`. - let mut new: Vec<DeconstructedPat<'_>> = split_wildcard - .iter_missing(pcx) - .filter_map(|missing_ctor| { - // Check if this variant is marked `doc(hidden)` - if missing_ctor.is_doc_hidden_variant(pcx) - || missing_ctor.is_unstable_variant(pcx) - { - hide_variant_show_wild = true; - return None; - } - Some(DeconstructedPat::wild_from_ctor(pcx, missing_ctor.clone())) - }) - .collect(); - - if hide_variant_show_wild { - new.push(DeconstructedPat::wildcard(pcx.ty.clone())) - } - - new - }; - - witnesses - .into_iter() - .flat_map(|witness| { - new_patterns.iter().map(move |pat| { - Witness( - witness - .0 - .iter() - .chain(once(pat)) - .map(DeconstructedPat::clone_and_forget_reachability) - .collect(), - ) - }) - }) - .collect() - } else { - witnesses - .into_iter() - .map(|witness| witness.apply_constructor(pcx, ctor)) - .collect() - }; - WithWitnesses(new_witnesses) - } - } - } -} - -#[derive(Copy, Clone, Debug)] -enum ArmType { - FakeExtraWildcard, - RealArm, -} - -/// A witness of non-exhaustiveness for error reporting, represented -/// as a list of patterns (in reverse order of construction) with -/// wildcards inside to represent elements that can take any inhabitant -/// of the type as a value. -/// -/// A witness against a list of patterns should have the same types -/// and length as the pattern matched against. Because Rust `match` -/// is always against a single pattern, at the end the witness will -/// have length 1, but in the middle of the algorithm, it can contain -/// multiple patterns. -/// -/// For example, if we are constructing a witness for the match against -/// -/// ``` -/// struct Pair(Option<(u32, u32)>, bool); -/// -/// match (p: Pair) { -/// Pair(None, _) => {} -/// Pair(_, false) => {} -/// } -/// ``` -/// -/// We'll perform the following steps: -/// 1. Start with an empty witness -/// `Witness(vec![])` -/// 2. Push a witness `true` against the `false` -/// `Witness(vec![true])` -/// 3. Push a witness `Some(_)` against the `None` -/// `Witness(vec![true, Some(_)])` -/// 4. Apply the `Pair` constructor to the witnesses -/// `Witness(vec![Pair(Some(_), true)])` -/// -/// The final `Pair(Some(_), true)` is then the resulting witness. -pub(crate) struct Witness<'p>(Vec<DeconstructedPat<'p>>); - -impl<'p> Witness<'p> { - /// Asserts that the witness contains a single pattern, and returns it. - fn single_pattern(self) -> DeconstructedPat<'p> { - assert_eq!(self.0.len(), 1); - self.0.into_iter().next().unwrap() - } - - /// Constructs a partial witness for a pattern given a list of - /// patterns expanded by the specialization step. - /// - /// When a pattern P is discovered to be useful, this function is used bottom-up - /// to reconstruct a complete witness, e.g., a pattern P' that covers a subset - /// of values, V, where each value in that set is not covered by any previously - /// used patterns and is covered by the pattern P'. Examples: - /// - /// left_ty: tuple of 3 elements - /// pats: [10, 20, _] => (10, 20, _) - /// - /// left_ty: struct X { a: (bool, &'static str), b: usize} - /// pats: [(false, "foo"), 42] => X { a: (false, "foo"), b: 42 } - fn apply_constructor(mut self, pcx: PatCtxt<'_, 'p>, ctor: &Constructor) -> Self { - let pat = { - let len = self.0.len(); - let arity = ctor.arity(pcx); - let pats = self.0.drain((len - arity)..).rev(); - let fields = Fields::from_iter(pcx.cx, pats); - DeconstructedPat::new(ctor.clone(), fields, pcx.ty.clone()) - }; - - self.0.push(pat); - - self - } -} - -/// Algorithm from <http://moscova.inria.fr/~maranget/papers/warn/index.html>. -/// The algorithm from the paper has been modified to correctly handle empty -/// types. The changes are: -/// (0) We don't exit early if the pattern matrix has zero rows. We just -/// continue to recurse over columns. -/// (1) all_constructors will only return constructors that are statically -/// possible. E.g., it will only return `Ok` for `Result<T, !>`. -/// -/// This finds whether a (row) vector `v` of patterns is 'useful' in relation -/// to a set of such vectors `m` - this is defined as there being a set of -/// inputs that will match `v` but not any of the sets in `m`. -/// -/// All the patterns at each column of the `matrix ++ v` matrix must have the same type. -/// -/// This is used both for reachability checking (if a pattern isn't useful in -/// relation to preceding patterns, it is not reachable) and exhaustiveness -/// checking (if a wildcard pattern is useful in relation to a matrix, the -/// matrix isn't exhaustive). -/// -/// `is_under_guard` is used to inform if the pattern has a guard. If it -/// has one it must not be inserted into the matrix. This shouldn't be -/// relied on for soundness. -fn is_useful<'p>( - cx: &MatchCheckCtx<'_, 'p>, - matrix: &Matrix<'p>, - v: &PatStack<'p>, - witness_preference: ArmType, - is_under_guard: bool, - is_top_level: bool, -) -> Usefulness<'p> { - let Matrix { patterns: rows, .. } = matrix; - - // The base case. We are pattern-matching on () and the return value is - // based on whether our matrix has a row or not. - // NOTE: This could potentially be optimized by checking rows.is_empty() - // first and then, if v is non-empty, the return value is based on whether - // the type of the tuple we're checking is inhabited or not. - if v.is_empty() { - let ret = if rows.is_empty() { - Usefulness::new_useful(witness_preference) - } else { - Usefulness::new_not_useful(witness_preference) - }; - return ret; - } - - debug_assert!(rows.iter().all(|r| r.len() == v.len())); - - let ty = v.head().ty(); - let is_non_exhaustive = cx.is_foreign_non_exhaustive_enum(ty); - let pcx = PatCtxt { cx, ty, is_top_level, is_non_exhaustive }; - - // If the first pattern is an or-pattern, expand it. - let mut ret = Usefulness::new_not_useful(witness_preference); - if v.head().is_or_pat() { - // We try each or-pattern branch in turn. - let mut matrix = matrix.clone(); - for v in v.expand_or_pat() { - let usefulness = is_useful(cx, &matrix, &v, witness_preference, is_under_guard, false); - ret.extend(usefulness); - // If pattern has a guard don't add it to the matrix. - if !is_under_guard { - // We push the already-seen patterns into the matrix in order to detect redundant - // branches like `Some(_) | Some(0)`. - matrix.push(v); - } - } - } else { - let v_ctor = v.head().ctor(); - - // FIXME: implement `overlapping_range_endpoints` lint - - // We split the head constructor of `v`. - let split_ctors = v_ctor.split(pcx, matrix.heads().map(DeconstructedPat::ctor)); - // For each constructor, we compute whether there's a value that starts with it that would - // witness the usefulness of `v`. - let start_matrix = matrix; - for ctor in split_ctors { - // We cache the result of `Fields::wildcards` because it is used a lot. - let spec_matrix = start_matrix.specialize_constructor(pcx, &ctor); - let v = v.pop_head_constructor(cx, &ctor); - let usefulness = - is_useful(cx, &spec_matrix, &v, witness_preference, is_under_guard, false); - let usefulness = usefulness.apply_constructor(pcx, start_matrix, &ctor); - - // FIXME: implement `non_exhaustive_omitted_patterns` lint - - ret.extend(usefulness); - } - }; - - if ret.is_useful() { - v.head().set_reachable(); - } - - ret -} - -/// The arm of a match expression. -#[derive(Clone, Copy)] -pub(crate) struct MatchArm<'p> { - pub(crate) pat: &'p DeconstructedPat<'p>, - pub(crate) has_guard: bool, -} - -/// Indicates whether or not a given arm is reachable. -#[derive(Clone, Debug)] -pub(crate) enum Reachability { - /// The arm is reachable. This additionally carries a set of or-pattern branches that have been - /// found to be unreachable despite the overall arm being reachable. Used only in the presence - /// of or-patterns, otherwise it stays empty. - // FIXME: store unreachable subpattern IDs - Reachable, - /// The arm is unreachable. - Unreachable, -} - -/// The output of checking a match for exhaustiveness and arm reachability. -pub(crate) struct UsefulnessReport<'p> { - /// For each arm of the input, whether that arm is reachable after the arms above it. - pub(crate) _arm_usefulness: Vec<(MatchArm<'p>, Reachability)>, - /// If the match is exhaustive, this is empty. If not, this contains witnesses for the lack of - /// exhaustiveness. - pub(crate) non_exhaustiveness_witnesses: Vec<DeconstructedPat<'p>>, -} - -/// The entrypoint for the usefulness algorithm. Computes whether a match is exhaustive and which -/// of its arms are reachable. -/// -/// Note: the input patterns must have been lowered through -/// `check_match::MatchVisitor::lower_pattern`. -pub(crate) fn compute_match_usefulness<'p>( - cx: &MatchCheckCtx<'_, 'p>, - arms: &[MatchArm<'p>], - scrut_ty: &Ty, -) -> UsefulnessReport<'p> { - let mut matrix = Matrix::empty(); - let arm_usefulness = arms - .iter() - .copied() - .map(|arm| { - let v = PatStack::from_pattern(arm.pat); - is_useful(cx, &matrix, &v, RealArm, arm.has_guard, true); - if !arm.has_guard { - matrix.push(v); - } - let reachability = if arm.pat.is_reachable() { - Reachability::Reachable - } else { - Reachability::Unreachable - }; - (arm, reachability) - }) - .collect(); - - let wild_pattern = cx.pattern_arena.alloc(DeconstructedPat::wildcard(scrut_ty.clone())); - let v = PatStack::from_pattern(wild_pattern); - let usefulness = is_useful(cx, &matrix, &v, FakeExtraWildcard, false, true); - let non_exhaustiveness_witnesses = match usefulness { - WithWitnesses(pats) => pats.into_iter().map(Witness::single_pattern).collect(), - NoWitnesses { .. } => panic!("bug"), - }; - UsefulnessReport { _arm_usefulness: arm_usefulness, non_exhaustiveness_witnesses } -} - -pub(crate) mod helper { - // Copy-pasted from rust/compiler/rustc_data_structures/src/captures.rs - /// "Signaling" trait used in impl trait to tag lifetimes that you may - /// need to capture but don't really need for other reasons. - /// Basically a workaround; see [this comment] for details. - /// - /// [this comment]: https://github.com/rust-lang/rust/issues/34511#issuecomment-373423999 - // FIXME(eddyb) false positive, the lifetime parameter is "phantom" but needed. - #[allow(unused_lifetimes)] - pub(crate) trait Captures<'a> {} - - impl<'a, T: ?Sized> Captures<'a> for T {} -} diff --git a/crates/hir-ty/src/lib.rs b/crates/hir-ty/src/lib.rs index 19052a18b1..8d180f9861 100644 --- a/crates/hir-ty/src/lib.rs +++ b/crates/hir-ty/src/lib.rs @@ -15,6 +15,9 @@ extern crate rustc_abi; #[cfg(not(feature = "in-rust-tree"))] extern crate ra_ap_rustc_abi as rustc_abi; +// No need to use the in-tree one. +extern crate ra_ap_rustc_pattern_analysis as rustc_pattern_analysis; + mod builder; mod chalk_db; mod chalk_ext; diff --git a/crates/rust-analyzer/tests/slow-tests/tidy.rs b/crates/rust-analyzer/tests/slow-tests/tidy.rs index db192cf8fe..d3146ab767 100644 --- a/crates/rust-analyzer/tests/slow-tests/tidy.rs +++ b/crates/rust-analyzer/tests/slow-tests/tidy.rs @@ -154,6 +154,7 @@ fn check_licenses() { Apache-2.0 Apache-2.0 OR BSL-1.0 Apache-2.0 OR MIT +Apache-2.0 WITH LLVM-exception Apache-2.0 WITH LLVM-exception OR Apache-2.0 OR MIT Apache-2.0/MIT BSD-3-Clause |