mirror of
https://github.com/rust-lang/rust-analyzer
synced 2024-12-26 21:13:37 +00:00
Auto merge of #16420 - Nadrieril:use-upstream-pattern-analysis, r=Veykril
Use upstream exhaustiveness checker! Because it has been librarified! The extra `Apache-2.0 WITH LLVM-exception` license is for `rustc_apfloat`. Also this duplicates `rustc_index` because the other upstream deps are still on an earlier version. They should be bumpable now though. Good thing is that we don't need this new crate to be synchronized with the others, which will make our lives easier.
This commit is contained in:
bors
commit
0d52934d19
11 changed files with 603 additions and 1952 deletions
100
Cargo.lock
generated
100
Cargo.lock
generated
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@ -166,7 +166,7 @@ checksum = "5676cea088c32290fe65c82895be9d06dd21e0fa49bb97ca840529e9417ab71a"
|
|||
dependencies = [
|
||||
"proc-macro2",
|
||||
"quote",
|
||||
"syn",
|
||||
"syn 2.0.39",
|
||||
"synstructure",
|
||||
]
|
||||
|
||||
|
|
@ -312,6 +312,17 @@ dependencies = [
|
|||
"parking_lot_core",
|
||||
]
|
||||
|
||||
[[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"
|
||||
|
|
@ -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",
|
||||
]
|
||||
|
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|
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@ -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",
|
||||
]
|
||||
|
||||
|
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@ -1455,10 +1490,24 @@ 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"
|
||||
|
|
@ -1593,7 +1642,7 @@ dependencies = [
|
|||
"heck",
|
||||
"proc-macro2",
|
||||
"quote",
|
||||
"syn",
|
||||
"syn 2.0.39",
|
||||
]
|
||||
|
||||
[[package]]
|
||||
|
|
@ -1608,6 +1657,16 @@ version = "1.1.0"
|
|||
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"
|
||||
|
|
@ -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"
|
||||
|
|
@ -1770,6 +1829,17 @@ dependencies = [
|
|||
"winapi",
|
||||
]
|
||||
|
||||
[[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"
|
||||
|
|
@ -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]]
|
||||
|
|
|
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|
|
@ -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.
|
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sourcegen = { path = "./crates/sourcegen" }
|
||||
|
|
|
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|
|
@ -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 {
|
||||
|
|
|
|||
|
|
@ -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
|
||||
|
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|
||||
# local deps
|
||||
|
|
|
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|
|
@ -11,6 +11,7 @@ use hir_def::{ItemContainerId, Lookup};
|
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use hir_expand::name;
|
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use itertools::Itertools;
|
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use rustc_hash::FxHashSet;
|
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use rustc_pattern_analysis::usefulness::{compute_match_usefulness, ValidityConstraint};
|
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use triomphe::Arc;
|
||||
use typed_arena::Arena;
|
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|
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|
|
@ -18,8 +19,7 @@ use crate::{
|
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db::HirDatabase,
|
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diagnostics::match_check::{
|
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self,
|
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deconstruct_pat::DeconstructedPat,
|
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usefulness::{compute_match_usefulness, MatchCheckCtx},
|
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pat_analysis::{self, DeconstructedPat, MatchCheckCtx, WitnessPat},
|
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},
|
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display::HirDisplay,
|
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InferenceResult, Ty, TyExt,
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|
|
@ -152,7 +152,14 @@ impl ExprValidator {
|
|||
}
|
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|
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let pattern_arena = Arena::new();
|
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let cx = MatchCheckCtx::new(self.owner.module(db.upcast()), self.owner, db, &pattern_arena);
|
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let ty_arena = Arena::new();
|
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let cx = MatchCheckCtx::new(
|
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self.owner.module(db.upcast()),
|
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self.owner,
|
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db,
|
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&pattern_arena,
|
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&ty_arena,
|
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);
|
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|
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let mut m_arms = Vec::with_capacity(arms.len());
|
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let mut has_lowering_errors = false;
|
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|
|
@ -178,9 +185,10 @@ impl ExprValidator {
|
|||
// If we had a NotUsefulMatchArm diagnostic, we could
|
||||
// check the usefulness of each pattern as we added it
|
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// to the matrix here.
|
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let m_arm = match_check::MatchArm {
|
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let m_arm = pat_analysis::MatchArm {
|
||||
pat: self.lower_pattern(&cx, arm.pat, db, &body, &mut has_lowering_errors),
|
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has_guard: arm.guard.is_some(),
|
||||
arm_data: (),
|
||||
};
|
||||
m_arms.push(m_arm);
|
||||
if !has_lowering_errors {
|
||||
|
|
@ -197,7 +205,15 @@ impl ExprValidator {
|
|||
return;
|
||||
}
|
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|
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let report = compute_match_usefulness(&cx, &m_arms, scrut_ty);
|
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let report = match compute_match_usefulness(
|
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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
|
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|
|
@ -213,7 +229,7 @@ impl ExprValidator {
|
|||
|
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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))
|
||||
}
|
||||
}
|
||||
|
|
|
|||
|
|
@ -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,
|
||||
|
|
|
|||
File diff suppressed because it is too large
Load diff
475
crates/hir-ty/src/diagnostics/match_check/pat_analysis.rs
Normal file
475
crates/hir-ty/src/diagnostics/match_check/pat_analysis.rs
Normal file
|
|
@ -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()
|
||||
}
|
||||
}
|
||||
|
|
@ -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 {}
|
||||
}
|
||||
|
|
@ -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;
|
||||
|
|
|
|||
|
|
@ -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
|
||||
|
|
|
|||
Loading…
Reference in a new issue