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Implement destructuring for all aggregates and for references

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This commit is contained in:
Oliver Scherer 2020-07-01 15:10:51 +02:00
parent 34c62e0abc
commit b2532a8730
18 changed files with 312 additions and 115 deletions
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3
compiler/rustc_mir/src/const_eval/mod.rs
View file

@ -93,8 +93,7 @@ pub(crate) fn deref_const<'tcx>(
MemPlaceMeta::None => mplace.layout.ty,
MemPlaceMeta::Poison => bug!("poison metadata in `deref_const`: {:#?}", mplace),
// In case of unsized types, figure out the real type behind.
MemPlaceMeta::Meta(scalar) => match mplace.layout.ty.kind {
ty::Dynamic(..) => ecx.read_drop_type_from_vtable(scalar).unwrap().1,
MemPlaceMeta::Meta(scalar) => match mplace.layout.ty.kind() {
ty::Str => bug!("there's no sized equivalent of a `str`"),
ty::Slice(elem_ty) => tcx.mk_array(elem_ty, scalar.to_machine_usize(&tcx).unwrap()),
_ => bug!(

35
compiler/rustc_mir_build/src/build/matches/test.rs
View file

@ -409,7 +409,40 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let deref_ty = match *ty.kind() {
ty::Ref(_, deref_ty, _) => deref_ty,
_ => bug!("non_scalar_compare called on non-reference type: {}", ty),
_ => {
trace!("non_scalar_compare called on non-reference type: {}", ty);
// Backcompat hack: due to non-structural matches not being a hard error, we can
// reach this for types that have manual `Eq` or `PartialEq` impls.
assert!(!ty.is_structural_eq_shallow(self.hir.tcx()));
let ref_ty = self.hir.tcx().mk_imm_ref(self.hir.tcx().lifetimes.re_erased, ty);
// let y = &place;
let y = self.temp(ref_ty, source_info.span);
self.cfg.push_assign(
block,
source_info,
y,
Rvalue::Ref(self.hir.tcx().lifetimes.re_erased, BorrowKind::Shared, place),
);
val = Operand::Move(y);
// let temp = expect;
let temp = self.temp(ty, source_info.span);
self.cfg.push_assign(
block,
source_info,
temp,
Rvalue::Use(expect),
);
// reftemp = &temp;
let reftemp = self.temp(ref_ty, source_info.span);
self.cfg.push_assign(
block,
source_info,
reftemp,
Rvalue::Ref(self.hir.tcx().lifetimes.re_erased, BorrowKind::Shared, temp),
);
expect = Operand::Move(reftemp);
ty
},
};
let eq_def_id = self.hir.tcx().require_lang_item(LangItem::PartialEq, None);

110
compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
View file

@ -28,10 +28,13 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
debug!("const_to_pat: cv={:#?} id={:?}", cv, id);
debug!("const_to_pat: cv.ty={:?} span={:?}", cv.ty, span);
self.tcx.infer_ctxt().enter(|infcx| {
let pat = self.tcx.infer_ctxt().enter(|infcx| {
let mut convert = ConstToPat::new(self, id, span, infcx);
convert.to_pat(cv, mir_structural_match_violation)
})
});
debug!("const_to_pat: pat={:?}", pat);
pat
}
}
@ -45,6 +48,10 @@ struct ConstToPat<'a, 'tcx> {
// value.
saw_const_match_error: Cell<bool>,
// For backcompat we need to keep allowing non-structurally-eq types behind references.
// See also all the `cant-hide-behind` tests.
behind_reference: Cell<bool>,
// inference context used for checking `T: Structural` bounds.
infcx: InferCtxt<'a, 'tcx>,
@ -65,6 +72,7 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
param_env: pat_ctxt.param_env,
include_lint_checks: pat_ctxt.include_lint_checks,
saw_const_match_error: Cell::new(false),
behind_reference: Cell::new(false),
}
}
@ -233,7 +241,18 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
tcx.sess.span_err(span, "cannot use unions in constant patterns");
PatKind::Wild
}
// keep old code until future-compat upgraded to errors.
// If the type is not structurally comparable, just emit the constant directly,
// causing the pattern match code to treat it opaquely.
// FIXME: This code doesn't emit errors itself, the caller emits the errors.
// So instead of specific errors, you just get blanket errors about the whole
// const type. See
// https://github.com/rust-lang/rust/pull/70743#discussion_r404701963 for
// details.
// Backwards compatibility hack because we can't cause hard errors on these
// types, so we compare them via `PartialEq::eq` at runtime.
ty::Adt(..) if !self.type_marked_structural(cv.ty) && self.behind_reference.get() => {
PatKind::Constant { value: cv }
}
ty::Adt(adt_def, _) if !self.type_marked_structural(cv.ty) => {
debug!("adt_def {:?} has !type_marked_structural for cv.ty: {:?}", adt_def, cv.ty);
let path = tcx.def_path_str(adt_def.did);
@ -246,28 +265,6 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
tcx.sess.span_err(span, &msg);
PatKind::Wild
}
// keep old code until future-compat upgraded to errors.
ty::Ref(_, adt_ty, _) if adt_ty.is_adt() && !self.type_marked_structural(adt_ty) => {
let adt_def =
if let ty::Adt(adt_def, _) = adt_ty.kind() { adt_def } else { unreachable!() };
debug!(
"adt_def {:?} has !type_marked_structural for adt_ty: {:?}",
adt_def, adt_ty
);
// HACK(estebank): Side-step ICE #53708, but anything other than erroring here
// would be wrong. Returnging `PatKind::Wild` is not technically correct.
let path = tcx.def_path_str(adt_def.did);
let msg = format!(
"to use a constant of type `{}` in a pattern, \
`{}` must be annotated with `#[derive(PartialEq, Eq)]`",
path, path,
);
self.saw_const_match_error.set(true);
tcx.sess.span_err(span, &msg);
PatKind::Wild
}
ty::Adt(adt_def, substs) if adt_def.is_enum() => {
let destructured = tcx.destructure_const(param_env.and(cv));
PatKind::Variant {
@ -293,7 +290,68 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
slice: None,
suffix: Vec::new(),
},
_ => PatKind::Constant { value: cv },
ty::Ref(_, pointee_ty, ..) => match *pointee_ty.kind() {
// These are not allowed and will error elsewhere anyway.
ty::Dynamic(..) => PatKind::Constant { value: cv },
// `&str` and `&[u8]` are represented as `ConstValue::Slice`, let's keep using this
// optimization for now.
ty::Str => PatKind::Constant { value: cv },
ty::Slice(elem_ty) if elem_ty == tcx.types.u8 => PatKind::Constant { value: cv },
// `b"foo"` produces a `&[u8; 3]`, but you can't use constants of array type when
// matching against references, you can only use byte string literals.
// FIXME: clean this up, likely by permitting array patterns when matching on slices
ty::Array(elem_ty, _) if elem_ty == tcx.types.u8 => PatKind::Constant { value: cv },
// Cannot merge this with the catch all branch below, because the `const_deref`
// changes the type from slice to array, and slice patterns behave differently from
// array patterns.
ty::Slice(..) => {
let old = self.behind_reference.replace(true);
let array = tcx.deref_const(self.param_env.and(cv));
let val = PatKind::Deref {
subpattern: Pat {
kind: Box::new(PatKind::Slice {
prefix: tcx
.destructure_const(param_env.and(array))
.fields
.iter()
.map(|val| self.recur(val))
.collect(),
slice: None,
suffix: vec![],
}),
span,
ty: pointee_ty,
},
};
self.behind_reference.set(old);
val
}
// Backwards compatibility hack. Don't take away the reference, since
// `PartialEq::eq` takes a reference, this makes the rest of the matching logic
// simpler.
ty::Adt(..) if !self.type_marked_structural(pointee_ty) => {
PatKind::Constant { value: cv }
}
_ => {
let old = self.behind_reference.replace(true);
let val = PatKind::Deref {
subpattern: self.recur(tcx.deref_const(self.param_env.and(cv))),
};
self.behind_reference.set(old);
val
}
},
ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::FnDef(..) => {
PatKind::Constant { value: cv }
}
// FIXME: these can have very suprising behaviour where optimization levels or other
// compilation choices change the runtime behaviour of the match.
// See https://github.com/rust-lang/rust/issues/70861 for examples.
ty::FnPtr(..) | ty::RawPtr(..) => PatKind::Constant { value: cv },
_ => {
tcx.sess.delay_span_bug(span, &format!("cannot make a pattern out of {}", cv.ty));
PatKind::Wild
}
};
Pat { span, ty: cv.ty, kind: Box::new(kind) }

2
library/std/src/ffi/os_str.rs
View file

@ -94,7 +94,7 @@ pub struct OsString {
// `OsStr::from_inner` current implementation relies
// on `OsStr` being layout-compatible with `Slice`.
// When attribute privacy is implemented, `OsStr` should be annotated as `#[repr(transparent)]`.
// Anyway, `OsStr` representation and layout are considered implementation detail, are
// Anyway, `OsStr` representation and layout are considered implementation details, are
// not documented and must not be relied upon.
pub struct OsStr {
inner: Slice,

2
src/test/ui/consts/consts-in-patterns.rs
View file

@ -19,8 +19,6 @@ pub fn main() {
assert_eq!(y, 2);
let z = match &() {
ZST => 9,
// FIXME: this should not be required
_ => 42,
};
assert_eq!(z, 9);
let z = match b"" {

3
src/test/ui/consts/match_ice.rs
View file

@ -10,10 +10,9 @@ fn main() {
match C {
C => {}
//~^ ERROR to use a constant of type `S` in a pattern, `S` must be annotated with
//~| ERROR to use a constant of type `S` in a pattern, `S` must be annotated with
}
const K: &T = &T;
match K { //~ ERROR non-exhaustive patterns: `&T` not covered
match K {
K => {}
}
}

21
src/test/ui/consts/match_ice.stderr
View file

@ -4,24 +4,5 @@ error: to use a constant of type `S` in a pattern, `S` must be annotated with `#
LL | C => {}
| ^
error[E0004]: non-exhaustive patterns: `&T` not covered
--> $DIR/match_ice.rs:16:11
|
LL | struct T;
| --------- `T` defined here
...
LL | match K {
| ^ pattern `&T` not covered
|
= help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
= note: the matched value is of type `&T`
error: aborting due to previous error
error: to use a constant of type `S` in a pattern, `S` must be annotated with `#[derive(PartialEq, Eq)]`
--> $DIR/match_ice.rs:11:9
|
LL | C => {}
| ^
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0004`.

46
src/test/ui/match/pattern-deref-miscompile.rs Normal file
View file

@ -0,0 +1,46 @@
// run-pass
fn main() {
match b"." as &[u8] {
b"." if true => {},
b"." => panic!(),
b".." => panic!(),
b"" => panic!(),
_ => panic!(),
}
match b"." as &[u8] {
b"." if false => panic!(),
b"." => {},
b".." => panic!(),
b"" => panic!(),
_ => panic!(),
}
match b".." as &[u8] {
b"." if true => panic!(), // the miscompile caused this arm to be reached
b"." => panic!(),
b".." => {},
b"" => panic!(),
_ => panic!(),
}
match b".." as &[u8] {
b"." if false => panic!(),
b"." => panic!(),
b".." => {},
b"" => panic!(),
_ => panic!(),
}
match b"" as &[u8] {
b"." if true => panic!(),
b"." => panic!(),
b".." => panic!(),
b"" => {},
_ => panic!(),
}
match b"" as &[u8] {
b"." if false => panic!(),
b"." => panic!(),
b".." => panic!(),
b"" => {},
_ => panic!(),
}
}

8
src/test/ui/pattern/const-pat-ice.rs
View file

@ -1,10 +1,4 @@
// failure-status: 101
// rustc-env:RUST_BACKTRACE=0
// normalize-stderr-test "note: rustc 1.* running on .*" -> "note: rustc VERSION running on TARGET"
// normalize-stderr-test "note: compiler flags: .*" -> "note: compiler flags: FLAGS"
// normalize-stderr-test "/_match.rs:[0-9]+:[0-9]+" -> "/_match.rs:LL:CC"
// This is a repro test for an ICE in our pattern handling of constants.
// check-pass
const FOO: &&&u32 = &&&42;

13
src/test/ui/pattern/const-pat-ice.stderr
View file

@ -1,13 +0,0 @@
thread 'rustc' panicked at 'assertion failed: rows.iter().all(|r| r.len() == v.len())', compiler/rustc_mir_build/src/thir/pattern/_match.rs:LL:CC
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md
note: rustc VERSION running on TARGET
note: compiler flags: FLAGS

2
src/test/ui/pattern/usefulness/exhaustive_integer_patterns.rs
View file

@ -160,7 +160,7 @@ fn main() {
match &0 {
&42 => {}
&FOO => {} //~ ERROR unreachable pattern
BAR => {} // Not detected as unreachable because `try_eval_bits` fails on `BAR`.
BAR => {} //~ ERROR unreachable pattern
_ => {}
}

8
src/test/ui/pattern/usefulness/exhaustive_integer_patterns.stderr
View file

@ -135,6 +135,12 @@ error: unreachable pattern
LL | &FOO => {}
| ^^^^
error: aborting due to 15 previous errors
error: unreachable pattern
--> $DIR/exhaustive_integer_patterns.rs:163:9
|
LL | BAR => {}
| ^^^
error: aborting due to 16 previous errors
For more information about this error, try `rustc --explain E0004`.

6
src/test/ui/pattern/usefulness/slice-pattern-const-2.rs
View file

@ -6,19 +6,19 @@ fn main() {
match s {
MAGIC_TEST => (),
[0x00, 0x00, 0x00, 0x00] => (),
[4, 5, 6, 7] => (), // FIXME(oli-obk): this should warn, but currently does not
[4, 5, 6, 7] => (), //~ ERROR unreachable pattern
_ => (),
}
match s {
[0x00, 0x00, 0x00, 0x00] => (),
MAGIC_TEST => (),
[4, 5, 6, 7] => (), // FIXME(oli-obk): this should warn, but currently does not
[4, 5, 6, 7] => (), //~ ERROR unreachable pattern
_ => (),
}
match s {
[0x00, 0x00, 0x00, 0x00] => (),
[4, 5, 6, 7] => (),
MAGIC_TEST => (), // FIXME(oli-obk): this should warn, but currently does not
MAGIC_TEST => (), //~ ERROR unreachable pattern
_ => (),
}
const FOO: [u32; 1] = [4];

26
src/test/ui/pattern/usefulness/slice-pattern-const-2.stderr
View file

@ -1,8 +1,8 @@
error: unreachable pattern
--> $DIR/slice-pattern-const-2.rs:28:9
--> $DIR/slice-pattern-const-2.rs:9:9
|
LL | FOO => (),
| ^^^
LL | [4, 5, 6, 7] => (),
| ^^^^^^^^^^^^
|
note: the lint level is defined here
--> $DIR/slice-pattern-const-2.rs:1:9
@ -10,5 +10,23 @@ note: the lint level is defined here
LL | #![deny(unreachable_patterns)]
| ^^^^^^^^^^^^^^^^^^^^
error: aborting due to previous error
error: unreachable pattern
--> $DIR/slice-pattern-const-2.rs:15:9
|
LL | [4, 5, 6, 7] => (),
| ^^^^^^^^^^^^
error: unreachable pattern
--> $DIR/slice-pattern-const-2.rs:21:9
|
LL | MAGIC_TEST => (),
| ^^^^^^^^^^
error: unreachable pattern
--> $DIR/slice-pattern-const-2.rs:28:9
|
LL | FOO => (),
| ^^^
error: aborting due to 4 previous errors

6
src/test/ui/pattern/usefulness/slice-pattern-const-3.rs
View file

@ -6,19 +6,19 @@ fn main() {
match s {
MAGIC_TEST => (),
["0x00", "0x00", "0x00", "0x00"] => (),
["4", "5", "6", "7"] => (), // FIXME(oli-obk): this should warn, but currently does not
["4", "5", "6", "7"] => (), //~ ERROR unreachable pattern
_ => (),
}
match s {
["0x00", "0x00", "0x00", "0x00"] => (),
MAGIC_TEST => (),
["4", "5", "6", "7"] => (), // FIXME(oli-obk): this should warn, but currently does not
["4", "5", "6", "7"] => (), //~ ERROR unreachable pattern
_ => (),
}
match s {
["0x00", "0x00", "0x00", "0x00"] => (),
["4", "5", "6", "7"] => (),
MAGIC_TEST => (), // FIXME(oli-obk): this should warn, but currently does not
MAGIC_TEST => (), //~ ERROR unreachable pattern
_ => (),
}
const FOO: [&str; 1] = ["boo"];

26
src/test/ui/pattern/usefulness/slice-pattern-const-3.stderr
View file

@ -1,8 +1,8 @@
error: unreachable pattern
--> $DIR/slice-pattern-const-3.rs:28:9
--> $DIR/slice-pattern-const-3.rs:9:9
|
LL | FOO => (),
| ^^^
LL | ["4", "5", "6", "7"] => (),
| ^^^^^^^^^^^^^^^^^^^^
|
note: the lint level is defined here
--> $DIR/slice-pattern-const-3.rs:1:9
@ -10,5 +10,23 @@ note: the lint level is defined here
LL | #![deny(unreachable_patterns)]
| ^^^^^^^^^^^^^^^^^^^^
error: aborting due to previous error
error: unreachable pattern
--> $DIR/slice-pattern-const-3.rs:15:9
|
LL | ["4", "5", "6", "7"] => (),
| ^^^^^^^^^^^^^^^^^^^^
error: unreachable pattern
--> $DIR/slice-pattern-const-3.rs:21:9
|
LL | MAGIC_TEST => (),
| ^^^^^^^^^^
error: unreachable pattern
--> $DIR/slice-pattern-const-3.rs:28:9
|
LL | FOO => (),
| ^^^
error: aborting due to 4 previous errors

34
src/test/ui/pattern/usefulness/slice-patterns-exhaustiveness.rs
View file

@ -83,14 +83,38 @@ fn main() {
const CONST: &[bool] = &[true];
match s {
//~^ ERROR `&[..]` not covered
//~^ ERROR `&[]` and `&[_, _, ..]` not covered
&[true] => {}
}
match s {
//~^ ERROR `&[]` and `&[_, _, ..]` not covered
CONST => {}
}
match s {
//~^ ERROR `&[true]` not covered
[] => {},
[false] => {},
CONST => {},
//~^ ERROR `&[]` and `&[_, _, ..]` not covered
CONST => {}
&[false] => {}
}
match s {
//~^ ERROR `&[]` and `&[_, _, ..]` not covered
&[false] => {}
CONST => {}
}
match s {
//~^ ERROR `&[_, _, ..]` not covered
&[] => {}
CONST => {}
}
match s {
//~^ ERROR `&[false]` not covered
&[] => {}
CONST => {}
&[_, _, ..] => {}
}
match s {
[] => {}
[false] => {}
CONST => {}
[_, _, ..] => {}
}
const CONST1: &[bool; 1] = &[true];

48
src/test/ui/pattern/usefulness/slice-patterns-exhaustiveness.stderr
View file

@ -115,26 +115,62 @@ LL | match s {
= help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
= note: the matched value is of type `&[bool]`
error[E0004]: non-exhaustive patterns: `&[..]` not covered
error[E0004]: non-exhaustive patterns: `&[]` and `&[_, _, ..]` not covered
--> $DIR/slice-patterns-exhaustiveness.rs:85:11
|
LL | match s {
| ^ pattern `&[..]` not covered
| ^ patterns `&[]` and `&[_, _, ..]` not covered
|
= help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
= note: the matched value is of type `&[bool]`
error[E0004]: non-exhaustive patterns: `&[true]` not covered
error[E0004]: non-exhaustive patterns: `&[]` and `&[_, _, ..]` not covered
--> $DIR/slice-patterns-exhaustiveness.rs:89:11
|
LL | match s {
| ^ pattern `&[true]` not covered
| ^ patterns `&[]` and `&[_, _, ..]` not covered
|
= help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
= note: the matched value is of type `&[bool]`
error[E0004]: non-exhaustive patterns: `&[]` and `&[_, _, ..]` not covered
--> $DIR/slice-patterns-exhaustiveness.rs:93:11
|
LL | match s {
| ^ patterns `&[]` and `&[_, _, ..]` not covered
|
= help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
= note: the matched value is of type `&[bool]`
error[E0004]: non-exhaustive patterns: `&[]` and `&[_, _, ..]` not covered
--> $DIR/slice-patterns-exhaustiveness.rs:98:11
|
LL | match s {
| ^ patterns `&[]` and `&[_, _, ..]` not covered
|
= help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
= note: the matched value is of type `&[bool]`
error[E0004]: non-exhaustive patterns: `&[_, _, ..]` not covered
--> $DIR/slice-patterns-exhaustiveness.rs:103:11
|
LL | match s {
| ^ pattern `&[_, _, ..]` not covered
|
= help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
= note: the matched value is of type `&[bool]`
error[E0004]: non-exhaustive patterns: `&[false]` not covered
--> $DIR/slice-patterns-exhaustiveness.rs:97:11
--> $DIR/slice-patterns-exhaustiveness.rs:108:11
|
LL | match s {
| ^ pattern `&[false]` not covered
|
= help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
= note: the matched value is of type `&[bool]`
error[E0004]: non-exhaustive patterns: `&[false]` not covered
--> $DIR/slice-patterns-exhaustiveness.rs:121:11
|
LL | match s1 {
| ^^ pattern `&[false]` not covered
@ -142,6 +178,6 @@ LL | match s1 {
= help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
= note: the matched value is of type `&[bool; 1]`
error: aborting due to 16 previous errors
error: aborting due to 20 previous errors
For more information about this error, try `rustc --explain E0004`.