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Change untagged_unions to not allow union fields with drop #56440

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Change untagged_unions to not allow union fields with drop #56440

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acf82c7
Change untagged_unions to not allow union fields with drop
bluss Dec 19, 2018
bfac2f7
Update libcore/std for union fields with drop
bluss Dec 19, 2018
d17e54f
Update tests for union fields with drop rule change
bluss Dec 19, 2018
776d5d4
Use union field's span and emit a note for helping about ManuallyDrop
bluss Dec 19, 2018
0950bdf
Update ui tests for union fields with drop rule change
bluss Dec 19, 2018
f4b2d71
Fix additional run-pass tests for no drop in union
bluss Dec 22, 2018
87c66a8
Add note to TyS::needs_drop about union dependency on it
bluss Jan 13, 2019
acd71e9
Update union ui tests for manuallydrop note change
bluss Jan 14, 2019
0eda54f
Update smallvec to 0.6.8
bluss Jan 20, 2019
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40 changes: 20 additions & 20 deletions Cargo.lock
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -363,7 +363,7 @@ dependencies = [
"semver 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
"serde 1.0.82 (registry+https://github.com/rust-lang/crates.io-index)",
"serde_derive 1.0.81 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
"toml 0.4.10 (registry+https://github.com/rust-lang/crates.io-index)",
"unicode-normalization 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
"url 1.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
Expand Down Expand Up @@ -517,7 +517,7 @@ dependencies = [
"crossbeam-utils 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
"parking_lot 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",
"rand 0.5.5 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
]

[[package]]
Expand Down Expand Up @@ -1551,7 +1551,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
dependencies = [
"libc 0.2.46 (registry+https://github.com/rust-lang/crates.io-index)",
"rand 0.5.5 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
"winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
]

Expand Down Expand Up @@ -2084,7 +2084,7 @@ dependencies = [
"rustc_target 0.0.0",
"scoped-tls 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
"serialize 0.0.0",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
"syntax 0.0.0",
"syntax_pos 0.0.0",
"tempfile 3.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
Expand Down Expand Up @@ -2128,7 +2128,7 @@ dependencies = [
"rustc-hash 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
"rustc-rayon 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
"rustc-rayon-core 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
"stable_deref_trait 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
]

Expand Down Expand Up @@ -2164,7 +2164,7 @@ name = "rustc-ap-serialize"
version = "306.0.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
dependencies = [
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
]

[[package]]
Expand All @@ -2180,7 +2180,7 @@ dependencies = [
"rustc-ap-serialize 306.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
"rustc-ap-syntax_pos 306.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
"scoped-tls 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
]

[[package]]
Expand Down Expand Up @@ -2266,7 +2266,7 @@ dependencies = [
"scopeguard 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
"serde 1.0.82 (registry+https://github.com/rust-lang/crates.io-index)",
"serde_json 1.0.33 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
"syn 0.15.22 (registry+https://github.com/rust-lang/crates.io-index)",
"winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
]
Expand All @@ -2280,7 +2280,7 @@ dependencies = [
"rustc_data_structures 0.0.0",
"rustc_errors 0.0.0",
"rustc_target 0.0.0",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
"syntax 0.0.0",
"syntax_pos 0.0.0",
]
Expand All @@ -2291,7 +2291,7 @@ version = "0.0.0"
dependencies = [
"bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
"rustc_cratesio_shim 0.0.0",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
]

[[package]]
Expand Down Expand Up @@ -2396,7 +2396,7 @@ dependencies = [
"rustc-rayon-core 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
"rustc_cratesio_shim 0.0.0",
"serialize 0.0.0",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
"stable_deref_trait 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
]

Expand Down Expand Up @@ -2429,7 +2429,7 @@ dependencies = [
"rustc_typeck 0.0.0",
"scoped-tls 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
"serialize 0.0.0",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
"syntax 0.0.0",
"syntax_ext 0.0.0",
"syntax_pos 0.0.0",
Expand Down Expand Up @@ -2535,7 +2535,7 @@ dependencies = [
"rustc_errors 0.0.0",
"rustc_target 0.0.0",
"serialize 0.0.0",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
"syntax 0.0.0",
"syntax_pos 0.0.0",
]
Expand Down Expand Up @@ -2653,7 +2653,7 @@ dependencies = [
"rustc 0.0.0",
"rustc_data_structures 0.0.0",
"rustc_target 0.0.0",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
"syntax 0.0.0",
"syntax_pos 0.0.0",
]
Expand All @@ -2680,7 +2680,7 @@ dependencies = [
"rustc_errors 0.0.0",
"rustc_platform_intrinsics 0.0.0",
"rustc_target 0.0.0",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
"syntax 0.0.0",
"syntax_pos 0.0.0",
]
Expand Down Expand Up @@ -2852,7 +2852,7 @@ dependencies = [
name = "serialize"
version = "0.0.0"
dependencies = [
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
]

[[package]]
Expand All @@ -2872,7 +2872,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"

[[package]]
name = "smallvec"
version = "0.6.7"
version = "0.6.8"
source = "registry+https://github.com/rust-lang/crates.io-index"
dependencies = [
"unreachable 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
Expand Down Expand Up @@ -3020,7 +3020,7 @@ dependencies = [
"rustc_target 0.0.0",
"scoped-tls 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
"serialize 0.0.0",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
"syntax_pos 0.0.0",
]

Expand All @@ -3033,7 +3033,7 @@ dependencies = [
"rustc_data_structures 0.0.0",
"rustc_errors 0.0.0",
"rustc_target 0.0.0",
"smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
"syntax 0.0.0",
"syntax_pos 0.0.0",
]
Expand Down Expand Up @@ -3619,7 +3619,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
"checksum shell-escape 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "170a13e64f2a51b77a45702ba77287f5c6829375b04a69cf2222acd17d0cfab9"
"checksum shlex 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7fdf1b9db47230893d76faad238fd6097fd6d6a9245cd7a4d90dbd639536bbd2"
"checksum siphasher 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "0df90a788073e8d0235a67e50441d47db7c8ad9debd91cbf43736a2a92d36537"
"checksum smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)" = "b73ea3738b47563803ef814925e69be00799a8c07420be8b996f8e98fb2336db"
"checksum smallvec 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)" = "88aea073965ab29f6edb5493faf96ad662fb18aa9eeb186a3b7057951605ed15"
"checksum socket2 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)" = "c4d11a52082057d87cb5caa31ad812f4504b97ab44732cd8359df2e9ff9f48e7"
"checksum stable_deref_trait 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ffbc596e092fe5f598b12ef46cc03754085ac2f4d8c739ad61c4ae266cc3b3fa"
"checksum string_cache 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)" = "25d70109977172b127fe834e5449e5ab1740b9ba49fa18a2020f509174f25423"
Expand Down
5 changes: 3 additions & 2 deletions src/libcore/slice/rotate.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@ use ptr;
union RawArray<T> {
/// Ensure this is appropriately aligned for T, and is big
/// enough for two elements even if T is enormous.
typed: [T; 2],
typed: [MaybeUninit<T>; 2],
/// For normally-sized types, especially things like u8, having more
/// than 2 in the buffer is necessary for usefulness, so pad it out
/// enough to be helpful, but not so big as to risk overflow.
Expand Down Expand Up @@ -73,7 +73,8 @@ pub unsafe fn ptr_rotate<T>(mut left: usize, mid: *mut T, mut right: usize) {
}

let mut rawarray = MaybeUninit::<RawArray<T>>::uninitialized();
let buf = &mut (*rawarray.as_mut_ptr()).typed as *mut [T; 2] as *mut T;
let buf = &mut (*rawarray.as_mut_ptr()).typed as *mut [MaybeUninit<T>; 2]
as *mut [T; 2] as *mut T;

let dim = mid.sub(left).add(right);
if left <= right {
Expand Down
2 changes: 1 addition & 1 deletion src/librustc/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,7 @@ parking_lot = "0.6"
byteorder = { version = "1.1", features = ["i128"]}
chalk-engine = { version = "0.9.0", default-features=false }
rustc_fs_util = { path = "../librustc_fs_util" }
smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
smallvec = { version = "0.6.8", features = ["union", "may_dangle"] }

# Note that these dependencies are a lie, they're just here to get linkage to
# work.
Expand Down
2 changes: 2 additions & 0 deletions src/librustc/ty/util.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -740,6 +740,8 @@ impl<'a, 'tcx> ty::TyS<'tcx> {
///
/// (Note that this implies that if `ty` has a destructor attached,
/// then `needs_drop` will definitely return `true` for `ty`.)
///
/// Note that this method is used to check eligible types in unions.
#[inline]
pub fn needs_drop(&'tcx self,
tcx: TyCtxt<'a, 'tcx, 'tcx>,
Expand Down
2 changes: 1 addition & 1 deletion src/librustc_allocator/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -16,4 +16,4 @@ rustc_target = { path = "../librustc_target" }
syntax = { path = "../libsyntax" }
syntax_pos = { path = "../libsyntax_pos" }
log = "0.4"
smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
smallvec = { version = "0.6.8", features = ["union", "may_dangle"] }
2 changes: 1 addition & 1 deletion src/librustc_apfloat/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -10,4 +10,4 @@ path = "lib.rs"
[dependencies]
bitflags = "1.0"
rustc_cratesio_shim = { path = "../librustc_cratesio_shim" }
smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
smallvec = { version = "0.6.8", features = ["union", "may_dangle"] }
2 changes: 1 addition & 1 deletion src/librustc_data_structures/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@ stable_deref_trait = "1.0.0"
rustc-rayon = "0.1.1"
rustc-rayon-core = "0.1.1"
rustc-hash = "1.0.1"
smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
smallvec = { version = "0.6.8", features = ["union", "may_dangle"] }

[dependencies.parking_lot]
version = "0.6"
Expand Down
2 changes: 1 addition & 1 deletion src/librustc_driver/Cargo.toml
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Expand Up @@ -35,6 +35,6 @@ rustc_codegen_utils = { path = "../librustc_codegen_utils" }
rustc_typeck = { path = "../librustc_typeck" }
serialize = { path = "../libserialize" }
syntax = { path = "../libsyntax" }
smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
smallvec = { version = "0.6.8", features = ["union", "may_dangle"] }
syntax_ext = { path = "../libsyntax_ext" }
syntax_pos = { path = "../libsyntax_pos" }
2 changes: 1 addition & 1 deletion src/librustc_mir/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -25,4 +25,4 @@ syntax = { path = "../libsyntax" }
syntax_pos = { path = "../libsyntax_pos" }
byteorder = { version = "1.1", features = ["i128"] }
rustc_apfloat = { path = "../librustc_apfloat" }
smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
smallvec = { version = "0.6.8", features = ["union", "may_dangle"] }
2 changes: 1 addition & 1 deletion src/librustc_traits/Cargo.toml
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Expand Up @@ -18,4 +18,4 @@ rustc_target = { path = "../librustc_target" }
syntax = { path = "../libsyntax" }
syntax_pos = { path = "../libsyntax_pos" }
chalk-engine = { version = "0.9.0", default-features=false }
smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
smallvec = { version = "0.6.8", features = ["union", "may_dangle"] }
2 changes: 1 addition & 1 deletion src/librustc_typeck/Cargo.toml
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Expand Up @@ -17,6 +17,6 @@ rustc_data_structures = { path = "../librustc_data_structures" }
rustc_errors = { path = "../librustc_errors" }
rustc_platform_intrinsics = { path = "../librustc_platform_intrinsics" }
rustc_target = { path = "../librustc_target" }
smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
smallvec = { version = "0.6.8", features = ["union", "may_dangle"] }
syntax = { path = "../libsyntax" }
syntax_pos = { path = "../libsyntax_pos" }
32 changes: 32 additions & 0 deletions src/librustc_typeck/check/mod.rs
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Expand Up @@ -1302,9 +1302,41 @@ fn check_union<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
def.destructor(tcx); // force the destructor to be evaluated
check_representable(tcx, span, def_id);

check_union_fields(tcx, span, def_id);
check_packed(tcx, span, def_id);
}

fn check_union_fields<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
_sp: Span,
item_def_id: DefId)
-> bool {
// Without the feature we check Copy types only later
if !tcx.features().untagged_unions {
return true;
}
let t = tcx.type_of(item_def_id);
if let ty::Adt(def, substs) = t.sty {
if def.is_union() {
let fields = &def.non_enum_variant().fields;
for field in fields {
let field_ty = field.ty(tcx, substs);
// We are currently checking the type this field came from, so it must be local
let field_span = tcx.hir().span_if_local(field.did).unwrap();
let param_env = tcx.param_env(field.did);
if field_ty.needs_drop(tcx, param_env) {
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Hmm. In general, the needs_drop accessor is a "heuristic", basically used for generating more efficient MIR. I guess though that it is relevant to our semantics in terms of the NLL borrow check as well. I think I might prefer if we made a "language definition" version of this function at some point -- or maybe for now it suffices to amend the rustc documentation for this function to note that it is used for checking union fields and the like.

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Great, updated docs. Yes, it seems like this method is sliding towards having to be more exact.

struct_span_err!(tcx.sess, field_span, E0730,
"unions may not contain fields that need dropping")
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Eventually, it would be nice if we could say with more detail which type needs to be dropped

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but I guess it doesn't have to be part of this PR

.span_note(field_span,
"`std::mem::ManuallyDrop` can be used to wrap the type")
.emit();
return false;
}
}
}
}
return true;
}

fn check_opaque<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
def_id: DefId,
Expand Down
4 changes: 4 additions & 0 deletions src/librustc_typeck/diagnostics.rs
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Expand Up @@ -4831,6 +4831,10 @@ fn make_recursive_type() -> impl Sized {
```
"##,

E0730: r##"
A `union` can not have fields with destructors.
"##,

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@bluss bluss Dec 19, 2018 •
edited
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Do we have a system for assigning error numbers? Yes, the text is a bit lacking here.

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We do not really have a system, no. You just pick one.

}

register_diagnostics! {
Expand Down
2 changes: 1 addition & 1 deletion src/libserialize/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -9,4 +9,4 @@ path = "lib.rs"
crate-type = ["dylib", "rlib"]

[dependencies]
smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
smallvec = { version = "0.6.8", features = ["union", "may_dangle"] }
14 changes: 7 additions & 7 deletions src/libstd/panicking.rs
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Expand Up @@ -16,7 +16,7 @@ use cell::RefCell;
use core::panic::{PanicInfo, Location};
use fmt;
use intrinsics;
use mem;
use mem::{self, ManuallyDrop};
use ptr;
use raw;
use sys::stdio::panic_output;
Expand Down Expand Up @@ -238,8 +238,8 @@ pub use realstd::rt::update_panic_count;
pub unsafe fn try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>> {
#[allow(unions_with_drop_fields)]
union Data<F, R> {
f: F,
r: R,
f: ManuallyDrop<F>,
r: ManuallyDrop<R>,
}

// We do some sketchy operations with ownership here for the sake of
Expand Down Expand Up @@ -270,7 +270,7 @@ pub unsafe fn try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>> {
let mut any_data = 0;
let mut any_vtable = 0;
let mut data = Data {
f,
f: ManuallyDrop::new(f)
};

let r = __rust_maybe_catch_panic(do_call::<F, R>,
Expand All @@ -280,7 +280,7 @@ pub unsafe fn try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>> {

return if r == 0 {
debug_assert!(update_panic_count(0) == 0);
Ok(data.r)
Ok(ManuallyDrop::into_inner(data.r))
} else {
update_panic_count(-1);
debug_assert!(update_panic_count(0) == 0);
Expand All @@ -293,8 +293,8 @@ pub unsafe fn try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>> {
fn do_call<F: FnOnce() -> R, R>(data: *mut u8) {
unsafe {
let data = data as *mut Data<F, R>;
let f = ptr::read(&mut (*data).f);
ptr::write(&mut (*data).r, f());
let f = ptr::read(&mut *(*data).f);
ptr::write(&mut *(*data).r, f());
}
}
}
Expand Down
2 changes: 1 addition & 1 deletion src/libsyntax/Cargo.toml
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Expand Up @@ -17,4 +17,4 @@ syntax_pos = { path = "../libsyntax_pos" }
rustc_errors = { path = "../librustc_errors" }
rustc_data_structures = { path = "../librustc_data_structures" }
rustc_target = { path = "../librustc_target" }
smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
smallvec = { version = "0.6.8", features = ["union", "may_dangle"] }
2 changes: 1 addition & 1 deletion src/libsyntax_ext/Cargo.toml
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Expand Up @@ -15,5 +15,5 @@ syntax = { path = "../libsyntax" }
syntax_pos = { path = "../libsyntax_pos" }
rustc_data_structures = { path = "../librustc_data_structures" }
rustc_target = { path = "../librustc_target" }
smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
smallvec = { version = "0.6.8", features = ["union", "may_dangle"] }
log = "0.4"
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