Implement the alternative `try` desugaring
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index 2be2fca..de2b850 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -1923,7 +1923,7 @@ fn lower_expr_for(
/// ControlFlow::Break(residual) =>
/// #[allow(unreachable_code)]
/// // If there is an enclosing `try {...}`:
- /// break 'catch_target Try::from_residual(residual),
+ /// break 'catch_target Residual::into_try_type(residual),
/// // Otherwise:
/// return Try::from_residual(residual),
/// }
@@ -1973,7 +1973,11 @@ fn lower_expr_try(&mut self, span: Span, sub_expr: &Expr) -> hir::ExprKind<'hir>
let (residual_local, residual_local_nid) = self.pat_ident(try_span, residual_ident);
let residual_expr = self.expr_ident_mut(try_span, residual_ident, residual_local_nid);
let from_residual_expr = self.wrap_in_try_constructor(
- hir::LangItem::TryTraitFromResidual,
+ if self.catch_scope.is_some() {
+ hir::LangItem::ResidualIntoTryType
+ } else {
+ hir::LangItem::TryTraitFromResidual
+ },
try_span,
self.arena.alloc(residual_expr),
unstable_span,
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 9cb17ea..1f36454 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -183,7 +183,12 @@ fn new(tcx: TyCtxt<'hir>, resolver: &'a mut ResolverAstLowering) -> Self {
impl_trait_defs: Vec::new(),
impl_trait_bounds: Vec::new(),
allow_contracts: [sym::contracts_internals].into(),
- allow_try_trait: [sym::try_trait_v2, sym::yeet_desugar_details].into(),
+ allow_try_trait: [
+ sym::try_trait_v2,
+ sym::try_trait_v2_residual,
+ sym::yeet_desugar_details,
+ ]
+ .into(),
allow_pattern_type: [sym::pattern_types, sym::pattern_type_range_trait].into(),
allow_gen_future: if tcx.features().async_fn_track_caller() {
[sym::gen_future, sym::closure_track_caller].into()
diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs
index e454ed5..0b236ce 100644
--- a/compiler/rustc_hir/src/lang_items.rs
+++ b/compiler/rustc_hir/src/lang_items.rs
@@ -372,6 +372,7 @@ pub fn extract(attrs: &[impl AttributeExt]) -> Option<(Symbol, Span)> {
TryTraitFromOutput, sym::from_output, from_output_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
TryTraitBranch, sym::branch, branch_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
TryTraitFromYeet, sym::from_yeet, from_yeet_fn, Target::Fn, GenericRequirement::None;
+ ResidualIntoTryType, sym::into_try_type, into_try_type_fn, Target::Method(MethodKind::Trait { body: true }), GenericRequirement::None;
CoercePointeeValidated, sym::coerce_pointee_validated, coerce_pointee_validated_trait, Target::Trait, GenericRequirement::Exact(0);
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index b6d1ff2..b3428fa 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1260,6 +1260,7 @@
into_async_iter_into_iter,
into_future,
into_iter,
+ into_try_type,
intra_doc_pointers,
intrinsics,
intrinsics_unaligned_volatile_load,
@@ -2280,6 +2281,7 @@
try_from_fn,
try_into,
try_trait_v2,
+ try_trait_v2_residual,
try_update,
tt,
tuple,
diff --git a/library/core/src/ops/try_trait.rs b/library/core/src/ops/try_trait.rs
index e1f2ebc..374e59e 100644
--- a/library/core/src/ops/try_trait.rs
+++ b/library/core/src/ops/try_trait.rs
@@ -359,11 +359,20 @@ pub fn from_yeet<T, Y>(yeeted: Y) -> T
/// and in the other direction,
/// `<Result<Infallible, E> as Residual<T>>::TryType = Result<T, E>`.
#[unstable(feature = "try_trait_v2_residual", issue = "91285")]
-#[rustc_const_unstable(feature = "const_try", issue = "74935")]
-pub const trait Residual<O> {
+#[rustc_const_unstable(feature = "const_try_residual", issue = "91285")]
+pub const trait Residual<O>: Sized {
/// The "return" type of this meta-function.
#[unstable(feature = "try_trait_v2_residual", issue = "91285")]
- type TryType: Try<Output = O, Residual = Self>;
+ type TryType: [const] Try<Output = O, Residual = Self>;
+
+ /// Here for convenience in the `?` desugaring.
+ /// Probably should not be stabilized, as it should never be overridden.
+ /// (without a `final fn` of some form, cc RFC#3678)
+ #[unstable(feature = "try_trait_v2_residual", issue = "91285")]
+ #[lang = "into_try_type"]
+ fn into_try_type(self) -> Self::TryType {
+ FromResidual::from_residual(self)
+ }
}
#[unstable(feature = "pub_crate_should_not_need_unstable_attr", issue = "none")]
diff --git a/library/std/src/sys/pal/unix/kernel_copy/tests.rs b/library/std/src/sys/pal/unix/kernel_copy/tests.rs
index 54d8f8e..15dee76 100644
--- a/library/std/src/sys/pal/unix/kernel_copy/tests.rs
+++ b/library/std/src/sys/pal/unix/kernel_copy/tests.rs
@@ -50,7 +50,7 @@ fn copy_specialization() -> Result<()> {
"inner Take allowed reading beyond end of file, some bytes should be left"
);
- let mut sink = sink.into_inner()?;
+ let mut sink = sink.into_inner().map_err(io::Error::from)?;
sink.seek(SeekFrom::Start(0))?;
let mut copied = Vec::new();
sink.read_to_end(&mut copied)?;
diff --git a/tests/mir-opt/pre-codegen/option_bubble_debug.option_traits.PreCodegen.after.panic-abort.mir b/tests/mir-opt/pre-codegen/option_bubble_debug.option_traits.PreCodegen.after.panic-abort.mir
index 5b40106..94c430e 100644
--- a/tests/mir-opt/pre-codegen/option_bubble_debug.option_traits.PreCodegen.after.panic-abort.mir
+++ b/tests/mir-opt/pre-codegen/option_bubble_debug.option_traits.PreCodegen.after.panic-abort.mir
@@ -34,7 +34,7 @@
}
bb3: {
- _0 = <Option<u32> as FromResidual<Option<Infallible>>>::from_residual(const Option::<Infallible>::None) -> [return: bb4, unwind unreachable];
+ _0 = <Option<Infallible> as Residual<u32>>::into_try_type(const Option::<Infallible>::None) -> [return: bb4, unwind unreachable];
}
bb4: {
diff --git a/tests/mir-opt/pre-codegen/option_bubble_debug.option_traits.PreCodegen.after.panic-unwind.mir b/tests/mir-opt/pre-codegen/option_bubble_debug.option_traits.PreCodegen.after.panic-unwind.mir
index bda9e9d..4305805 100644
--- a/tests/mir-opt/pre-codegen/option_bubble_debug.option_traits.PreCodegen.after.panic-unwind.mir
+++ b/tests/mir-opt/pre-codegen/option_bubble_debug.option_traits.PreCodegen.after.panic-unwind.mir
@@ -34,7 +34,7 @@
}
bb3: {
- _0 = <Option<u32> as FromResidual<Option<Infallible>>>::from_residual(const Option::<Infallible>::None) -> [return: bb4, unwind continue];
+ _0 = <Option<Infallible> as Residual<u32>>::into_try_type(const Option::<Infallible>::None) -> [return: bb4, unwind continue];
}
bb4: {
diff --git a/tests/ui/try-block/try-block-bad-type.rs b/tests/ui/try-block/try-block-bad-type.rs
index 00cd0af..c302496 100644
--- a/tests/ui/try-block/try-block-bad-type.rs
+++ b/tests/ui/try-block/try-block-bad-type.rs
@@ -4,7 +4,7 @@
pub fn main() {
let res: Result<u32, std::array::TryFromSliceError> = try {
- Err("")?; //~ ERROR `?` couldn't convert the error
+ Err("")?; //~ ERROR mismatched types
5
};
diff --git a/tests/ui/try-block/try-block-bad-type.stderr b/tests/ui/try-block/try-block-bad-type.stderr
index cf1cd60..9df01a4 100644
--- a/tests/ui/try-block/try-block-bad-type.stderr
+++ b/tests/ui/try-block/try-block-bad-type.stderr
@@ -1,16 +1,15 @@
-error[E0277]: `?` couldn't convert the error to `TryFromSliceError`
- --> $DIR/try-block-bad-type.rs:7:16
+error[E0308]: mismatched types
+ --> $DIR/try-block-bad-type.rs:7:9
|
LL | Err("")?;
- | -------^ the trait `From<&str>` is not implemented for `TryFromSliceError`
- | |
- | this can't be annotated with `?` because it has type `Result<_, &str>`
+ | ^^^^^^^^ expected `Result<u32, TryFromSliceError>`, found `Result<_, &str>`
|
- = note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
-help: the trait `From<&str>` is not implemented for `TryFromSliceError`
- but trait `From<Infallible>` is implemented for it
- --> $SRC_DIR/core/src/array/mod.rs:LL:COL
- = help: for that trait implementation, expected `Infallible`, found `&str`
+ = note: expected enum `Result<u32, TryFromSliceError>`
+ found enum `Result<_, &str>`
+help: consider using `Result::expect` to unwrap the `Result<_, &str>` value, panicking if the value is a `Result::Err`
+ |
+LL | Err("")?.expect("REASON");
+ | +++++++++++++++++
error[E0271]: type mismatch resolving `<Result<i32, i32> as Try>::Output == &str`
--> $DIR/try-block-bad-type.rs:12:9
@@ -42,5 +41,5 @@
error: aborting due to 5 previous errors
-Some errors have detailed explanations: E0271, E0277.
+Some errors have detailed explanations: E0271, E0277, E0308.
For more information about an error, try `rustc --explain E0271`.
