split try trait in twain

Author: bend-n

compiler/rustc_ast_lowering/src/expr.rs

@@ -564,8 +564,8 @@ impl<'hir, R: ResolverAstLoweringExt<'hir>> LoweringContext<'_, 'hir, R> {
         hir::ExprKind::Loop(block, opt_label, hir::LoopSource::While, span)
     }
 
-    /// Desugar `try { <stmts>; <expr> }` into `{ <stmts>; ::std::ops::Try::from_output(<expr>) }`,
-    /// `try { <stmts>; }` into `{ <stmts>; ::std::ops::Try::from_output(()) }`
+    /// Desugar `try { <stmts>; <expr> }` into `{ <stmts>; ::std::ops::FromOutput::from_output(<expr>) }`,
+    /// `try { <stmts>; }` into `{ <stmts>; ::std::ops::FromOutput::from_output(()) }`
     /// and save the block id to use it as a break target for desugaring of the `?` operator.
     fn lower_expr_try_block(&mut self, body: &Block, opt_ty: Option<&Ty>) -> hir::ExprKind<'hir> {
         let body_hir_id = self.lower_node_id(body.id);
@@ -600,7 +600,7 @@ impl<'hir, R: ResolverAstLoweringExt<'hir>> LoweringContext<'_, 'hir, R> {
             let ok_wrapped_span =
                 this.mark_span_with_reason(DesugaringKind::TryBlock, tail_expr.span, None);
 
-            // `::std::ops::Try::from_output($tail_expr)`
+            // `::std::ops::FromOutput::from_output($tail_expr)`
             block.expr = Some(this.wrap_in_try_constructor(
                 hir::LangItem::TryTraitFromOutput,
                 try_span,

compiler/rustc_middle/src/mir/interpret/error.rs

@@ -941,7 +941,7 @@ pub struct InterpResult<'tcx, T = ()> {
     res: Result<T, InterpErrorInfo<'tcx>>,
     guard: Guard,
 }
-
+#[cfg(bootstrap)]
 impl<'tcx, T> ops::Try for InterpResult<'tcx, T> {
     type Output = T;
     type Residual = InterpResult<'tcx, convert::Infallible>;
@@ -959,6 +959,26 @@ impl<'tcx, T> ops::Try for InterpResult<'tcx, T> {
         }
     }
 }
+#[cfg(not(bootstrap))]
+impl<'tcx, T> ops::Branch for InterpResult<'tcx, T> {
+    type Output = T;
+    type Residual = InterpResult<'tcx, convert::Infallible>;
+
+    #[inline]
+    fn branch(self) -> ops::ControlFlow<Self::Residual, Self::Output> {
+        match self.disarm() {
+            Ok(v) => ops::ControlFlow::Continue(v),
+            Err(e) => ops::ControlFlow::Break(InterpResult::new(Err(e))),
+        }
+    }
+}
+#[cfg(not(bootstrap))]
+impl<'tcx, T> ops::FromOutput for InterpResult<'tcx, T> {
+    #[inline]
+    fn from_output(output: Self::Output) -> Self {
+        InterpResult::new(Ok(output))
+    }
+}
 
 impl<'tcx, T> ops::Residual<T> for InterpResult<'tcx, convert::Infallible> {
     type TryType = InterpResult<'tcx, T>;

compiler/rustc_span/src/symbol.rs

@@ -225,6 +225,7 @@ symbols! {
         Forward,
         From,
         FromIterator,
+        FromOutput,
         FromResidual,
         GlobalAlloc,
         Hash,

compiler/rustc_trait_selection/src/error_reporting/traits/call_kind.rs

@@ -32,9 +32,8 @@ impl CallDesugaringKind {
         match self {
             Self::ForLoopIntoIter => tcx.get_diagnostic_item(sym::IntoIterator).unwrap(),
             Self::ForLoopNext => tcx.require_lang_item(LangItem::Iterator, DUMMY_SP),
-            Self::QuestionBranch | Self::TryBlockFromOutput => {
-                tcx.require_lang_item(LangItem::Try, DUMMY_SP)
-            }
+            Self::TryBlockFromOutput => tcx.get_diagnostic_item(sym::FromOutput).unwrap(),
+            Self::QuestionBranch => tcx.require_lang_item(LangItem::Try, DUMMY_SP),
             Self::QuestionFromResidual => tcx.get_diagnostic_item(sym::FromResidual).unwrap(),
             Self::Await => tcx.get_diagnostic_item(sym::IntoFuture).unwrap(),
         }

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -207,6 +207,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             ObligationCauseCode::QuestionMark,
                         ) && !(
                             self.tcx.is_diagnostic_item(sym::FromResidual, main_trait_predicate.def_id())
+                            || self.tcx.is_diagnostic_item(sym::FromOutput, main_trait_predicate.def_id())
                                 || self.tcx.is_lang_item(main_trait_predicate.def_id(), LangItem::Try)
                         );
                         let is_unsize =
@@ -392,6 +393,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                                 // `std::marker::Sized` is not implemented for `T`" as we will point
                                 // at the type param with a label to suggest constraining it.
                                 && !self.tcx.is_diagnostic_item(sym::FromResidual, leaf_trait_predicate.def_id())
+                                && !self.tcx.is_diagnostic_item(sym::FromOutput, leaf_trait_predicate.def_id())
                                     // Don't say "the trait `FromResidual<Option<Infallible>>` is
                                     // not implemented for `Result<T, E>`".
                             {
@@ -2214,7 +2216,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 candidates = specific_candidates;
             }
             if let &[(cand, def_id)] = &candidates[..] {
-                if self.tcx.is_diagnostic_item(sym::FromResidual, cand.def_id)
+                if (self.tcx.is_diagnostic_item(sym::FromResidual, cand.def_id)
+                    || self.tcx.is_diagnostic_item(sym::FromOutput, cand.def_id))
                     && !self.tcx.features().enabled(sym::try_trait_v2)
                 {
                     return false;

compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs

@@ -3852,8 +3852,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 let mut parent_trait_pred =
                     self.resolve_vars_if_possible(data.derived.parent_trait_pred);
                 let parent_def_id = parent_trait_pred.def_id();
-                if tcx.is_diagnostic_item(sym::FromResidual, parent_def_id)
-                    && !tcx.features().enabled(sym::try_trait_v2)
+                if (self.tcx.is_diagnostic_item(sym::FromResidual, parent_def_id)
+                    || self.tcx.is_diagnostic_item(sym::FromOutput, parent_def_id))
+                    && !self.tcx.features().enabled(sym::try_trait_v2)
                 {
                     // If `#![feature(try_trait_v2)]` is not enabled, then there's no point on
                     // talking about `FromResidual<Result<A, B>>`, as the end user has nothing they

library/core/src/iter/adapters/mod.rs

@@ -1,6 +1,6 @@
 use crate::iter::InPlaceIterable;
 use crate::num::NonZero;
-use crate::ops::{ChangeOutputType, ControlFlow, FromResidual, Residual, Try};
+use crate::ops::{Branch, ChangeOutputType, ControlFlow, FromOutput, FromResidual, Residual, Try};
 
 mod array_chunks;
 mod by_ref_sized;
@@ -163,15 +163,15 @@ where
     let value = f(shunt);
     match residual {
         Some(r) => FromResidual::from_residual(r),
-        None => Try::from_output(value),
+        None => FromOutput::from_output(value),
     }
 }
 
 impl<I, R> Iterator for GenericShunt<'_, I, R>
 where
     I: Iterator<Item: Try<Residual = R>>,
 {
-    type Item = <I::Item as Try>::Output;
+    type Item = <I::Item as Branch>::Output;
 
     fn next(&mut self) -> Option<Self::Item> {
         self.try_for_each(ControlFlow::Break).break_value()
@@ -192,7 +192,7 @@ where
         T: Try<Output = B>,
     {
         self.iter
-            .try_fold(init, |acc, x| match Try::branch(x) {
+            .try_fold(init, |acc, x| match x.branch() {
                 ControlFlow::Continue(x) => ControlFlow::from_try(f(acc, x)),
                 ControlFlow::Break(r) => {
                     *self.residual = Some(r);

library/core/src/iter/traits/iterator.rs

@@ -9,7 +9,7 @@ use crate::array;
 use crate::cmp::{self, Ordering};
 use crate::marker::Destruct;
 use crate::num::NonZero;
-use crate::ops::{ChangeOutputType, ControlFlow, FromResidual, Residual, Try};
+use crate::ops::{Branch, ChangeOutputType, ControlFlow, FromOutput, FromResidual, Residual, Try};
 
 fn _assert_is_dyn_compatible(_: &dyn Iterator<Item = ()>) {}
 
@@ -2168,7 +2168,7 @@ pub const trait Iterator {
     where
         Self: Sized,
         Self::Item: Try<Residual: Residual<B>>,
-        B: FromIterator<<Self::Item as Try>::Output>,
+        B: FromIterator<<Self::Item as Branch>::Output>,
     {
         try_process(ByRefSized(self), |i| i.collect())
     }
@@ -2781,12 +2781,12 @@ pub const trait Iterator {
     {
         let first = match self.next() {
             Some(i) => i,
-            None => return Try::from_output(None),
+            None => return FromOutput::from_output(None),
         };
 
         match self.try_fold(first, f).branch() {
             ControlFlow::Break(r) => FromResidual::from_residual(r),
-            ControlFlow::Continue(i) => Try::from_output(Some(i)),
+            ControlFlow::Continue(i) => FromOutput::from_output(Some(i)),
         }
     }
 
@@ -3067,14 +3067,14 @@ pub const trait Iterator {
         {
             move |(), x| match f(&x).branch() {
                 ControlFlow::Continue(false) => ControlFlow::Continue(()),
-                ControlFlow::Continue(true) => ControlFlow::Break(Try::from_output(Some(x))),
-                ControlFlow::Break(r) => ControlFlow::Break(FromResidual::from_residual(r)),
+                ControlFlow::Continue(true) => ControlFlow::Break(<_>::from_output(Some(x))),
+                ControlFlow::Break(r) => ControlFlow::Break(<_>::from_residual(r)),
             }
         }
 
         match self.try_fold((), check(f)) {
             ControlFlow::Break(x) => x,
-            ControlFlow::Continue(()) => Try::from_output(None),
+            ControlFlow::Continue(()) => <_>::from_output(None),
         }
     }
 

library/core/src/ops/control_flow.rs

@@ -102,15 +102,10 @@ pub enum ControlFlow<B, C = ()> {
 
 #[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 #[rustc_const_unstable(feature = "const_try", issue = "74935")]
-impl<B, C> const ops::Try for ControlFlow<B, C> {
+impl<B, C> const ops::Branch for ControlFlow<B, C> {
     type Output = C;
     type Residual = ControlFlow<B, convert::Infallible>;
 
-    #[inline]
-    fn from_output(output: Self::Output) -> Self {
-        ControlFlow::Continue(output)
-    }
-
     #[inline]
     fn branch(self) -> ControlFlow<Self::Residual, Self::Output> {
         match self {
@@ -119,7 +114,14 @@ impl<B, C> const ops::Try for ControlFlow<B, C> {
         }
     }
 }
-
+#[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
+#[rustc_const_unstable(feature = "const_try", issue = "74935")]
+impl<B, C> const ops::FromOutput for ControlFlow<B, C> {
+    #[inline]
+    fn from_output(output: Self::Output) -> Self {
+        ControlFlow::Continue(output)
+    }
+}
 #[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
 #[rustc_const_unstable(feature = "const_try", issue = "74935")]
 // Note: manually specifying the residual type instead of using the default to work around

library/core/src/ops/mod.rs

@@ -196,9 +196,9 @@ pub use self::reborrow::{CoerceShared, Reborrow};
 pub use self::try_trait::Residual;
 #[unstable(feature = "try_trait_v2_yeet", issue = "96374")]
 pub use self::try_trait::Yeet;
-pub(crate) use self::try_trait::{ChangeOutputType, NeverShortCircuit};
 #[unstable(feature = "try_trait_v2", issue = "84277", old_name = "try_trait")]
-pub use self::try_trait::{FromResidual, Try};
+pub use self::try_trait::{Branch, FromOutput, FromResidual, Try};
+pub(crate) use self::try_trait::{ChangeOutputType, NeverShortCircuit};
 #[unstable(feature = "coerce_unsized", issue = "18598")]
 pub use self::unsize::CoerceUnsized;
 #[unstable(feature = "dispatch_from_dyn", issue = "none")]