Rollup merge of rust-lang#138081 - eholk:yield-feature, r=oli-obk

compiler-errors · web-flow · commit bc45cdb27a23 · 2025-03-06T15:40:05.000-05:00
Move `yield` expressions behind their own feature gate In order to make progress with the `iter!` macro (e.g. in rust-lang#137725), we need `yield` expressions to be available without the `coroutines` feature. This PR moves `yield` to be guarded by the `yield_expr` feature so that we can stabilize that independently (or at least, concurrently with the `iter_macro` feature). Note that once `yield` is stable, it will still be an error to use `yield` expressions outside something like a generator or coroutine, and these features remain unstable. r? `@oli-obk`
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
@@ -1690,6 +1690,19 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let yielded =
             opt_expr.as_ref().map(|x| self.lower_expr(x)).unwrap_or_else(|| self.expr_unit(span));
 
+        if !self.tcx.features().yield_expr()
+            && !self.tcx.features().coroutines()
+            && !self.tcx.features().gen_blocks()
+        {
+            rustc_session::parse::feature_err(
+                &self.tcx.sess,
+                sym::yield_expr,
+                span,
+                fluent_generated::ast_lowering_yield,
+            )
+            .emit();
+        }
+
         let is_async_gen = match self.coroutine_kind {
             Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)) => false,
             Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _)) => true,
@@ -1714,28 +1727,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     None,
                 );
             }
-            Some(hir::CoroutineKind::Coroutine(_)) => {
-                if !self.tcx.features().coroutines() {
-                    rustc_session::parse::feature_err(
-                        &self.tcx.sess,
-                        sym::coroutines,
-                        span,
-                        fluent_generated::ast_lowering_yield,
-                    )
-                    .emit();
-                }
-                false
-            }
+            Some(hir::CoroutineKind::Coroutine(_)) => false,
             None => {
-                if !self.tcx.features().coroutines() {
-                    rustc_session::parse::feature_err(
-                        &self.tcx.sess,
-                        sym::coroutines,
-                        span,
-                        fluent_generated::ast_lowering_yield,
-                    )
-                    .emit();
-                }
                 let suggestion = self.current_item.map(|s| s.shrink_to_lo());
                 self.dcx().emit_err(YieldInClosure { span, suggestion });
                 self.coroutine_kind = Some(hir::CoroutineKind::Coroutine(Movability::Movable));
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
@@ -670,6 +670,7 @@ declare_features! (
     (unstable, xop_target_feature, "1.81.0", Some(127208)),
     /// Allows `do yeet` expressions
     (unstable, yeet_expr, "1.62.0", Some(96373)),
+    (unstable, yield_expr, "CURRENT_RUSTC_VERSION", Some(43122)),
     // !!!!    !!!!    !!!!    !!!!   !!!!    !!!!    !!!!    !!!!    !!!!    !!!!    !!!!
     // Features are listed in alphabetical order. Tidy will fail if you don't keep it this way.
     // !!!!    !!!!    !!!!    !!!!   !!!!    !!!!    !!!!    !!!!    !!!!    !!!!    !!!!
diff --git a/tests/ui/coroutine/gen_block.e2024.stderr b/tests/ui/coroutine/gen_block.e2024.stderr
@@ -18,16 +18,6 @@ LL |     let _ = #[coroutine] || {};
    = help: add `#![feature(coroutines)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error[E0658]: yield syntax is experimental
-  --> $DIR/gen_block.rs:16:16
-   |
-LL |     let _ = || yield true;
-   |                ^^^^^^^^^^
-   |
-   = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
-   = help: add `#![feature(coroutines)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
 error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
   --> $DIR/gen_block.rs:16:16
    |
@@ -39,23 +29,13 @@ help: use `#[coroutine]` to make this closure a coroutine
 LL |     let _ = #[coroutine] || yield true;
    |             ++++++++++++
 
-error[E0658]: yield syntax is experimental
-  --> $DIR/gen_block.rs:20:29
-   |
-LL |     let _ = #[coroutine] || yield true;
-   |                             ^^^^^^^^^^
-   |
-   = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
-   = help: add `#![feature(coroutines)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
 error[E0282]: type annotations needed
   --> $DIR/gen_block.rs:7:13
    |
 LL |     let x = gen {};
    |             ^^^^^^ cannot infer type
 
-error: aborting due to 6 previous errors
+error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0282, E0658.
 For more information about an error, try `rustc --explain E0282`.
diff --git a/tests/ui/coroutine/gen_block.none.stderr b/tests/ui/coroutine/gen_block.none.stderr
@@ -71,7 +71,7 @@ LL |     let _ = || yield true;
    |                ^^^^^^^^^^
    |
    = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
-   = help: add `#![feature(coroutines)]` to the crate attributes to enable
+   = help: add `#![feature(yield_expr)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
@@ -92,7 +92,7 @@ LL |     let _ = #[coroutine] || yield true;
    |                             ^^^^^^^^^^
    |
    = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
-   = help: add `#![feature(coroutines)]` to the crate attributes to enable
+   = help: add `#![feature(yield_expr)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error: aborting due to 11 previous errors
diff --git a/tests/ui/coroutine/gen_block.rs b/tests/ui/coroutine/gen_block.rs
@@ -14,12 +14,12 @@ fn main() {
     //[none]~^ ERROR: cannot find
 
     let _ = || yield true; //[none]~ ERROR yield syntax is experimental
-    //~^ ERROR yield syntax is experimental
+    //[none]~^ ERROR yield syntax is experimental
     //~^^ ERROR `yield` can only be used in
 
     let _ = #[coroutine] || yield true; //[none]~ ERROR yield syntax is experimental
     //~^ ERROR `#[coroutine]` attribute is an experimental feature
-    //~^^ ERROR yield syntax is experimental
+    //[none]~^^ ERROR yield syntax is experimental
 
     let _ = #[coroutine] || {};
     //~^ ERROR `#[coroutine]` attribute is an experimental feature
diff --git a/tests/ui/feature-gates/feature-gate-coroutines.e2024.stderr b/tests/ui/feature-gates/feature-gate-coroutines.e2024.stderr
@@ -45,7 +45,7 @@ LL |     yield true;
    |     ^^^^^^^^^^
    |
    = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
-   = help: add `#![feature(coroutines)]` to the crate attributes to enable
+   = help: add `#![feature(yield_expr)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
@@ -66,7 +66,7 @@ LL |     let _ = || yield true;
    |                ^^^^^^^^^^
    |
    = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
-   = help: add `#![feature(coroutines)]` to the crate attributes to enable
+   = help: add `#![feature(yield_expr)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
diff --git a/tests/ui/feature-gates/feature-gate-coroutines.none.stderr b/tests/ui/feature-gates/feature-gate-coroutines.none.stderr
@@ -45,7 +45,7 @@ LL |     yield true;
    |     ^^^^^^^^^^
    |
    = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
-   = help: add `#![feature(coroutines)]` to the crate attributes to enable
+   = help: add `#![feature(yield_expr)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
@@ -66,7 +66,7 @@ LL |     let _ = || yield true;
    |                ^^^^^^^^^^
    |
    = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
-   = help: add `#![feature(coroutines)]` to the crate attributes to enable
+   = help: add `#![feature(yield_expr)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
diff --git a/tests/ui/feature-gates/feature-gate-yield-expr.rs b/tests/ui/feature-gates/feature-gate-yield-expr.rs
@@ -0,0 +1,9 @@
+//@ edition: 2024
+#![feature(stmt_expr_attributes)]
+
+fn main() {
+    yield (); //~ ERROR yield syntax is experimental
+    //~^ ERROR yield syntax is experimental
+    //~^^ ERROR `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
+    //~^^^ ERROR yield expression outside of coroutine literal
+}
diff --git a/tests/ui/feature-gates/feature-gate-yield-expr.stderr b/tests/ui/feature-gates/feature-gate-yield-expr.stderr
@@ -0,0 +1,41 @@
+error[E0658]: yield syntax is experimental
+  --> $DIR/feature-gate-yield-expr.rs:5:5
+   |
+LL |     yield ();
+   |     ^^^^^^^^
+   |
+   = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
+   = help: add `#![feature(coroutines)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error[E0658]: yield syntax is experimental
+  --> $DIR/feature-gate-yield-expr.rs:5:5
+   |
+LL |     yield ();
+   |     ^^^^^^^^
+   |
+   = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
+   = help: add `#![feature(yield_expr)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
+  --> $DIR/feature-gate-yield-expr.rs:5:5
+   |
+LL |     yield ();
+   |     ^^^^^^^^
+   |
+help: use `#[coroutine]` to make this closure a coroutine
+   |
+LL | #[coroutine] fn main() {
+   | ++++++++++++
+
+error[E0627]: yield expression outside of coroutine literal
+  --> $DIR/feature-gate-yield-expr.rs:5:5
+   |
+LL |     yield ();
+   |     ^^^^^^^^
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0627, E0658.
+For more information about an error, try `rustc --explain E0627`.
