Feature gate coroutine yield usage

compiler/rustc_ast_lowering/src/expr.rs

@@ -1504,12 +1504,22 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     fn lower_expr_yield(&mut self, span: Span, opt_expr: Option<&Expr>) -> hir::ExprKind<'hir> {
         match self.coroutine_kind {
-            Some(hir::CoroutineKind::Coroutine) => {}
             Some(hir::CoroutineKind::Gen(_)) => {}
             Some(hir::CoroutineKind::Async(_)) => {
                 self.tcx.sess.emit_err(AsyncCoroutinesNotSupported { span });
             }
-            None => self.coroutine_kind = Some(hir::CoroutineKind::Coroutine),
+            Some(hir::CoroutineKind::Coroutine) | None => {
+                if !self.tcx.features().coroutines {
+                    rustc_session::parse::feature_err(
+                        &self.tcx.sess.parse_sess,
+                        sym::coroutines,
+                        span,
+                        "yield syntax is experimental",
+                    )
+                    .emit();
+                }
+                self.coroutine_kind = Some(hir::CoroutineKind::Coroutine)
+            }
         }
 
         let expr =

tests/ui/coroutine/gen_block.e2024.stderr

@@ -1,9 +1,19 @@
+error[E0658]: yield syntax is experimental
+  --> $DIR/gen_block.rs:15:16
+   |
+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
+
 error[E0282]: type annotations needed
   --> $DIR/gen_block.rs:6:17
    |
 LL |     let x = gen {};
    |                 ^^ cannot infer type
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0282`.
+Some errors have detailed explanations: E0282, E0658.
+For more information about an error, try `rustc --explain E0282`.

tests/ui/coroutine/gen_block.none.stderr

@@ -25,7 +25,7 @@ LL |     gen {};
    |     ^^^ not found in this scope
 
 error[E0658]: yield syntax is experimental
-  --> $DIR/gen_block.rs:14:16
+  --> $DIR/gen_block.rs:15:16
    |
 LL |     let _ = || yield true;
    |                ^^^^^^^^^^
@@ -33,7 +33,17 @@ 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
 
-error: aborting due to 5 previous errors
+error[E0658]: yield syntax is experimental
+  --> $DIR/gen_block.rs:15:16
+   |
+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: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 6 previous errors
 
 Some errors have detailed explanations: E0422, E0658.
 For more information about an error, try `rustc --explain E0422`.

tests/ui/coroutine/gen_block.rs

@@ -12,6 +12,6 @@ fn main() {
     gen {};
     //[none]~^ ERROR: cannot find
 
-    // FIXME(gen_blocks): should also error in 2024 edition
     let _ = || yield true; //[none]~ ERROR yield syntax is experimental
+    //~^ ERROR yield syntax is experimental
 }

tests/ui/feature-gates/feature-gate-coroutines.e2024.stderr

@@ -1,9 +1,28 @@
+error[E0658]: yield syntax is experimental
+  --> $DIR/feature-gate-coroutines.rs:5:5
+   |
+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
+
+error[E0658]: yield syntax is experimental
+  --> $DIR/feature-gate-coroutines.rs:9:16
+   |
+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
+
 error[E0627]: yield expression outside of coroutine literal
   --> $DIR/feature-gate-coroutines.rs:5:5
    |
 LL |     yield true;
    |     ^^^^^^^^^^
 
-error: aborting due to previous error
+error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0627`.
+Some errors have detailed explanations: E0627, E0658.
+For more information about an error, try `rustc --explain E0627`.

tests/ui/feature-gates/feature-gate-coroutines.none.stderr

@@ -8,7 +8,7 @@ LL |     yield true;
    = help: add `#![feature(coroutines)]` to the crate attributes to enable
 
 error[E0658]: yield syntax is experimental
-  --> $DIR/feature-gate-coroutines.rs:8:16
+  --> $DIR/feature-gate-coroutines.rs:9:16
    |
 LL |     let _ = || yield true;
    |                ^^^^^^^^^^
@@ -17,7 +17,7 @@ LL |     let _ = || yield true;
    = help: add `#![feature(coroutines)]` to the crate attributes to enable
 
 error[E0658]: yield syntax is experimental
-  --> $DIR/feature-gate-coroutines.rs:14:5
+  --> $DIR/feature-gate-coroutines.rs:16:5
    |
 LL |     yield;
    |     ^^^^^
@@ -26,7 +26,7 @@ LL |     yield;
    = help: add `#![feature(coroutines)]` to the crate attributes to enable
 
 error[E0658]: yield syntax is experimental
-  --> $DIR/feature-gate-coroutines.rs:15:5
+  --> $DIR/feature-gate-coroutines.rs:17:5
    |
 LL |     yield 0;
    |     ^^^^^^^
@@ -34,13 +34,33 @@ LL |     yield 0;
    = 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
 
+error[E0658]: yield syntax is experimental
+  --> $DIR/feature-gate-coroutines.rs:5:5
+   |
+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
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0658]: yield syntax is experimental
+  --> $DIR/feature-gate-coroutines.rs:9:16
+   |
+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: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error[E0627]: yield expression outside of coroutine literal
   --> $DIR/feature-gate-coroutines.rs:5:5
    |
 LL |     yield true;
    |     ^^^^^^^^^^
 
-error: aborting due to 5 previous errors
+error: aborting due to 7 previous errors
 
 Some errors have detailed explanations: E0627, E0658.
 For more information about an error, try `rustc --explain E0627`.

tests/ui/feature-gates/feature-gate-coroutines.rs

@@ -2,10 +2,12 @@
 //[e2024] compile-flags: --edition 2024 -Zunstable-options
 
 fn main() {
-    yield true; //[none]~ ERROR yield syntax is experimental
+    yield true; //~ ERROR yield syntax is experimental
                 //~^ ERROR yield expression outside of coroutine literal
+                //[none]~^^ ERROR yield syntax is experimental
 
-    let _ = || yield true; //[none]~ ERROR yield syntax is experimental
+    let _ = || yield true; //~ ERROR yield syntax is experimental
+    //[none]~^ ERROR yield syntax is experimental
 }
 
 #[cfg(FALSE)]