diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index e94e26a63bc6f..aceee07a7341c 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -1232,7 +1232,7 @@ impl Expr {
             ExprKind::Closure(..) => ExprPrecedence::Closure,
             ExprKind::Block(..) => ExprPrecedence::Block,
             ExprKind::TryBlock(..) => ExprPrecedence::TryBlock,
-            ExprKind::Async(..) => ExprPrecedence::Async,
+            ExprKind::Gen(..) => ExprPrecedence::Gen,
             ExprKind::Await(..) => ExprPrecedence::Await,
             ExprKind::Assign(..) => ExprPrecedence::Assign,
             ExprKind::AssignOp(..) => ExprPrecedence::AssignOp,
@@ -1401,11 +1401,9 @@ pub enum ExprKind {
     Closure(Box<Closure>),
     /// A block (`'label: { ... }`).
     Block(P<Block>, Option<Label>),
-    /// An async block (`async move { ... }`).
-    ///
-    /// The async block used to have a `NodeId`, which was removed in favor of
-    /// using the parent `NodeId` of the parent `Expr`.
-    Async(CaptureBy, P<Block>),
+    /// An `async` block (`async move { ... }`),
+    /// or a `gen` block (`gen move { ... }`)
+    Gen(CaptureBy, P<Block>, GenBlockKind),
     /// An await expression (`my_future.await`). Span is of await keyword.
     Await(P<Expr>, Span),
 
@@ -1495,6 +1493,28 @@ pub enum ExprKind {
     Err,
 }
 
+/// Used to differentiate between `async {}` blocks and `gen {}` blocks.
+#[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq)]
+pub enum GenBlockKind {
+    Async,
+    Gen,
+}
+
+impl fmt::Display for GenBlockKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.modifier().fmt(f)
+    }
+}
+
+impl GenBlockKind {
+    pub fn modifier(&self) -> &'static str {
+        match self {
+            GenBlockKind::Async => "async",
+            GenBlockKind::Gen => "gen",
+        }
+    }
+}
+
 /// The explicit `Self` type in a "qualified path". The actual
 /// path, including the trait and the associated item, is stored
 /// separately. `position` represents the index of the associated
@@ -2357,6 +2377,12 @@ pub enum Async {
     No,
 }
 
+#[derive(Copy, Clone, Encodable, Decodable, Debug)]
+pub enum Gen {
+    Yes { span: Span, closure_id: NodeId, return_impl_trait_id: NodeId },
+    No,
+}
+
 impl Async {
     pub fn is_async(self) -> bool {
         matches!(self, Async::Yes { .. })
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index ba2887146cfe4..0634ee970ec5e 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -1418,7 +1418,7 @@ pub fn noop_visit_expr<T: MutVisitor>(
             vis.visit_block(blk);
             visit_opt(label, |label| vis.visit_label(label));
         }
-        ExprKind::Async(_capture_by, body) => {
+        ExprKind::Gen(_capture_by, body, _) => {
             vis.visit_block(body);
         }
         ExprKind::Await(expr, await_kw_span) => {
diff --git a/compiler/rustc_ast/src/token.rs b/compiler/rustc_ast/src/token.rs
index dd879a14567c8..914c97a14ac0d 100644
--- a/compiler/rustc_ast/src/token.rs
+++ b/compiler/rustc_ast/src/token.rs
@@ -197,6 +197,7 @@ pub fn ident_can_begin_expr(name: Symbol, span: Span, is_raw: bool) -> bool {
             kw::Continue,
             kw::False,
             kw::For,
+            kw::Gen,
             kw::If,
             kw::Let,
             kw::Loop,
diff --git a/compiler/rustc_ast/src/util/classify.rs b/compiler/rustc_ast/src/util/classify.rs
index f9f1c0cf956be..821fca6656cdd 100644
--- a/compiler/rustc_ast/src/util/classify.rs
+++ b/compiler/rustc_ast/src/util/classify.rs
@@ -46,7 +46,7 @@ pub fn expr_trailing_brace(mut expr: &ast::Expr) -> Option<&ast::Expr> {
             Closure(closure) => {
                 expr = &closure.body;
             }
-            Async(..) | Block(..) | ForLoop(..) | If(..) | Loop(..) | Match(..) | Struct(..)
+            Gen(..) | Block(..) | ForLoop(..) | If(..) | Loop(..) | Match(..) | Struct(..)
             | TryBlock(..) | While(..) => break Some(expr),
             _ => break None,
         }
diff --git a/compiler/rustc_ast/src/util/parser.rs b/compiler/rustc_ast/src/util/parser.rs
index d3e43e2023541..13768c1201791 100644
--- a/compiler/rustc_ast/src/util/parser.rs
+++ b/compiler/rustc_ast/src/util/parser.rs
@@ -285,7 +285,7 @@ pub enum ExprPrecedence {
     Block,
     TryBlock,
     Struct,
-    Async,
+    Gen,
     Await,
     Err,
 }
@@ -351,7 +351,7 @@ impl ExprPrecedence {
             | ExprPrecedence::ConstBlock
             | ExprPrecedence::Block
             | ExprPrecedence::TryBlock
-            | ExprPrecedence::Async
+            | ExprPrecedence::Gen
             | ExprPrecedence::Struct
             | ExprPrecedence::Err => PREC_PAREN,
         }
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
index e66c4a9ee267d..e091961a14438 100644
--- a/compiler/rustc_ast/src/visit.rs
+++ b/compiler/rustc_ast/src/visit.rs
@@ -872,7 +872,7 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
             walk_list!(visitor, visit_label, opt_label);
             visitor.visit_block(block);
         }
-        ExprKind::Async(_, body) => {
+        ExprKind::Gen(_, body, _) => {
             visitor.visit_block(body);
         }
         ExprKind::Await(expr, _) => visitor.visit_expr(expr),
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index b82f878ea87e0..d6fa74dc3e6f2 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -183,7 +183,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     self.arena.alloc_from_iter(arms.iter().map(|x| self.lower_arm(x))),
                     hir::MatchSource::Normal,
                 ),
-                ExprKind::Async(capture_clause, block) => self.make_async_expr(
+                ExprKind::Gen(capture_clause, block, GenBlockKind::Async) => self.make_async_expr(
                     *capture_clause,
                     e.id,
                     None,
@@ -317,6 +317,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         rest,
                     )
                 }
+                ExprKind::Gen(capture_clause, block, GenBlockKind::Gen) => self.make_gen_expr(
+                    *capture_clause,
+                    e.id,
+                    None,
+                    e.span,
+                    hir::CoroutineSource::Block,
+                    |this| this.with_new_scopes(|this| this.lower_block_expr(block)),
+                ),
                 ExprKind::Yield(opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()),
                 ExprKind::Err => hir::ExprKind::Err(
                     self.tcx.sess.delay_span_bug(e.span, "lowered ExprKind::Err"),
@@ -661,6 +669,57 @@ impl<'hir> LoweringContext<'_, 'hir> {
         }))
     }
 
+    /// Lower a `gen` construct to a generator that implements `Iterator`.
+    ///
+    /// This results in:
+    ///
+    /// ```text
+    /// static move? |()| -> () {
+    ///     <body>
+    /// }
+    /// ```
+    pub(super) fn make_gen_expr(
+        &mut self,
+        capture_clause: CaptureBy,
+        closure_node_id: NodeId,
+        _yield_ty: Option<hir::FnRetTy<'hir>>,
+        span: Span,
+        gen_kind: hir::CoroutineSource,
+        body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
+    ) -> hir::ExprKind<'hir> {
+        let output = hir::FnRetTy::DefaultReturn(self.lower_span(span));
+
+        // The closure/generator `FnDecl` takes a single (resume) argument of type `input_ty`.
+        let fn_decl = self.arena.alloc(hir::FnDecl {
+            inputs: &[],
+            output,
+            c_variadic: false,
+            implicit_self: hir::ImplicitSelfKind::None,
+            lifetime_elision_allowed: false,
+        });
+
+        let body = self.lower_body(move |this| {
+            this.coroutine_kind = Some(hir::CoroutineKind::Gen(gen_kind));
+
+            let res = body(this);
+            (&[], res)
+        });
+
+        // `static |()| -> () { body }`:
+        hir::ExprKind::Closure(self.arena.alloc(hir::Closure {
+            def_id: self.local_def_id(closure_node_id),
+            binder: hir::ClosureBinder::Default,
+            capture_clause,
+            bound_generic_params: &[],
+            fn_decl,
+            body,
+            fn_decl_span: self.lower_span(span),
+            fn_arg_span: None,
+            movability: Some(Movability::Movable),
+            constness: hir::Constness::NotConst,
+        }))
+    }
+
     /// Forwards a possible `#[track_caller]` annotation from `outer_hir_id` to
     /// `inner_hir_id` in case the `async_fn_track_caller` feature is enabled.
     pub(super) fn maybe_forward_track_caller(
@@ -712,7 +771,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let full_span = expr.span.to(await_kw_span);
         match self.coroutine_kind {
             Some(hir::CoroutineKind::Async(_)) => {}
-            Some(hir::CoroutineKind::Coroutine) | None => {
+            Some(hir::CoroutineKind::Coroutine) | Some(hir::CoroutineKind::Gen(_)) | None => {
                 self.tcx.sess.emit_err(AwaitOnlyInAsyncFnAndBlocks {
                     await_kw_span,
                     item_span: self.current_item,
@@ -936,8 +995,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 }
                 Some(movability)
             }
-            Some(hir::CoroutineKind::Async(_)) => {
-                panic!("non-`async` closure body turned `async` during lowering");
+            Some(hir::CoroutineKind::Gen(_)) | Some(hir::CoroutineKind::Async(_)) => {
+                panic!("non-`async`/`gen` closure body turned `async`/`gen` during lowering");
             }
             None => {
                 if movability == Movability::Static {
@@ -1445,11 +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 =
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 34532967d9e24..a1bd2679137d6 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -554,7 +554,12 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
         "consider removing `for<...>`"
     );
     gate_all!(more_qualified_paths, "usage of qualified paths in this context is experimental");
-    gate_all!(coroutines, "yield syntax is experimental");
+    for &span in spans.get(&sym::yield_expr).iter().copied().flatten() {
+        if !span.at_least_rust_2024() {
+            gate_feature_post!(&visitor, coroutines, span, "yield syntax is experimental");
+        }
+    }
+    gate_all!(gen_blocks, "gen blocks are experimental");
     gate_all!(raw_ref_op, "raw address of syntax is experimental");
     gate_all!(const_trait_impl, "const trait impls are experimental");
     gate_all!(
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
index 269cb8f238021..e84af12d3f9c7 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
@@ -445,8 +445,8 @@ impl<'a> State<'a> {
                 self.ibox(0);
                 self.print_block_with_attrs(blk, attrs);
             }
-            ast::ExprKind::Async(capture_clause, blk) => {
-                self.word_nbsp("async");
+            ast::ExprKind::Gen(capture_clause, blk, kind) => {
+                self.word_nbsp(kind.modifier());
                 self.print_capture_clause(*capture_clause);
                 // cbox/ibox in analogy to the `ExprKind::Block` arm above
                 self.cbox(0);
diff --git a/compiler/rustc_borrowck/src/borrowck_errors.rs b/compiler/rustc_borrowck/src/borrowck_errors.rs
index 2ceec1b5658de..6731ef1230660 100644
--- a/compiler/rustc_borrowck/src/borrowck_errors.rs
+++ b/compiler/rustc_borrowck/src/borrowck_errors.rs
@@ -373,11 +373,12 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         span: Span,
         yield_span: Span,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+        let coroutine_kind = self.body.coroutine.as_ref().unwrap().coroutine_kind;
         let mut err = struct_span_err!(
             self,
             span,
             E0626,
-            "borrow may still be in use when coroutine yields",
+            "borrow may still be in use when {coroutine_kind:#} yields",
         );
         err.span_label(yield_span, "possible yield occurs here");
         err
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 928c25d106179..247200dcd2695 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -2491,11 +2491,17 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
         let (sugg_span, suggestion) = match tcx.sess.source_map().span_to_snippet(args_span) {
             Ok(string) => {
-                if string.starts_with("async ") {
-                    let pos = args_span.lo() + BytePos(6);
-                    (args_span.with_lo(pos).with_hi(pos), "move ")
-                } else if string.starts_with("async|") {
-                    let pos = args_span.lo() + BytePos(5);
+                let coro_prefix = if string.starts_with("async") {
+                    // `async` is 5 chars long. Not using `.len()` to avoid the cast from `usize` to `u32`
+                    Some(5)
+                } else if string.starts_with("gen") {
+                    // `gen` is 3 chars long
+                    Some(3)
+                } else {
+                    None
+                };
+                if let Some(n) = coro_prefix {
+                    let pos = args_span.lo() + BytePos(n);
                     (args_span.with_lo(pos).with_hi(pos), " move")
                 } else {
                     (args_span.shrink_to_lo(), "move ")
@@ -2505,6 +2511,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         };
         let kind = match use_span.coroutine_kind() {
             Some(coroutine_kind) => match coroutine_kind {
+                CoroutineKind::Gen(kind) => match kind {
+                    CoroutineSource::Block => "gen block",
+                    CoroutineSource::Closure => "gen closure",
+                    _ => bug!("gen block/closure expected, but gen function found."),
+                },
                 CoroutineKind::Async(async_kind) => match async_kind {
                     CoroutineSource::Block => "async block",
                     CoroutineSource::Closure => "async closure",
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index e630ac7c4faee..d38cfbc54d7ac 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -698,6 +698,20 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                             " of async function"
                         }
                     },
+                    Some(hir::CoroutineKind::Gen(gen)) => match gen {
+                        hir::CoroutineSource::Block => " of gen block",
+                        hir::CoroutineSource::Closure => " of gen closure",
+                        hir::CoroutineSource::Fn => {
+                            let parent_item =
+                                hir.get_by_def_id(hir.get_parent_item(mir_hir_id).def_id);
+                            let output = &parent_item
+                                .fn_decl()
+                                .expect("coroutine lowered from gen fn should be in fn")
+                                .output;
+                            span = output.span();
+                            " of gen function"
+                        }
+                    },
                     Some(hir::CoroutineKind::Coroutine) => " of coroutine",
                     None => " of closure",
                 };
diff --git a/compiler/rustc_builtin_macros/src/assert/context.rs b/compiler/rustc_builtin_macros/src/assert/context.rs
index 6733b9e56addf..2a4bfe9e200f0 100644
--- a/compiler/rustc_builtin_macros/src/assert/context.rs
+++ b/compiler/rustc_builtin_macros/src/assert/context.rs
@@ -294,7 +294,7 @@ impl<'cx, 'a> Context<'cx, 'a> {
             // sync with the `rfc-2011-nicer-assert-messages/all-expr-kinds.rs` test.
             ExprKind::Assign(_, _, _)
             | ExprKind::AssignOp(_, _, _)
-            | ExprKind::Async(_, _)
+            | ExprKind::Gen(_, _, _)
             | ExprKind::Await(_, _)
             | ExprKind::Block(_, _)
             | ExprKind::Break(_, _)
diff --git a/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs b/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
index 5900c764073df..1a85eb8dd7970 100644
--- a/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
+++ b/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
@@ -560,6 +560,9 @@ pub fn push_item_name(tcx: TyCtxt<'_>, def_id: DefId, qualified: bool, output: &
 
 fn coroutine_kind_label(coroutine_kind: Option<CoroutineKind>) -> &'static str {
     match coroutine_kind {
+        Some(CoroutineKind::Gen(CoroutineSource::Block)) => "gen_block",
+        Some(CoroutineKind::Gen(CoroutineSource::Closure)) => "gen_closure",
+        Some(CoroutineKind::Gen(CoroutineSource::Fn)) => "gen_fn",
         Some(CoroutineKind::Async(CoroutineSource::Block)) => "async_block",
         Some(CoroutineKind::Async(CoroutineSource::Closure)) => "async_closure",
         Some(CoroutineKind::Async(CoroutineSource::Fn)) => "async_fn",
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 695de54eefa0a..72100863bb522 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -456,6 +456,8 @@ declare_features! (
     (unstable, ffi_returns_twice, "1.34.0", Some(58314), None),
     /// Allows using `#[repr(align(...))]` on function items
     (unstable, fn_align, "1.53.0", Some(82232), None),
+    /// Allows defining gen blocks and `gen fn`.
+    (unstable, gen_blocks, "CURRENT_RUSTC_VERSION", Some(117078), None),
     /// Infer generic args for both consts and types.
     (unstable, generic_arg_infer, "1.55.0", Some(85077), None),
     /// An extension to the `generic_associated_types` feature, allowing incomplete features.
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 259af4f565bda..22ee39634a56d 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -1513,6 +1513,9 @@ pub enum CoroutineKind {
     /// An explicit `async` block or the body of an async function.
     Async(CoroutineSource),
 
+    /// An explicit `gen` block or the body of a `gen` function.
+    Gen(CoroutineSource),
+
     /// A coroutine literal created via a `yield` inside a closure.
     Coroutine,
 }
@@ -1529,6 +1532,14 @@ impl fmt::Display for CoroutineKind {
                 k.fmt(f)
             }
             CoroutineKind::Coroutine => f.write_str("coroutine"),
+            CoroutineKind::Gen(k) => {
+                if f.alternate() {
+                    f.write_str("`gen` ")?;
+                } else {
+                    f.write_str("gen ")?
+                }
+                k.fmt(f)
+            }
         }
     }
 }
@@ -2242,6 +2253,7 @@ impl From<CoroutineKind> for YieldSource {
             // Guess based on the kind of the current coroutine.
             CoroutineKind::Coroutine => Self::Yield,
             CoroutineKind::Async(_) => Self::Await { expr: None },
+            CoroutineKind::Gen(_) => Self::Yield,
         }
     }
 }
diff --git a/compiler/rustc_hir_typeck/src/check.rs b/compiler/rustc_hir_typeck/src/check.rs
index e7060dac844b9..14cd3881a068d 100644
--- a/compiler/rustc_hir_typeck/src/check.rs
+++ b/compiler/rustc_hir_typeck/src/check.rs
@@ -58,15 +58,16 @@ pub(super) fn check_fn<'a, 'tcx>(
     if let Some(kind) = body.coroutine_kind
         && can_be_coroutine.is_some()
     {
-        let yield_ty = if kind == hir::CoroutineKind::Coroutine {
-            let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
-                kind: TypeVariableOriginKind::TypeInference,
-                span,
-            });
-            fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
-            yield_ty
-        } else {
-            Ty::new_unit(tcx)
+        let yield_ty = match kind {
+            hir::CoroutineKind::Gen(..) | hir::CoroutineKind::Coroutine => {
+                let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
+                    kind: TypeVariableOriginKind::TypeInference,
+                    span,
+                });
+                fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
+                yield_ty
+            }
+            hir::CoroutineKind::Async(..) => Ty::new_unit(tcx),
         };
 
         // Resume type defaults to `()` if the coroutine has no argument.
diff --git a/compiler/rustc_hir_typeck/src/closure.rs b/compiler/rustc_hir_typeck/src/closure.rs
index 47bde21ceb2eb..b102ddd8d866d 100644
--- a/compiler/rustc_hir_typeck/src/closure.rs
+++ b/compiler/rustc_hir_typeck/src/closure.rs
@@ -652,6 +652,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         },
                     )
                 }
+                Some(hir::CoroutineKind::Gen(hir::CoroutineSource::Fn)) => {
+                    todo!("gen closures do not exist yet")
+                }
 
                 _ => astconv.ty_infer(None, decl.output.span()),
             },
diff --git a/compiler/rustc_middle/src/mir/terminator.rs b/compiler/rustc_middle/src/mir/terminator.rs
index affa83fa34858..c2aa015f4b7e7 100644
--- a/compiler/rustc_middle/src/mir/terminator.rs
+++ b/compiler/rustc_middle/src/mir/terminator.rs
@@ -148,8 +148,15 @@ impl<O> AssertKind<O> {
             RemainderByZero(_) => "attempt to calculate the remainder with a divisor of zero",
             ResumedAfterReturn(CoroutineKind::Coroutine) => "coroutine resumed after completion",
             ResumedAfterReturn(CoroutineKind::Async(_)) => "`async fn` resumed after completion",
+            ResumedAfterReturn(CoroutineKind::Gen(_)) => {
+                "`gen fn` should just keep returning `None` after completion"
+            }
             ResumedAfterPanic(CoroutineKind::Coroutine) => "coroutine resumed after panicking",
             ResumedAfterPanic(CoroutineKind::Async(_)) => "`async fn` resumed after panicking",
+            ResumedAfterPanic(CoroutineKind::Gen(_)) => {
+                "`gen fn` should just keep returning `None` after panicking"
+            }
+
             BoundsCheck { .. } | MisalignedPointerDereference { .. } => {
                 bug!("Unexpected AssertKind")
             }
@@ -236,10 +243,15 @@ impl<O> AssertKind<O> {
             DivisionByZero(_) => middle_assert_divide_by_zero,
             RemainderByZero(_) => middle_assert_remainder_by_zero,
             ResumedAfterReturn(CoroutineKind::Async(_)) => middle_assert_async_resume_after_return,
+            ResumedAfterReturn(CoroutineKind::Gen(_)) => {
+                bug!("gen blocks can be resumed after they return and will keep returning `None`")
+            }
             ResumedAfterReturn(CoroutineKind::Coroutine) => {
                 middle_assert_coroutine_resume_after_return
             }
             ResumedAfterPanic(CoroutineKind::Async(_)) => middle_assert_async_resume_after_panic,
+            // FIXME(gen_blocks): custom error message for `gen` blocks
+            ResumedAfterPanic(CoroutineKind::Gen(_)) => middle_assert_async_resume_after_panic,
             ResumedAfterPanic(CoroutineKind::Coroutine) => {
                 middle_assert_coroutine_resume_after_panic
             }
diff --git a/compiler/rustc_middle/src/traits/select.rs b/compiler/rustc_middle/src/traits/select.rs
index bc6856bc9009e..f33421bbaa6c1 100644
--- a/compiler/rustc_middle/src/traits/select.rs
+++ b/compiler/rustc_middle/src/traits/select.rs
@@ -144,6 +144,10 @@ pub enum SelectionCandidate<'tcx> {
     /// generated for an async construct.
     FutureCandidate,
 
+    /// Implementation of an `Iterator` trait by one of the generator types
+    /// generated for a gen construct.
+    IteratorCandidate,
+
     /// Implementation of a `Fn`-family trait by one of the anonymous
     /// types generated for a fn pointer type (e.g., `fn(int) -> int`)
     FnPointerCandidate {
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index a669ff8d96115..0b3b6700cec1b 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -782,6 +782,17 @@ impl<'tcx> TyCtxt<'tcx> {
         matches!(self.coroutine_kind(def_id), Some(hir::CoroutineKind::Async(_)))
     }
 
+    /// Returns `true` if the node pointed to by `def_id` is a general coroutine that implements `Coroutine`.
+    /// This means it is neither an `async` or `gen` construct.
+    pub fn is_general_coroutine(self, def_id: DefId) -> bool {
+        matches!(self.coroutine_kind(def_id), Some(hir::CoroutineKind::Coroutine))
+    }
+
+    /// Returns `true` if the node pointed to by `def_id` is a coroutine for a gen construct.
+    pub fn coroutine_is_gen(self, def_id: DefId) -> bool {
+        matches!(self.coroutine_kind(def_id), Some(hir::CoroutineKind::Gen(_)))
+    }
+
     pub fn stability(self) -> &'tcx stability::Index {
         self.stability_index(())
     }
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index be48c0e8926b7..d29d1902404f0 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -749,6 +749,7 @@ impl<'tcx> TyCtxt<'tcx> {
             DefKind::Coroutine => match self.coroutine_kind(def_id).unwrap() {
                 rustc_hir::CoroutineKind::Async(..) => "async closure",
                 rustc_hir::CoroutineKind::Coroutine => "coroutine",
+                rustc_hir::CoroutineKind::Gen(..) => "gen closure",
             },
             _ => def_kind.descr(def_id),
         }
@@ -766,6 +767,7 @@ impl<'tcx> TyCtxt<'tcx> {
             DefKind::Coroutine => match self.coroutine_kind(def_id).unwrap() {
                 rustc_hir::CoroutineKind::Async(..) => "an",
                 rustc_hir::CoroutineKind::Coroutine => "a",
+                rustc_hir::CoroutineKind::Gen(..) => "a",
             },
             _ => def_kind.article(),
         }
diff --git a/compiler/rustc_mir_transform/src/coroutine.rs b/compiler/rustc_mir_transform/src/coroutine.rs
index fa56d59dd80b2..50d244d2831d4 100644
--- a/compiler/rustc_mir_transform/src/coroutine.rs
+++ b/compiler/rustc_mir_transform/src/coroutine.rs
@@ -224,7 +224,7 @@ struct SuspensionPoint<'tcx> {
 
 struct TransformVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
-    is_async_kind: bool,
+    coroutine_kind: hir::CoroutineKind,
     state_adt_ref: AdtDef<'tcx>,
     state_args: GenericArgsRef<'tcx>,
 
@@ -249,6 +249,47 @@ struct TransformVisitor<'tcx> {
 }
 
 impl<'tcx> TransformVisitor<'tcx> {
+    fn insert_none_ret_block(&self, body: &mut Body<'tcx>) -> BasicBlock {
+        let block = BasicBlock::new(body.basic_blocks.len());
+
+        let source_info = SourceInfo::outermost(body.span);
+
+        let (kind, idx) = self.coroutine_state_adt_and_variant_idx(true);
+        assert_eq!(self.state_adt_ref.variant(idx).fields.len(), 0);
+        let statements = vec![Statement {
+            kind: StatementKind::Assign(Box::new((
+                Place::return_place(),
+                Rvalue::Aggregate(Box::new(kind), IndexVec::new()),
+            ))),
+            source_info,
+        }];
+
+        body.basic_blocks_mut().push(BasicBlockData {
+            statements,
+            terminator: Some(Terminator { source_info, kind: TerminatorKind::Return }),
+            is_cleanup: false,
+        });
+
+        block
+    }
+
+    fn coroutine_state_adt_and_variant_idx(
+        &self,
+        is_return: bool,
+    ) -> (AggregateKind<'tcx>, VariantIdx) {
+        let idx = VariantIdx::new(match (is_return, self.coroutine_kind) {
+            (true, hir::CoroutineKind::Coroutine) => 1, // CoroutineState::Complete
+            (false, hir::CoroutineKind::Coroutine) => 0, // CoroutineState::Yielded
+            (true, hir::CoroutineKind::Async(_)) => 0,  // Poll::Ready
+            (false, hir::CoroutineKind::Async(_)) => 1, // Poll::Pending
+            (true, hir::CoroutineKind::Gen(_)) => 0,    // Option::None
+            (false, hir::CoroutineKind::Gen(_)) => 1,   // Option::Some
+        });
+
+        let kind = AggregateKind::Adt(self.state_adt_ref.did(), idx, self.state_args, None, None);
+        (kind, idx)
+    }
+
     // Make a `CoroutineState` or `Poll` variant assignment.
     //
     // `core::ops::CoroutineState` only has single element tuple variants,
@@ -261,31 +302,44 @@ impl<'tcx> TransformVisitor<'tcx> {
         is_return: bool,
         statements: &mut Vec<Statement<'tcx>>,
     ) {
-        let idx = VariantIdx::new(match (is_return, self.is_async_kind) {
-            (true, false) => 1,  // CoroutineState::Complete
-            (false, false) => 0, // CoroutineState::Yielded
-            (true, true) => 0,   // Poll::Ready
-            (false, true) => 1,  // Poll::Pending
-        });
+        let (kind, idx) = self.coroutine_state_adt_and_variant_idx(is_return);
 
-        let kind = AggregateKind::Adt(self.state_adt_ref.did(), idx, self.state_args, None, None);
+        match self.coroutine_kind {
+            // `Poll::Pending`
+            CoroutineKind::Async(_) => {
+                if !is_return {
+                    assert_eq!(self.state_adt_ref.variant(idx).fields.len(), 0);
 
-        // `Poll::Pending`
-        if self.is_async_kind && idx == VariantIdx::new(1) {
-            assert_eq!(self.state_adt_ref.variant(idx).fields.len(), 0);
+                    // FIXME(swatinem): assert that `val` is indeed unit?
+                    statements.push(Statement {
+                        kind: StatementKind::Assign(Box::new((
+                            Place::return_place(),
+                            Rvalue::Aggregate(Box::new(kind), IndexVec::new()),
+                        ))),
+                        source_info,
+                    });
+                    return;
+                }
+            }
+            // `Option::None`
+            CoroutineKind::Gen(_) => {
+                if is_return {
+                    assert_eq!(self.state_adt_ref.variant(idx).fields.len(), 0);
 
-            // FIXME(swatinem): assert that `val` is indeed unit?
-            statements.push(Statement {
-                kind: StatementKind::Assign(Box::new((
-                    Place::return_place(),
-                    Rvalue::Aggregate(Box::new(kind), IndexVec::new()),
-                ))),
-                source_info,
-            });
-            return;
+                    statements.push(Statement {
+                        kind: StatementKind::Assign(Box::new((
+                            Place::return_place(),
+                            Rvalue::Aggregate(Box::new(kind), IndexVec::new()),
+                        ))),
+                        source_info,
+                    });
+                    return;
+                }
+            }
+            CoroutineKind::Coroutine => {}
         }
 
-        // else: `Poll::Ready(x)`, `CoroutineState::Yielded(x)` or `CoroutineState::Complete(x)`
+        // else: `Poll::Ready(x)`, `CoroutineState::Yielded(x)`, `CoroutineState::Complete(x)`, or `Option::Some(x)`
         assert_eq!(self.state_adt_ref.variant(idx).fields.len(), 1);
 
         statements.push(Statement {
@@ -1263,10 +1317,13 @@ fn create_coroutine_resume_function<'tcx>(
     }
 
     if can_return {
-        cases.insert(
-            1,
-            (RETURNED, insert_panic_block(tcx, body, ResumedAfterReturn(coroutine_kind))),
-        );
+        let block = match coroutine_kind {
+            CoroutineKind::Async(_) | CoroutineKind::Coroutine => {
+                insert_panic_block(tcx, body, ResumedAfterReturn(coroutine_kind))
+            }
+            CoroutineKind::Gen(_) => transform.insert_none_ret_block(body),
+        };
+        cases.insert(1, (RETURNED, block));
     }
 
     insert_switch(body, cases, &transform, TerminatorKind::Unreachable);
@@ -1439,18 +1496,28 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
         };
 
         let is_async_kind = matches!(body.coroutine_kind(), Some(CoroutineKind::Async(_)));
-        let (state_adt_ref, state_args) = if is_async_kind {
-            // Compute Poll<return_ty>
-            let poll_did = tcx.require_lang_item(LangItem::Poll, None);
-            let poll_adt_ref = tcx.adt_def(poll_did);
-            let poll_args = tcx.mk_args(&[body.return_ty().into()]);
-            (poll_adt_ref, poll_args)
-        } else {
-            // Compute CoroutineState<yield_ty, return_ty>
-            let state_did = tcx.require_lang_item(LangItem::CoroutineState, None);
-            let state_adt_ref = tcx.adt_def(state_did);
-            let state_args = tcx.mk_args(&[yield_ty.into(), body.return_ty().into()]);
-            (state_adt_ref, state_args)
+        let (state_adt_ref, state_args) = match body.coroutine_kind().unwrap() {
+            CoroutineKind::Async(_) => {
+                // Compute Poll<return_ty>
+                let poll_did = tcx.require_lang_item(LangItem::Poll, None);
+                let poll_adt_ref = tcx.adt_def(poll_did);
+                let poll_args = tcx.mk_args(&[body.return_ty().into()]);
+                (poll_adt_ref, poll_args)
+            }
+            CoroutineKind::Gen(_) => {
+                // Compute Option<yield_ty>
+                let option_did = tcx.require_lang_item(LangItem::Option, None);
+                let option_adt_ref = tcx.adt_def(option_did);
+                let option_args = tcx.mk_args(&[body.yield_ty().unwrap().into()]);
+                (option_adt_ref, option_args)
+            }
+            CoroutineKind::Coroutine => {
+                // Compute CoroutineState<yield_ty, return_ty>
+                let state_did = tcx.require_lang_item(LangItem::CoroutineState, None);
+                let state_adt_ref = tcx.adt_def(state_did);
+                let state_args = tcx.mk_args(&[yield_ty.into(), body.return_ty().into()]);
+                (state_adt_ref, state_args)
+            }
         };
         let ret_ty = Ty::new_adt(tcx, state_adt_ref, state_args);
 
@@ -1518,7 +1585,7 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
         // or Poll::Ready(x) and Poll::Pending respectively depending on `is_async_kind`.
         let mut transform = TransformVisitor {
             tcx,
-            is_async_kind,
+            coroutine_kind: body.coroutine_kind().unwrap(),
             state_adt_ref,
             state_args,
             remap,
diff --git a/compiler/rustc_parse/messages.ftl b/compiler/rustc_parse/messages.ftl
index e0778f72bfe6e..9bedd7b8a338a 100644
--- a/compiler/rustc_parse/messages.ftl
+++ b/compiler/rustc_parse/messages.ftl
@@ -278,6 +278,9 @@ parse_found_expr_would_be_stmt = expected expression, found `{$token}`
 parse_function_body_equals_expr = function body cannot be `= expression;`
     .suggestion = surround the expression with `{"{"}` and `{"}"}` instead of `=` and `;`
 
+parse_gen_block = `gen` blocks are not yet implemented
+    .help = only the keyword is reserved for now
+
 parse_generic_args_in_pat_require_turbofish_syntax = generic args in patterns require the turbofish syntax
 
 parse_generic_parameters_without_angle_brackets = generic parameters without surrounding angle brackets
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index aeb4fd0a304aa..c0e94d15da0bf 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -520,6 +520,14 @@ pub(crate) struct CatchAfterTry {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(parse_gen_block)]
+#[help]
+pub(crate) struct GenBlock {
+    #[primary_span]
+    pub span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(parse_comma_after_base_struct)]
 #[note]
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 5157106f4e269..0b5ec9b59ea80 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -9,7 +9,7 @@ use super::{
 use crate::errors;
 use crate::maybe_recover_from_interpolated_ty_qpath;
 use ast::mut_visit::{noop_visit_expr, MutVisitor};
-use ast::{Path, PathSegment};
+use ast::{GenBlockKind, Path, PathSegment};
 use core::mem;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
@@ -1441,14 +1441,20 @@ impl<'a> Parser<'a> {
             } else if this.token.uninterpolated_span().at_least_rust_2018() {
                 // `Span:.at_least_rust_2018()` is somewhat expensive; don't get it repeatedly.
                 if this.check_keyword(kw::Async) {
-                    if this.is_async_block() {
+                    if this.is_gen_block(kw::Async) {
                         // Check for `async {` and `async move {`.
-                        this.parse_async_block()
+                        this.parse_gen_block()
                     } else {
                         this.parse_expr_closure()
                     }
                 } else if this.eat_keyword(kw::Await) {
                     this.recover_incorrect_await_syntax(lo, this.prev_token.span)
+                } else if this.token.uninterpolated_span().at_least_rust_2024() {
+                    if this.is_gen_block(kw::Gen) {
+                        this.parse_gen_block()
+                    } else {
+                        this.parse_expr_lit()
+                    }
                 } else {
                     this.parse_expr_lit()
                 }
@@ -1848,7 +1854,7 @@ impl<'a> Parser<'a> {
         let lo = self.prev_token.span;
         let kind = ExprKind::Yield(self.parse_expr_opt()?);
         let span = lo.to(self.prev_token.span);
-        self.sess.gated_spans.gate(sym::coroutines, span);
+        self.sess.gated_spans.gate(sym::yield_expr, span);
         let expr = self.mk_expr(span, kind);
         self.maybe_recover_from_bad_qpath(expr)
     }
@@ -3059,18 +3065,24 @@ impl<'a> Parser<'a> {
             && self.token.uninterpolated_span().at_least_rust_2018()
     }
 
-    /// Parses an `async move? {...}` expression.
-    fn parse_async_block(&mut self) -> PResult<'a, P<Expr>> {
+    /// Parses an `async move? {...}` or `gen move? {...}` expression.
+    fn parse_gen_block(&mut self) -> PResult<'a, P<Expr>> {
         let lo = self.token.span;
-        self.expect_keyword(kw::Async)?;
+        let kind = if self.eat_keyword(kw::Async) {
+            GenBlockKind::Async
+        } else {
+            assert!(self.eat_keyword(kw::Gen));
+            self.sess.gated_spans.gate(sym::gen_blocks, lo.to(self.token.span));
+            GenBlockKind::Gen
+        };
         let capture_clause = self.parse_capture_clause()?;
         let (attrs, body) = self.parse_inner_attrs_and_block()?;
-        let kind = ExprKind::Async(capture_clause, body);
+        let kind = ExprKind::Gen(capture_clause, body, kind);
         Ok(self.mk_expr_with_attrs(lo.to(self.prev_token.span), kind, attrs))
     }
 
-    fn is_async_block(&self) -> bool {
-        self.token.is_keyword(kw::Async)
+    fn is_gen_block(&self, kw: Symbol) -> bool {
+        self.token.is_keyword(kw)
             && ((
                 // `async move {`
                 self.is_keyword_ahead(1, &[kw::Move])
@@ -3596,7 +3608,7 @@ impl MutVisitor for CondChecker<'_> {
             | ExprKind::Match(_, _)
             | ExprKind::Closure(_)
             | ExprKind::Block(_, _)
-            | ExprKind::Async(_, _)
+            | ExprKind::Gen(_, _, _)
             | ExprKind::TryBlock(_)
             | ExprKind::Underscore
             | ExprKind::Path(_, _)
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 982f601c0d5a2..4c76ade013932 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -2297,9 +2297,9 @@ impl<'a> Parser<'a> {
         // `pub` is added in case users got confused with the ordering like `async pub fn`,
         // only if it wasn't preceded by `default` as `default pub` is invalid.
         let quals: &[Symbol] = if check_pub {
-            &[kw::Pub, kw::Const, kw::Async, kw::Unsafe, kw::Extern]
+            &[kw::Pub, kw::Gen, kw::Const, kw::Async, kw::Unsafe, kw::Extern]
         } else {
-            &[kw::Const, kw::Async, kw::Unsafe, kw::Extern]
+            &[kw::Gen, kw::Const, kw::Async, kw::Unsafe, kw::Extern]
         };
         self.check_keyword_case(kw::Fn, case) // Definitely an `fn`.
             // `$qual fn` or `$qual $qual`:
@@ -2353,6 +2353,9 @@ impl<'a> Parser<'a> {
         let async_start_sp = self.token.span;
         let asyncness = self.parse_asyncness(case);
 
+        let _gen_start_sp = self.token.span;
+        let genness = self.parse_genness(case);
+
         let unsafe_start_sp = self.token.span;
         let unsafety = self.parse_unsafety(case);
 
@@ -2368,6 +2371,10 @@ impl<'a> Parser<'a> {
             }
         }
 
+        if let Gen::Yes { span, .. } = genness {
+            self.sess.emit_err(errors::GenBlock { span });
+        }
+
         if !self.eat_keyword_case(kw::Fn, case) {
             // It is possible for `expect_one_of` to recover given the contents of
             // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 597303cae73e2..53c6d8acff154 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -11,6 +11,7 @@ mod stmt;
 mod ty;
 
 use crate::lexer::UnmatchedDelim;
+use ast::Gen;
 pub use attr_wrapper::AttrWrapper;
 pub use diagnostics::AttemptLocalParseRecovery;
 pub(crate) use expr::ForbiddenLetReason;
@@ -1126,6 +1127,16 @@ impl<'a> Parser<'a> {
         }
     }
 
+    /// Parses genness: `gen` or nothing.
+    fn parse_genness(&mut self, case: Case) -> Gen {
+        if self.token.span.at_least_rust_2024() && self.eat_keyword_case(kw::Gen, case) {
+            let span = self.prev_token.uninterpolated_span();
+            Gen::Yes { span, closure_id: DUMMY_NODE_ID, return_impl_trait_id: DUMMY_NODE_ID }
+        } else {
+            Gen::No
+        }
+    }
+
     /// Parses unsafety: `unsafe` or nothing.
     fn parse_unsafety(&mut self, case: Case) -> Unsafe {
         if self.eat_keyword_case(kw::Unsafe, case) {
diff --git a/compiler/rustc_passes/src/hir_stats.rs b/compiler/rustc_passes/src/hir_stats.rs
index 24087a4eabbcd..f915c1057d6c4 100644
--- a/compiler/rustc_passes/src/hir_stats.rs
+++ b/compiler/rustc_passes/src/hir_stats.rs
@@ -567,10 +567,10 @@ impl<'v> ast_visit::Visitor<'v> for StatCollector<'v> {
             (self, e, e.kind, Id::None, ast, Expr, ExprKind),
             [
                 Array, ConstBlock, Call, MethodCall, Tup, Binary, Unary, Lit, Cast, Type, Let,
-                If, While, ForLoop, Loop, Match, Closure, Block, Async, Await, TryBlock, Assign,
+                If, While, ForLoop, Loop, Match, Closure, Block, Await, TryBlock, Assign,
                 AssignOp, Field, Index, Range, Underscore, Path, AddrOf, Break, Continue, Ret,
                 InlineAsm, FormatArgs, OffsetOf, MacCall, Struct, Repeat, Paren, Try, Yield, Yeet,
-                Become, IncludedBytes, Err
+                Become, IncludedBytes, Gen, Err
             ]
         );
         ast_visit::walk_expr(self, e)
diff --git a/compiler/rustc_resolve/src/def_collector.rs b/compiler/rustc_resolve/src/def_collector.rs
index 356d7f365fe71..13df7efe636d8 100644
--- a/compiler/rustc_resolve/src/def_collector.rs
+++ b/compiler/rustc_resolve/src/def_collector.rs
@@ -260,7 +260,7 @@ impl<'a, 'b, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'b, 'tcx> {
                     Async::No => closure_def,
                 }
             }
-            ExprKind::Async(_, _) => self.create_def(expr.id, DefPathData::ClosureExpr, expr.span),
+            ExprKind::Gen(_, _, _) => self.create_def(expr.id, DefPathData::ClosureExpr, expr.span),
             _ => self.parent_def,
         };
 
diff --git a/compiler/rustc_resolve/src/ident.rs b/compiler/rustc_resolve/src/ident.rs
index f2fd4b0bf60c4..1a50bd5ec9865 100644
--- a/compiler/rustc_resolve/src/ident.rs
+++ b/compiler/rustc_resolve/src/ident.rs
@@ -1083,7 +1083,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 for rib in ribs {
                     match rib.kind {
                         RibKind::Normal
-                        | RibKind::ClosureOrAsync
+                        | RibKind::FnOrCoroutine
                         | RibKind::Module(..)
                         | RibKind::MacroDefinition(..)
                         | RibKind::ForwardGenericParamBan => {
@@ -1156,7 +1156,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 for rib in ribs {
                     let has_generic_params: HasGenericParams = match rib.kind {
                         RibKind::Normal
-                        | RibKind::ClosureOrAsync
+                        | RibKind::FnOrCoroutine
                         | RibKind::Module(..)
                         | RibKind::MacroDefinition(..)
                         | RibKind::InlineAsmSym
@@ -1240,7 +1240,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 for rib in ribs {
                     let has_generic_params = match rib.kind {
                         RibKind::Normal
-                        | RibKind::ClosureOrAsync
+                        | RibKind::FnOrCoroutine
                         | RibKind::Module(..)
                         | RibKind::MacroDefinition(..)
                         | RibKind::InlineAsmSym
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 42ca407cddf69..3be962dab90b9 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -177,8 +177,8 @@ pub(crate) enum RibKind<'a> {
     /// upvars).
     AssocItem,
 
-    /// We passed through a closure. Disallow labels.
-    ClosureOrAsync,
+    /// We passed through a function, closure or coroutine signature. Disallow labels.
+    FnOrCoroutine,
 
     /// We passed through an item scope. Disallow upvars.
     Item(HasGenericParams),
@@ -215,7 +215,7 @@ impl RibKind<'_> {
     pub(crate) fn contains_params(&self) -> bool {
         match self {
             RibKind::Normal
-            | RibKind::ClosureOrAsync
+            | RibKind::FnOrCoroutine
             | RibKind::ConstantItem(..)
             | RibKind::Module(_)
             | RibKind::MacroDefinition(_)
@@ -231,7 +231,7 @@ impl RibKind<'_> {
             RibKind::Normal | RibKind::MacroDefinition(..) => false,
 
             RibKind::AssocItem
-            | RibKind::ClosureOrAsync
+            | RibKind::FnOrCoroutine
             | RibKind::Item(..)
             | RibKind::ConstantItem(..)
             | RibKind::Module(..)
@@ -924,9 +924,9 @@ impl<'a: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast,
         debug!("(resolving function) entering function");
 
         // Create a value rib for the function.
-        self.with_rib(ValueNS, RibKind::ClosureOrAsync, |this| {
+        self.with_rib(ValueNS, RibKind::FnOrCoroutine, |this| {
             // Create a label rib for the function.
-            this.with_label_rib(RibKind::ClosureOrAsync, |this| {
+            this.with_label_rib(RibKind::FnOrCoroutine, |this| {
                 match fn_kind {
                     FnKind::Fn(_, _, sig, _, generics, body) => {
                         this.visit_generics(generics);
@@ -4287,7 +4287,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                 ..
             }) => {
                 self.with_rib(ValueNS, RibKind::Normal, |this| {
-                    this.with_label_rib(RibKind::ClosureOrAsync, |this| {
+                    this.with_label_rib(RibKind::FnOrCoroutine, |this| {
                         // Resolve arguments:
                         this.resolve_params(&fn_decl.inputs);
                         // No need to resolve return type --
@@ -4304,7 +4304,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                     })
                 });
             }
-            // For closures, ClosureOrAsyncRibKind is added in visit_fn
+            // For closures, RibKind::FnOrCoroutine is added in visit_fn
             ExprKind::Closure(box ast::Closure {
                 binder: ClosureBinder::For { ref generic_params, span },
                 ..
@@ -4321,8 +4321,8 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                 );
             }
             ExprKind::Closure(..) => visit::walk_expr(self, expr),
-            ExprKind::Async(..) => {
-                self.with_label_rib(RibKind::ClosureOrAsync, |this| visit::walk_expr(this, expr));
+            ExprKind::Gen(..) => {
+                self.with_label_rib(RibKind::FnOrCoroutine, |this| visit::walk_expr(this, expr));
             }
             ExprKind::Repeat(ref elem, ref ct) => {
                 self.visit_expr(elem);
diff --git a/compiler/rustc_smir/src/rustc_smir/mod.rs b/compiler/rustc_smir/src/rustc_smir/mod.rs
index 928536721c95f..219f6d284dd83 100644
--- a/compiler/rustc_smir/src/rustc_smir/mod.rs
+++ b/compiler/rustc_smir/src/rustc_smir/mod.rs
@@ -880,18 +880,28 @@ impl<'tcx> Stable<'tcx> for mir::AggregateKind<'tcx> {
     }
 }
 
+impl<'tcx> Stable<'tcx> for rustc_hir::CoroutineSource {
+    type T = stable_mir::mir::CoroutineSource;
+    fn stable(&self, _: &mut Tables<'tcx>) -> Self::T {
+        use rustc_hir::CoroutineSource;
+        match self {
+            CoroutineSource::Block => stable_mir::mir::CoroutineSource::Block,
+            CoroutineSource::Closure => stable_mir::mir::CoroutineSource::Closure,
+            CoroutineSource::Fn => stable_mir::mir::CoroutineSource::Fn,
+        }
+    }
+}
+
 impl<'tcx> Stable<'tcx> for rustc_hir::CoroutineKind {
     type T = stable_mir::mir::CoroutineKind;
-    fn stable(&self, _: &mut Tables<'tcx>) -> Self::T {
-        use rustc_hir::{CoroutineKind, CoroutineSource};
+    fn stable(&self, tables: &mut Tables<'tcx>) -> Self::T {
+        use rustc_hir::CoroutineKind;
         match self {
-            CoroutineKind::Async(async_gen) => {
-                let async_gen = match async_gen {
-                    CoroutineSource::Block => stable_mir::mir::CoroutineSource::Block,
-                    CoroutineSource::Closure => stable_mir::mir::CoroutineSource::Closure,
-                    CoroutineSource::Fn => stable_mir::mir::CoroutineSource::Fn,
-                };
-                stable_mir::mir::CoroutineKind::Async(async_gen)
+            CoroutineKind::Async(source) => {
+                stable_mir::mir::CoroutineKind::Async(source.stable(tables))
+            }
+            CoroutineKind::Gen(source) => {
+                stable_mir::mir::CoroutineKind::Gen(source.stable(tables))
             }
             CoroutineKind::Coroutine => stable_mir::mir::CoroutineKind::Coroutine,
         }
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index ff61143a12ba2..ba362c0596575 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -98,6 +98,7 @@ symbols! {
         Builtin:            "builtin",
         Catch:              "catch",
         Default:            "default",
+        Gen:                "gen",
         MacroRules:         "macro_rules",
         Raw:                "raw",
         Union:              "union",
@@ -225,6 +226,7 @@ symbols! {
         IpAddr,
         IrTyKind,
         Is,
+        Item,
         ItemContext,
         IterEmpty,
         IterOnce,
@@ -817,6 +819,7 @@ symbols! {
         future_trait,
         gdb_script_file,
         ge,
+        gen_blocks,
         gen_future,
         gen_kill,
         generator_clone,
@@ -1778,6 +1781,7 @@ symbols! {
         xmm_reg,
         yeet_desugar_details,
         yeet_expr,
+        yield_expr,
         ymm_reg,
         zmm_reg,
     }
@@ -2188,8 +2192,9 @@ impl Symbol {
         self >= kw::Abstract && self <= kw::Yield
     }
 
-    fn is_unused_keyword_conditional(self, edition: impl FnOnce() -> Edition) -> bool {
-        self == kw::Try && edition() >= Edition::Edition2018
+    fn is_unused_keyword_conditional(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
+        self == kw::Try && edition().at_least_rust_2018()
+            || self == kw::Gen && edition().at_least_rust_2024()
     }
 
     pub fn is_reserved(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
diff --git a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
index 0c214ca875382..e6bfa62acc884 100644
--- a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
@@ -199,7 +199,15 @@ pub(super) trait GoalKind<'tcx>:
         goal: Goal<'tcx, Self>,
     ) -> QueryResult<'tcx>;
 
-    /// A coroutine (that doesn't come from an `async` desugaring) is known to
+    /// A coroutine (that comes from a `gen` desugaring) is known to implement
+    /// `Iterator<Item = O>`, where `O` is given by the generator's yield type
+    /// that was computed during type-checking.
+    fn consider_builtin_iterator_candidate(
+        ecx: &mut EvalCtxt<'_, 'tcx>,
+        goal: Goal<'tcx, Self>,
+    ) -> QueryResult<'tcx>;
+
+    /// A coroutine (that doesn't come from an `async` or `gen` desugaring) is known to
     /// implement `Coroutine<R, Yield = Y, Return = O>`, given the resume, yield,
     /// and return types of the coroutine computed during type-checking.
     fn consider_builtin_coroutine_candidate(
@@ -552,6 +560,8 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             G::consider_builtin_pointee_candidate(self, goal)
         } else if lang_items.future_trait() == Some(trait_def_id) {
             G::consider_builtin_future_candidate(self, goal)
+        } else if lang_items.iterator_trait() == Some(trait_def_id) {
+            G::consider_builtin_iterator_candidate(self, goal)
         } else if lang_items.gen_trait() == Some(trait_def_id) {
             G::consider_builtin_coroutine_candidate(self, goal)
         } else if lang_items.discriminant_kind_trait() == Some(trait_def_id) {
diff --git a/compiler/rustc_trait_selection/src/solve/project_goals/mod.rs b/compiler/rustc_trait_selection/src/solve/project_goals/mod.rs
index 4950a444ffb50..b31b916f5ef79 100644
--- a/compiler/rustc_trait_selection/src/solve/project_goals/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/project_goals/mod.rs
@@ -485,6 +485,37 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
         )
     }
 
+    fn consider_builtin_iterator_candidate(
+        ecx: &mut EvalCtxt<'_, 'tcx>,
+        goal: Goal<'tcx, Self>,
+    ) -> QueryResult<'tcx> {
+        let self_ty = goal.predicate.self_ty();
+        let ty::Coroutine(def_id, args, _) = *self_ty.kind() else {
+            return Err(NoSolution);
+        };
+
+        // Coroutines are not Iterators unless they come from `gen` desugaring
+        let tcx = ecx.tcx();
+        if !tcx.coroutine_is_gen(def_id) {
+            return Err(NoSolution);
+        }
+
+        let term = args.as_coroutine().yield_ty().into();
+
+        Self::consider_implied_clause(
+            ecx,
+            goal,
+            ty::ProjectionPredicate {
+                projection_ty: ty::AliasTy::new(ecx.tcx(), goal.predicate.def_id(), [self_ty]),
+                term,
+            }
+            .to_predicate(tcx),
+            // Technically, we need to check that the iterator type is Sized,
+            // but that's already proven by the generator being WF.
+            [],
+        )
+    }
+
     fn consider_builtin_coroutine_candidate(
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
@@ -496,7 +527,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
 
         // `async`-desugared coroutines do not implement the coroutine trait
         let tcx = ecx.tcx();
-        if tcx.coroutine_is_async(def_id) {
+        if !tcx.is_general_coroutine(def_id) {
             return Err(NoSolution);
         }
 
@@ -523,7 +554,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
                 term,
             }
             .to_predicate(tcx),
-            // Technically, we need to check that the future type is Sized,
+            // Technically, we need to check that the coroutine type is Sized,
             // but that's already proven by the coroutine being WF.
             [],
         )
diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
index fa91a125b6acc..0d5d492afec0e 100644
--- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
@@ -335,6 +335,30 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
         ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
     }
 
+    fn consider_builtin_iterator_candidate(
+        ecx: &mut EvalCtxt<'_, 'tcx>,
+        goal: Goal<'tcx, Self>,
+    ) -> QueryResult<'tcx> {
+        if goal.predicate.polarity != ty::ImplPolarity::Positive {
+            return Err(NoSolution);
+        }
+
+        let ty::Coroutine(def_id, _, _) = *goal.predicate.self_ty().kind() else {
+            return Err(NoSolution);
+        };
+
+        // Coroutines are not iterators unless they come from `gen` desugaring
+        let tcx = ecx.tcx();
+        if !tcx.coroutine_is_gen(def_id) {
+            return Err(NoSolution);
+        }
+
+        // Gen coroutines unconditionally implement `Iterator`
+        // Technically, we need to check that the iterator output type is Sized,
+        // but that's already proven by the coroutines being WF.
+        ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+    }
+
     fn consider_builtin_coroutine_candidate(
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
@@ -350,7 +374,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
 
         // `async`-desugared coroutines do not implement the coroutine trait
         let tcx = ecx.tcx();
-        if tcx.coroutine_is_async(def_id) {
+        if !tcx.is_general_coroutine(def_id) {
             return Err(NoSolution);
         }
 
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index b9a08056ad162..3087b734cf274 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -2425,6 +2425,21 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         CoroutineKind::Async(CoroutineSource::Closure) => {
                             format!("future created by async closure is not {trait_name}")
                         }
+                        CoroutineKind::Gen(CoroutineSource::Fn) => self
+                            .tcx
+                            .parent(coroutine_did)
+                            .as_local()
+                            .map(|parent_did| hir.local_def_id_to_hir_id(parent_did))
+                            .and_then(|parent_hir_id| hir.opt_name(parent_hir_id))
+                            .map(|name| {
+                                format!("iterator returned by `{name}` is not {trait_name}")
+                            })?,
+                        CoroutineKind::Gen(CoroutineSource::Block) => {
+                            format!("iterator created by gen block is not {trait_name}")
+                        }
+                        CoroutineKind::Gen(CoroutineSource::Closure) => {
+                            format!("iterator created by gen closure is not {trait_name}")
+                        }
                     })
                 })
                 .unwrap_or_else(|| format!("{future_or_coroutine} is not {trait_name}"));
@@ -2905,7 +2920,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             }
             ObligationCauseCode::SizedCoroutineInterior(coroutine_def_id) => {
                 let what = match self.tcx.coroutine_kind(coroutine_def_id) {
-                    None | Some(hir::CoroutineKind::Coroutine) => "yield",
+                    None | Some(hir::CoroutineKind::Coroutine) | Some(hir::CoroutineKind::Gen(_)) => "yield",
                     Some(hir::CoroutineKind::Async(..)) => "await",
                 };
                 err.note(format!(
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
index 353a69ef6d324..030813a4ac372 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
@@ -1614,6 +1614,9 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             hir::CoroutineKind::Async(hir::CoroutineSource::Block) => "an async block",
             hir::CoroutineKind::Async(hir::CoroutineSource::Fn) => "an async function",
             hir::CoroutineKind::Async(hir::CoroutineSource::Closure) => "an async closure",
+            hir::CoroutineKind::Gen(hir::CoroutineSource::Block) => "a gen block",
+            hir::CoroutineKind::Gen(hir::CoroutineSource::Fn) => "a gen function",
+            hir::CoroutineKind::Gen(hir::CoroutineSource::Closure) => "a gen closure",
         })
     }
 
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index af30d9121d1a8..20aa3cec87335 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -1798,7 +1798,7 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
                 let self_ty = selcx.infcx.shallow_resolve(obligation.predicate.self_ty());
 
                 let lang_items = selcx.tcx().lang_items();
-                if [lang_items.gen_trait(), lang_items.future_trait()].contains(&Some(trait_ref.def_id))
+                if [lang_items.gen_trait(), lang_items.future_trait(), lang_items.iterator_trait()].contains(&Some(trait_ref.def_id))
                     || selcx.tcx().fn_trait_kind_from_def_id(trait_ref.def_id).is_some()
                 {
                     true
@@ -2015,6 +2015,8 @@ fn confirm_select_candidate<'cx, 'tcx>(
                 confirm_coroutine_candidate(selcx, obligation, data)
             } else if lang_items.future_trait() == Some(trait_def_id) {
                 confirm_future_candidate(selcx, obligation, data)
+            } else if lang_items.iterator_trait() == Some(trait_def_id) {
+                confirm_iterator_candidate(selcx, obligation, data)
             } else if selcx.tcx().fn_trait_kind_from_def_id(trait_def_id).is_some() {
                 if obligation.predicate.self_ty().is_closure() {
                     confirm_closure_candidate(selcx, obligation, data)
@@ -2135,6 +2137,50 @@ fn confirm_future_candidate<'cx, 'tcx>(
         .with_addl_obligations(obligations)
 }
 
+fn confirm_iterator_candidate<'cx, 'tcx>(
+    selcx: &mut SelectionContext<'cx, 'tcx>,
+    obligation: &ProjectionTyObligation<'tcx>,
+    nested: Vec<PredicateObligation<'tcx>>,
+) -> Progress<'tcx> {
+    let ty::Coroutine(_, args, _) =
+        selcx.infcx.shallow_resolve(obligation.predicate.self_ty()).kind()
+    else {
+        unreachable!()
+    };
+    let gen_sig = args.as_coroutine().poly_sig();
+    let Normalized { value: gen_sig, obligations } = normalize_with_depth(
+        selcx,
+        obligation.param_env,
+        obligation.cause.clone(),
+        obligation.recursion_depth + 1,
+        gen_sig,
+    );
+
+    debug!(?obligation, ?gen_sig, ?obligations, "confirm_future_candidate");
+
+    let tcx = selcx.tcx();
+    let iter_def_id = tcx.require_lang_item(LangItem::Iterator, None);
+
+    let predicate = super::util::iterator_trait_ref_and_outputs(
+        tcx,
+        iter_def_id,
+        obligation.predicate.self_ty(),
+        gen_sig,
+    )
+    .map_bound(|(trait_ref, yield_ty)| {
+        debug_assert_eq!(tcx.associated_item(obligation.predicate.def_id).name, sym::Item);
+
+        ty::ProjectionPredicate {
+            projection_ty: ty::AliasTy::new(tcx, obligation.predicate.def_id, trait_ref.args),
+            term: yield_ty.into(),
+        }
+    });
+
+    confirm_param_env_candidate(selcx, obligation, predicate, false)
+        .with_addl_obligations(nested)
+        .with_addl_obligations(obligations)
+}
+
 fn confirm_builtin_candidate<'cx, 'tcx>(
     selcx: &mut SelectionContext<'cx, 'tcx>,
     obligation: &ProjectionTyObligation<'tcx>,
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index ee50a36be55b1..722f1d6bbb64d 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -114,6 +114,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     self.assemble_coroutine_candidates(obligation, &mut candidates);
                 } else if lang_items.future_trait() == Some(def_id) {
                     self.assemble_future_candidates(obligation, &mut candidates);
+                } else if lang_items.iterator_trait() == Some(def_id) {
+                    self.assemble_iterator_candidates(obligation, &mut candidates);
                 }
 
                 self.assemble_closure_candidates(obligation, &mut candidates);
@@ -211,9 +213,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // type/region parameters.
         let self_ty = obligation.self_ty().skip_binder();
         match self_ty.kind() {
-            // async constructs get lowered to a special kind of coroutine that
+            // `async`/`gen` constructs get lowered to a special kind of coroutine that
             // should *not* `impl Coroutine`.
-            ty::Coroutine(did, ..) if !self.tcx().coroutine_is_async(*did) => {
+            ty::Coroutine(did, ..) if self.tcx().is_general_coroutine(*did) => {
                 debug!(?self_ty, ?obligation, "assemble_coroutine_candidates",);
 
                 candidates.vec.push(CoroutineCandidate);
@@ -243,6 +245,23 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         }
     }
 
+    fn assemble_iterator_candidates(
+        &mut self,
+        obligation: &PolyTraitObligation<'tcx>,
+        candidates: &mut SelectionCandidateSet<'tcx>,
+    ) {
+        let self_ty = obligation.self_ty().skip_binder();
+        if let ty::Coroutine(did, ..) = self_ty.kind() {
+            // gen constructs get lowered to a special kind of coroutine that
+            // should directly `impl Iterator`.
+            if self.tcx().coroutine_is_gen(*did) {
+                debug!(?self_ty, ?obligation, "assemble_iterator_candidates",);
+
+                candidates.vec.push(IteratorCandidate);
+            }
+        }
+    }
+
     /// Checks for the artificial impl that the compiler will create for an obligation like `X :
     /// FnMut<..>` where `X` is a closure type.
     ///
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index fce439f21fa29..952184175f4dd 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -93,6 +93,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 ImplSource::Builtin(BuiltinImplSource::Misc, vtable_future)
             }
 
+            IteratorCandidate => {
+                let vtable_iterator = self.confirm_iterator_candidate(obligation)?;
+                ImplSource::Builtin(BuiltinImplSource::Misc, vtable_iterator)
+            }
+
             FnPointerCandidate { is_const } => {
                 let data = self.confirm_fn_pointer_candidate(obligation, is_const)?;
                 ImplSource::Builtin(BuiltinImplSource::Misc, data)
@@ -780,6 +785,36 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         Ok(nested)
     }
 
+    fn confirm_iterator_candidate(
+        &mut self,
+        obligation: &PolyTraitObligation<'tcx>,
+    ) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
+        // Okay to skip binder because the args on coroutine types never
+        // touch bound regions, they just capture the in-scope
+        // type/region parameters.
+        let self_ty = self.infcx.shallow_resolve(obligation.self_ty().skip_binder());
+        let ty::Coroutine(coroutine_def_id, args, _) = *self_ty.kind() else {
+            bug!("closure candidate for non-closure {:?}", obligation);
+        };
+
+        debug!(?obligation, ?coroutine_def_id, ?args, "confirm_iterator_candidate");
+
+        let gen_sig = args.as_coroutine().poly_sig();
+
+        let trait_ref = super::util::iterator_trait_ref_and_outputs(
+            self.tcx(),
+            obligation.predicate.def_id(),
+            obligation.predicate.no_bound_vars().expect("iterator has no bound vars").self_ty(),
+            gen_sig,
+        )
+        .map_bound(|(trait_ref, ..)| trait_ref);
+
+        let nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
+        debug!(?trait_ref, ?nested, "iterator candidate obligations");
+
+        Ok(nested)
+    }
+
     #[instrument(skip(self), level = "debug")]
     fn confirm_closure_candidate(
         &mut self,
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 67cb39bc00459..cf52e6726a17c 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -1888,6 +1888,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 | ClosureCandidate { .. }
                 | CoroutineCandidate
                 | FutureCandidate
+                | IteratorCandidate
                 | FnPointerCandidate { .. }
                 | BuiltinObjectCandidate
                 | BuiltinUnsizeCandidate
@@ -1916,6 +1917,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 | ClosureCandidate { .. }
                 | CoroutineCandidate
                 | FutureCandidate
+                | IteratorCandidate
                 | FnPointerCandidate { .. }
                 | BuiltinObjectCandidate
                 | BuiltinUnsizeCandidate
@@ -1950,6 +1952,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 | ClosureCandidate { .. }
                 | CoroutineCandidate
                 | FutureCandidate
+                | IteratorCandidate
                 | FnPointerCandidate { .. }
                 | BuiltinObjectCandidate
                 | BuiltinUnsizeCandidate
@@ -1964,6 +1967,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 | ClosureCandidate { .. }
                 | CoroutineCandidate
                 | FutureCandidate
+                | IteratorCandidate
                 | FnPointerCandidate { .. }
                 | BuiltinObjectCandidate
                 | BuiltinUnsizeCandidate
@@ -2070,6 +2074,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 | ClosureCandidate { .. }
                 | CoroutineCandidate
                 | FutureCandidate
+                | IteratorCandidate
                 | FnPointerCandidate { .. }
                 | BuiltinObjectCandidate
                 | BuiltinUnsizeCandidate
@@ -2080,6 +2085,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 | ClosureCandidate { .. }
                 | CoroutineCandidate
                 | FutureCandidate
+                | IteratorCandidate
                 | FnPointerCandidate { .. }
                 | BuiltinObjectCandidate
                 | BuiltinUnsizeCandidate
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
index 67681fb6ec115..bbde0c82743b4 100644
--- a/compiler/rustc_trait_selection/src/traits/util.rs
+++ b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -297,6 +297,17 @@ pub fn future_trait_ref_and_outputs<'tcx>(
     sig.map_bound(|sig| (trait_ref, sig.return_ty))
 }
 
+pub fn iterator_trait_ref_and_outputs<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    iterator_def_id: DefId,
+    self_ty: Ty<'tcx>,
+    sig: ty::PolyGenSig<'tcx>,
+) -> ty::Binder<'tcx, (ty::TraitRef<'tcx>, Ty<'tcx>)> {
+    assert!(!self_ty.has_escaping_bound_vars());
+    let trait_ref = ty::TraitRef::new(tcx, iterator_def_id, [self_ty]);
+    sig.map_bound(|sig| (trait_ref, sig.yield_ty))
+}
+
 pub fn impl_item_is_final(tcx: TyCtxt<'_>, assoc_item: &ty::AssocItem) -> bool {
     assoc_item.defaultness(tcx).is_final()
         && tcx.defaultness(assoc_item.container_id(tcx)).is_final()
diff --git a/compiler/rustc_ty_utils/src/instance.rs b/compiler/rustc_ty_utils/src/instance.rs
index 0e9d79c15c3e0..c0fe13ac9965b 100644
--- a/compiler/rustc_ty_utils/src/instance.rs
+++ b/compiler/rustc_ty_utils/src/instance.rs
@@ -258,6 +258,19 @@ fn resolve_associated_item<'tcx>(
                     debug_assert!(tcx.defaultness(trait_item_id).has_value());
                     Some(Instance::new(trait_item_id, rcvr_args))
                 }
+            } else if Some(trait_ref.def_id) == lang_items.iterator_trait() {
+                let ty::Coroutine(coroutine_def_id, args, _) = *rcvr_args.type_at(0).kind() else {
+                    bug!()
+                };
+                if Some(trait_item_id) == tcx.lang_items().next_fn() {
+                    // `Iterator::next` is generated by the compiler.
+                    Some(Instance { def: ty::InstanceDef::Item(coroutine_def_id), args })
+                } else {
+                    // All other methods are default methods of the `Iterator` trait.
+                    // (this assumes that `ImplSource::Builtin` is only used for methods on `Iterator`)
+                    debug_assert!(tcx.defaultness(trait_item_id).has_value());
+                    Some(Instance::new(trait_item_id, rcvr_args))
+                }
             } else if Some(trait_ref.def_id) == lang_items.gen_trait() {
                 let ty::Coroutine(coroutine_def_id, args, _) = *rcvr_args.type_at(0).kind() else {
                     bug!()
diff --git a/compiler/stable_mir/src/mir/body.rs b/compiler/stable_mir/src/mir/body.rs
index c2e79eaaf3ffe..b686004b2fef5 100644
--- a/compiler/stable_mir/src/mir/body.rs
+++ b/compiler/stable_mir/src/mir/body.rs
@@ -137,6 +137,7 @@ pub enum UnOp {
 pub enum CoroutineKind {
     Async(CoroutineSource),
     Coroutine,
+    Gen(CoroutineSource),
 }
 
 #[derive(Clone, Debug)]
diff --git a/src/tools/clippy/clippy_lints/src/suspicious_operation_groupings.rs b/src/tools/clippy/clippy_lints/src/suspicious_operation_groupings.rs
index d10f10ef87e81..7dff37a2b8ff5 100644
--- a/src/tools/clippy/clippy_lints/src/suspicious_operation_groupings.rs
+++ b/src/tools/clippy/clippy_lints/src/suspicious_operation_groupings.rs
@@ -578,7 +578,7 @@ fn ident_difference_expr_with_base_location(
         | (Assign(_, _, _), Assign(_, _, _))
         | (TryBlock(_), TryBlock(_))
         | (Await(_, _), Await(_, _))
-        | (Async(_, _), Async(_, _))
+        | (Gen(_, _, _), Gen(_, _, _))
         | (Block(_, _), Block(_, _))
         | (Closure(_), Closure(_))
         | (Match(_, _), Match(_, _))
diff --git a/src/tools/clippy/clippy_utils/src/ast_utils.rs b/src/tools/clippy/clippy_utils/src/ast_utils.rs
index a78ff02021f25..a2c61e07b70ad 100644
--- a/src/tools/clippy/clippy_utils/src/ast_utils.rs
+++ b/src/tools/clippy/clippy_utils/src/ast_utils.rs
@@ -211,7 +211,7 @@ pub fn eq_expr(l: &Expr, r: &Expr) -> bool {
                 && eq_fn_decl(lf, rf)
                 && eq_expr(le, re)
         },
-        (Async(lc, lb), Async(rc, rb)) => lc == rc && eq_block(lb, rb),
+        (Gen(lc, lb, lk), Gen(rc, rb, rk)) => lc == rc && eq_block(lb, rb) && lk == rk,
         (Range(lf, lt, ll), Range(rf, rt, rl)) => ll == rl && eq_expr_opt(lf, rf) && eq_expr_opt(lt, rt),
         (AddrOf(lbk, lm, le), AddrOf(rbk, rm, re)) => lbk == rbk && lm == rm && eq_expr(le, re),
         (Path(lq, lp), Path(rq, rp)) => both(lq, rq, eq_qself) && eq_path(lp, rp),
diff --git a/src/tools/clippy/clippy_utils/src/sugg.rs b/src/tools/clippy/clippy_utils/src/sugg.rs
index ae8ee371ffae3..836f8cc19168a 100644
--- a/src/tools/clippy/clippy_utils/src/sugg.rs
+++ b/src/tools/clippy/clippy_utils/src/sugg.rs
@@ -190,7 +190,7 @@ impl<'a> Sugg<'a> {
                 (snip, false) => Sugg::MaybeParen(snip),
                 (snip, true) => Sugg::NonParen(snip),
             },
-            ast::ExprKind::Async(..)
+            ast::ExprKind::Gen(..)
             | ast::ExprKind::Block(..)
             | ast::ExprKind::Break(..)
             | ast::ExprKind::Call(..)
diff --git a/src/tools/rustfmt/src/closures.rs b/src/tools/rustfmt/src/closures.rs
index a09146e95924f..16b8ce7a916a4 100644
--- a/src/tools/rustfmt/src/closures.rs
+++ b/src/tools/rustfmt/src/closures.rs
@@ -188,7 +188,7 @@ fn rewrite_closure_expr(
     fn allow_multi_line(expr: &ast::Expr) -> bool {
         match expr.kind {
             ast::ExprKind::Match(..)
-            | ast::ExprKind::Async(..)
+            | ast::ExprKind::Gen(..)
             | ast::ExprKind::Block(..)
             | ast::ExprKind::TryBlock(..)
             | ast::ExprKind::Loop(..)
diff --git a/src/tools/rustfmt/src/expr.rs b/src/tools/rustfmt/src/expr.rs
index acde880932968..8c2262fde811e 100644
--- a/src/tools/rustfmt/src/expr.rs
+++ b/src/tools/rustfmt/src/expr.rs
@@ -367,7 +367,7 @@ pub(crate) fn format_expr(
                 ))
             }
         }
-        ast::ExprKind::Async(capture_by, ref block) => {
+        ast::ExprKind::Gen(capture_by, ref block, ref kind) => {
             let mover = if capture_by == ast::CaptureBy::Value {
                 "move "
             } else {
@@ -375,7 +375,7 @@ pub(crate) fn format_expr(
             };
             if let rw @ Some(_) = rewrite_single_line_block(
                 context,
-                format!("async {mover}").as_str(),
+                format!("{kind} {mover}").as_str(),
                 block,
                 Some(&expr.attrs),
                 None,
@@ -386,7 +386,7 @@ pub(crate) fn format_expr(
                 // 6 = `async `
                 let budget = shape.width.saturating_sub(6);
                 Some(format!(
-                    "async {mover}{}",
+                    "{kind} {mover}{}",
                     rewrite_block(
                         block,
                         Some(&expr.attrs),
@@ -1371,7 +1371,7 @@ pub(crate) fn can_be_overflowed_expr(
         }
 
         // Handle always block-like expressions
-        ast::ExprKind::Async(..) | ast::ExprKind::Block(..) | ast::ExprKind::Closure(..) => true,
+        ast::ExprKind::Gen(..) | ast::ExprKind::Block(..) | ast::ExprKind::Closure(..) => true,
 
         // Handle `[]` and `{}`-like expressions
         ast::ExprKind::Array(..) | ast::ExprKind::Struct(..) => {
diff --git a/src/tools/rustfmt/src/utils.rs b/src/tools/rustfmt/src/utils.rs
index 79a759d68ce80..fd49030bf1b4a 100644
--- a/src/tools/rustfmt/src/utils.rs
+++ b/src/tools/rustfmt/src/utils.rs
@@ -473,7 +473,7 @@ pub(crate) fn is_block_expr(context: &RewriteContext<'_>, expr: &ast::Expr, repr
         | ast::ExprKind::If(..)
         | ast::ExprKind::Block(..)
         | ast::ExprKind::ConstBlock(..)
-        | ast::ExprKind::Async(..)
+        | ast::ExprKind::Gen(..)
         | ast::ExprKind::Loop(..)
         | ast::ExprKind::ForLoop(..)
         | ast::ExprKind::TryBlock(..)
diff --git a/tests/ui/coroutine/gen_block.e2024.stderr b/tests/ui/coroutine/gen_block.e2024.stderr
new file mode 100644
index 0000000000000..f250e2f79c77d
--- /dev/null
+++ b/tests/ui/coroutine/gen_block.e2024.stderr
@@ -0,0 +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 2 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
new file mode 100644
index 0000000000000..012a8308c7f7a
--- /dev/null
+++ b/tests/ui/coroutine/gen_block.none.stderr
@@ -0,0 +1,49 @@
+error: expected identifier, found reserved keyword `yield`
+  --> $DIR/gen_block.rs:9:19
+   |
+LL |     let y = gen { yield 42 };
+   |             ---   ^^^^^ expected identifier, found reserved keyword
+   |             |
+   |             while parsing this struct
+
+error[E0422]: cannot find struct, variant or union type `gen` in this scope
+  --> $DIR/gen_block.rs:6:13
+   |
+LL |     let x = gen {};
+   |             ^^^ not found in this scope
+
+error[E0422]: cannot find struct, variant or union type `gen` in this scope
+  --> $DIR/gen_block.rs:9:13
+   |
+LL |     let y = gen { yield 42 };
+   |             ^^^ not found in this scope
+
+error[E0422]: cannot find struct, variant or union type `gen` in this scope
+  --> $DIR/gen_block.rs:12:5
+   |
+LL |     gen {};
+   |     ^^^ not found in this scope
+
+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[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`.
diff --git a/tests/ui/coroutine/gen_block.rs b/tests/ui/coroutine/gen_block.rs
new file mode 100644
index 0000000000000..852c7c455a69f
--- /dev/null
+++ b/tests/ui/coroutine/gen_block.rs
@@ -0,0 +1,17 @@
+// revisions: e2024 none
+//[e2024] compile-flags: --edition 2024 -Zunstable-options
+#![cfg_attr(e2024, feature(gen_blocks))]
+
+fn main() {
+    let x = gen {};
+    //[none]~^ ERROR: cannot find
+    //[e2024]~^^ ERROR: type annotations needed
+    let y = gen { yield 42 };
+    //[none]~^ ERROR: found reserved keyword `yield`
+    //[none]~| ERROR: cannot find
+    gen {};
+    //[none]~^ ERROR: cannot find
+
+    let _ = || yield true; //[none]~ ERROR yield syntax is experimental
+    //~^ ERROR yield syntax is experimental
+}
diff --git a/tests/ui/coroutine/gen_block_is_coro.rs b/tests/ui/coroutine/gen_block_is_coro.rs
new file mode 100644
index 0000000000000..c66ccefba85e6
--- /dev/null
+++ b/tests/ui/coroutine/gen_block_is_coro.rs
@@ -0,0 +1,18 @@
+//compile-flags: --edition 2024 -Zunstable-options
+#![feature(coroutines, coroutine_trait, gen_blocks)]
+
+use std::ops::Coroutine;
+
+fn foo() -> impl Coroutine<Yield = u32, Return = ()> { //~ ERROR: Coroutine` is not satisfied
+    gen { yield 42 }
+}
+
+fn bar() -> impl Coroutine<Yield = i64, Return = ()> { //~ ERROR: Coroutine` is not satisfied
+    gen { yield 42 }
+}
+
+fn baz() -> impl Coroutine<Yield = i32, Return = ()> { //~ ERROR: Coroutine` is not satisfied
+    gen { yield 42 }
+}
+
+fn main() {}
diff --git a/tests/ui/coroutine/gen_block_is_coro.stderr b/tests/ui/coroutine/gen_block_is_coro.stderr
new file mode 100644
index 0000000000000..83a674fa53ce3
--- /dev/null
+++ b/tests/ui/coroutine/gen_block_is_coro.stderr
@@ -0,0 +1,21 @@
+error[E0277]: the trait bound `{gen block@$DIR/gen_block_is_coro.rs:7:5: 7:21}: Coroutine` is not satisfied
+  --> $DIR/gen_block_is_coro.rs:6:13
+   |
+LL | fn foo() -> impl Coroutine<Yield = u32, Return = ()> {
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Coroutine` is not implemented for `{gen block@$DIR/gen_block_is_coro.rs:7:5: 7:21}`
+
+error[E0277]: the trait bound `{gen block@$DIR/gen_block_is_coro.rs:11:5: 11:21}: Coroutine` is not satisfied
+  --> $DIR/gen_block_is_coro.rs:10:13
+   |
+LL | fn bar() -> impl Coroutine<Yield = i64, Return = ()> {
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Coroutine` is not implemented for `{gen block@$DIR/gen_block_is_coro.rs:11:5: 11:21}`
+
+error[E0277]: the trait bound `{gen block@$DIR/gen_block_is_coro.rs:15:5: 15:21}: Coroutine` is not satisfied
+  --> $DIR/gen_block_is_coro.rs:14:13
+   |
+LL | fn baz() -> impl Coroutine<Yield = i32, Return = ()> {
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Coroutine` is not implemented for `{gen block@$DIR/gen_block_is_coro.rs:15:5: 15:21}`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/coroutine/gen_block_is_iter.rs b/tests/ui/coroutine/gen_block_is_iter.rs
new file mode 100644
index 0000000000000..92625cf7c2843
--- /dev/null
+++ b/tests/ui/coroutine/gen_block_is_iter.rs
@@ -0,0 +1,19 @@
+// revisions: next old
+//compile-flags: --edition 2024 -Zunstable-options
+//[next] compile-flags: -Ztrait-solver=next
+// check-pass
+#![feature(gen_blocks)]
+
+fn foo() -> impl Iterator<Item = u32> {
+    gen { yield 42 }
+}
+
+fn bar() -> impl Iterator<Item = i64> {
+    gen { yield 42 }
+}
+
+fn baz() -> impl Iterator<Item = i32> {
+    gen { yield 42 }
+}
+
+fn main() {}
diff --git a/tests/ui/coroutine/gen_block_is_no_future.rs b/tests/ui/coroutine/gen_block_is_no_future.rs
new file mode 100644
index 0000000000000..9476651973873
--- /dev/null
+++ b/tests/ui/coroutine/gen_block_is_no_future.rs
@@ -0,0 +1,8 @@
+//compile-flags: --edition 2024 -Zunstable-options
+#![feature(gen_blocks)]
+
+fn foo() -> impl std::future::Future { //~ ERROR is not a future
+    gen { yield 42 }
+}
+
+fn main() {}
diff --git a/tests/ui/coroutine/gen_block_is_no_future.stderr b/tests/ui/coroutine/gen_block_is_no_future.stderr
new file mode 100644
index 0000000000000..db0c3c19b5811
--- /dev/null
+++ b/tests/ui/coroutine/gen_block_is_no_future.stderr
@@ -0,0 +1,12 @@
+error[E0277]: `{gen block@$DIR/gen_block_is_no_future.rs:5:5: 5:21}` is not a future
+  --> $DIR/gen_block_is_no_future.rs:4:13
+   |
+LL | fn foo() -> impl std::future::Future {
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^ `{gen block@$DIR/gen_block_is_no_future.rs:5:5: 5:21}` is not a future
+   |
+   = help: the trait `Future` is not implemented for `{gen block@$DIR/gen_block_is_no_future.rs:5:5: 5:21}`
+   = note: {gen block@$DIR/gen_block_is_no_future.rs:5:5: 5:21} must be a future or must implement `IntoFuture` to be awaited
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/coroutine/gen_block_iterate.rs b/tests/ui/coroutine/gen_block_iterate.rs
new file mode 100644
index 0000000000000..18e1bb8877233
--- /dev/null
+++ b/tests/ui/coroutine/gen_block_iterate.rs
@@ -0,0 +1,35 @@
+// revisions: next old
+//compile-flags: --edition 2024 -Zunstable-options
+//[next] compile-flags: -Ztrait-solver=next
+// run-pass
+#![feature(gen_blocks)]
+
+fn foo() -> impl Iterator<Item = u32> {
+    gen { yield 42; for x in 3..6 { yield x } }
+}
+
+fn moved() -> impl Iterator<Item = u32> {
+    let mut x = "foo".to_string();
+    gen move {
+        yield 42;
+        if x == "foo" { return }
+        x.clear();
+        for x in 3..6 { yield x }
+    }
+}
+
+fn main() {
+    let mut iter = foo();
+    assert_eq!(iter.next(), Some(42));
+    assert_eq!(iter.next(), Some(3));
+    assert_eq!(iter.next(), Some(4));
+    assert_eq!(iter.next(), Some(5));
+    assert_eq!(iter.next(), None);
+    // `gen` blocks are fused
+    assert_eq!(iter.next(), None);
+
+    let mut iter = moved();
+    assert_eq!(iter.next(), Some(42));
+    assert_eq!(iter.next(), None);
+
+}
diff --git a/tests/ui/coroutine/gen_block_move.fixed b/tests/ui/coroutine/gen_block_move.fixed
new file mode 100644
index 0000000000000..5c6c8062322da
--- /dev/null
+++ b/tests/ui/coroutine/gen_block_move.fixed
@@ -0,0 +1,17 @@
+// compile-flags: --edition 2024 -Zunstable-options
+// run-rustfix
+#![feature(gen_blocks)]
+
+fn moved() -> impl Iterator<Item = u32> {
+    let mut x = "foo".to_string();
+    gen move { //~ ERROR: gen block may outlive the current function
+        yield 42;
+        if x == "foo" { return }
+        x.clear();
+        for x in 3..6 { yield x }
+    }
+}
+
+fn main() {
+    for _ in moved() {}
+}
diff --git a/tests/ui/coroutine/gen_block_move.rs b/tests/ui/coroutine/gen_block_move.rs
new file mode 100644
index 0000000000000..abbf8132476c4
--- /dev/null
+++ b/tests/ui/coroutine/gen_block_move.rs
@@ -0,0 +1,17 @@
+// compile-flags: --edition 2024 -Zunstable-options
+// run-rustfix
+#![feature(gen_blocks)]
+
+fn moved() -> impl Iterator<Item = u32> {
+    let mut x = "foo".to_string();
+    gen { //~ ERROR: gen block may outlive the current function
+        yield 42;
+        if x == "foo" { return }
+        x.clear();
+        for x in 3..6 { yield x }
+    }
+}
+
+fn main() {
+    for _ in moved() {}
+}
diff --git a/tests/ui/coroutine/gen_block_move.stderr b/tests/ui/coroutine/gen_block_move.stderr
new file mode 100644
index 0000000000000..b93ac65f5e7d2
--- /dev/null
+++ b/tests/ui/coroutine/gen_block_move.stderr
@@ -0,0 +1,30 @@
+error[E0373]: gen block may outlive the current function, but it borrows `x`, which is owned by the current function
+  --> $DIR/gen_block_move.rs:7:5
+   |
+LL | /     gen {
+LL | |         yield 42;
+LL | |         if x == "foo" { return }
+LL | |         x.clear();
+   | |         - `x` is borrowed here
+LL | |         for x in 3..6 { yield x }
+LL | |     }
+   | |_____^ may outlive borrowed value `x`
+   |
+note: gen block is returned here
+  --> $DIR/gen_block_move.rs:7:5
+   |
+LL | /     gen {
+LL | |         yield 42;
+LL | |         if x == "foo" { return }
+LL | |         x.clear();
+LL | |         for x in 3..6 { yield x }
+LL | |     }
+   | |_____^
+help: to force the gen block to take ownership of `x` (and any other referenced variables), use the `move` keyword
+   |
+LL |     gen move {
+   |         ++++
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0373`.
diff --git a/tests/ui/coroutine/gen_fn.e2024.stderr b/tests/ui/coroutine/gen_fn.e2024.stderr
new file mode 100644
index 0000000000000..41bd04d976912
--- /dev/null
+++ b/tests/ui/coroutine/gen_fn.e2024.stderr
@@ -0,0 +1,10 @@
+error: `gen` blocks are not yet implemented
+  --> $DIR/gen_fn.rs:4:1
+   |
+LL | gen fn foo() {}
+   | ^^^
+   |
+   = help: only the keyword is reserved for now
+
+error: aborting due to previous error
+
diff --git a/tests/ui/coroutine/gen_fn.none.stderr b/tests/ui/coroutine/gen_fn.none.stderr
new file mode 100644
index 0000000000000..5e7bd9d8bbfbf
--- /dev/null
+++ b/tests/ui/coroutine/gen_fn.none.stderr
@@ -0,0 +1,8 @@
+error: expected one of `#`, `async`, `const`, `default`, `extern`, `fn`, `pub`, `unsafe`, or `use`, found `gen`
+  --> $DIR/gen_fn.rs:4:1
+   |
+LL | gen fn foo() {}
+   | ^^^ expected one of 9 possible tokens
+
+error: aborting due to previous error
+
diff --git a/tests/ui/coroutine/gen_fn.rs b/tests/ui/coroutine/gen_fn.rs
new file mode 100644
index 0000000000000..9566660dfb566
--- /dev/null
+++ b/tests/ui/coroutine/gen_fn.rs
@@ -0,0 +1,8 @@
+// revisions: e2024 none
+//[e2024] compile-flags: --edition 2024 -Zunstable-options
+
+gen fn foo() {}
+//[none]~^ ERROR: expected one of `#`, `async`, `const`, `default`, `extern`, `fn`, `pub`, `unsafe`, or `use`, found `gen`
+//[e2024]~^^ ERROR: `gen` blocks are not yet implemented
+
+fn main() {}
diff --git a/tests/ui/coroutine/self_referential_gen_block.rs b/tests/ui/coroutine/self_referential_gen_block.rs
new file mode 100644
index 0000000000000..14daa2e9c3570
--- /dev/null
+++ b/tests/ui/coroutine/self_referential_gen_block.rs
@@ -0,0 +1,17 @@
+// compile-flags: --edition 2024 -Zunstable-options
+#![feature(gen_blocks)]
+//! This test checks that we don't allow self-referential generators
+
+fn main() {
+    let mut x = {
+        let mut x = gen {
+            let y = 42;
+            let z = &y; //~ ERROR: borrow may still be in use when `gen` block yields
+            yield 43;
+            panic!("{z}");
+        };
+        x.next();
+        Box::new(x)
+    };
+    x.next();
+}
diff --git a/tests/ui/coroutine/self_referential_gen_block.stderr b/tests/ui/coroutine/self_referential_gen_block.stderr
new file mode 100644
index 0000000000000..586f53df8f260
--- /dev/null
+++ b/tests/ui/coroutine/self_referential_gen_block.stderr
@@ -0,0 +1,11 @@
+error[E0626]: borrow may still be in use when `gen` block yields
+  --> $DIR/self_referential_gen_block.rs:9:21
+   |
+LL |             let z = &y;
+   |                     ^^
+LL |             yield 43;
+   |             -------- possible yield occurs here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0626`.
diff --git a/tests/ui/feature-gates/feature-gate-coroutines.stderr b/tests/ui/feature-gates/feature-gate-coroutines.e2024.stderr
similarity index 59%
rename from tests/ui/feature-gates/feature-gate-coroutines.stderr
rename to tests/ui/feature-gates/feature-gate-coroutines.e2024.stderr
index dd56164390118..2e529236ad8fe 100644
--- a/tests/ui/feature-gates/feature-gate-coroutines.stderr
+++ b/tests/ui/feature-gates/feature-gate-coroutines.e2024.stderr
@@ -1,5 +1,5 @@
 error[E0658]: yield syntax is experimental
-  --> $DIR/feature-gate-coroutines.rs:2:5
+  --> $DIR/feature-gate-coroutines.rs:5:5
    |
 LL |     yield true;
    |     ^^^^^^^^^^
@@ -8,30 +8,21 @@ LL |     yield true;
    = help: add `#![feature(coroutines)]` to the crate attributes to enable
 
 error[E0658]: yield syntax is experimental
-  --> $DIR/feature-gate-coroutines.rs:8:5
+  --> $DIR/feature-gate-coroutines.rs:9:16
    |
-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
-
-error[E0658]: yield syntax is experimental
-  --> $DIR/feature-gate-coroutines.rs:9:5
-   |
-LL |     yield 0;
-   |     ^^^^^^^
+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:2:5
+  --> $DIR/feature-gate-coroutines.rs:5:5
    |
 LL |     yield true;
    |     ^^^^^^^^^^
 
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
 Some errors have detailed explanations: E0627, E0658.
 For more information about an error, try `rustc --explain E0627`.
diff --git a/tests/ui/feature-gates/feature-gate-coroutines.none.stderr b/tests/ui/feature-gates/feature-gate-coroutines.none.stderr
new file mode 100644
index 0000000000000..ab24805e46777
--- /dev/null
+++ b/tests/ui/feature-gates/feature-gate-coroutines.none.stderr
@@ -0,0 +1,66 @@
+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[E0658]: yield syntax is experimental
+  --> $DIR/feature-gate-coroutines.rs:16:5
+   |
+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
+
+error[E0658]: yield syntax is experimental
+  --> $DIR/feature-gate-coroutines.rs:17:5
+   |
+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 7 previous errors
+
+Some errors have detailed explanations: E0627, E0658.
+For more information about an error, try `rustc --explain E0627`.
diff --git a/tests/ui/feature-gates/feature-gate-coroutines.rs b/tests/ui/feature-gates/feature-gate-coroutines.rs
index c3c5aec88248a..53b58d486a804 100644
--- a/tests/ui/feature-gates/feature-gate-coroutines.rs
+++ b/tests/ui/feature-gates/feature-gate-coroutines.rs
@@ -1,10 +1,18 @@
+// revisions: e2024 none
+//[e2024] compile-flags: --edition 2024 -Zunstable-options
+
 fn main() {
     yield true; //~ ERROR yield syntax is experimental
                 //~^ ERROR yield expression outside of coroutine literal
+                //[none]~^^ ERROR yield syntax is experimental
+
+    let _ = || yield true; //~ ERROR yield syntax is experimental
+    //[none]~^ ERROR yield syntax is experimental
 }
 
 #[cfg(FALSE)]
 fn foo() {
-    yield; //~ ERROR yield syntax is experimental
-    yield 0; //~ ERROR yield syntax is experimental
+    // Ok in 2024 edition
+    yield; //[none]~ ERROR yield syntax is experimental
+    yield 0; //[none]~ ERROR yield syntax is experimental
 }
diff --git a/tests/ui/feature-gates/feature-gate-gen_blocks.e2024.stderr b/tests/ui/feature-gates/feature-gate-gen_blocks.e2024.stderr
new file mode 100644
index 0000000000000..1462c41e957b2
--- /dev/null
+++ b/tests/ui/feature-gates/feature-gate-gen_blocks.e2024.stderr
@@ -0,0 +1,28 @@
+error[E0658]: gen blocks are experimental
+  --> $DIR/feature-gate-gen_blocks.rs:5:5
+   |
+LL |     gen {};
+   |     ^^^^^
+   |
+   = note: see issue #117078 <https://github.com/rust-lang/rust/issues/117078> for more information
+   = help: add `#![feature(gen_blocks)]` to the crate attributes to enable
+
+error[E0658]: gen blocks are experimental
+  --> $DIR/feature-gate-gen_blocks.rs:13:5
+   |
+LL |     gen {};
+   |     ^^^^^
+   |
+   = note: see issue #117078 <https://github.com/rust-lang/rust/issues/117078> for more information
+   = help: add `#![feature(gen_blocks)]` to the crate attributes to enable
+
+error[E0282]: type annotations needed
+  --> $DIR/feature-gate-gen_blocks.rs:5:9
+   |
+LL |     gen {};
+   |         ^^ cannot infer type
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0282, E0658.
+For more information about an error, try `rustc --explain E0282`.
diff --git a/tests/ui/feature-gates/feature-gate-gen_blocks.none.stderr b/tests/ui/feature-gates/feature-gate-gen_blocks.none.stderr
new file mode 100644
index 0000000000000..b448c35e84626
--- /dev/null
+++ b/tests/ui/feature-gates/feature-gate-gen_blocks.none.stderr
@@ -0,0 +1,9 @@
+error[E0422]: cannot find struct, variant or union type `gen` in this scope
+  --> $DIR/feature-gate-gen_blocks.rs:5:5
+   |
+LL |     gen {};
+   |     ^^^ not found in this scope
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0422`.
diff --git a/tests/ui/feature-gates/feature-gate-gen_blocks.rs b/tests/ui/feature-gates/feature-gate-gen_blocks.rs
new file mode 100644
index 0000000000000..e2e1574a36a0f
--- /dev/null
+++ b/tests/ui/feature-gates/feature-gate-gen_blocks.rs
@@ -0,0 +1,15 @@
+// revisions: e2024 none
+//[e2024] compile-flags: --edition 2024 -Zunstable-options
+
+fn main() {
+    gen {};
+    //[none]~^ ERROR: cannot find struct, variant or union type `gen`
+    //[e2024]~^^ ERROR: gen blocks are experimental
+    //[e2024]~| ERROR: type annotations needed
+}
+
+#[cfg(FALSE)]
+fn foo() {
+    gen {};
+    //[e2024]~^ ERROR: gen blocks are experimental
+}