From fd342411e24a8ae159555beb747ae9a27cf75ddf Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Mon, 23 Jun 2025 04:24:21 +0000
Subject: [PATCH 1/5] Bump wasmparser from 0.224.1 to 0.235.0

Bumps [wasmparser](https://github.com/bytecodealliance/wasm-tools) from 0.224.1 to 0.235.0.
- [Release notes](https://github.com/bytecodealliance/wasm-tools/releases)
- [Commits](https://github.com/bytecodealliance/wasm-tools/commits)

---
updated-dependencies:
- dependency-name: wasmparser
  dependency-version: 0.235.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
---
 Cargo.lock                                | 4 ++--
 src/hyperlight_component_macro/Cargo.toml | 2 +-
 src/hyperlight_component_util/Cargo.toml  | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 26019e9d4..c545d3145 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3666,9 +3666,9 @@ dependencies = [
 
 [[package]]
 name = "wasmparser"
-version = "0.224.1"
+version = "0.235.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "04f17a5917c2ddd3819e84c661fae0d6ba29d7b9c1f0e96c708c65a9c4188e11"
+checksum = "161296c618fa2d63f6ed5fffd1112937e803cb9ec71b32b01a76321555660917"
 dependencies = [
  "bitflags 2.9.1",
  "hashbrown",
diff --git a/src/hyperlight_component_macro/Cargo.toml b/src/hyperlight_component_macro/Cargo.toml
index b23c0fef9..8c90c88b3 100644
--- a/src/hyperlight_component_macro/Cargo.toml
+++ b/src/hyperlight_component_macro/Cargo.toml
@@ -16,7 +16,7 @@ name = "hyperlight_component_macro"
 proc-macro = true
 
 [dependencies]
-wasmparser = { version = "0.224.0" }
+wasmparser = { version = "0.235.0" }
 quote = { version = "1.0.38" }
 proc-macro2 = { version = "1.0.95" }
 syn = { version = "2.0.104" }
diff --git a/src/hyperlight_component_util/Cargo.toml b/src/hyperlight_component_util/Cargo.toml
index ece9bdb79..57451dbcd 100644
--- a/src/hyperlight_component_util/Cargo.toml
+++ b/src/hyperlight_component_util/Cargo.toml
@@ -15,7 +15,7 @@ Shared implementation for the procedural macros that generate Hyperlight host an
 name = "hyperlight_component_util"
 
 [dependencies]
-wasmparser = { version = "0.224.0" }
+wasmparser = { version = "0.235.0" }
 quote = { version = "1.0.38" }
 proc-macro2 = { version = "1.0.95" }
 syn = { version = "2.0.104" }

From 157d84d67c6111a34fc1179363919096c0b2e715 Mon Sep 17 00:00:00 2001
From: James Sturtevant <jsturtevant@gmail.com>
Date: Fri, 27 Jun 2025 16:38:45 -0700
Subject: [PATCH 2/5] Updates for wasmparser apis

This was a bit more involved due to a big change in the way function return types are handled.  The orginal change was done in https://github.com/WebAssembly/component-model/pull/368 and put initially put behind a feature flag in https://github.com/bytecodealliance/wasm-tools/pull/1670. In 0.226.0 version of wasmparser this feature flag was removed simplify the return results.  This in turn simplifies the handling of the results here as well.

Signed-off-by: James Sturtevant <jsturtevant@gmail.com>
---
 .../src/elaborate.rs                          | 35 ++++++++-----------
 src/hyperlight_component_util/src/etypes.rs   |  8 +----
 src/hyperlight_component_util/src/hl.rs       | 16 ++++-----
 src/hyperlight_component_util/src/rtypes.rs   |  9 +++--
 .../src/substitute.rs                         |  9 ++---
 src/hyperlight_component_util/src/wf.rs       |  6 ++--
 src/tests/rust_guests/witguest/Cargo.lock     |  4 +--
 7 files changed, 34 insertions(+), 53 deletions(-)

diff --git a/src/hyperlight_component_util/src/elaborate.rs b/src/hyperlight_component_util/src/elaborate.rs
index c38051725..bff05737a 100644
--- a/src/hyperlight_component_util/src/elaborate.rs
+++ b/src/hyperlight_component_util/src/elaborate.rs
@@ -24,14 +24,14 @@ limitations under the License.
 //! substitute.rs for more details of the approach here).
 
 use wasmparser::{
-    ComponentAlias, ComponentDefinedType, ComponentFuncResult, ComponentFuncType,
-    ComponentOuterAliasKind, ComponentType, ComponentTypeDeclaration, ComponentTypeRef,
-    ComponentValType, CompositeInnerType, CoreType, InstanceTypeDeclaration, ModuleTypeDeclaration,
-    OuterAliasKind, PrimitiveValType, TypeBounds, TypeRef,
+    ComponentAlias, ComponentDefinedType, ComponentFuncType, ComponentOuterAliasKind,
+    ComponentType, ComponentTypeDeclaration, ComponentTypeRef, ComponentValType,
+    CompositeInnerType, CoreType, InstanceTypeDeclaration, ModuleTypeDeclaration, OuterAliasKind,
+    PrimitiveValType, TypeBounds, TypeRef,
 };
 
 use crate::etypes::{
-    self, BoundedTyvar, Component, CoreDefined, CoreExportDecl, CoreExternDesc, CoreModule,
+    BoundedTyvar, Component, CoreDefined, CoreExportDecl, CoreExternDesc, CoreModule,
     CoreOrComponentExternDesc, Ctx, Defined, ExternDecl, ExternDesc, FloatWidth, Func, Handleable,
     Instance, IntWidth, Name, Param, QualifiedInstance, RecordField, Resource, ResourceId,
     TypeBound, Tyvar, Value, VariantCase,
@@ -366,6 +366,7 @@ impl<'p, 'a> Ctx<'p, 'a> {
                 PrimitiveValType::F64 => Value::F(FloatWidth::F64),
                 PrimitiveValType::Char => Value::Char,
                 PrimitiveValType::String => Value::String,
+                PrimitiveValType::ErrorContext => panic!("async not yet supported"),
             }),
         }
     }
@@ -428,9 +429,12 @@ impl<'p, 'a> Ctx<'p, 'a> {
                 Defined::Handleable(h) => Ok(Value::Borrow(h.clone())),
                 _ => Err(Error::HandleToNonResource),
             },
-            ComponentDefinedType::Future(_)
-            | ComponentDefinedType::Stream(_)
-            | ComponentDefinedType::ErrorContext => panic!("async not yet supported"),
+            ComponentDefinedType::Future(_) | ComponentDefinedType::Stream(_) => {
+                panic!("async not yet supported")
+            }
+            ComponentDefinedType::FixedSizeList(vt, _) => {
+                Ok(Value::List(Box::new(self.elab_value(vt)?)))
+            }
         }
     }
 
@@ -446,18 +450,9 @@ impl<'p, 'a> Ctx<'p, 'a> {
                     })
                 })
                 .collect::<Result<Vec<_>, Error<'a>>>()?,
-            result: match &ft.results {
-                ComponentFuncResult::Unnamed(vt) => etypes::Result::Unnamed(self.elab_value(vt)?),
-                ComponentFuncResult::Named(rs) => etypes::Result::Named(
-                    rs.iter()
-                        .map(|(n, vt)| {
-                            Ok(Param {
-                                name: Name { name: n },
-                                ty: self.elab_value(vt)?,
-                            })
-                        })
-                        .collect::<Result<Vec<_>, Error<'a>>>()?,
-                ),
+            result: match &ft.result {
+                Some(vt) => Some(self.elab_value(vt)?),
+                None => None,
             },
         })
     }
diff --git a/src/hyperlight_component_util/src/etypes.rs b/src/hyperlight_component_util/src/etypes.rs
index 0cec42887..62693c67a 100644
--- a/src/hyperlight_component_util/src/etypes.rs
+++ b/src/hyperlight_component_util/src/etypes.rs
@@ -136,17 +136,11 @@ pub struct Param<'a> {
     pub ty: Value<'a>,
 }
 
-#[derive(Debug, Clone)]
-pub enum Result<'a> {
-    Unnamed(Value<'a>),
-    Named(Vec<Param<'a>>),
-}
-
 /// functype_e in the specification
 #[derive(Debug, Clone)]
 pub struct Func<'a> {
     pub params: Vec<Param<'a>>,
-    pub result: Result<'a>,
+    pub result: Option<Value<'a>>,
 }
 
 /// In the spec, this does not exist, but a validation rule ensures an
diff --git a/src/hyperlight_component_util/src/hl.rs b/src/hyperlight_component_util/src/hl.rs
index 5a8e984f3..fa1a081aa 100644
--- a/src/hyperlight_component_util/src/hl.rs
+++ b/src/hyperlight_component_util/src/hl.rs
@@ -19,7 +19,7 @@ use proc_macro2::{Ident, TokenStream};
 use quote::{format_ident, quote};
 
 use crate::emit::{State, kebab_to_cons, kebab_to_var};
-use crate::etypes::{self, Defined, Handleable, TypeBound, Tyvar, Value};
+use crate::etypes::{Defined, Handleable, TypeBound, Tyvar, Value};
 use crate::rtypes;
 
 /// Construct a string that can be used "on the wire" to identify a
@@ -653,14 +653,13 @@ pub fn emit_hl_unmarshal_param(s: &mut State, id: Ident, pt: &Value) -> TokenStr
 ///
 /// Precondition: the result type must only be a named result if there
 /// are no names in it (i.e. a unit type)
-pub fn emit_hl_unmarshal_result(s: &mut State, id: Ident, rt: &etypes::Result) -> TokenStream {
+pub fn emit_hl_unmarshal_result(s: &mut State, id: Ident, rt: &Option<Value<'_>>) -> TokenStream {
     match rt {
-        etypes::Result::Named(rs) if rs.is_empty() => quote! { () },
-        etypes::Result::Unnamed(vt) => {
+        Some(vt) => {
             let toks = emit_hl_unmarshal_value(s, id, vt);
             quote! { { #toks }.0 }
         }
-        _ => panic!("named results not supported"),
+        None => quote! { () },
     }
 }
 
@@ -678,13 +677,12 @@ pub fn emit_hl_marshal_param(s: &mut State, id: Ident, pt: &Value) -> TokenStrea
 ///
 /// Precondition: the result type must only be a named result if there
 /// are no names in it (a unit type)
-pub fn emit_hl_marshal_result(s: &mut State, id: Ident, rt: &etypes::Result) -> TokenStream {
+pub fn emit_hl_marshal_result(s: &mut State, id: Ident, rt: &Option<Value<'_>>) -> TokenStream {
     match rt {
-        etypes::Result::Named(rs) if rs.is_empty() => quote! { ::alloc::vec::Vec::new() },
-        etypes::Result::Unnamed(vt) => {
+        None => quote! { ::alloc::vec::Vec::new() },
+        Some(vt) => {
             let toks = emit_hl_marshal_value(s, id, vt);
             quote! { { #toks } }
         }
-        _ => panic!("named results not supported"),
     }
 }
diff --git a/src/hyperlight_component_util/src/rtypes.rs b/src/hyperlight_component_util/src/rtypes.rs
index a6b2266a3..e90d8ad06 100644
--- a/src/hyperlight_component_util/src/rtypes.rs
+++ b/src/hyperlight_component_util/src/rtypes.rs
@@ -30,7 +30,7 @@ use crate::emit::{
 };
 use crate::etypes::{
     Component, Defined, ExternDecl, ExternDesc, Func, Handleable, ImportExport, Instance, Param,
-    Result, TypeBound, Tyvar, Value,
+    TypeBound, Tyvar, Value,
 };
 
 /// When referring to an instance or resource trait, emit a token
@@ -521,11 +521,10 @@ pub fn emit_func_param(s: &mut State, p: &Param) -> TokenStream {
 ///
 /// Precondition: the result type must only be a named result if there
 /// are no names in it (i.e. a unit type)
-pub fn emit_func_result(s: &mut State, r: &Result) -> TokenStream {
+pub fn emit_func_result(s: &mut State, r: &Option<Value<'_>>) -> TokenStream {
     match r {
-        Result::Unnamed(vt) => emit_value(s, vt),
-        Result::Named(rs) if rs.is_empty() => quote! { () },
-        _ => panic!("multiple named function results are not currently supported"),
+        Some(vt) => emit_value(s, vt),
+        None => quote! { () },
     }
 }
 
diff --git a/src/hyperlight_component_util/src/substitute.rs b/src/hyperlight_component_util/src/substitute.rs
index 94f95cf7b..c0dca8429 100644
--- a/src/hyperlight_component_util/src/substitute.rs
+++ b/src/hyperlight_component_util/src/substitute.rs
@@ -134,13 +134,10 @@ where
         pts.iter().map(|pt| self.param(pt)).collect()
     }
 
-    fn result(
-        &self,
-        rt: &crate::etypes::Result<'a>,
-    ) -> Result<crate::etypes::Result<'a>, Self::Error> {
+    fn result(&self, rt: &Option<Value<'a>>) -> Result<Option<Value<'a>>, Self::Error> {
         Ok(match rt {
-            crate::etypes::Result::Unnamed(vt) => crate::etypes::Result::Unnamed(self.value(vt)?),
-            crate::etypes::Result::Named(pts) => crate::etypes::Result::Named(self.params(pts)?),
+            Some(vt) => Some(self.value(vt)?),
+            None => None,
         })
     }
 
diff --git a/src/hyperlight_component_util/src/wf.rs b/src/hyperlight_component_util/src/wf.rs
index db15a7613..b93d1cdfc 100644
--- a/src/hyperlight_component_util/src/wf.rs
+++ b/src/hyperlight_component_util/src/wf.rs
@@ -268,10 +268,8 @@ impl<'p, 'a> Ctx<'p, 'a> {
             .iter()
             .try_for_each(|fp: &'r Param<'a>| self.wf_value(param_pos, &fp.ty))?;
         match &ft.result {
-            crate::etypes::Result::Unnamed(vt) => self.wf_value(result_pos, vt),
-            crate::etypes::Result::Named(ps) => ps
-                .iter()
-                .try_for_each(|fp: &'r Param<'a>| self.wf_value(result_pos, &fp.ty)),
+            Some(vt) => self.wf_value(result_pos, vt),
+            None => Ok(()),
         }
     }
     fn wf_type_bound<'r>(
diff --git a/src/tests/rust_guests/witguest/Cargo.lock b/src/tests/rust_guests/witguest/Cargo.lock
index a1edc4b10..bcb5b4813 100644
--- a/src/tests/rust_guests/witguest/Cargo.lock
+++ b/src/tests/rust_guests/witguest/Cargo.lock
@@ -500,9 +500,9 @@ checksum = "06abde3611657adf66d383f00b093d7faecc7fa57071cce2578660c9f1010821"
 
 [[package]]
 name = "wasmparser"
-version = "0.224.1"
+version = "0.235.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "04f17a5917c2ddd3819e84c661fae0d6ba29d7b9c1f0e96c708c65a9c4188e11"
+checksum = "161296c618fa2d63f6ed5fffd1112937e803cb9ec71b32b01a76321555660917"
 dependencies = [
  "bitflags",
  "hashbrown",

From 231e8bff6d4d620b5fcea62d0ab0186721996660 Mon Sep 17 00:00:00 2001
From: James Sturtevant <jsturtevant@gmail.com>
Date: Tue, 1 Jul 2025 00:45:11 +0000
Subject: [PATCH 3/5] fixup! Updates for wasmparser apis

Signed-off-by: James Sturtevant <jsturtevant@gmail.com>
---
 src/hyperlight_component_util/src/etypes.rs     | 4 +++-
 src/hyperlight_component_util/src/hl.rs         | 6 +++---
 src/hyperlight_component_util/src/rtypes.rs     | 6 +++---
 src/hyperlight_component_util/src/substitute.rs | 5 ++++-
 4 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/src/hyperlight_component_util/src/etypes.rs b/src/hyperlight_component_util/src/etypes.rs
index 62693c67a..78ce056ab 100644
--- a/src/hyperlight_component_util/src/etypes.rs
+++ b/src/hyperlight_component_util/src/etypes.rs
@@ -136,11 +136,13 @@ pub struct Param<'a> {
     pub ty: Value<'a>,
 }
 
+pub type Result<'a> = Option<Value<'a>>;
+
 /// functype_e in the specification
 #[derive(Debug, Clone)]
 pub struct Func<'a> {
     pub params: Vec<Param<'a>>,
-    pub result: Option<Value<'a>>,
+    pub result: Result<'a>,
 }
 
 /// In the spec, this does not exist, but a validation rule ensures an
diff --git a/src/hyperlight_component_util/src/hl.rs b/src/hyperlight_component_util/src/hl.rs
index fa1a081aa..21fc71ad5 100644
--- a/src/hyperlight_component_util/src/hl.rs
+++ b/src/hyperlight_component_util/src/hl.rs
@@ -19,7 +19,7 @@ use proc_macro2::{Ident, TokenStream};
 use quote::{format_ident, quote};
 
 use crate::emit::{State, kebab_to_cons, kebab_to_var};
-use crate::etypes::{Defined, Handleable, TypeBound, Tyvar, Value};
+use crate::etypes::{self, Defined, Handleable, TypeBound, Tyvar, Value};
 use crate::rtypes;
 
 /// Construct a string that can be used "on the wire" to identify a
@@ -653,7 +653,7 @@ pub fn emit_hl_unmarshal_param(s: &mut State, id: Ident, pt: &Value) -> TokenStr
 ///
 /// Precondition: the result type must only be a named result if there
 /// are no names in it (i.e. a unit type)
-pub fn emit_hl_unmarshal_result(s: &mut State, id: Ident, rt: &Option<Value<'_>>) -> TokenStream {
+pub fn emit_hl_unmarshal_result(s: &mut State, id: Ident, rt: &etypes::Result<'_>) -> TokenStream {
     match rt {
         Some(vt) => {
             let toks = emit_hl_unmarshal_value(s, id, vt);
@@ -677,7 +677,7 @@ pub fn emit_hl_marshal_param(s: &mut State, id: Ident, pt: &Value) -> TokenStrea
 ///
 /// Precondition: the result type must only be a named result if there
 /// are no names in it (a unit type)
-pub fn emit_hl_marshal_result(s: &mut State, id: Ident, rt: &Option<Value<'_>>) -> TokenStream {
+pub fn emit_hl_marshal_result(s: &mut State, id: Ident, rt: &etypes::Result) -> TokenStream {
     match rt {
         None => quote! { ::alloc::vec::Vec::new() },
         Some(vt) => {
diff --git a/src/hyperlight_component_util/src/rtypes.rs b/src/hyperlight_component_util/src/rtypes.rs
index e90d8ad06..907f88b12 100644
--- a/src/hyperlight_component_util/src/rtypes.rs
+++ b/src/hyperlight_component_util/src/rtypes.rs
@@ -29,8 +29,8 @@ use crate::emit::{
     split_wit_name,
 };
 use crate::etypes::{
-    Component, Defined, ExternDecl, ExternDesc, Func, Handleable, ImportExport, Instance, Param,
-    TypeBound, Tyvar, Value,
+    self, Component, Defined, ExternDecl, ExternDesc, Func, Handleable, ImportExport, Instance,
+    Param, TypeBound, Tyvar, Value,
 };
 
 /// When referring to an instance or resource trait, emit a token
@@ -521,7 +521,7 @@ pub fn emit_func_param(s: &mut State, p: &Param) -> TokenStream {
 ///
 /// Precondition: the result type must only be a named result if there
 /// are no names in it (i.e. a unit type)
-pub fn emit_func_result(s: &mut State, r: &Option<Value<'_>>) -> TokenStream {
+pub fn emit_func_result(s: &mut State, r: &etypes::Result<'_>) -> TokenStream {
     match r {
         Some(vt) => emit_value(s, vt),
         None => quote! { () },
diff --git a/src/hyperlight_component_util/src/substitute.rs b/src/hyperlight_component_util/src/substitute.rs
index c0dca8429..f885dcb55 100644
--- a/src/hyperlight_component_util/src/substitute.rs
+++ b/src/hyperlight_component_util/src/substitute.rs
@@ -134,7 +134,10 @@ where
         pts.iter().map(|pt| self.param(pt)).collect()
     }
 
-    fn result(&self, rt: &Option<Value<'a>>) -> Result<Option<Value<'a>>, Self::Error> {
+    fn result(
+        &self,
+        rt: &crate::etypes::Result<'a>,
+    ) -> Result<crate::etypes::Result<'a>, Self::Error> {
         Ok(match rt {
             Some(vt) => Some(self.value(vt)?),
             None => None,

From 4bab02e6ebdb02bb29f31e2e365ae16f64b70659 Mon Sep 17 00:00:00 2001
From: James Sturtevant <jsturtevant@gmail.com>
Date: Tue, 1 Jul 2025 17:14:22 +0000
Subject: [PATCH 4/5] Add test to make sure fixed length works

Signed-off-by: James Sturtevant <jsturtevant@gmail.com>
---
 src/hyperlight_host/tests/wit_test.rs      | 4 ++++
 src/tests/rust_guests/witguest/guest.wit   | 1 +
 src/tests/rust_guests/witguest/src/main.rs | 3 +++
 3 files changed, 8 insertions(+)

diff --git a/src/hyperlight_host/tests/wit_test.rs b/src/hyperlight_host/tests/wit_test.rs
index e42441dd8..58572cad4 100644
--- a/src/hyperlight_host/tests/wit_test.rs
+++ b/src/hyperlight_host/tests/wit_test.rs
@@ -155,6 +155,9 @@ impl test::wit::Roundtrip for Host {
     ) -> test::wit::roundtrip::Testenum {
         x
     }
+    fn roundtrip_fix_list(&mut self, x: Vec<u8>) -> Vec<u8> {
+        x
+    }
 
     fn roundtrip_no_result(&mut self, _x: u32) {}
 }
@@ -331,6 +334,7 @@ mod wit_test {
     make_test! { roundtrip_flags_large, in arb_largeflags() }
     make_test! { roundtrip_variant,     in arb_testvariant() }
     make_test! { roundtrip_enum,        in arb_testenum() }
+    make_test! { roundtrip_fix_list,    : Vec<u8> }
 
     #[test]
     fn test_simple_func() {
diff --git a/src/tests/rust_guests/witguest/guest.wit b/src/tests/rust_guests/witguest/guest.wit
index 30b4969c5..b99e35ef9 100644
--- a/src/tests/rust_guests/witguest/guest.wit
+++ b/src/tests/rust_guests/witguest/guest.wit
@@ -26,6 +26,7 @@ interface roundtrip {
   roundtrip-option: func(x: option<string>) -> option<string>;
   roundtrip-result: func(x: result<char, string>) -> result<char, string>;
   roundtrip-no-result: func(x: u32);
+  roundtrip-fix-list: func(x: list<u8, 4>) -> list<u8, 4>;
 
   record testrecord {
     contents: string,
diff --git a/src/tests/rust_guests/witguest/src/main.rs b/src/tests/rust_guests/witguest/src/main.rs
index 1edf44ec1..cb71aa0e4 100644
--- a/src/tests/rust_guests/witguest/src/main.rs
+++ b/src/tests/rust_guests/witguest/src/main.rs
@@ -113,6 +113,9 @@ impl test::wit::Roundtrip for Guest {
     ) -> test::wit::roundtrip::Testenum {
         (Host {}).roundtrip_enum(x)
     }
+    fn roundtrip_fix_list(&mut self, x: Vec<u8>) -> Vec<u8> {
+        (Host {}).roundtrip_fix_list(x)
+    }
     fn roundtrip_no_result(&mut self, x: u32) {
         (Host {}).roundtrip_no_result(x)
     }

From f7bc8435f0c06ef8a32b8840fa7fb2a152106ad1 Mon Sep 17 00:00:00 2001
From: James Sturtevant <jsturtevant@gmail.com>
Date: Tue, 1 Jul 2025 19:36:14 +0000
Subject: [PATCH 5/5] Handle fixed list with different API

Signed-off-by: James Sturtevant <jsturtevant@gmail.com>
---
 .../src/elaborate.rs                          |  4 +--
 src/hyperlight_component_util/src/etypes.rs   |  1 +
 src/hyperlight_component_util/src/hl.rs       | 33 +++++++++++++++++++
 src/hyperlight_component_util/src/rtypes.rs   |  5 +++
 .../src/substitute.rs                         |  1 +
 src/hyperlight_component_util/src/wf.rs       |  1 +
 src/hyperlight_host/tests/wit_test.rs         | 10 ++++--
 src/tests/rust_guests/witguest/guest.wit      |  1 +
 src/tests/rust_guests/witguest/src/main.rs    |  7 +++-
 9 files changed, 57 insertions(+), 6 deletions(-)

diff --git a/src/hyperlight_component_util/src/elaborate.rs b/src/hyperlight_component_util/src/elaborate.rs
index bff05737a..28a5f0f0e 100644
--- a/src/hyperlight_component_util/src/elaborate.rs
+++ b/src/hyperlight_component_util/src/elaborate.rs
@@ -432,8 +432,8 @@ impl<'p, 'a> Ctx<'p, 'a> {
             ComponentDefinedType::Future(_) | ComponentDefinedType::Stream(_) => {
                 panic!("async not yet supported")
             }
-            ComponentDefinedType::FixedSizeList(vt, _) => {
-                Ok(Value::List(Box::new(self.elab_value(vt)?)))
+            ComponentDefinedType::FixedSizeList(vt, size) => {
+                Ok(Value::FixList(Box::new(self.elab_value(vt)?), *size))
             }
         }
     }
diff --git a/src/hyperlight_component_util/src/etypes.rs b/src/hyperlight_component_util/src/etypes.rs
index 78ce056ab..5723eaf9a 100644
--- a/src/hyperlight_component_util/src/etypes.rs
+++ b/src/hyperlight_component_util/src/etypes.rs
@@ -83,6 +83,7 @@ pub enum Value<'a> {
     Char,
     String,
     List(Box<Value<'a>>),
+    FixList(Box<Value<'a>>, u32),
     Record(Vec<RecordField<'a>>),
     Tuple(Vec<Value<'a>>),
     Flags(Vec<Name<'a>>),
diff --git a/src/hyperlight_component_util/src/hl.rs b/src/hyperlight_component_util/src/hl.rs
index 21fc71ad5..781328688 100644
--- a/src/hyperlight_component_util/src/hl.rs
+++ b/src/hyperlight_component_util/src/hl.rs
@@ -223,6 +223,20 @@ pub fn emit_hl_unmarshal_value(s: &mut State, id: Ident, vt: &Value) -> TokenStr
                 (#retid, cursor)
             }
         }
+        Value::FixList(vt, _size) => {
+            let inid = format_ident!("{}_elem", id);
+            let vtun = emit_hl_unmarshal_value(s, inid.clone(), vt);
+            quote! {
+                let mut cursor = 0;
+                let arr = ::core::array::from_fn(|_i| {
+                    let #inid = &#id[cursor..];
+                    let (x, b) = { #vtun };
+                    cursor += b;
+                    x
+                });
+                (arr, cursor)
+            }
+        }
         Value::Record(_) => panic!("record not at top level of valtype"),
         Value::Tuple(vts) => {
             let inid = format_ident!("{}_elem", id);
@@ -515,6 +529,25 @@ pub fn emit_hl_marshal_value(s: &mut State, id: Ident, vt: &Value) -> TokenStrea
                 #retid
             }
         }
+        Value::FixList(vt, _size) => {
+            // Optimize for byte arrays ie. [u8; N]
+            if matches!(vt.as_ref(), Value::S(_) | Value::U(_) | Value::F(_)) {
+                quote! {
+                    alloc::vec::Vec::from(#id.as_slice())
+                }
+            } else {
+                let retid = format_ident!("{}_fixlist", id);
+                let inid = format_ident!("{}_elem", id);
+                let vtun = emit_hl_marshal_value(s, inid.clone(), vt);
+                quote! {
+                    let mut #retid = alloc::vec::Vec::new();
+                    for #inid in #id {
+                        #retid.extend({ #vtun })
+                    }
+                    #retid
+                }
+            }
+        }
         Value::Record(_) => panic!("record not at top level of valtype"),
         Value::Tuple(vts) => {
             let retid = format_ident!("{}_tuple", id);
diff --git a/src/hyperlight_component_util/src/rtypes.rs b/src/hyperlight_component_util/src/rtypes.rs
index 907f88b12..e9b8ded61 100644
--- a/src/hyperlight_component_util/src/rtypes.rs
+++ b/src/hyperlight_component_util/src/rtypes.rs
@@ -281,6 +281,11 @@ pub fn emit_value(s: &mut State, vt: &Value) -> TokenStream {
             let vt = emit_value(s, vt);
             quote! { alloc::vec::Vec<#vt> }
         }
+        Value::FixList(vt, size) => {
+            let vt = emit_value(s, vt);
+            let size = *size as usize;
+            quote! { [#vt; #size] }
+        }
         Value::Record(_) => panic!("record not at top level of valtype"),
         Value::Tuple(vts) => {
             let vts = vts.iter().map(|vt| emit_value(s, vt)).collect::<Vec<_>>();
diff --git a/src/hyperlight_component_util/src/substitute.rs b/src/hyperlight_component_util/src/substitute.rs
index f885dcb55..5ea07d609 100644
--- a/src/hyperlight_component_util/src/substitute.rs
+++ b/src/hyperlight_component_util/src/substitute.rs
@@ -96,6 +96,7 @@ where
             Value::Char => Value::Char,
             Value::String => Value::String,
             Value::List(vt) => Value::List(Box::new(self.value(vt)?)),
+            Value::FixList(vt, size) => Value::FixList(Box::new(self.value(vt)?), *size),
             Value::Record(rfs) => Value::Record(self.record_fields(rfs)?),
             Value::Variant(vcs) => Value::Variant(self.variant_cases(vcs)?),
             Value::Flags(ns) => Value::Flags(ns.clone()),
diff --git a/src/hyperlight_component_util/src/wf.rs b/src/hyperlight_component_util/src/wf.rs
index b93d1cdfc..20321d6d7 100644
--- a/src/hyperlight_component_util/src/wf.rs
+++ b/src/hyperlight_component_util/src/wf.rs
@@ -213,6 +213,7 @@ impl<'p, 'a> Ctx<'p, 'a> {
             Value::Char => Ok(()),
             Value::String => Ok(()),
             Value::List(vt) => self.wf_value(p_, vt),
+            Value::FixList(vt, _) => self.wf_value(p_, vt),
             Value::Record(rfs) => anon_err.and(self.wf_record_fields(p_, rfs)),
             Value::Variant(vcs) => anon_err.and(self.wf_variant_cases(p_, vcs)),
             Value::Flags(ns) => anon_err.and(error_if_duplicates_by(
diff --git a/src/hyperlight_host/tests/wit_test.rs b/src/hyperlight_host/tests/wit_test.rs
index 58572cad4..403553379 100644
--- a/src/hyperlight_host/tests/wit_test.rs
+++ b/src/hyperlight_host/tests/wit_test.rs
@@ -155,7 +155,10 @@ impl test::wit::Roundtrip for Host {
     ) -> test::wit::roundtrip::Testenum {
         x
     }
-    fn roundtrip_fix_list(&mut self, x: Vec<u8>) -> Vec<u8> {
+    fn roundtrip_fix_list(&mut self, x: [u8; 4]) -> [u8; 4] {
+        x
+    }
+    fn roundtrip_fix_list_string(&mut self, x: [String; 4]) -> [String; 4] {
         x
     }
 
@@ -334,10 +337,11 @@ mod wit_test {
     make_test! { roundtrip_flags_large, in arb_largeflags() }
     make_test! { roundtrip_variant,     in arb_testvariant() }
     make_test! { roundtrip_enum,        in arb_testenum() }
-    make_test! { roundtrip_fix_list,    : Vec<u8> }
+    make_test! { roundtrip_fix_list,    : [u8; 4] }
+    make_test! { roundtrip_fix_list_string, : [String; 4] }
 
     #[test]
-    fn test_simple_func() {
+    fn test_roundtrip_no_result() {
         sb().roundtrip().roundtrip_no_result(42);
     }
 
diff --git a/src/tests/rust_guests/witguest/guest.wit b/src/tests/rust_guests/witguest/guest.wit
index b99e35ef9..07afc0d73 100644
--- a/src/tests/rust_guests/witguest/guest.wit
+++ b/src/tests/rust_guests/witguest/guest.wit
@@ -27,6 +27,7 @@ interface roundtrip {
   roundtrip-result: func(x: result<char, string>) -> result<char, string>;
   roundtrip-no-result: func(x: u32);
   roundtrip-fix-list: func(x: list<u8, 4>) -> list<u8, 4>;
+  roundtrip-fix-list-string: func(x: list<string, 4>) -> list<string, 4>;
 
   record testrecord {
     contents: string,
diff --git a/src/tests/rust_guests/witguest/src/main.rs b/src/tests/rust_guests/witguest/src/main.rs
index cb71aa0e4..d9e610029 100644
--- a/src/tests/rust_guests/witguest/src/main.rs
+++ b/src/tests/rust_guests/witguest/src/main.rs
@@ -21,6 +21,8 @@ extern crate alloc;
 extern crate hyperlight_guest;
 
 mod bindings;
+use alloc::string::String;
+
 use bindings::*;
 
 struct Guest {}
@@ -113,9 +115,12 @@ impl test::wit::Roundtrip for Guest {
     ) -> test::wit::roundtrip::Testenum {
         (Host {}).roundtrip_enum(x)
     }
-    fn roundtrip_fix_list(&mut self, x: Vec<u8>) -> Vec<u8> {
+    fn roundtrip_fix_list(&mut self, x: [u8; 4]) -> [u8; 4] {
         (Host {}).roundtrip_fix_list(x)
     }
+    fn roundtrip_fix_list_string(&mut self, x: [String; 4]) -> [String; 4] {
+        (Host {}).roundtrip_fix_list_string(x)
+    }
     fn roundtrip_no_result(&mut self, x: u32) {
         (Host {}).roundtrip_no_result(x)
     }