diff --git a/lib/src/modules/mod.rs b/lib/src/modules/mod.rs
index d6dbcdfed..0d7dab5bb 100644
--- a/lib/src/modules/mod.rs
+++ b/lib/src/modules/mod.rs
@@ -492,7 +492,7 @@ pub mod mods {
 
             /// Returns the documentation for the current field.
             pub fn doc(&self) -> Option<&str> {
-                self.struct_field.doc.as_deref()
+                self.struct_field.doc
             }
         }
 
diff --git a/lib/src/scanner/mod.rs b/lib/src/scanner/mod.rs
index 9a2cbce42..3d5d346a7 100644
--- a/lib/src/scanner/mod.rs
+++ b/lib/src/scanner/mod.rs
@@ -703,6 +703,7 @@ impl<'r> Scanner<'r> {
                 &module_root_descriptor,
                 module_output.as_deref(),
                 generate_fields_for_enums,
+                false,
             );
 
             if let Some(module_output) = module_output {
diff --git a/lib/src/symbols/mod.rs b/lib/src/symbols/mod.rs
index f006a080b..6fddb9080 100644
--- a/lib/src/symbols/mod.rs
+++ b/lib/src/symbols/mod.rs
@@ -357,6 +357,7 @@ mod tests {
             &TestProto2::descriptor(),
             None,
             true,
+            false,
         );
 
         assert_eq!(test.lookup("int32_zero").unwrap().ty(), Type::Integer);
@@ -436,6 +437,7 @@ mod tests {
             &descriptor,
             Some(message.as_ref()),
             true,
+            false,
         );
 
         assert_eq!(
diff --git a/lib/src/types/structure.rs b/lib/src/types/structure.rs
index 9fb9d3d94..460c09448 100644
--- a/lib/src/types/structure.rs
+++ b/lib/src/types/structure.rs
@@ -99,12 +99,15 @@ pub(crate) struct StructField {
     /// Field type and value.
     pub type_value: TypeValue,
     /// Access control list (ACL) for accessing this struct field.
+    #[serde(skip)]
     pub acl: Option<Vec<AclEntry>>,
     /// Deprecation notice that must be shown when the field is used in a
     /// rule. This is `None` for non-deprecated fields.
+    #[serde(skip)]
     pub deprecation_notice: Option<DeprecationNotice>,
     /// Description of the field extracted from the .proto file.
-    pub doc: Option<String>,
+    #[serde(skip)]
+    pub doc: Option<&'static str>,
 }
 
 /// A dynamic structure with one or more fields.
@@ -347,11 +350,8 @@ impl Struct {
     /// be [`None`].
     ///
     /// The `generate_fields_for_enums` controls whether the enums defined
-    /// by the proto will be included as fields in the structure. Enums are
-    /// required only at compile time, so that the compiler can look up the
-    /// enums by name and resolve their values, but at scan time enums are
-    /// not necessary because their values are already embedded in the code.
-    /// The scanner never asks for an enum by field index.
+    /// by the proto will be included in the structure. These are required
+    /// only at compile time, or when constant folding is disabled.
     ///
     /// Also notice that a .proto file can define enums at the top level,
     /// outside any message. Those enums will be handled as if they were
@@ -383,6 +383,7 @@ impl Struct {
         msg_descriptor: &MessageDescriptor,
         msg: Option<&dyn MessageDyn>,
         generate_fields_for_enums: bool,
+        generate_compile_time_fields: bool,
     ) -> Rc<Self> {
         let syntax = msg_descriptor.file_descriptor().syntax();
         let mut fields = Vec::new();
@@ -403,18 +404,21 @@ impl Struct {
                     &ty,
                     msg.and_then(|msg| fd.get_singular(msg)),
                     generate_fields_for_enums,
+                    generate_compile_time_fields,
                     syntax,
                 ),
                 RuntimeFieldType::Repeated(ty) => Self::new_array(
                     &ty,
                     msg.map(|msg| fd.get_repeated(msg)),
                     generate_fields_for_enums,
+                    generate_compile_time_fields,
                 ),
                 RuntimeFieldType::Map(key_ty, value_ty) => Self::new_map(
                     &key_ty,
                     &value_ty,
                     msg.map(|msg| fd.get_map(msg)),
                     generate_fields_for_enums,
+                    generate_compile_time_fields,
                     syntax,
                 ),
             };
@@ -437,10 +441,22 @@ impl Struct {
                 StructField {
                     // Index is initially zero, will be adjusted later.
                     type_value: value,
-                    acl: Self::acl(&fd),
-                    deprecation_notice: Self::deprecation_notice(&fd),
+                    acl: if generate_compile_time_fields {
+                        Self::acl(&fd)
+                    } else {
+                        None
+                    },
+                    deprecation_notice: if generate_compile_time_fields {
+                        Self::deprecation_notice(&fd)
+                    } else {
+                        None
+                    },
                     number,
-                    doc: Self::field_doc(msg_descriptor.full_name(), number),
+                    doc: if generate_compile_time_fields {
+                        Self::field_doc(msg_descriptor.full_name(), number)
+                    } else {
+                        None
+                    },
                 },
             ));
         }
@@ -788,7 +804,7 @@ impl Struct {
             })
     }
 
-    fn field_doc(msg_name: &str, field_number: u64) -> Option<String> {
+    fn field_doc(msg_name: &str, field_number: u64) -> Option<&'static str> {
         use crate::modules::field_docs::FIELD_DOCS;
         let idx = FIELD_DOCS
             .binary_search_by(|&(name, number, _)| match name.cmp(msg_name) {
@@ -796,7 +812,7 @@ impl Struct {
                 ord => ord,
             })
             .ok()?;
-        Some(FIELD_DOCS[idx].2.to_string())
+        Some(FIELD_DOCS[idx].2)
     }
 
     /// Given a protobuf type and value returns a [`TypeValue`].
@@ -823,6 +839,7 @@ impl Struct {
         ty: &RuntimeType,
         value: Option<ReflectValueRef>,
         enum_as_fields: bool,
+        generate_compile_time_fields: bool,
         syntax: Syntax,
     ) -> TypeValue {
         match ty {
@@ -880,12 +897,14 @@ impl Struct {
                         msg_descriptor,
                         value,
                         enum_as_fields,
+                        generate_compile_time_fields,
                     )
                 } else {
                     Self::from_proto_descriptor_and_msg(
                         msg_descriptor,
                         None,
                         enum_as_fields,
+                        generate_compile_time_fields,
                     )
                 };
                 TypeValue::Struct(structure)
@@ -897,6 +916,7 @@ impl Struct {
         ty: &RuntimeType,
         repeated: Option<ReflectRepeatedRef>,
         enum_as_fields: bool,
+        generate_compile_time_fields: bool,
     ) -> TypeValue {
         let array = match ty {
             RuntimeType::I32 => {
@@ -904,7 +924,7 @@ impl Struct {
                     Array::Integers(
                         repeated
                             .into_iter()
-                            .map(|value| value.to_i32().unwrap() as i64)
+                            .map(|value| Self::value_as_i64(value))
                             .collect(),
                     )
                 } else {
@@ -916,7 +936,7 @@ impl Struct {
                     Array::Integers(
                         repeated
                             .into_iter()
-                            .map(|value| value.to_i64().unwrap())
+                            .map(|value| Self::value_as_i64(value))
                             .collect(),
                     )
                 } else {
@@ -928,7 +948,7 @@ impl Struct {
                     Array::Integers(
                         repeated
                             .into_iter()
-                            .map(|value| value.to_u32().unwrap() as i64)
+                            .map(|value| Self::value_as_i64(value))
                             .collect(),
                     )
                 } else {
@@ -936,14 +956,23 @@ impl Struct {
                 }
             }
             RuntimeType::U64 => {
-                todo!()
+                if let Some(repeated) = repeated {
+                    Array::Integers(
+                        repeated
+                            .into_iter()
+                            .map(|value| Self::value_as_i64(value))
+                            .collect(),
+                    )
+                } else {
+                    Array::Integers(vec![])
+                }
             }
             RuntimeType::F32 => {
                 if let Some(repeated) = repeated {
                     Array::Floats(
                         repeated
                             .into_iter()
-                            .map(|value| value.to_f32().unwrap() as f64)
+                            .map(|value| Self::value_as_f64(value))
                             .collect(),
                     )
                 } else {
@@ -955,7 +984,7 @@ impl Struct {
                     Array::Floats(
                         repeated
                             .into_iter()
-                            .map(|value| value.to_f64().unwrap())
+                            .map(|value| Self::value_as_f64(value))
                             .collect(),
                     )
                 } else {
@@ -967,7 +996,7 @@ impl Struct {
                     Array::Bools(
                         repeated
                             .into_iter()
-                            .map(|value| value.to_bool().unwrap())
+                            .map(|value| Self::value_as_bool(value))
                             .collect(),
                     )
                 } else {
@@ -1026,6 +1055,7 @@ impl Struct {
                                     msg_descriptor,
                                     value,
                                     enum_as_fields,
+                                    generate_compile_time_fields,
                                 )
                             })
                             .collect(),
@@ -1036,6 +1066,7 @@ impl Struct {
                             msg_descriptor,
                             None,
                             enum_as_fields,
+                            generate_compile_time_fields,
                         ),
                     ])
                 }
@@ -1050,6 +1081,7 @@ impl Struct {
         value_ty: &RuntimeType,
         map: Option<ReflectMapRef>,
         enum_as_fields: bool,
+        generate_compile_time_fields: bool,
         syntax: Syntax,
     ) -> TypeValue {
         let map = match key_ty {
@@ -1057,6 +1089,7 @@ impl Struct {
                 value_ty,
                 map,
                 enum_as_fields,
+                generate_compile_time_fields,
                 syntax,
             ),
             RuntimeType::I32
@@ -1066,6 +1099,7 @@ impl Struct {
                 value_ty,
                 map,
                 enum_as_fields,
+                generate_compile_time_fields,
                 syntax,
             ),
             ty => {
@@ -1080,6 +1114,7 @@ impl Struct {
         value_ty: &RuntimeType,
         map: Option<ReflectMapRef>,
         enum_as_fields: bool,
+        generate_compile_time_fields: bool,
         syntax: Syntax,
     ) -> Map {
         if let Some(map) = map {
@@ -1091,6 +1126,7 @@ impl Struct {
                         value_ty,
                         Some(value),
                         enum_as_fields,
+                        generate_compile_time_fields,
                         syntax,
                     ),
                 );
@@ -1102,6 +1138,7 @@ impl Struct {
                     value_ty,
                     None,
                     enum_as_fields,
+                    generate_compile_time_fields,
                     syntax,
                 )),
                 map: Default::default(),
@@ -1113,6 +1150,7 @@ impl Struct {
         value_ty: &RuntimeType,
         map: Option<ReflectMapRef>,
         enum_as_fields: bool,
+        generate_compile_time_fields: bool,
         syntax: Syntax,
     ) -> Map {
         if let Some(map) = map {
@@ -1124,6 +1162,7 @@ impl Struct {
                         value_ty,
                         Some(value),
                         enum_as_fields,
+                        generate_compile_time_fields,
                         syntax,
                     ),
                 );
@@ -1135,6 +1174,7 @@ impl Struct {
                     value_ty,
                     None,
                     enum_as_fields,
+                    generate_compile_time_fields,
                     syntax,
                 )),
                 map: Default::default(),
@@ -1146,12 +1186,14 @@ impl Struct {
         msg_descriptor: &MessageDescriptor,
         value: ReflectValueRef,
         enum_as_fields: bool,
+        generate_compile_time_fields: bool,
     ) -> Rc<Self> {
         if let ReflectValueRef::Message(m) = value {
             Struct::from_proto_descriptor_and_msg(
                 msg_descriptor,
                 Some(m.deref()),
                 enum_as_fields,
+                generate_compile_time_fields,
             )
         } else {
             unreachable!()
@@ -1226,6 +1268,7 @@ impl From<&dyn RegisteredModule> for Rc<Struct> {
             &module.root_descriptor(),
             None,
             true,
+            true,
         );
 
         // Get a mutable reference for the module's structure. This is
@@ -1308,6 +1351,7 @@ mod tests {
             &TestProto2::descriptor(),
             None,
             true,
+            true,
         );
 
         let structure = Rc::<Struct>::get_mut(&mut structure).unwrap();