diff --git a/src/ir.rs b/src/ir.rs
index 48ac76f..5308405 100644
--- a/src/ir.rs
+++ b/src/ir.rs
@@ -15,6 +15,7 @@
 mod arbitrary;
 pub mod ast;
 mod eval;
+mod fields;
 mod pretty;
 mod strings;
 mod top_level;
diff --git a/src/ir/ast.rs b/src/ir/ast.rs
index 88820b6..8d86fdf 100644
--- a/src/ir/ast.rs
+++ b/src/ir/ast.rs
@@ -1,4 +1,5 @@
 use crate::eval::PrimitiveType;
+pub use crate::ir::fields::Fields;
 use crate::syntax::{ConstantType, Location};
 use internment::ArcIntern;
 use proptest::arbitrary::Arbitrary;
@@ -247,7 +248,7 @@ impl Value {
 pub enum Type {
     Primitive(PrimitiveType),
     Function(Vec<Type>, Box<Type>),
-    Structure(HashMap<ArcIntern<String>, Type>),
+    Structure(Fields<Type>),
 }
 
 impl Type {
@@ -281,7 +282,7 @@ pub enum TypeOrVar {
     Primitive(PrimitiveType),
     Variable(Location, ArcIntern<String>),
     Function(Vec<TypeOrVar>, Box<TypeOrVar>),
-    Structure(HashMap<ArcIntern<String>, TypeOrVar>),
+    Structure(Fields<TypeOrVar>),
 }
 
 impl Default for TypeOrVar {
@@ -330,7 +331,7 @@ impl TypeOrVar {
             TypeOrVar::Primitive(_) => false,
 
             TypeOrVar::Structure(fields) => {
-                fields.values_mut().any(|x| x.replace(name, replace_with))
+                fields.types_mut().any(|x| x.replace(name, replace_with))
             }
         }
     }
@@ -344,7 +345,7 @@ impl TypeOrVar {
             TypeOrVar::Function(args, ret) => {
                 args.iter().all(TypeOrVar::is_resolved) && ret.is_resolved()
             }
-            TypeOrVar::Structure(fields) => fields.values().all(TypeOrVar::is_resolved),
+            TypeOrVar::Structure(fields) => fields.types().all(TypeOrVar::is_resolved),
         }
     }
 }
@@ -364,7 +365,7 @@ impl PartialEq<Type> for TypeOrVar {
 
             Type::Structure(fields1) => match self {
                 TypeOrVar::Structure(fields2) => {
-                    fields1.len() == fields2.len()
+                    fields1.count() == fields2.count()
                         && fields1.iter().all(|(name, subtype)| {
                             fields2.get(name).map(|x| x == subtype).unwrap_or(false)
                         })
@@ -418,9 +419,7 @@ impl<T: Into<Type>> From<T> for TypeOrVar {
                 args.into_iter().map(Into::into).collect(),
                 Box::new((*ret).into()),
             ),
-            Type::Structure(fields) => {
-                TypeOrVar::Structure(fields.into_iter().map(|(n, t)| (n, t.into())).collect())
-            }
+            Type::Structure(fields) => TypeOrVar::Structure(fields.map(Into::into)),
         }
     }
 }
@@ -450,16 +449,21 @@ impl TryFrom<TypeOrVar> for Type {
             TypeOrVar::Primitive(t) => Ok(Type::Primitive(t)),
 
             TypeOrVar::Structure(fields) => {
-                let mut new_fields = HashMap::with_capacity(fields.len());
+                let mut new_fields = Fields::new(fields.ordering());
+                let mut errored = false;
 
                 for (name, field) in fields.iter() {
                     if let Ok(new_field) = field.clone().try_into() {
                         new_fields.insert(name.clone(), new_field);
                     } else {
-                        return Err(TypeOrVar::Structure(fields));
+                        errored = true;
                     }
                 }
 
+                if errored {
+                    return Err(TypeOrVar::Structure(fields));
+                }
+
                 Ok(Type::Structure(new_fields))
             }
 
diff --git a/src/ir/fields.rs b/src/ir/fields.rs
new file mode 100644
index 0000000..71a541c
--- /dev/null
+++ b/src/ir/fields.rs
@@ -0,0 +1,101 @@
+use internment::ArcIntern;
+use std::fmt;
+
+#[derive(Clone, PartialEq, Eq)]
+pub struct Fields<T> {
+    ordering: FieldOrdering,
+    fields: Vec<(ArcIntern<String>, T)>,
+}
+
+impl<T: fmt::Debug> fmt::Debug for Fields<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Fields:")?;
+        self.fields.fmt(f)
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum FieldOrdering {
+    Standard,
+}
+
+impl<T> Default for Fields<T> {
+    fn default() -> Self {
+        Self::new(FieldOrdering::Standard)
+    }
+}
+
+impl<T> Fields<T> {
+    pub fn new(ordering: FieldOrdering) -> Fields<T> {
+        Fields {
+            ordering,
+            fields: vec![],
+        }
+    }
+
+    pub fn ordering(&self) -> FieldOrdering {
+        self.ordering
+    }
+
+    pub fn insert(&mut self, name: ArcIntern<String>, t: T) {
+        self.fields.push((name, t));
+    }
+
+    pub fn get(&self, name: &ArcIntern<String>) -> Option<&T> {
+        for (n, res) in self.fields.iter() {
+            if n == name {
+                return Some(res);
+            }
+        }
+
+        None
+    }
+
+    pub fn map<T2, F: Fn(T) -> T2>(self, f: F) -> Fields<T2> {
+        Fields {
+            ordering: self.ordering,
+            fields: self.fields.into_iter().map(|(n, t)| (n, f(t))).collect(),
+        }
+    }
+
+    pub fn count(&self) -> usize {
+        self.fields.len()
+    }
+
+    pub fn has_field(&self, name: &ArcIntern<String>) -> bool {
+        self.fields.iter().any(|(current, _)| current == name)
+    }
+
+    pub fn remove_field(&mut self, name: &ArcIntern<String>) -> Option<T> {
+        let mut field_index = None;
+
+        for (idx, (current, _)) in self.fields.iter().enumerate() {
+            if current == name {
+                field_index = Some(idx);
+                break;
+            }
+        }
+
+        field_index.map(|i| self.fields.remove(i).1)
+    }
+
+    pub fn iter(&self) -> impl Iterator<Item = (&ArcIntern<String>, &T)> {
+        self.fields.iter().map(|(x, y)| (x, y))
+    }
+
+    pub fn into_iter(self) -> impl Iterator<Item = (ArcIntern<String>, T)> {
+        self.fields.into_iter()
+    }
+
+    pub fn field_names(&self) -> impl Iterator<Item = &ArcIntern<String>> {
+        self.fields.iter().map(|(n, _)| n)
+    }
+
+    pub fn types(&self) -> impl Iterator<Item = &T> {
+        self.fields.iter().map(|(_, x)| x)
+    }
+
+    pub fn types_mut(&mut self) -> impl Iterator<Item = &mut T> {
+        self.fields.iter_mut().map(|(_, x)| x)
+    }
+}
diff --git a/src/type_infer/convert.rs b/src/type_infer/convert.rs
index 1e103d3..c6c9a88 100644
--- a/src/type_infer/convert.rs
+++ b/src/type_infer/convert.rs
@@ -149,15 +149,15 @@ fn convert_top_level(
             convert_statement(stmt, constraint_db, renames, bindings),
         )),
 
-        syntax::TopLevel::Structure(_loc, name, fields) => TopLevelItem::Type(
-            name.intern(),
-            ir::TypeOrVar::Structure(
-                fields
-                    .into_iter()
-                    .map(|(name, t)| (name.intern(), convert_type(t, constraint_db)))
-                    .collect(),
-            ),
-        ),
+        syntax::TopLevel::Structure(_loc, name, fields) => {
+            let mut updated_fields = ir::Fields::default();
+
+            for (name, field_type) in fields.into_iter() {
+                updated_fields.insert(name.intern(), convert_type(field_type, constraint_db));
+            }
+
+            TopLevelItem::Type(name.intern(), ir::TypeOrVar::Structure(updated_fields))
+        }
     }
 }
 
@@ -294,7 +294,7 @@ fn convert_expression(
 
         syntax::Expression::Constructor(loc, name, fields) => {
             let mut result_fields = HashMap::new();
-            let mut type_fields = HashMap::new();
+            let mut type_fields = ir::Fields::default();
             let mut prereqs = vec![];
             let result_type = ir::TypeOrVar::new();
 
@@ -479,18 +479,18 @@ fn convert_type(ty: syntax::Type, constraint_db: &mut Vec<Constraint>) -> ir::Ty
             }
             Ok(v) => ir::TypeOrVar::Primitive(v),
         },
-        syntax::Type::Struct(fields) => ir::TypeOrVar::Structure(
-            fields
-                .into_iter()
-                .map(|(n, t)| {
-                    (
-                        n.intern(),
-                        t.map(|x| convert_type(x, constraint_db))
-                            .unwrap_or_else(ir::TypeOrVar::new),
-                    )
-                })
-                .collect(),
-        ),
+        syntax::Type::Struct(fields) => {
+            let mut new_fields = ir::Fields::default();
+
+            for (name, field_type) in fields.into_iter() {
+                let new_field_type = field_type
+                    .map(|x| convert_type(x, constraint_db))
+                    .unwrap_or_else(ir::TypeOrVar::new);
+                new_fields.insert(name.intern(), new_field_type);
+            }
+
+            ir::TypeOrVar::Structure(new_fields)
+        }
     }
 }
 
diff --git a/src/type_infer/finalize.rs b/src/type_infer/finalize.rs
index 1990332..03edec2 100644
--- a/src/type_infer/finalize.rs
+++ b/src/type_infer/finalize.rs
@@ -134,12 +134,9 @@ fn finalize_type(ty: TypeOrVar, resolutions: &TypeResolutions) -> Type {
                 .collect(),
             Box::new(finalize_type(*ret, resolutions)),
         ),
-        TypeOrVar::Structure(fields) => Type::Structure(
-            fields
-                .into_iter()
-                .map(|(name, subtype)| (name, finalize_type(subtype, resolutions)))
-                .collect(),
-        ),
+        TypeOrVar::Structure(fields) => {
+            Type::Structure(fields.map(|subtype| finalize_type(subtype, resolutions)))
+        }
     }
 }
 
diff --git a/src/type_infer/solve.rs b/src/type_infer/solve.rs
index e2c715e..e0b69a7 100644
--- a/src/type_infer/solve.rs
+++ b/src/type_infer/solve.rs
@@ -446,7 +446,7 @@ pub fn solve_constraints(
                     TypeOrVar::Structure(mut fields),
                     field,
                     result_type,
-                ) => match fields.remove(&field) {
+                ) => match fields.remove_field(&field) {
                     None => {
                         let reconstituted = TypeOrVar::Structure(fields);
                         tracing::trace!(structure_type = %reconstituted, %field, "no field found in type");
@@ -772,12 +772,12 @@ pub fn solve_constraints(
                     TypeOrVar::Structure(fields1),
                     TypeOrVar::Structure(mut fields2),
                 ) => {
-                    if fields1.len() == fields2.len()
-                        && fields1.keys().all(|x| fields2.contains_key(x))
+                    if fields1.count() == fields2.count()
+                        && fields1.field_names().all(|x| fields2.has_field(x))
                     {
                         for (name, subtype1) in fields1.into_iter() {
                             let subtype2 = fields2
-                                .remove(&name)
+                                .remove_field(&name)
                                 .expect("can find matching field after equivalence check");
                             new_constraints.push(Constraint::Equivalent(
                                 loc.clone(),