feat(interface-types) Re-implement Type.

The semantics of “types” have changed since the previous draft. Now, a
type is like a regular WebAssembly type but with Interface Types.

src/ast.rs

@@ -60,6 +60,16 @@ pub(crate) enum AdapterKind {
     Export,
 }
 
+/// Represents a type signature.
+#[derive(PartialEq, Debug)]
+pub struct Type {
+    /// Types for the parameters.
+    pub inputs: Vec<InterfaceType>,
+
+    /// Types for the results.
+    pub outputs: Vec<InterfaceType>,
+}
+
 /// Represents an exported function signature.
 #[derive(PartialEq, Debug)]
 pub struct Export<'input> {
@@ -89,55 +99,6 @@ pub struct Import<'input> {
     pub output_types: Vec<InterfaceType>,
 }
 
-/// Represents a structural type.
-#[derive(PartialEq, Debug)]
-pub struct Type<'input> {
-    /// The type name.
-    pub name: &'input str,
-
-    /// The field names.
-    field_names: Vec<&'input str>,
-
-    /// The field types.
-    field_types: Vec<InterfaceType>,
-}
-
-impl<'input> Type<'input> {
-    /// Creates a new `Type`.
-    ///
-    /// The constructor panics if there is the length of `names` is
-    /// different than the length of `types`.
-    pub fn new(type_name: &'input str, names: Vec<&'input str>, types: Vec<InterfaceType>) -> Self {
-        assert_eq!(
-            names.len(),
-            types.len(),
-            "There must be the same number of field names than field types."
-        );
-
-        Self {
-            name: type_name,
-            field_names: names,
-            field_types: types,
-        }
-    }
-
-    /// Adds a new field to the type.
-    pub fn add_field(&mut self, name: &'input str, ty: InterfaceType) {
-        self.field_names.push(name);
-        self.field_types.push(ty);
-    }
-
-    /// Returns the field names.
-    pub fn field_names(&self) -> &Vec<&'input str> {
-        &self.field_names
-    }
-
-    /// Returns the field types.
-    pub fn field_types(&self) -> &Vec<InterfaceType> {
-        &self.field_types
-    }
-}
-
 /// Represents an adapter.
 #[derive(PartialEq, Debug)]
 pub enum Adapter<'input> {
@@ -179,12 +140,12 @@ pub enum Adapter<'input> {
 /// definition.
 #[derive(PartialEq, Default, Debug)]
 pub struct Interfaces<'input> {
+    /// All the types.
+    pub types: Vec<Type>,
+
     /// All the exported functions.
     pub exports: Vec<Export<'input>>,
 
-    /// All the types.
-    pub types: Vec<Type<'input>>,
-
     /// All the imported functions.
     pub imports: Vec<Import<'input>>,