Add interfaces as a proof-of-concept experimental feature

internal/compiler/generator.rs

@@ -463,7 +463,7 @@ pub fn for_each_const_properties(
                 ElementType::Builtin(_) => {
                     unreachable!("builtin element should have been resolved")
                 }
-                ElementType::Global | ElementType::Error => break,
+                ElementType::Global | ElementType::Interface | ElementType::Error => break,
             }
         }
         for c in all_prop {

internal/compiler/langtype.rs

@@ -405,6 +405,8 @@ pub enum ElementType {
     Error,
     /// This should be the base type of the root element of a global component
     Global,
+    /// This should be the base type of the root element of an interface
+    Interface,
 }
 
 impl PartialEq for ElementType {
@@ -413,7 +415,9 @@ impl PartialEq for ElementType {
             (Self::Component(a), Self::Component(b)) => Rc::ptr_eq(a, b),
             (Self::Builtin(a), Self::Builtin(b)) => Rc::ptr_eq(a, b),
             (Self::Native(a), Self::Native(b)) => Rc::ptr_eq(a, b),
-            (Self::Error, Self::Error) | (Self::Global, Self::Global) => true,
+            (Self::Error, Self::Error)
+            | (Self::Global, Self::Global)
+            | (Self::Interface, Self::Interface) => true,
             _ => false,
         }
     }
@@ -615,6 +619,7 @@ impl ElementType {
             ElementType::Native(_) => None, // Too late, caller should call this function before the native class lowering
             ElementType::Error => None,
             ElementType::Global => None,
+            ElementType::Interface => None,
         }
     }
 }
@@ -627,6 +632,7 @@ impl Display for ElementType {
             Self::Native(b) => b.class_name.fmt(f),
             Self::Error => write!(f, "<error>"),
             Self::Global => Ok(()),
+            Self::Interface => Ok(()),
         }
     }
 }

internal/compiler/namedreference.rs

@@ -117,7 +117,9 @@ impl NamedReference {
                 ElementType::Native(n) => {
                     return n.properties.get(self.name()).is_none_or(|pi| !pi.is_native_output());
                 }
-                crate::langtype::ElementType::Error | crate::langtype::ElementType::Global => {
+                crate::langtype::ElementType::Error
+                | crate::langtype::ElementType::Global
+                | crate::langtype::ElementType::Interface => {
                     return true;
                 }
             }