Ignore when components export type definitions (#5051)

* allow a ComponentTypeRef::Type to point to a component TypeDef

* component matching: don't assert exported Interface type definitions are "defined"

types may be exported by their name for consumption by some component
runtimes, but in wasmtime this doesn't matter (we lift and lower to
types, not define them) so we should ignore these.

* component-model instance tests: show that an import can export a type definition

this is meaningless, but it should be accepted. (previously rejected)

crates/environ/src/component/types.rs

@@ -469,6 +469,7 @@ impl ComponentTypesBuilder {
                 self.core_outer_type(0, TypeIndex::from_u32(*ty))
             }
             wasmparser::ComponentTypeRef::Func(ty)
+            | wasmparser::ComponentTypeRef::Type(_, ty)
             | wasmparser::ComponentTypeRef::Instance(ty)
             | wasmparser::ComponentTypeRef::Component(ty) => {
                 self.component_outer_type(0, ComponentTypeIndex::from_u32(*ty))
@@ -476,9 +477,6 @@ impl ComponentTypesBuilder {
             wasmparser::ComponentTypeRef::Value(..) => {
                 unimplemented!("references to value types");
             }
-            wasmparser::ComponentTypeRef::Type(..) => {
-                unimplemented!("references to types");
-            }
         }
     }
 

crates/wasmtime/src/component/matching.rs

@@ -72,6 +72,12 @@ impl TypeChecker<'_> {
         // the actual type. It's ok, though, to have extra exports in the actual
         // type.
         for (name, expected) in expected.exports.iter() {
+            // Interface types may be exported from a component in order to give them a name, but
+            // they don't have a definition in the sense that this search is interested in, so
+            // ignore them.
+            if let TypeDef::Interface(_) = expected {
+                continue;
+            }
             let actual = self
                 .strings
                 .lookup(name)

tests/misc_testsuite/component-model/instance.wast

@@ -179,6 +179,12 @@
   ))
 )
 
+(component
+  (import "host" (instance $i
+    (type $rec (record (field "x" (record)) (field "y" string)))
+    (export "some-record" (type (eq $rec)))))
+)
+
 (component
   (import "host" (instance $i
     (export "nested" (instance