wit-parser: Fix types leaking across interfaces (#822)

This fixes an internal bug where types were accidentally leaking across
interfaces, panicking when used. This commit fixes the issue by properly
fixing the "reset the state" after resolution of each interface and then
additionally adds some more testing per-interface to the `ui` tests.

crates/wit-parser/src/ast/resolve.rs

@@ -35,7 +35,6 @@ impl Resolver {
         for interface in document.interfaces() {
             let name = &interface.name.name;
             let instance = self.resolve(name, &interface.items, &interface.docs)?;
-            *self = Resolver::default();
 
             if interface_map.insert(name.to_string(), instance).is_some() {
                 return Err(Error {
@@ -174,6 +173,8 @@ impl Resolver {
             }
         }
 
+        self.anon_types.clear();
+
         Ok(Interface {
             name: name.to_string(),
             docs: self.docs(docs),

crates/wit-parser/tests/all.rs

@@ -116,6 +116,7 @@ impl Runner<'_> {
             }
         } else {
             let instance = result?;
+            test_world(&instance);
             to_json(&instance)
         };
 
@@ -379,3 +380,20 @@ fn to_json(world: &World) -> String {
         ty.map(translate_type)
     }
 }
+
+fn test_world(world: &World) {
+    for (_, interface) in world.imports.iter() {
+        test_interface(interface);
+    }
+    for (_, interface) in world.exports.iter() {
+        test_interface(interface);
+    }
+    if let Some(default) = &world.default {
+        test_interface(default);
+    }
+}
+
+fn test_interface(interface: &Interface) {
+    let mut sizes = SizeAlign::default();
+    sizes.fill(interface);
+}

crates/wit-parser/tests/ui/shared-types.wit

@@ -0,0 +1,8 @@
+world foo {
+  import foo: interface {
+    a: func() -> list<u8>
+  }
+  default export interface {
+    a: func() -> tuple<list<u8>>
+  }
+}

crates/wit-parser/tests/ui/shared-types.wit.result

@@ -0,0 +1,50 @@
+{
+  "name": "foo",
+  "default": {
+    "types": [
+      {
+        "idx": 0,
+        "list": "u8"
+      },
+      {
+        "idx": 1,
+        "tuple": {
+          "types": [
+            "type-0"
+          ]
+        }
+      }
+    ],
+    "functions": [
+      {
+        "name": "a",
+        "params": [],
+        "results": [
+          "type-1"
+        ]
+      }
+    ]
+  },
+  "imports": [
+    [
+      "foo",
+      {
+        "types": [
+          {
+            "idx": 0,
+            "list": "u8"
+          }
+        ],
+        "functions": [
+          {
+            "name": "a",
+            "params": [],
+            "results": [
+              "type-0"
+            ]
+          }
+        ]
+      }
+    ]
+  ]
+}