Now query() returns maybe

src/collector/context.js

@@ -48,7 +48,7 @@ export default class Context {
         this._scope.addExport(name, reference);
     }
 
-    query(name: string, params: ?(?Type)[]): Type {
+    query(name: string, params: ?(?Type)[]): ?Type {
         const param = wu(this._params).find(p => p.name === name);
 
         if (param) {

src/collector/definitions.js

@@ -54,7 +54,7 @@ function processInterfaceDeclaration(ctx: Context, node: InterfaceDeclaration) {
         const {name} = extend.id;
         const type = ctx.query(name);
 
-        invariant(type.id);
+        invariant(type && type.id);
 
         const reference = t.createReference(t.clone(type.id));
 
@@ -85,7 +85,7 @@ function processClassDeclaration(ctx: Context, node: ClassDeclaration) {
 
     const base = ctx.query(node.superClass.name);
 
-    invariant(base.id);
+    invariant(base && base.id);
 
     const baseRef = t.createReference(t.clone(base.id));
     const intersection = t.createIntersection([baseRef, type]);
@@ -269,8 +269,12 @@ function makeReference(ctx: Context, node: GenericTypeAnnotation): ?Type {
 
     const type = ctx.query(name, params);
 
+    if (!type) {
+        return null;
+    }
+
     if (!type.id) {
-        return type;
+        return t.clone(type);
     }
 
     return t.createReference(t.clone(type.id));

src/collector/index.js

@@ -86,7 +86,7 @@ export default class Collector {
         }
     }
 
-    _query(scope: Scope, name: string, params: (?Type)[]): Type {
+    _query(scope: Scope, name: string, params: (?Type)[]): ?Type {
         let result = scope.query(name, params);
 
         // TODO: warning.
@@ -153,11 +153,7 @@ export default class Collector {
             case 'special':
             default:
                 const resolve = id => this._fund.take(id);
-                const type = result.call(params, resolve);
-
-                invariant(type);
-
-                return type;
+                return result.call(params, resolve);
         }
     }
 
@@ -165,7 +161,9 @@ export default class Collector {
         for (const [scope, name] of module.exports()) {
             const type = this._query(scope, name, []);
 
-            this._fund.put(type, true);
+            if (type) {
+                this._fund.put(type, true);
+            }
         }
     }
 }