implement gatherPossibleValues on ExternalDeclaration - fixes #957

src/Declaration.js

@@ -116,6 +116,10 @@ export class ExternalDeclaration {
 		}
 	}
 
+	gatherPossibleValues ( values ) {
+		values.add( UNKNOWN );
+	}
+
 	getName ( es ) {
 		if ( this.name === '*' ) {
 			return this.module.name;

test/function/call-external-function/_config.js

@@ -0,0 +1,11 @@
+module.exports = {
+	description: 'handles call of aliased external function (#957)',
+	warnings () {},
+	context: {
+		require ( id ) {
+			if ( id === 'foo' ) {
+				return () => 42;
+			}
+		}
+	}
+};

test/function/call-external-function/foo.js

@@ -0,0 +1,2 @@
+import foo from 'foo';
+export default foo;

test/function/call-external-function/main.js

@@ -0,0 +1,4 @@
+import foo_ from './foo.js';
+
+var foo = foo_;
+assert.equal( foo(), 42 );