fix inference of object members on library prefix

pkg/analyzer/lib/src/generated/static_type_analyzer.dart

Index: pkg/analyzer/lib/src/generated/static_type_analyzer.dart
diff --git a/pkg/analyzer/lib/src/generated/static_type_analyzer.dart b/pkg/analyzer/lib/src/generated/static_type_analyzer.dart
index c9efc5d5735cb33a3d146d0a027f570f5745d20d..b6a959579daa8cde9549549b49bf7337665f73c5 100644
--- a/pkg/analyzer/lib/src/generated/static_type_analyzer.dart
+++ b/pkg/analyzer/lib/src/generated/static_type_analyzer.dart
@@ -1762,12 +1762,11 @@ class StaticTypeAnalyzer extends SimpleAstVisitor<Object> {
    * being called is one of the object methods.
    */
   bool _inferMethodInvocationObject(MethodInvocation node) {
-    // If we have a call like `toString()` don't infer it.
-    //
-    // Either: it's really `this.toString()` and we shouldn't need inference,
-    // or it's a call to a function that happens to be called `toString()` and
-    // we shouldn't infer.
-    if (node.target == null) {
+    // If we have a call like `toString()` or `libraryPrefix.toString()` don't
+    // infer it.
+    Expression target = node.realTarget;
+    if (target == null ||
+        target is SimpleIdentifier && target.staticElement is PrefixElement) {
       return false;
     }