8019480: Javac crashes when method is called on a type-variable receiver from lambda expression

Summary: Logic for shortcircuiting speculative attribution doesn't handle type-variable receivers
Reviewed-by: jjg, vromero

src/share/classes/com/sun/tools/javac/comp/DeferredAttr.java

@@ -941,6 +941,10 @@ public class DeferredAttr extends JCTree.Visitor {
                     attribSpeculative(rec, env, attr.unknownTypeExprInfo).type :
                     env.enclClass.sym.type;
 
+            while (site.hasTag(TYPEVAR)) {
+                site = site.getUpperBound();
+            }
+
             ListBuffer<Type> args = ListBuffer.lb();
             for (int i = 0; i < tree.args.length(); i ++) {
                 args.append(Type.noType);

test/tools/javac/lambda/8019480/T8019480.java

+/*
+ * @test /nodynamiccopyright/
+ * @bug 8019480
+ * @summary Javac crashes when method is called on a type-variable receiver from lambda expression
+ * @author  Maurizio Cimadamore
+ * @compile/fail/ref=T8019480.out -XDrawDiagnostics T8019480.java
+ */
+import java.util.*;
+
+class T8019480<U> {
+    interface Predicate<T> {
+       void m(T t);
+    }
+
+    interface Stream<T> {
+       void forEach(Predicate<T> pt);
+    }
+
+    void test(U current, Stream<U> stream) {
+        List<U> list3 = new ArrayList<>();
+        stream.forEach(i -> list3.add(current.clone()));
+    }
+}

test/tools/javac/lambda/8019480/T8019480.out

+T8019480.java:21:46: compiler.err.report.access: clone(), protected, java.lang.Object
+T8019480.java:21:34: compiler.err.cant.apply.symbols: kindname.method, add, java.lang.Object,{(compiler.misc.inapplicable.method: kindname.method, java.util.Collection, add(U), (compiler.misc.no.conforming.assignment.exists: (compiler.misc.inconvertible.types: java.lang.Object, U))),(compiler.misc.inapplicable.method: kindname.method, java.util.List, add(U), (compiler.misc.no.conforming.assignment.exists: (compiler.misc.inconvertible.types: java.lang.Object, U))),(compiler.misc.inapplicable.method: kindname.method, java.util.List, add(int,U), (compiler.misc.arg.length.mismatch))}
+2 errors