8057794: Compiler Error when obtaining .class property

Ensuring a non-null type and sym for illegal T.class to prevent downstream errors.

Reviewed-by: mcimadamore

langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Attr.java

@@ -3195,8 +3195,9 @@ public class Attr extends JCTree.Visitor {
                 elt = ((ArrayType)elt).elemtype;
             if (elt.hasTag(TYPEVAR)) {
                 log.error(tree.pos(), "type.var.cant.be.deref");
-                result = types.createErrorType(tree.type);
-                return;
+                result = tree.type = types.createErrorType(tree.name, site.tsym, site);
+                tree.sym = tree.type.tsym;
+                return ;
             }
         }
 

langtools/test/tools/javac/lambda/T8057794.java

@@ -0,0 +1,12 @@
+/**
+ * @test    /nodynamiccopyright/
+ * @bug     8057794
+ * @summary The tree for TypeVar.class does not have a type set, which leads to an NPE when
+ *          checking if deferred attribution is needed
+ * @compile/fail/ref=T8057794.out -XDrawDiagnostics T8057794.java
+ */
+class T8057794<T> {
+    void t() {
+        System.out.println(T.class.getSimpleName());
+    }
+}

langtools/test/tools/javac/lambda/T8057794.out

@@ -0,0 +1,2 @@
+T8057794.java:10:29: compiler.err.type.var.cant.be.deref
+1 error