8317336: Assertion error thrown during 'this' escape analysis

Reviewed-by: vromero

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

@@ -678,7 +678,11 @@ public void visitForLoop(JCForLoop tree) {
 
     @Override
     public void visitForeachLoop(JCEnhancedForLoop tree) {
-        visitLooped(tree, super::visitForeachLoop);
+        visitLooped(tree, foreach -> {
+            scan(foreach.expr);
+            refs.discardExprs(depth);       // we don't handle iterator() yet
+            scan(foreach.body);
+        });
     }
 
     @Override
@@ -729,7 +733,10 @@ public void visitReturn(JCReturn tree) {
 
     @Override
     public void visitLambda(JCLambda lambda) {
-        visitDeferred(() -> visitScoped(false, () -> super.visitLambda(lambda)));
+        visitDeferred(() -> visitScoped(false, () -> {
+            scan(lambda.body);
+            refs.discardExprs(depth);       // needed in case body is a JCExpression
+        }));
     }
 
     @Override

test/langtools/tools/javac/warnings/ThisEscape.java

@@ -601,4 +601,20 @@ public static final class Sub1 extends ThisEscapeSealed {
         public static final class Sub2 extends ThisEscapeSealed {
         }
     }
+
+    // Verify no assertion error occurs (JDK-8317336)
+    public static class ThisEscapeAssertionError {
+        public ThisEscapeAssertionError() {
+            System.out.println((Supplier<Object>)() -> this);
+        }
+    }
+
+    // Verify no assertion error occurs (JDK-8317336)
+    public static class ThisEscapeAssertionError2 {
+        public ThisEscapeAssertionError2() {
+            ThisEscapeAssertionError2[] array = new ThisEscapeAssertionError2[] { this };
+            for (Object obj : array)
+                ;
+        }
+    }
 }