8181911: Lambda Analyzer causes compile-time error

When copying Env<AttrContext> for Analyzer, detach returnResult from the outer context.

Reviewed-by: mcimadamore

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

@@ -336,12 +336,28 @@ public class Analyzer {
     };
 
     /**
-     * Analyze an AST node if needed.
+     * Create a copy of Env if needed.
      */
-    void analyzeIfNeeded(JCTree tree, Env<AttrContext> env) {
+    Env<AttrContext> copyEnvIfNeeded(JCTree tree, Env<AttrContext> env) {
         if (!analyzerModes.isEmpty() &&
                 !env.info.isSpeculative &&
                 TreeInfo.isStatement(tree)) {
+            Env<AttrContext> analyzeEnv =
+                    env.dup(env.tree, env.info.dup(env.info.scope.dupUnshared(env.info.scope.owner)));
+            analyzeEnv.info.returnResult = analyzeEnv.info.returnResult != null ?
+                    attr.new ResultInfo(analyzeEnv.info.returnResult.pkind,
+                                        analyzeEnv.info.returnResult.pt) : null;
+            return analyzeEnv;
+        } else {
+            return null;
+        }
+    }
+
+    /**
+     * Analyze an AST node if needed.
+     */
+    void analyzeIfNeeded(JCTree tree, Env<AttrContext> env) {
+        if (env != null) {
             JCStatement stmt = (JCStatement)tree;
             analyze(stmt, env);
         }

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

@@ -718,8 +718,7 @@ public class Attr extends JCTree.Visitor {
     /** Derived visitor method: attribute a statement or definition tree.
      */
     public Type attribStat(JCTree tree, Env<AttrContext> env) {
-        Env<AttrContext> analyzeEnv =
-                env.dup(tree, env.info.dup(env.info.scope.dupUnshared(env.info.scope.owner)));
+        Env<AttrContext> analyzeEnv = analyzer.copyEnvIfNeeded(tree, env);
         try {
             return attribTree(tree, env, statInfo);
         } finally {

langtools/test/tools/javac/lambda/LambdaConv28.java

@@ -0,0 +1,32 @@
+/*
+ * @test /nodynamiccopyright/
+ * @bug 8181911
+ * @summary Verify that the analyzer does not affect ordinary compilation.
+ * @compile/ref=LambdaConv28.out -XDrawDiagnostics -XDfind=lambda LambdaConv28.java
+ */
+
+class LambdaConv28 {
+
+    public void test(A a) {
+        test(()-> {
+            return new I() {
+                public <T> void t() {
+                }
+            };
+        });
+        test(new A() {
+            public I get() {
+                return null;
+            }
+        });
+    }
+
+    public interface I {
+        public <T> void t();
+    }
+
+    public interface A {
+        public I get();
+    }
+
+}

langtools/test/tools/javac/lambda/LambdaConv28.out

@@ -0,0 +1,2 @@
+LambdaConv28.java:17:22: compiler.warn.potential.lambda.found
+1 warning