8186694: JShell: speed-up compilation by reusing compiler instances

Generalizing ReusableContext and using it in JShell to speed up processing.

Reviewed-by: mcimadamore, rfield

test/langtools/tools/javac/tree/ScopeClassHeaderTest.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2013, 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug     8186694
+ * @summary Verify that taking a Scope inside a class header
+ *          does not taint internal structures
+ * @modules jdk.compiler
+ * @run main ScopeClassHeaderTest
+ */
+
+import com.sun.source.tree.CompilationUnitTree;
+import com.sun.source.tree.Scope;
+import com.sun.source.util.JavacTask;
+import com.sun.source.util.TreePathScanner;
+import com.sun.source.util.Trees;
+
+import java.io.IOException;
+import java.net.URI;
+import java.util.ArrayList;
+import java.util.Collections;
+
+import javax.tools.JavaCompiler;
+import javax.tools.JavaFileObject;
+import javax.tools.JavaFileObject.Kind;
+import javax.tools.SimpleJavaFileObject;
+import javax.tools.ToolProvider;
+
+import com.sun.source.tree.IdentifierTree;
+
+public class ScopeClassHeaderTest {
+
+    public static void main(String... args) throws Exception {
+        verifyScopeForClassHeader();
+    }
+
+    private static void verifyScopeForClassHeader() throws Exception {
+        JavaCompiler tool = ToolProvider.getSystemJavaCompiler();
+        JavaFileObject source = new SimpleJavaFileObject(URI.create("mem://Test.java"), Kind.SOURCE) {
+            @Override public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException {
+                return "import java.util.*; class O { public void m() { class X<T extends ArrayList> { public void test() { String o; } } } }";
+            }
+            @Override public boolean isNameCompatible(String simpleName, Kind kind) {
+                return !"module-info".equals(simpleName);
+            }
+        };
+        Iterable<? extends JavaFileObject> fos = Collections.singletonList(source);
+        JavacTask task = (JavacTask) tool.getTask(null, null, null, new ArrayList<String>(), null, fos);
+        final Trees trees = Trees.instance(task);
+        CompilationUnitTree cu = task.parse().iterator().next();
+
+        task.analyze();
+
+        new TreePathScanner<Void, Void>() {
+            @Override
+            public Void visitIdentifier(IdentifierTree node, Void p) {
+                if (node.getName().contentEquals("ArrayList") || node.getName().contentEquals("String")) {
+                    Scope scope = trees.getScope(getCurrentPath());
+                    System.err.println("scope: " + scope);
+                }
+                return super.visitIdentifier(node, p);
+            }
+        }.scan(cu, null);
+    }
+}