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 * Copyright (c) 2003, 2019, 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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
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 * questions.
 */

package jdk.javadoc.internal.tool;

import com.sun.source.util.TreePath;
import com.sun.tools.javac.code.Flags;
import com.sun.tools.javac.code.Symbol.*;
import com.sun.tools.javac.comp.MemberEnter;
import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.tree.JCTree.*;
import com.sun.tools.javac.tree.TreeInfo;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.List;
import com.sun.tools.javac.util.Names;

import static com.sun.tools.javac.code.Flags.*;
import static com.sun.tools.javac.code.Kinds.Kind.*;

 Javadoc's own memberEnter phase does a few things above and beyond that
 done by javac.
 
This is NOT part of any supported API.
 If you write code that depends on this, you do so at your own risk.
 This code and its internal interfaces are subject to change or
 deletion without notice.
/**
 *  Javadoc's own memberEnter phase does a few things above and beyond that
 *  done by javac.
 *
 *  <p><b>This is NOT part of any supported API.
 *  If you write code that depends on this, you do so at your own risk.
 *  This code and its internal interfaces are subject to change or
 *  deletion without notice.</b>
 */
public class JavadocMemberEnter extends MemberEnter {
    public static JavadocMemberEnter instance0(Context context) {
        MemberEnter instance = context.get(memberEnterKey);
        if (instance == null)
            instance = new JavadocMemberEnter(context);
        return (JavadocMemberEnter)instance;
    }

    public static void preRegister(Context context) {
        context.put(memberEnterKey, (Context.Factory<MemberEnter>)JavadocMemberEnter::new);
    }

    final ToolEnvironment toolEnv;


    protected JavadocMemberEnter(Context context) {
        super(context);
        toolEnv = ToolEnvironment.instance(context);
    }

    @Override
    public void visitMethodDef(JCMethodDecl tree) {
        super.visitMethodDef(tree);
        MethodSymbol meth = tree.sym;
        if (meth == null || meth.kind != MTH) return;
        TreePath treePath = toolEnv.getTreePath(env.toplevel, env.enclClass, tree);
        // do not add those methods that may be mandated by the spec,
        // or those that are synthesized, thus if it does not exist in
        // tree best to let other logic determine the TreePath.
        if (env.enclClass.defs.contains(tree)) {
            toolEnv.setElementToTreePath(meth, treePath);
        }
        // release resources
        // handle constructors for record types specially, because of downstream checks
        if ((env.enclClass.mods.flags & Flags.RECORD) != 0 && TreeInfo.isConstructor(tree)) {
            tree.body.stats = List.nil();
        } else {
        tree.body = null;
        }
    }

    @Override
    public void visitVarDef(JCVariableDecl tree) {
        if (tree.init != null) {
            boolean isFinal = (tree.mods.flags & FINAL) != 0
                    || (env.enclClass.mods.flags & INTERFACE) != 0;
            if (!isFinal || containsNonConstantExpression(tree.init)) {
                // Avoid unnecessary analysis and release resources.
                // In particular, remove non-constant expressions
                // which may trigger Attr.attribClass, since
                // method bodies are also removed, in visitMethodDef.
                tree.init = null;
            }
        }
        super.visitVarDef(tree);
        if (tree.sym != null && tree.sym.kind == VAR && !isParameter(tree.sym)) {
            toolEnv.setElementToTreePath(tree.sym, toolEnv.getTreePath(env.toplevel, env.enclClass, tree));
        }
    }

    private static boolean isParameter(VarSymbol var) {
        return (var.flags() & Flags.PARAMETER) != 0;
    }

    
Simple analysis of an expression tree to see if it contains tree nodes
for any non-constant expression. This does not include checking references
to other fields which may or may not be constant.
/**
     * Simple analysis of an expression tree to see if it contains tree nodes
     * for any non-constant expression. This does not include checking references
     * to other fields which may or may not be constant.
     */
    private static boolean containsNonConstantExpression(JCExpression tree) {
        return new MaybeConstantExpressionScanner().containsNonConstantExpression(tree);
    }

    
See JLS 15.18, Constant Expression
/**
     * See JLS 15.18, Constant Expression
     */
    private static class MaybeConstantExpressionScanner extends JCTree.Visitor {
        boolean maybeConstantExpr = true;

        public boolean containsNonConstantExpression(JCExpression tree) {
            scan(tree);
            return !maybeConstantExpr;
        }

        public void scan(JCTree tree) {
            // short circuit scan when end result is definitely false
            if (maybeConstantExpr && tree != null)
                tree.accept(this);
        }

        @Override
        /** default for any non-overridden visit method. */
        public void visitTree(JCTree tree) {
            maybeConstantExpr = false;
        }

        @Override
        public void visitBinary(JCBinary tree) {
            switch (tree.getTag()) {
                case MUL: case DIV: case MOD:
                case PLUS: case MINUS:
                case SL: case SR: case USR:
                case LT: case LE: case GT: case GE:
                case EQ: case NE:
                case BITAND: case BITXOR: case BITOR:
                case AND: case OR:
                    break;
                default:
                    maybeConstantExpr = false;
            }
        }

        @Override
        public void visitConditional(JCConditional tree) {
            scan(tree.cond);
            scan(tree.truepart);
            scan(tree.falsepart);
        }

        @Override
        public void visitIdent(JCIdent tree) { }

        @Override
        public void visitLiteral(JCLiteral tree) { }

        @Override
        public void visitParens(JCParens tree) {
            scan(tree.expr);
        }

        @Override
        public void visitSelect(JCTree.JCFieldAccess tree) {
            scan(tree.selected);
        }

        @Override
        public void visitTypeCast(JCTypeCast tree) {
            scan(tree.clazz);
            scan(tree.expr);
        }

        @Override
        public void visitTypeIdent(JCPrimitiveTypeTree tree) { }

        @Override
        public void visitUnary(JCUnary tree) {
            switch (tree.getTag()) {
                case POS: case NEG: case COMPL: case NOT:
                    break;
                default:
                    maybeConstantExpr = false;
            }
        }
    }
}