attr.java

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                log.error(tree.thrown.head.pos(),
                          "throws.not.allowed.in.intf.annotation");
            for (List<JCExpression> l = tree.thrown; l.nonEmpty(); l = l.tail)
                chk.checkType(l.head.pos(), l.head.type, syms.throwableType);

            if (tree.body == null) {
                // Empty bodies are only allowed for
                // abstract, native, or interface methods, or for methods
                // in a retrofit signature class.
                if ((owner.flags() & INTERFACE) == 0 &&
                    (tree.mods.flags & (ABSTRACT | NATIVE)) == 0 &&
                    !relax)
                    log.error(tree.pos(), "missing.meth.body.or.decl.abstract");
                if (tree.defaultValue != null) {
                    if ((owner.flags() & ANNOTATION) == 0)
                        log.error(tree.pos(),
                                  "default.allowed.in.intf.annotation.member");
                }
            } else if ((owner.flags() & INTERFACE) != 0) {
                log.error(tree.body.pos(), "intf.meth.cant.have.body");
            } else if ((tree.mods.flags & ABSTRACT) != 0) {
                log.error(tree.pos(), "abstract.meth.cant.have.body");
            } else if ((tree.mods.flags & NATIVE) != 0) {
                log.error(tree.pos(), "native.meth.cant.have.body");
            } else {
                // Add an implicit super() call unless an explicit call to
                // super(...) or this(...) is given
                // or we are compiling class java.lang.Object.
                if (tree.name == names.init && owner.type != syms.objectType) {
                    JCBlock body = tree.body;
                    if (body.stats.isEmpty() ||
                        !TreeInfo.isSelfCall(body.stats.head)) {
                        body.stats = body.stats.
                            prepend(memberEnter.SuperCall(make.at(body.pos),
                                                          List.<Type>nil(),
                                                          List.<JCVariableDecl>nil(),
                                                          false));
                    } else if ((env.enclClass.sym.flags() & ENUM) != 0 &&
                               (tree.mods.flags & GENERATEDCONSTR) == 0 &&
                               TreeInfo.isSuperCall(body.stats.head)) {
                        // enum constructors are not allowed to call super
                        // directly, so make sure there aren't any super calls
                        // in enum constructors, except in the compiler
                        // generated one.
                        log.error(tree.body.stats.head.pos(),
                                  "call.to.super.not.allowed.in.enum.ctor",
                                  env.enclClass.sym);
                    }
                }

                // Attribute method body.
                attribStat(tree.body, localEnv);
            }
            localEnv.info.scope.leave();
            result = tree.type = m.type;
            chk.validateAnnotations(tree.mods.annotations, m);

        }
        finally {
            chk.setLint(prevLint);
        }
    }

    public void visitVarDef(JCVariableDecl tree) {
        // Local variables have not been entered yet, so we need to do it now:
        if (env.info.scope.owner.kind == MTH) {
            if (tree.sym != null) {
                // parameters have already been entered
                env.info.scope.enter(tree.sym);
            } else {
                memberEnter.memberEnter(tree, env);
                annotate.flush();
            }
        }

        // Check that the variable's declared type is well-formed.
        chk.validate(tree.vartype);

        VarSymbol v = tree.sym;
        Lint lint = env.info.lint.augment(v.attributes_field, v.flags());
        Lint prevLint = chk.setLint(lint);

        try {
            chk.checkDeprecatedAnnotation(tree.pos(), v);

            if (tree.init != null) {
                if ((v.flags_field & FINAL) != 0 && tree.init.getTag() != JCTree.NEWCLASS) {
                    // In this case, `v' is final.  Ensure that it's initializer is
                    // evaluated.
                    v.getConstValue(); // ensure initializer is evaluated
                } else {
                    // Attribute initializer in a new environment
                    // with the declared variable as owner.
                    // Check that initializer conforms to variable's declared type.
                    Env<AttrContext> initEnv = memberEnter.initEnv(tree, env);
                    initEnv.info.lint = lint;
                    // In order to catch self-references, we set the variable's
                    // declaration position to maximal possible value, effectively
                    // marking the variable as undefined.
                    v.pos = Position.MAXPOS;
                    attribExpr(tree.init, initEnv, v.type);
                    v.pos = tree.pos;
                }
            }
            result = tree.type = v.type;
            chk.validateAnnotations(tree.mods.annotations, v);
        }
        finally {
            chk.setLint(prevLint);
        }
    }

    public void visitSkip(JCSkip tree) {
        result = null;
    }

    public void visitBlock(JCBlock tree) {
        if (env.info.scope.owner.kind == TYP) {
            // Block is a static or instance initializer;
            // let the owner of the environment be a freshly
            // created BLOCK-method.
            Env<AttrContext> localEnv =
                env.dup(tree, env.info.dup(env.info.scope.dupUnshared()));
            localEnv.info.scope.owner =
                new MethodSymbol(tree.flags | BLOCK, names.empty, null,
                                 env.info.scope.owner);
            if ((tree.flags & STATIC) != 0) localEnv.info.staticLevel++;
            attribStats(tree.stats, localEnv);
        } else {
            // Create a new local environment with a local scope.
            Env<AttrContext> localEnv =
                env.dup(tree, env.info.dup(env.info.scope.dup()));
            attribStats(tree.stats, localEnv);
            localEnv.info.scope.leave();
        }
        result = null;
    }

    public void visitDoLoop(JCDoWhileLoop tree) {
        attribStat(tree.body, env.dup(tree));
        attribExpr(tree.cond, env, syms.booleanType);
        result = null;
    }

    public void visitWhileLoop(JCWhileLoop tree) {
        attribExpr(tree.cond, env, syms.booleanType);
        attribStat(tree.body, env.dup(tree));
        result = null;
    }

    public void visitForLoop(JCForLoop tree) {
        Env<AttrContext> loopEnv =
            env.dup(env.tree, env.info.dup(env.info.scope.dup()));
        attribStats(tree.init, loopEnv);
        if (tree.cond != null) attribExpr(tree.cond, loopEnv, syms.booleanType);
        loopEnv.tree = tree; // before, we were not in loop!
        attribStats(tree.step, loopEnv);
        attribStat(tree.body, loopEnv);
        loopEnv.info.scope.leave();
        result = null;
    }

    public void visitForeachLoop(JCEnhancedForLoop tree) {
        Env<AttrContext> loopEnv =
            env.dup(env.tree, env.info.dup(env.info.scope.dup()));
        attribStat(tree.var, loopEnv);
        Type exprType = types.upperBound(attribExpr(tree.expr, loopEnv));
        chk.checkNonVoid(tree.pos(), exprType);
        Type elemtype = types.elemtype(exprType); // perhaps expr is an array?
        if (elemtype == null) {
            // or perhaps expr implements Iterable<T>?
            Type base = types.asSuper(exprType, syms.iterableType.tsym);
            if (base == null) {
                log.error(tree.expr.pos(), "foreach.not.applicable.to.type");
                elemtype = syms.errType;
            } else {
                List<Type> iterableParams = base.allparams();
                elemtype = iterableParams.isEmpty()
                    ? syms.objectType
                    : types.upperBound(iterableParams.head);
            }
        }
        chk.checkType(tree.expr.pos(), elemtype, tree.var.sym.type);
        loopEnv.tree = tree; // before, we were not in loop!
        attribStat(tree.body, loopEnv);
        loopEnv.info.scope.leave();
        result = null;
    }

    public void visitLabelled(JCLabeledStatement tree) {
        // Check that label is not used in an enclosing statement
        Env<AttrContext> env1 = env;
        while (env1 != null && env1.tree.getTag() != JCTree.CLASSDEF) {
            if (env1.tree.getTag() == JCTree.LABELLED &&
                ((JCLabeledStatement) env1.tree).label == tree.label) {
                log.error(tree.pos(), "label.already.in.use",
                          tree.label);
                break;
            }
            env1 = env1.next;
        }

        attribStat(tree.body, env.dup(tree));
        result = null;
    }

    public void visitSwitch(JCSwitch tree) {
        Type seltype = attribExpr(tree.selector, env);

        Env<AttrContext> switchEnv =
            env.dup(tree, env.info.dup(env.info.scope.dup()));

        boolean enumSwitch =
            allowEnums &&
            (seltype.tsym.flags() & Flags.ENUM) != 0;
        if (!enumSwitch)
            seltype = chk.checkType(tree.selector.pos(), seltype, syms.intType);

        // Attribute all cases and
        // check that there are no duplicate case labels or default clauses.
        Set<Object> labels = new HashSet<Object>(); // The set of case labels.
        boolean hasDefault = false;      // Is there a default label?
        for (List<JCCase> l = tree.cases; l.nonEmpty(); l = l.tail) {
            JCCase c = l.head;
            Env<AttrContext> caseEnv =
                switchEnv.dup(c, env.info.dup(switchEnv.info.scope.dup()));
            if (c.pat != null) {
                if (enumSwitch) {
                    Symbol sym = enumConstant(c.pat, seltype);
                    if (sym == null) {
                        log.error(c.pat.pos(), "enum.const.req");
                    } else if (!labels.add(sym)) {
                        log.error(c.pos(), "duplicate.case.label");
                    }
                } else {
                    Type pattype = attribExpr(c.pat, switchEnv, seltype);
                    if (pattype.tag != ERROR) {
                        if (pattype.constValue() == null) {
                            log.error(c.pat.pos(), "const.expr.req");
                        } else if (labels.contains(pattype.constValue())) {
                            log.error(c.pos(), "duplicate.case.label");
                        } else {
                            labels.add(pattype.constValue());
                        }
                    }
                }
            } else if (hasDefault) {
                log.error(c.pos(), "duplicate.default.label");
            } else {
                hasDefault = true;
            }
            attribStats(c.stats, caseEnv);
            caseEnv.info.scope.leave();
            addVars(c.stats, switchEnv.info.scope);
        }

        switchEnv.info.scope.leave();
        result = null;
    }
    // where
        /** Add any variables defined in stats to the switch scope. */
        private static void addVars(List<JCStatement> stats, Scope switchScope) {
            for (;stats.nonEmpty(); stats = stats.tail) {
                JCTree stat = stats.head;
                if (stat.getTag() == JCTree.VARDEF)
                    switchScope.enter(((JCVariableDecl) stat).sym);
            }
        }
    // where
    /** Return the selected enumeration constant symbol, or null. */
    private Symbol enumConstant(JCTree tree, Type enumType) {
        if (tree.getTag() != JCTree.IDENT) {
            log.error(tree.pos(), "enum.label.must.be.unqualified.enum");
            return syms.errSymbol;
        }
        JCIdent ident = (JCIdent)tree;
        Name name = ident.name;
        for (Scope.Entry e = enumType.tsym.members().lookup(name);
             e.scope != null; e = e.next()) {
            if (e.sym.kind == VAR) {
                Symbol s = ident.sym = e.sym;
                ((VarSymbol)s).getConstValue(); // ensure initializer is evaluated
                ident.type = s.type;
                return ((s.flags_field & Flags.ENUM) == 0)
                    ? null : s;
            }
        }
        return null;
    }

    public void visitSynchronized(JCSynchronized tree) {
        chk.checkRefType(tree.pos(), attribExpr(tree.lock, env));
        attribStat(tree.body, env);
        result = null;
    }

    public void visitTry(JCTry tree) {
        // Attribute body
        attribStat(tree.body, env.dup(tree, env.info.dup()));

        // Attribute catch clauses
        for (List<JCCatch> l = tree.catchers; l.nonEmpty(); l = l.tail) {
            JCCatch c = l.head;
            Env<AttrContext> catchEnv =
                env.dup(c, env.info.dup(env.info.scope.dup()));
            Type ctype = attribStat(c.param, catchEnv);
            if (c.param.type.tsym.kind == Kinds.VAR) {
                c.param.sym.setData(ElementKind.EXCEPTION_PARAMETER);
            }
            chk.checkType(c.param.vartype.pos(),
                          chk.checkClassType(c.param.vartype.pos(), ctype),
                          syms.throwableType);
            attribStat(c.body, catchEnv);
            catchEnv.info.scope.leave();