transtypes.java

是一款用JAVA 编写的编译器 具有很强的编译功能

     *  If a bridge already exists in some other class, no new bridge is added.
     *  Instead, it is checked that the bridge symbol overrides the method symbol.
     *  (Spec ???).
     *  todo: what about bridges for privates???
     *
     *  @param pos     The source code position to be used for the definition.
     *  @param sym     The symbol for which a bridge might have to be added.
     *  @param origin  The class in which the bridge would go.
     *  @param bridges The list buffer to which the bridge would be added.
     */
    void addBridgeIfNeeded(DiagnosticPosition pos,
                           Symbol sym,
                           ClassSymbol origin,
                           ListBuffer<JCTree> bridges) {
        if (sym.kind == MTH &&
            sym.name != names.init &&
            (sym.flags() & (PRIVATE | SYNTHETIC | STATIC)) == 0 &&
            sym.isMemberOf(origin, types))
        {
            MethodSymbol meth = (MethodSymbol)sym;
            MethodSymbol bridge = meth.binaryImplementation(origin, types);
            MethodSymbol impl = meth.implementation(origin, types, true);
            if (bridge == null ||
                bridge == meth ||
                (impl != null && !bridge.owner.isSubClass(impl.owner, types))) {
                // No bridge was added yet.
                if (impl != null && isBridgeNeeded(meth, impl, origin.type)) {
                    addBridge(pos, meth, impl, origin, bridge==impl, bridges);
                } else if (impl == meth
                           && impl.owner != origin
                           && (impl.flags() & FINAL) == 0
                           && (meth.flags() & (ABSTRACT|PUBLIC)) == PUBLIC
                           && (origin.flags() & PUBLIC) > (impl.owner.flags() & PUBLIC)) { 
                    // this is to work around a horrible but permanent 
                    // reflection design error. 
                    addBridge(pos, meth, impl, origin, false, bridges); 
                }
            } else if ((bridge.flags() & SYNTHETIC) != 0) {
                MethodSymbol other = overridden.get(bridge);
                if (other != null && other != meth) {
                    if (impl == null || !impl.overrides(other, origin, types, true)) {
                        // Bridge for other symbol pair was added
                        log.error(pos, "name.clash.same.erasure.no.override",
                                  other, other.location(origin.type, types),
                                  meth,  meth.location(origin.type, types));
                    }
                }
            } else if (!bridge.overrides(meth, origin, types, true)) {
                // Accidental binary override without source override.
                if (bridge.owner == origin ||
                    types.asSuper(bridge.owner.type, meth.owner) == null)
                    // Don't diagnose the problem if it would already
                    // have been reported in the superclass
                    log.error(pos, "name.clash.same.erasure.no.override",
                              bridge, bridge.location(origin.type, types),
                              meth,  meth.location(origin.type, types));
            }
        }
    }
    // where
        /**
         * @param method The symbol for which a bridge might have to be added
         * @param impl The implementation of method
         * @param dest The type in which the bridge would go
         */
        private boolean isBridgeNeeded(MethodSymbol method,
                                       MethodSymbol impl,
                                       Type dest) {
            if (impl != method) {
                // If either method or impl have different erasures as
                // members of dest, a bridge is needed.
                Type method_erasure = method.erasure(types);
                if (!isSameMemberWhenErased(dest, method, method_erasure))
                    return true;
                Type impl_erasure = impl.erasure(types);
                if (!isSameMemberWhenErased(dest, impl, impl_erasure))
                    return true;

                // If the erasure of the return type is different, a
                // bridge is needed.
                return !types.isSameType(impl_erasure.getReturnType(),
                                         method_erasure.getReturnType());
            } else {
               // method and impl are the same...
                if ((method.flags() & ABSTRACT) != 0) {
                    // ...and abstract so a bridge is not needed.
                    // Concrete subclasses will bridge as needed.
                    return false;
                }

                // The erasure of the return type is always the same
                // for the same symbol.  Reducing the three tests in
                // the other branch to just one:
                return !isSameMemberWhenErased(dest, method, method.erasure(types));
            }
        }
        /**
         * Lookup the method as a member of the type.  Compare the
         * erasures.
         * @param type the class where to look for the method
         * @param method the method to look for in class
         * @param erasure the erasure of method
         */
        private boolean isSameMemberWhenErased(Type type,
                                               MethodSymbol method,
                                               Type erasure) {
            return types.isSameType(erasure(types.memberType(type, method)),
                                    erasure);
        }

    void addBridges(DiagnosticPosition pos,
                    TypeSymbol i,
                    ClassSymbol origin,
                    ListBuffer<JCTree> bridges) {
        for (Scope.Entry e = i.members().elems; e != null; e = e.sibling)
            addBridgeIfNeeded(pos, e.sym, origin, bridges);
        for (List<Type> l = types.interfaces(i.type); l.nonEmpty(); l = l.tail)
            addBridges(pos, l.head.tsym, origin, bridges);
    }

    /** Add all necessary bridges to some class appending them to list buffer.
     *  @param pos     The source code position to be used for the bridges.
     *  @param origin  The class in which the bridges go.
     *  @param bridges The list buffer to which the bridges are added.
     */
    void addBridges(DiagnosticPosition pos, ClassSymbol origin, ListBuffer<JCTree> bridges) {
        Type st = types.supertype(origin.type);
        while (st.tag == CLASS) {
//          if (isSpecialization(st))
            addBridges(pos, st.tsym, origin, bridges);
            st = types.supertype(st);
        }
        for (List<Type> l = types.interfaces(origin.type); l.nonEmpty(); l = l.tail)
//          if (isSpecialization(l.head))
            addBridges(pos, l.head.tsym, origin, bridges);
    }

/* ************************************************************************
 * Visitor methods
 *************************************************************************/

    /** Visitor argument: proto-type.
     */
    private Type pt;

    /** Visitor method: perform a type translation on tree.
     */
    public <T extends JCTree> T translate(T tree, Type pt) {
        Type prevPt = this.pt;
        try {
            this.pt = pt;
            return translate(tree);
        } finally {
            this.pt = prevPt;
        }
    }

    /** Visitor method: perform a type translation on list of trees.
     */
    public <T extends JCTree> List<T> translate(List<T> trees, Type pt) {
        Type prevPt = this.pt;
        List<T> res;
        try {
            this.pt = pt;
            res = translate(trees);
        } finally {
            this.pt = prevPt;
        }
        return res;
    }

    public void visitClassDef(JCClassDecl tree) {
        translateClass(tree.sym);
        result = tree;
    }

    JCMethodDecl currentMethod = null;
    public void visitMethodDef(JCMethodDecl tree) {
        JCMethodDecl previousMethod = currentMethod;
        try {
            currentMethod = tree;
            tree.restype = translate(tree.restype, null);
            tree.typarams = List.nil();
            tree.params = translateVarDefs(tree.params);
            tree.thrown = translate(tree.thrown, null);
            tree.body = translate(tree.body, tree.sym.erasure(types).getReturnType());
            tree.type = erasure(tree.type);
            result = tree;
        } finally {
            currentMethod = previousMethod;
        }

        // Check that we do not introduce a name clash by erasing types.
        for (Scope.Entry e = tree.sym.owner.members().lookup(tree.name);
             e.sym != null;
             e = e.next()) {
            if (e.sym != tree.sym &&
                types.isSameType(erasure(e.sym.type), tree.type)) {
                log.error(tree.pos(),
                          "name.clash.same.erasure", tree.sym,
                          e.sym);
                return;
            }
        }
    }

    public void visitVarDef(JCVariableDecl tree) {
        tree.vartype = translate(tree.vartype, null);
        tree.init = translate(tree.init, tree.sym.erasure(types));
        tree.type = erasure(tree.type);
        result = tree;
    }
        
    public void visitDoLoop(JCDoWhileLoop tree) {
        tree.body = translate(tree.body);
        tree.cond = translate(tree.cond, syms.booleanType);
        result = tree;
    }

    public void visitWhileLoop(JCWhileLoop tree) {
        tree.cond = translate(tree.cond, syms.booleanType);
        tree.body = translate(tree.body);
        result = tree;
    }

    public void visitForLoop(JCForLoop tree) {
        tree.init = translate(tree.init, null);
        if (tree.cond != null)
            tree.cond = translate(tree.cond, syms.booleanType);
        tree.step = translate(tree.step, null);
        tree.body = translate(tree.body);
        result = tree;
    }

    public void visitForeachLoop(JCEnhancedForLoop tree) {
        tree.var = translate(tree.var, null);
        Type iterableType = tree.expr.type;
        tree.expr = translate(tree.expr, erasure(tree.expr.type));
        if (types.elemtype(tree.expr.type) == null)
            tree.expr.type = iterableType; // preserve type for Lower
        tree.body = translate(tree.body);
        result = tree;
    }

    public void visitSwitch(JCSwitch tree) {
        Type selsuper = types.supertype(tree.selector.type);
        boolean enumSwitch = selsuper != null &&
            selsuper.tsym == syms.enumSym;
        Type target = enumSwitch ? erasure(tree.selector.type) : syms.intType;
        tree.selector = translate(tree.selector, target);
        tree.cases = translateCases(tree.cases);
        result = tree;
    }

    public void visitCase(JCCase tree) {
        tree.pat = translate(tree.pat, null);
        tree.stats = translate(tree.stats);
        result = tree;
    }

    public void visitSynchronized(JCSynchronized tree) {
        tree.lock = translate(tree.lock, erasure(tree.lock.type));
        tree.body = translate(tree.body);
        result = tree;
    }