while (!todo.isEmpty()){Environment<AttrContext> a = todo.remove();Environment<AttrContext> b = attribute(a);  // 标注Queue<Environment<AttrContext>> c = flow(b); // 数据流分析Queue<Pair<Environment<AttrContext>, JCClassDeclaration>> d = desugar(c); // 解语法糖generate(d);  // 生成字节码
//                        generate(desugar(flow(attribute(todo.remove()))));
}

 Type type = attr.attribTree(jcFieldAccess.selected, localEnvironment, protoKind, Type.noType); // protoKind=_TYPE|_PCK,Type.noType=JCNoType

 /** Find an unqualified identifier which matches a specified kind set.*  @param environment       The current environment.*  @param name      The identifier's name.*  @param kind      Indicates the possible symbol kinds (a subset of _VAL, _TYP, _PCK).**/public Symbol findIdentifier(Environment<AttrContext> environment, Name name, int kind) {Symbol bestSoFar = typeNotFound;Symbol symbol;if ((kind & _VAR) != 0) {symbol = findVariable(environment, name);if (symbol.exists()){return symbol;}else if (symbol.kind < bestSoFar.kind){bestSoFar = symbol;}}if ((kind & _TYP) != 0) {symbol = findType(environment, name);if (symbol.exists()){return symbol;}else if (symbol.kind < bestSoFar.kind){ // ??bestSoFar = symbol;}}if ((kind & _PCK) != 0){return classReader.enterPackage(name);}else{return bestSoFar;}}

/** Find unqualified variable or field with given name.*  Synthetic fields always skipped.*  @param environment     The current environment.*  @param name    The name of the variable or field.*/Symbol findVariable(Environment<AttrContext> environment, Name name) {Symbol bestSoFar = variableNotFound;Symbol symbol;Environment<AttrContext> env1 = environment;boolean staticOnly = false;while (env1.outer != null) {if (isStatic(env1)){staticOnly = true;}Entry entry = env1.info.scope.lookup(name);while (entry.scope != null &&(entry.symbol.kind != _VAR || (entry.symbol.flags_field & SYNTHETIC) != 0) // 非变量或者是合成的那就需要继续查找){entry = entry.next();}// 走到这里说明entry.symbol.kind==_VAR或者(entry.symbol.flags_field & SYNTHETIC)==0(非合成的变量）// 如果findVariable查找不到就要调用findField进行查找if(entry.scope != null){symbol = entry.symbol;}else{symbol = findField(env1, env1.enclosingClass.classSymbol.type, name, env1.enclosingClass.classSymbol);}if( symbol.exists()) {if( staticOnly &&symbol.kind == _VAR &&symbol.ownerSymbol.kind == _TYP &&(symbol.flags() & STATIC) == 0) {// 静态上下文中引用非静态的变量return new StaticError(symbol, this);}else{return symbol;}} else if (symbol.kind < bestSoFar.kind) {bestSoFar = symbol;}if ((env1.enclosingClass.classSymbol.flags() & STATIC) != 0){staticOnly = true;}env1 = env1.outer;}// end whilesymbol = findField(environment, symbolTable.predefinedClass.type, name, symbolTable.predefinedClass);if (symbol.exists()){return symbol;}if (bestSoFar.exists()){return bestSoFar;}Entry entry = environment.toplevel.namedImportScope.lookup(name);for (; entry.scope != null; entry = entry.next()) {symbol = entry.symbol;Type origin = entry.getOrigin().owner.type;if (symbol.kind == _VAR) {if (entry.symbol.ownerSymbol.type != origin){symbol = symbol.clone(entry.getOrigin().owner);}if(isAccessible(environment, origin, symbol)){return symbol;}else{return new AccessError(environment, origin, symbol, this);}}}Symbol origin = null;entry = environment.toplevel.starImportScope.lookup(name);for (; entry.scope != null; entry = entry.next()) {symbol = entry.symbol;if (symbol.kind != _VAR){continue;}// invariant: classSymbol.kind == _VARif (bestSoFar.kind < _AMBIGUOUS && symbol.ownerSymbol != bestSoFar.ownerSymbol){return new AmbiguityError(bestSoFar, symbol, this);}else if (bestSoFar.kind >= _VAR) {origin = entry.getOrigin().owner;if(isAccessible(environment, origin.type, symbol)){bestSoFar = symbol;}else{bestSoFar = new AccessError(environment, origin.type, symbol, this);}}}// ???if (bestSoFar.kind == _VAR && bestSoFar.ownerSymbol.type != origin.type){return bestSoFar.clone(origin);}else{return bestSoFar;}}

/** Find field. Synthetic fields are always skipped.*  @param environment The current environment.*  @param site    The original type from where the selection takes place.*  @param name    The name of the field.*  @param typeSymbol The class to search for the field. This is always a superclass or implemented interface of site's class.*/Symbol findField(Environment<AttrContext> environment,Type site,Name name,TypeSymbol typeSymbol) {while (typeSymbol.type.typeTag == TYPEVARIABLE){typeSymbol = typeSymbol.type.getUpperBound().typeSymbol;}Symbol bestSoFar = variableNotFound;Symbol symbol;// 查找本类Entry entry = typeSymbol.members().lookup(name);while (entry.scope != null) {// 符号是变量且不是合成的if (entry.symbol.kind == _VAR && (entry.symbol.flags_field & SYNTHETIC) == 0) {if(isAccessible(environment, site, entry.symbol)){return entry.symbol;}else{return new AccessError(environment, site, entry.symbol,this);}}entry = entry.next();}// 查找父类Type superType = types.supertype(typeSymbol.type);if (superType != null && (superType.typeTag == CLASS || superType.typeTag == TYPEVARIABLE)) {symbol = findField(environment, site, name, superType.typeSymbol); // 递归调用if (symbol.kind < bestSoFar.kind){bestSoFar = symbol;}}// 查找所有的接口类for (List<Type> l = types.interfaces(typeSymbol.type); bestSoFar.kind != _AMBIGUOUS && l.nonEmpty(); l = l.tail) {symbol = findField(environment, site, name, l.head.typeSymbol); // 递归调用if (bestSoFar.kind < _AMBIGUOUS && symbol.kind < _AMBIGUOUS && symbol.ownerSymbol != bestSoFar.ownerSymbol){bestSoFar = new AmbiguityError(bestSoFar, symbol, this);}else if (symbol.kind < bestSoFar.kind){bestSoFar = symbol;}}return bestSoFar;}