AST.FuncDef.GetExternDecln C# (CSharp) Метод

        public ISemantReturn<ImmutableList<Tuple<Env, ExternDecln>>> GetExternDecln(Env env) {
            var storageClass = this.Specs.GetStorageClass();
            var baseType = Semant(this.Specs.GetExprType, ref env);
            var name = this.Declr.Name;
            var type = Semant(this.Declr.DecorateType, baseType, ref env);

            var funcType = type as FunctionType;
            if (funcType == null) {
                throw new InvalidOperationException("Expected a function Type.");
            }

            switch (storageClass) {
                case StorageClass.AUTO:
                case StorageClass.EXTERN:
                case StorageClass.STATIC:
                    env = env.PushEntry(Env.EntryKind.GLOBAL, name, type);
                    break;
                case StorageClass.TYPEDEF:
                default:
                    throw new InvalidOperationException("Invalid storage class specifier for function definition.");
            }

            env = env.InScope();
            env = env.SetCurrentFunction(funcType);
            var stmt = SemantStmt(this.Stmt.GetStmt, ref env);
            env = env.OutScope();

            return SemantReturn.Create(env, ImmutableList.Create(Tuple.Create(env, new ABT.FuncDef(name, storageClass, funcType, stmt) as ExternDecln)));
        }
    }