template < typename T, int I > class X; 

X<int, __LINE__ > x0; 
X<int, __LINE__ > x1;

x0和x1将是不同的类型，如果它们不在文件的同一行中，则其他类似的声明也将是不同的类型.

x0 and x1 will be different types as will any other declarations like this if they are not on the same line in the file.