Why can you use the same name in struct definitions?

I recently found this code:

struct foo  { int foo; } foo;

And I compiled this snippet (with an empty main() function of course!), and it compiled without a warning. Why is this legal?

>Solution :

The compiler can tell them apart by the context in which they appear. C 2018 6.2.3, “Name spaces of identifiers,” says:

If more than one declaration of a particular identifier is visible at any point in a translation unit, the syntactic context disambiguates uses that refer to different entities. Thus, there are separate name spaces for various categories of identifiers, as follows:

— label names (disambiguated by the syntax of the label declaration and use);

— the tags of structures, unions, and enumerations (disambiguated by following any of the
keywords struct, union, or enum);

— the members of structures or unions; each structure or union has a separate name space for its members (disambiguated by the type of the expression used to access the member via the . or
-> operator);

— all other identifiers, called ordinary identifiers (declared in ordinary declarators or as enumeration constants).