c++ - Keyword struct before constructor name -

i amazed when saw code success compiled ms visual c++.

struct foo {     struct foo(int i): value(i) {}     int value; }; 

what means keyword struct in such strange context?

in contexts, can use elaborated type specifier struct foo, or equivalently class foo, instead of class name foo. can useful resolve ambiguities:

struct foo {};  // declares type foo foo;        // declares variable same name  foo bar;        // error: "foo" refers variable struct foo bar; // ok: "foo" explicitly refers class type 

however, can't use form when declaring constructor, compiler wrong accept code. specification constructor declaration (in c++11 12.1/1) allows class name itself, not elaborated type specifier.

in general, shouldn't surprised when visual c++ compiles kinds of wonky code. it's notorious non-standard extensions language.