The specification currently states that use declarations bring a name into a scope, but that's not exactly true, as imports are not available prior to the use declaration.
namespace A {
class C {}
}
namespace B {
// Same scope, 'A\C' should be available right?!
$c = new C();
use A\C;
}
Without this restriction, an engine could theoretically make an initial pass to import names from all use declarations, and therefore prevent a name resolution error from occurring.
18-namespaces.md
A namespace-use-declaration imports — that is, makes available — one or more names into a scope, optionally giving them each an alias.
The specification currently states that use declarations bring a name into a scope, but that's not exactly true, as imports are not available prior to the use declaration.
Without this restriction, an engine could theoretically make an initial pass to import names from all use declarations, and therefore prevent a name resolution error from occurring.
18-namespaces.md