import names are not unified

[adhusson]

Description

The as import keyword used in import "./file.sol" as name creates names considered distinct from other imports of the same file under the same name.

They should be unified when they wrap the exact same file.

Environment

solc 0.8.28

Steps to Reproduce

// imported.sol
contract C {}

// file1.sol
import "./imported.sol" as Imported;

// file2.sol
import "./imported.sol" as Imported;

// toplevel.sol
import "./file0.sol";
import "./file1.sol";

// Compilation fails with `Identifier already declared`.

Contrast the above with the 2 examples below, which both work:

// imported.sol
contract C {}

// file1.sol
import {C} from "./imported.sol";

// file2.sol
import {C} from "./imported.sol";

// toplevel.sol
import "./file0.sol";
import "./file1.sol";

// Compilation succeeds.

and

// imported.sol
contract C {}

// file1.sol
import {C as D} from "./imported.sol";

// file2.sol
import {C as D} from "./imported.sol";

// toplevel.sol
import "./file0.sol";
import "./file1.sol";

// Compilation succeeds.