mapping storageRef cannot be converted to mapping storage pointer

[haoyang9804]

Describe the bug

When I define a function that returns a mapping storage pointer and returns a state mapping variable (which is actually storage reference), Solang sometimes allows the behavior but sometimes forbids it.

Found by Erwin

To Reproduce
Use solang compile --target solana <program_path> to compile the two source code given below, you can find that the first fails the compilation while the second passes.
Expected behavior
The two source code should have the trigger the same compilation results. And I guess, they should both pass the compilation.

Screenshots
The compilation result of the first source code:

That of the second one.

Hyperledger Solang version
solang version v0.3.3

Include the complete solidity source code
The source code that fails the compilation

contract contract0 {
  mapping(int16 => int16) internal mapping14;
  mapping(int16 => int16) internal mapping17;

  function func8() internal returns (mapping(int16 => int16) storage mapping9, int16 var12) {
    int16 var20 = (int16(-32200));
    return ((true) ? mapping17 : mapping14, var20);
  }
}

The source that passes the compilation

contract contract0 {
  mapping(int16 => int16) internal mapping14;
  mapping(int16 => int16) internal mapping17;

  function func8() internal returns (mapping(int16 => int16) storage mapping9) {
    return ((true) ? mapping17 : mapping14);
  }
}