qt, wallet: Remove unused AskPassphraseDialog::Decrypt

Summary:
Co-authored-by: Sehyun Chung <sehyun@berkeley.edu>

This is a backport of [[bitcoin-core/gui#109 | core-gui#109]] [1/3]
bitcoin-core/gui@6e95011

Test Plan: `ninja all check-all`

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10737

Author: hebasto

src/qt/askpassphrasedialog.cpp

@@ -56,15 +56,6 @@ AskPassphraseDialog::AskPassphraseDialog(Mode _mode, QWidget *parent,
             ui->passEdit3->hide();
             setWindowTitle(tr("Unlock wallet"));
             break;
-        case Decrypt: // Ask passphrase
-            ui->warningLabel->setText(tr("This operation needs your wallet "
-                                         "passphrase to decrypt the wallet."));
-            ui->passLabel2->hide();
-            ui->passEdit2->hide();
-            ui->passLabel3->hide();
-            ui->passEdit3->hide();
-            setWindowTitle(tr("Decrypt wallet"));
-            break;
         case ChangePass: // Ask old passphrase + new passphrase x2
             setWindowTitle(tr("Change passphrase"));
             ui->warningLabel->setText(tr(
@@ -186,15 +177,6 @@ void AskPassphraseDialog::accept() {
                                       e.what());
             }
             break;
-        case Decrypt:
-            if (!model->setWalletEncrypted(false, oldpass)) {
-                QMessageBox::critical(this, tr("Wallet decryption failed"),
-                                      tr("The passphrase entered for the "
-                                         "wallet decryption was incorrect."));
-            } else {
-                QDialog::accept(); // Success
-            }
-            break;
         case ChangePass:
             if (newpass1 == newpass2) {
                 if (model->changePassphrase(oldpass, newpass1)) {
@@ -225,10 +207,7 @@ void AskPassphraseDialog::textChanged() {
             acceptable = !ui->passEdit2->text().isEmpty() &&
                          !ui->passEdit3->text().isEmpty();
             break;
-        case Unlock: // Old passphrase x1
-        case Decrypt:
-            acceptable = !ui->passEdit1->text().isEmpty();
-            break;
+        case Unlock:     // Old passphrase x1
         case ChangePass: // Old passphrase x1, new passphrase x2
             acceptable = !ui->passEdit1->text().isEmpty() &&
                          !ui->passEdit2->text().isEmpty() &&

src/qt/askpassphrasedialog.h

@@ -26,7 +26,6 @@ class AskPassphraseDialog : public QDialog {
         Encrypt,    /**< Ask passphrase twice and encrypt */
         Unlock,     /**< Ask passphrase and unlock */
         ChangePass, /**< Ask old passphrase + new passphrase twice */
-        Decrypt     /**< Ask passphrase and decrypt wallet */
     };
 
     explicit AskPassphraseDialog(Mode mode, QWidget *parent,

src/qt/walletview.cpp

@@ -350,10 +350,7 @@ void WalletView::encryptWallet(bool status) {
     if (!walletModel) {
         return;
     }
-
-    AskPassphraseDialog dlg(status ? AskPassphraseDialog::Encrypt
-                                   : AskPassphraseDialog::Decrypt,
-                            this);
+    AskPassphraseDialog dlg(AskPassphraseDialog::Encrypt, this);
     dlg.setModel(walletModel);
     dlg.exec();