Remove MsgHandleErrInternal::from_chan_maybe_close as it's useless

Technically funding_transaction_generated was fine using it, but
calling force_shutdown on an empty Channel inside the channel_state
lock isn't a big deal and almost any other use of it would be
unsafe.

Author: TheBlueMatt

src/ln/channel.rs

@@ -1004,6 +1004,7 @@ impl Channel {
 	#[inline]
 	/// Creates a set of keys for build_commitment_transaction to generate a transaction which we
 	/// will sign and send to our counterparty.
+	/// If an Err is returned, it is a ChannelError::Close (for get_outbound_funding_created)
 	fn build_remote_transaction_keys(&self) -> Result<TxCreationKeys, ChannelError> {
 		//TODO: Ensure that the payment_key derived here ends up in the library users' wallet as we
 		//may see payments to it!
@@ -2949,6 +2950,7 @@ impl Channel {
 		}
 	}
 
+	/// If an Err is returned, it is a ChannelError::Close (for get_outbound_funding_created)
 	fn get_outbound_funding_created_signature(&mut self) -> Result<(Signature, Transaction), ChannelError> {
 		let funding_script = self.get_funding_redeemscript();
 
@@ -2966,6 +2968,7 @@ impl Channel {
 	/// or if called on an inbound channel.
 	/// Note that channel_id changes during this call!
 	/// Do NOT broadcast the funding transaction until after a successful funding_signed call!
+	/// If an Err is returned, it is a ChannelError::Close.
 	pub fn get_outbound_funding_created(&mut self, funding_txo: OutPoint) -> Result<(msgs::FundingCreated, ChannelMonitor), ChannelError> {
 		if !self.channel_outbound {
 			panic!("Tried to create outbound funding_created message on an inbound channel!");

src/ln/channelmanager.rs

@@ -215,28 +215,6 @@ impl MsgHandleErrInternal {
 			shutdown_finish: None,
 		}
 	}
-	#[inline]
-	fn from_chan_maybe_close(err: ChannelError, channel_id: [u8; 32]) -> Self {
-		Self {
-			err: match err {
-				ChannelError::Ignore(msg) => HandleError {
-					err: msg,
-					action: Some(msgs::ErrorAction::IgnoreError),
-				},
-				ChannelError::Close(msg) => HandleError {
-					err: msg,
-					action: Some(msgs::ErrorAction::SendErrorMessage {
-						msg: msgs::ErrorMessage {
-							channel_id,
-							data: msg.to_string()
-						},
-					}),
-				},
-			},
-			needs_channel_force_close: true,
-			shutdown_finish: None,
-		}
-	}
 }
 
 /// Pass to fail_htlc_backwwards to indicate the reason to fail the payment
@@ -1363,7 +1341,9 @@ impl ChannelManager {
 				match channel_state.by_id.remove(temporary_channel_id) {
 					Some(mut chan) => {
 						(chan.get_outbound_funding_created(funding_txo)
-							.map_err(|e| MsgHandleErrInternal::from_chan_maybe_close(e, chan.channel_id()))
+							.map_err(|e| if let ChannelError::Close(msg) = e {
+								MsgHandleErrInternal::from_finish_shutdown(msg, chan.channel_id(), chan.force_shutdown(), None)
+							} else { unreachable!(); })
 						, chan)
 					},
 					None => return