Fix panic parsing seeds when account has qualified path

[mcintyre94]

This PR fixes a panic caused when Anchor parses seeds that reference an account imported from another file using its full path, eg in code like this:

    #[derive(Accounts)]
    pub struct LikePost<'info> {
        #[account(
            init,
            space = 448,
            payer = liker,
            seeds = [post.owner.as_ref() , post.id.to_le_bytes().as_ref()],
            bump
        )]
        pub like: Account<'info, dot::program::Like>,
        #[account(mut)]
        pub post: Account<'info, dot::program::Post>,
        #[account(mut)]
        pub liker: Signer<'info>,
        pub system_program: Program<'info, System>,
        pub rent: Sysvar<'info, Rent>,
    }

Here the post.owner and post.id seeds caused a panic.

The cause was:

anchor/lang/syn/src/idl/pda.rs

Line 225 in 8ce18c3

let strct = self.ctx.structs().find(|s| s.ident == account).unwrap();

When this runs the struct idents are mapped to non-qualified type names: ["Like", "LoadedLike", "DeletePostEvent", "User", "LoadedUser", "LikeDislikePostEvent", "UpdatePostEvent", "Post", "LoadedPost", "NewPostEvent", "CreateUser", "DeletePost", "LikePost", "CreatePost", "DislikePost", "UpdatePost", "Mutable", "Empty", "ProgramsMap", "WithPrograms", "CpiAccount"]

While the account was dot :: program :: Post. Since this doesn't match any of the unqualified struct names, it panics on the unwrap.

Here account comes from a call to:

anchor/lang/syn/src/lib.rs

Lines 199 to 209 in 8ce18c3

	pub fn ty_name(&self) -> Option<String> {
	match self {
	AccountField::Field(field) => match &field.ty {
	Ty::Account(account) => Some(parser::tts_to_string(&account.account_type_path)),
	Ty::ProgramAccount(account) => {
	Some(parser::tts_to_string(&account.account_type_path))
	}
	_ => None,
	},
	AccountField::CompositeField(field) => Some(field.symbol.clone()),
	}

This PR updates the call to ty_name to remove any import path from the account. So account is returned as Post and correctly matches the imported struct name, fixing the panic.

[vercel]

@mcintyre94 is attempting to deploy a commit to the coral-xyz Team on Vercel.

A member of the Team first needs to authorize it.

[Henry-E]

It might be nice to add this as one of the example seeds in the pda derivation example https://github.com/coral-xyz/anchor/tree/master/tests/pda-derivation , if only so that we verify in tests that this new macro code actually does solve the issue of panicking on imported seeds

[mcintyre94]

Thanks @Henry-E! I've updated the pda-derivation test to add a seed that triggers this error. When I run the test locally now with the current Anchor build it fails with the expected panic, with this branch it passes.
Updated in a new commit: 31baab3

[Henry-E]

Thanks very much for adding the test, really appreciate it!

Just running the CI now and will hopefully be able to merge once that's done.