vscode-ext: register correct spans in lsp server

before, we registered the wrong proc spans in the lsp server. this
resulted in the extension thinking there were still "todo" procs left.

src/main.rs

@@ -674,12 +674,11 @@ fn verify_files_main(
     // Register all relevant source units with the server
     for source_unit in &mut source_units {
         let source_unit = source_unit.enter();
-
         match *source_unit {
             SourceUnit::Decl(ref decl) => {
                 // only register procs since we do not check any other decls
                 if let DeclKind::ProcDecl(proc_decl) = decl {
-                    server.register_source_unit(proc_decl.borrow().span)?;
+                    server.register_source_unit(proc_decl.borrow().name.span)?;
                 }
             }
             SourceUnit::Raw(ref block) => server.register_source_unit(block.span)?,

src/servers/lsp.rs

@@ -328,14 +328,17 @@ impl Server for LspServer {
         translate: &mut TranslateExprs<'smt, 'ctx>,
     ) -> Result<(), ServerError> {
         result.emit_diagnostics(span, self, translate)?;
-        self.statuses
+        let prev = self
+            .statuses
             .insert(span, VerifyResult::from_prove_result(&result.prove_result));
+        assert!(prev.is_some());
         self.publish_verify_statuses()?;
         Ok(())
     }
 
     fn handle_not_checked(&mut self, span: Span) -> Result<(), ServerError> {
-        self.statuses.insert(span, VerifyResult::Unknown);
+        let prev = self.statuses.insert(span, VerifyResult::Unknown);
+        assert!(prev.is_some());
         self.publish_verify_statuses()?;
         Ok(())
     }