Shell: Make program-based completion with no actual token possible

31ca48e made this default to paths, but now that we have a few sensible
ways to complete things, let's make those work too.
For instance, prior to this `kill <tab>` would've suggested paths, but
now it will suggest processes.

Userland/Shell/AST.cpp

@@ -393,6 +393,7 @@ Vector<Line::CompletionSuggestion> Node::complete_for_editor(Shell& shell, size_
     auto result = hit_test_position(offset);
     if (!result.matching_node)
         return shell.complete_path("", "", 0, Shell::ExecutableOnly::No, result.closest_command_node.ptr(), nullptr, Shell::EscapeMode::Bareword);
+
     auto node = result.matching_node;
     if (node->is_bareword() || node != result.closest_node_with_semantic_meaning)
         node = result.closest_node_with_semantic_meaning;
@@ -744,6 +745,8 @@ HitTestResult CastToCommand::hit_test_position(size_t offset) const
     auto result = m_inner->hit_test_position(offset);
     if (!result.closest_node_with_semantic_meaning)
         result.closest_node_with_semantic_meaning = this;
+    if (!result.closest_command_node && position().contains(offset))
+        result.closest_command_node = this;
     return result;
 }
 

Userland/Shell/Shell.cpp

@@ -1678,9 +1678,9 @@ ErrorOr<Vector<Line::CompletionSuggestion>> Shell::complete_via_program_itself(s
     completion_command.argv.extend({ "--complete", "--" });
 
     struct Visitor : public AST::NodeVisitor {
-        Visitor(Shell& shell, AST::Node const& node)
+        Visitor(Shell& shell, AST::Position position)
             : shell(shell)
-            , completion_position(node.position())
+            , completion_position(position)
         {
             lists.empend();
         }
@@ -1824,7 +1824,7 @@ ErrorOr<Vector<Line::CompletionSuggestion>> Shell::complete_via_program_itself(s
         virtual void visit(AST::ReadWriteRedirection const*) override { }
         virtual void visit(AST::WriteAppendRedirection const*) override { }
         virtual void visit(AST::WriteRedirection const*) override { }
-    } visitor { *this, *node };
+    } visitor { *this, node ? node->position() : AST::Position() };
 
     command_node->visit(visitor);
     if (visitor.fail)