How to ask what the code means

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72

# How to ask what the code means

This guide shows how to follow a name through a project: where it is declared, what implements it, everywhere it is used, and what is wrong with it. It assumes Turbo MoonBit is installed and a language server is running — the status bar says `LSP: ready` when it is.

For moving around a file — searching, jumping to a line, switching windows — see [How to move around a file](navigate-code.md) instead.

## Put the cursor on a name

Any character of it will do. Every question below asks about the **position of the cursor**, not about a selection, so there is nothing to highlight first.

## Ask

| To find | Do | Shortcut |
| --- | --- | --- |
| What it is | **Code ▸ Describe symbol** | `F1` |
| Where it is declared | **Code ▸ Go to definition** | `F12` |
| Where its *type* is declared | **Code ▸ Go to type definition** | |
| What implements it | **Code ▸ Find implementations…** | |
| Everywhere it is used | **Code ▸ Find references…** | `Shift-F12` |

**Two of these five report nothing with moon-lsp.** The server advertises neither `typeDefinition` nor `implementation`, so **Go to type definition** and **Find implementations** answer nothing found however good the code is. The other three, and the two symbol searches below, all work. See [colouring and completion](../explanation/colouring-and-completion.md) for why this is written down rather than hidden behind a greyed-out menu item.

One answer takes you straight there. Several open a list showing each file, its line, and the text of that line:

```
References (3)
  main.mbt:1    fn helper() -> Int {
  main.mbt:7      helper()
  main.mbt:12     helper() + 1
```

Move with the arrow keys, `Enter` to go, `Esc` to stay where you are.

## When nothing comes back

Three different things look alike, and the status bar tells them apart:

| It says | Meaning |
| --- | --- |
| `No references found` | The server answered, and there are none |
| Anything else, such as `Loading…` | The server has not finished indexing. Wait a moment and ask again. |
| `LSP: off` on the status bar | No server is running. See [How to enable completion](enable-completion.md). |

The middle one is worth knowing: a server still indexing answers every question with nothing, and that is indistinguishable from a real answer unless the editor says so.

## Find something by name instead

- **Code ▸ Symbol in file…** lists what the file in front declares, indented, with each symbol's kind — an outline you can walk.
- **Code ▸ Symbol in project…** (`Ctrl-T`) asks for a name and searches everywhere. What counts as a match is the server's decision; moon-lsp matches loosely, so a few letters usually do.

## See what is wrong

**Code ▸ Problems…** lists every problem the server has reported, for **every file it has loaded** — usually more than the one you are editing. Choosing one goes to the line.

Lines with a problem carry a mark in the gutter, beside the line number:

| Mark | Meaning |
| --- | --- |
| `×` | An error |
| `!` | A warning |
| `i` | Information |
| `·` | A hint |

A line with more than one problem shows the worst of them.

**The marks need the line numbers.** They sit in the column that separates the numbers from the text, so hiding the gutter with **Options ▸ Line numbers** hides them too.

## See also

- Every item and its key: [Menus](../reference/menus.md)
- Getting a server running: [How to enable completion](enable-completion.md)
- What the editor asks, and why: [Colouring and completion](../explanation/colouring-and-completion.md)