---
title: "What the build checks"
description: "The declarations are read from the text without running it, and Run checks them before the compiler runs."
order: 30
section: "settings"
---

<!-- source: docs/indicators/settings/checks.md; generated by packages/cli/scripts/gen-indicator-docs.ts, do not edit -->

# What the build checks

The declarations are read from the text without running it, and **Run** checks them before the compiler runs.

## What it is

Declarations are literals: the extractor reads them from the text
without running it, and each kind checks its own default's shape, a
whole number for `param.int`, hex for `param.color`, one of the options
for `param.choice`. Every kind takes one options object, every key
optional, and a key the kind cannot use is refused by name. The Console
shows each refusal on the declaration's line:

```text
param.bool 'x' takes no min option (its value is not a number field)
```

![A toggle declared with a min option: its line underlined in the editor, the declarations row in the Console with the refusal, the error count in the status bar, and Run blocked](/wrun/images/checks-declaration.png)

- Line 7 is underlined as you type: the extractor reads the declaration
  before anything compiles.
- The Console row is tagged `declarations` and starts with the line
  number; the message names the kind, the setting and the option.
- The status bar counts the error, and Run answers "Cannot run: 1
  error(s) must be fixed first."

## The refusal table

| Mistake | What the Console says |
| --- | --- |
| a key the kind does not take | `param.int options accept only { required, min, max, description, label, step, group, row, hint, when, hide, slider, unit, unit_default, confirm }, not 'tooltip'` |
| a typed key on plain `param` | `param options accept only { required, min, max, description }, not 'label'` |
| a number-field key on a toggle | `param.bool 'x' takes no min option (its value is not a number field)` |
| a unit picker on a range | `param.range 'r' takes no unit option (a unit picker sits beside one number field, not a range)` |
| `hide` without `when` | `param.int 'x' declares hide without when; hide names what happens when the when param is off, so declare when beside it` |
| `when` naming a setting that is not a toggle | `param.int 'x' when names 'y', which is not a param.bool (when takes the NAME of a param.bool, e.g. when: "show_bands")` |
| a slider without both bounds | `param.int 'x' declares slider without min and max (a slider needs both bounds)` |
| a fractional `param.int` default | `param.int 'x' default must be an integer literal, not 1.5` |
| a choice default that is not an option | `param.choice 'm' default "c" is not one of its options (known: a, b)` |
| a color that is not hex | `param.color 'c' default takes "#rrggbb" or "#rrggbbaa", not 'red'` |
| a range without bounds | `param.range 'r' needs min and max (the two-handle slider's bounds), e.g. param.range("r", [1, 2], { min: 0, max: 100 })` |
| a list without `max` | `param.list 'l' needs max (the most items the dialog may hold), e.g. param.list("l", [1,2], { max: 8 })` |
| a list whose `max` alone crosses 128 | `param.list 'l' max 200 would put 201 params on the sheet (max slots and the count); hosted lanes cap params at 128, so max is at most 127` |
| a source default off the menu | `unknown field ohlcv.vwap for param.source 's' (known: open, high, low, close, hl2, hlc3, ohlc4, volume, hlcc4)` |
| a reference to the wrong kind | `output 'h' color references "@k", which is not a param.color` |
| a reference where no setting can paint | `draw.line 'ln' color references "@c", but a param paints an output, a renderer or a legend entry only; write a colour literal here` |
| a preset naming a composite | `preset 'A' sets 'band', which is not a declared param on the sheet (a composite is set by its members, e.g. band_lo)` |
| a preset value the setting cannot take | `preset 'A' value for 'mode' takes one of its options as a string (fast, slow), not "Zed"` |
| a name a composite already derives | `param 'band_lo' collides with the name param.range 'band' derives; rename one` |
| more than 128 settings | `the sheet would carry 129 params after expansion (a range derives two, a list max + 1, a session three, a unit list one more); hosted lanes cap params at 128` |
| a default above `max` | `Param 'length' (default): default above max` |
| `min` above `max` | `Param 'length' (min): min must be <= max` |
| a computed default (`param("n", base * 2)`) | `param 'n' default must be a numeric literal (expected a numeric literal)` |
| a string default on a number field (`param("mode", "ema")`) | `param 'mode' default must be a numeric literal (expected a numeric literal)` |
| a name built from a variable | `param names must be string literals (expected a string literal)` |

The rows by the page that explains them: the option rows on
[Options on a setting](options.md), the default rows on
[Setting kinds](kinds.md), the reference rows on
[The Style page](style-page.md), the preset rows on [Presets](presets.md),
the source default and the cap on [Picks, lanes, the cap](picks-and-lanes.md).

## Reserved names

A setting cannot take a name the chart keeps for itself: `symbol`,
`exchange`, `interval`, `transformations`, `ticksPerBar`, `currency`,
`runMode`, `devViewerTier`, `errorMessage`, `splineVisibility`,
`customScriptId`, `subType`, `scriptSource`, `catalogSource`, `wrunRef`,
`wrunRegistryRef`, `wrunRunTarget`, `wrunAlertOutputs`, `wrunDraftRef`,
`isProtectedScript`, `codeVisibility`, `hasGuide`, `scriptAuthor`, or
any name that starts with `__style__` ("param 'symbol' uses a reserved
name ...; rename it"). Every other name is free, `smooth`, `width` and
`opacity` included.

## Common errors

Each message with its symptom, its cause and its fix, beside the rest of
the build's refusals: [Common errors](../faq/common-errors.md). The full
grammar, every key and its legal values:
[Declarations and the sheet](../reference/declarations.md#the-declaration-grammar).

## Related

- [Setting kinds](kinds.md): the default each kind takes
- [Options on a setting](options.md): which kind takes which option
- [Presets](presets.md): the values a preset may name
- [Common errors](../faq/common-errors.md): symptom, cause and fix per message