Feature Request: Propagate and Validate Array Index Annotations from Immutable Variable Indexing

How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

Which OS are you using?

Windows

What is the issue affecting?

Annotations, Type Checking, Diagnostics/Syntax Checking

Expected Behaviour

The linter should propagate and validate the array index annotations from immutable variables, recognizing that the indices are constant and understanding the types associated with these indices.

local one = 1

---@class A
---@field [1] integer
---@field [2] string

---@type A
local a = {2, 'b'}

---@type integer
local b = a[one] -- no error

Actual Behaviour

The linter assumes that the value of the indices could be anything, even when the variables are immutable and clearly annotated. This leads to incorrect type warnings and reduces the effectiveness of the type checking.

local b = a[one] -- unexpectedly produces the following error; but 'local b = a[1]' does not.

Cannot assign string|integer to integer.

• string cannot match integer
• Type string cannot match integer Lua Diagnostics. (assign-type-mismatch)

Reproduction steps

Copy source in expected behavior into VS Code with extension v3.13.1 into a file with diagnostics enabled.

Additional Notes

I use prefer arrays instead of tables in my projects to avoid the cost of hashing the key and maximize the compressibility of the Lua script with external tools. Immutable local variables, used as enums, help maintain readability and maintainability. As noted by #2721 , a table seems unnecessary.

• Using the enum annotation doesn't change the resulting behavior.

• Using the alias annotation also doesn't change the resulting behavior.

---@alias a_1 1

---@type a_1
local one = 1

• The const annotation is not supported and would be another alternative to using alias.

Log File

No response

Tái hiện đoạn mã Lua được cung cấp trong extension Visual Studio Code với diagnostics được bật, sau đó lần theo entry point kiểm tra kiểu của chỉ mục mảng chịu trách nhiệm về cảnh báo assign-type-mismatch đã được báo cáo. Thay đổi được hoàn tất khi một chỉ mục cục bộ bất biến được xác thực là giá trị hằng của nó và ví dụ không còn báo cáo string|integer đối với phép gán số nguyên, trong khi việc lập chỉ mục trực tiếp vẫn đúng.