undefined-name

Flag an identifier that no resolution tier provides: not a local or a file binding, not a workspace sibling, not a whole-module using’s export, and not a Base/Core name. Such a read raises UndefVarError at runtime. The whole file is skipped when it evals, includes outside a known workspace, or usings a module the library cannot resolve — in those cases any name may exist; value reads inside macro calls and quoted code are likewise exempt. Off by default: the rule needs project context to be sound, so the language server enables it for workspace member files, while the CLI (resolving against a built-in Base/Core snapshot) leaves it opt-in for self-contained scripts.

raduis is a typo; no tier resolves it:

function area(radius)
    return pi * raduis^2
end

warning: undefined-name
 --> example.jl:2:17
  |
2 |     return pi * raduis^2
  |                 ^^^^^^ `raduis` is not defined