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Severity: error
Category: type-check
Stage: Stage 1

Description

The TypeScript any type does not exist in SJS. It is a silent unsafety escape hatch that defeats the entire type system. SJS provides two typed alternatives:

  • unknown — the value has an unknown type; must be narrowed before use.
  • dynamic — opts a value out of type checking entirely, for JS interop only.

Example

// ✗ error
function process(data: any) {    // SJS-E004
  return data.value
}

Fix

Use unknown when the type is genuinely not known but should be narrowed:

// ✓ correct — unknown, narrow before use
function process(data: unknown): string {
  if (typeof data === "object" && data !== null && "value" in data) {
    return String((data as { value: unknown }).value)
  }
  return ""
}

Use dynamic only at JS interop boundaries:

// ✓ correct — dynamic for third-party lib interop
const raw: dynamic = legacyLib.getData()
if (typeof raw === "string") {
  console.log(raw.toUpperCase())
}

Related codes

  • SJS-W001 — implicit dynamic propagation
  • SJS-L001 — dynamic used without narrowing
Documentation