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Sound mode S-01, pre-alpha
Design record 0007, Accepted

TSR0103

Calling a value of type 'Function' returns 'any'. Give '{0}' a function type.

A value of type 'Function' is called, which returns 'any'. Give it a real function type such as '() => unknown'.

Rule S-01: No `any` (level: strict). Reported by ts-r-check and ts-r-lsp in files that opt in to sound mode. See Sound mode.

What it means

Calling or constructing a value of type Function gives any, which would leak into sound code. It's reported at the call.

Example

Spec case from design record 0007 (checked by the record's case harness, not by this site's build)

// Calling a value of type Function returns any.
function invoke(fn: Function): unknown {
  return fn(); // @expect TSR0103
}
export const r: unknown = invoke(() => 1);

How to fix

Give the value a function type: fn: () => unknown, or one with the real parameter and return types.
Use a type parameter if callers pass different function types.

Sound mode is defined in design record 0007 (accepted 2026-10-15).