`TS8031`

프런트엔드 코드 RECURSION

A call cycle: a function that reaches itself, directly or through other functions.

레지스트리 설명과 컴파일러 메시지는 컴파일러 원문이라 한국어 페이지에서도 영어로 둡니다.

발생 조건

A call cycle: a function that reaches itself, directly or through other functions. WGSL has no call stack, so Tint rejects the emitted module (cyclic dependency found: 'a' -> 'b' -> 'a'); before this the front end accepted it and emitted it with zero diagnostics.

예제

"use typeshade"

function fold(x: f32): f32 {
  if (x < 1.) {
    return x
  }
  return fold(x * 0.5)
}

@fragment
export function main(@location(0) uv: vec2): vec4 {
  return vec4(uv, fold(uv.x * 8.), 1.)
}

빌드할 때 고정된 컴파일러로 이 프로그램을 컴파일하면 다음 진단이 나옵니다.

TS8031 error, 7행: Recursive call: "fold" -> "fold". WGSL has no call stack, so a function must not take part in a call cycle.

고치는 법

같은 프로그램을 고친 모습입니다. 진단 없이 컴파일됩니다.

"use typeshade"

function fold(x: f32): f32 {
  let y = x
  for (let i = 0; i < 8; i++) {
    if (y < 1.) {
      break
    }
    y = y * 0.5
  }
  return y
}

@fragment
export function main(@location(0) uv: vec2): vec4 {
  return vec4(uv, fold(uv.x * 8.), 1.)
}

이 코드가 적용하는 규칙

규칙 8.4 테스트: A function must not take part in a call cycle, directly or through other functions; the check reads the calls a body writes, and the calls a method call, an accessor and new lower to, before any optimisation, so a call in a branch the optimizer would drop is a cycle too.
규칙 8.18 테스트: A function whose parameter has a function type, written out (f: (x: f32) => f32) or through a type alias of one, takes a function: a function declared at the top of the file or of a namespace, a method, a static method, a constructor, a field that holds a function (Rule 8.16) and a local function (Rule 8.17).
규칙 8.19 테스트: A function that writes no return type returns what its body does, as TypeScript infers it: a function of the file or of a namespace, a local function (Rule 8.17), each instance of a generic function (Rule 8.9) and of a function that takes a function (Rule 8.18), a method, a getter and a field that holds a function (Rule 8.16) take the type of their first return with a value, the returns after it are typed against that type as against a written one, and one with no such return returns nothing.
규칙 12.6 테스트: A requirement the front end can check must be checked at the front end, in the author’s words, and not left to Tint or a driver.

함께 보기

소스

커밋 c66579bf에서 컴파일러가 이 코드를 내는 곳입니다. 파일마다 한 줄씩 적었습니다.

src/compiler/ts/lower/function.ts:583 (4곳)
src/compiler/ts/recursion.ts:202 (2곳)

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