실패와 전파

Scope and ownership

Use this chapter to inspect error propagation and locate incompatible operand or return types.

This page owns postfix Result propagation and callable-local Result or Option propagation. Types owns general type compatibility. Pattern matching owns case syntax. Blocks and control flow owns explicit returns and cleanup ordering. Functions and generics owns return annotations and inference. Diagnostic entries own code-specific explanations. Command entries own process results.

Propagation syntax

링크

문법 발췌 · source

EBNF

Propagation = PostfixExpression "?" ;

Expression precedence is specified by Expressions and operators.

규칙topaz.rule.failure-and-propagation.postfix

Postfix operand

Postfix ? takes the preceding postfix expression as its operand.

이유

Postfix placement keeps the operation that may fail next to the point that forwards its error. It follows the binding order of calls and member access.

예제 Result operand →

Values and early return

링크

규칙topaz.rule.failure-and-propagation.evaluate-once

Operand evaluation

In a named function, ? evaluates its Result operand once.

The corresponding lambda and callback behavior follows lambda and callback propagation.

이유

Repeated evaluation could repeat input, output, or mutation before deciding whether to return an error.

예제 Observe success and early error return →

규칙topaz.rule.failure-and-propagation.ok

Successful operand

When the operand produces Ok(value), ? yields value and evaluation continues in the enclosing named function.

The corresponding lambda and callback behavior follows lambda and callback propagation.

이유

A successful operation supplies the value needed by later expressions without ending the function.

예제 Observe success and early error return →

규칙topaz.rule.failure-and-propagation.err

Error return

When the operand produces Err(error), ? returns that Result with its error payload from the enclosing named function. Subsequent expressions in its body are skipped.

The corresponding lambda and callback behavior follows lambda and callback propagation.

이유

Preserving the error payload keeps failure information intact. Skipping the remaining body prevents later work from using a value that was not produced.

예제 Observe success and early error return →

규칙topaz.rule.failure-and-propagation.callback-propagation

Propagation returns from the current callable

Postfix ? in a lambda or callback targets that callable's own return. Each function boundary has one propagation destination. For a Result-returning lambda, an Ok yields its payload and an Err returns the original error Result from that invocation. In an Option-returning lambda, Some yields its payload and None returns None from that invocation. The remaining lambda body is skipped on either return. The surrounding function continues after the call and can propagate the returned value with its own ?.

A lambda using ? must return Result or Option. Propagating a Result from a lambda returning another type uses the same TPZ5001 rejection as the named function return rule. The expected callback type still applies. A Result-returning lambda does not satisfy a bool callback slot such as filter. An undetermined Result error type requires an annotation with TPZ5022 under the error annotation rule.

이유

Each function boundary gives ? one return destination. A standard function such as map or filter can call a callback without handling nonlocal control transfer.

예제 Mapping a propagating lambda produces an array of Results →None returns from its lambda while the caller continues →An integer-returning lambda cannot propagate a Result →A propagating lambda needs a determined Result error type →Filter rejects a Result-returning callback where bool is required →

진단 TPZ5001 →TPZ5022 →

규칙topaz.rule.failure-and-propagation.operand-fault

Operand fault

A runtime fault raised while evaluating the operand continues as a runtime fault.

An ordinary runtime fault follows fault termination.

A runtime fault remains a fault inside a lambda or callback. It is not a returned Err or None under lambda and callback propagation.

이유

A runtime fault interrupts evaluation, while an Err is an ordinary value. Keeping these paths distinct prevents propagation from silently converting a fault into a Result.

Operand and return types

링크

규칙topaz.rule.failure-and-propagation.result-type

Success type

For an operand of type Result<T, E>, operand? has type T.

이유

Successful propagation supplies the payload to the next expression. Its type is the success type because the Result wrapper has been handled.

예제 Result operand →Result return type →

규칙topaz.rule.failure-and-propagation.operand-required

Result operand requirement

In a named function returning Result, a propagation operand with a resolved non-Result type is rejected during checking with TPZ5001. Option-returning lambdas follow the callable propagation rule.

Option-returning lambdas follow lambda and callback propagation.

이유

A Result return needs an error Result to forward. An Option operand supplies no error payload for that Result return.

예제 Option operand →

진단 TPZ5001 →

규칙topaz.rule.failure-and-propagation.function-context

Enclosing function

Using ? without an enclosing function return context is rejected during checking with TPZ5001.

The corresponding lambda and callback behavior follows lambda and callback propagation.

이유

Propagation needs a function return target. Without one, the error has no destination.

예제 Propagation at top level →

진단 TPZ5001 →

규칙topaz.rule.failure-and-propagation.result-return

Result return requirement

Propagating a Result from a function with a resolved non-Result return type is rejected during checking with TPZ5001.

An undetermined Result error type follows the annotation requirement.

The corresponding lambda and callback behavior follows lambda and callback propagation.

이유

The enclosing return type must admit the error Result that propagation returns. Otherwise the function could produce a value outside its declared type.

예제 Integer return type →

진단 TPZ5001 →

규칙topaz.rule.failure-and-propagation.error-assignability

Error type compatibility

For an operand of type Result<T, E> in a function returning Result<U, F>, E must be assignable to F. Incompatible resolved error types produce TPZ5001 during checking. The propagation step does not compare T with U.

이유

An error can leave the function at this point, so it must fit the declared error type. The success payload remains local and can be transformed before return.

예제 Incompatible error types →Matching error types →

진단 TPZ5001 →

규칙topaz.rule.failure-and-propagation.error-annotation

Annotating an unresolved Result error type

If the Result error type cannot be determined, checking rejects the expression with TPZ5022 and requires a type annotation. Inference does not substitute a broad fallback type. This is the same diagnostic as the return annotation requirement.

This uses the same diagnostic as return annotation requirements. Lambda and callback propagation gives each lambda and callback its own return destination.

The corresponding lambda and callback behavior follows lambda and callback propagation.

이유

Return inference and Result error inference use the same annotation rule and diagnostic. The program therefore has a determined error type before emission.

예제 An unknown Result error type requires an annotation →A Result return annotation fixes the error type →A propagating lambda needs a determined Result error type →

진단 TPZ5022 →

Examples and counterexamples

링크

The checking examples pair rejected files with complete repairs. The execution example makes operand evaluation and continuation visible.

Option operand

링크

reject · checking · 검증 · 통과

example.tpzOption operand플레이그라운드 열기 →

function advance(value: Option<int>) -> Result<int, string> {
let number: int = value?
Ok(number + 1)
}

기록된 출력종료 코드 1

표준 출력 없음.

error[TPZ5001]: `?` requires a Result value, found `Option<int>`
 --> example.tpz:2:23
  |
2 |     let number: int = value?
  |                       ^^^^^^

example.tpz: 1 type diagnostic

$ topaz check example.tpz --compiler self · 기록에 사용한 토파즈 5.21.3

기대 결과

거절 단계 check. 종료 코드가 0이 아닙니다.

TPZ5001 →
result-required-for-propagation at example.tpz:2:23

표준 출력 없음.

관측한 단언 · 통과 · 5.21.3

2026-11-11T03:11:22.450Z · checking · sha256:81111a53ac5da2ebc403438922b42fc1dfdd68782c6324fed4219297b7a7e445

종료 코드 1.

표준 출력 없음.

관측한 표준 오류 출력

error[TPZ5001]: `?` requires a Result value, found `Option<int>`
--> example.tpz:2:23
|
2 | let number: int = value?
| ^^^^^^
example.tpz: 1 type diagnostic

통과 · expected nonzero; observed 1
통과 · checking TPZ5001; cause result-required-for-propagation; primary location asserted; additional diagnostics allow
통과 · stdout matches the authored expectation

Result operand

링크

check · checking · 검증 · 통과

example.tpzResult operand플레이그라운드 열기 →

function advance(value: Result<int, string>) -> Result<int, string> {
let number: int = value?
Ok(number + 1)
}
let success: Result<int, string> = advance(Ok(4))
let failure: Result<int, string> = advance(Err("missing"))

기록된 출력종료 코드 0

표준 출력 없음.

$ topaz check example.tpz --compiler self --format json · 기록에 사용한 토파즈 5.21.3

기대 결과

검사가 프로그램을 받아들입니다. 종료 코드 0.

표준 오류 출력 없음.

표준 출력 없음.

관측한 단언 · 통과 · 5.21.3

2026-11-06T13:59:24.4141902Z · checking · sha256:b6c3f574b78c558b526196fa04f5d835c9fe1df59d07397dbf4e5d279a3e1665

종료 코드 0.

표준 출력 없음.

표준 오류 출력 없음.

통과 · expected 0; observed 0
통과 · expected 0; observed 0
통과 · stdout matches the authored expectation
통과 · stderr matches the authored expectation

Integer return type

링크

reject · checking · 검증 · 통과

example.tpzInteger return type플레이그라운드 열기 →

function read(value: Result<int, string>) -> int {
value?
}

기록된 출력종료 코드 1

표준 출력 없음.

error[TPZ5001]: `?` propagates an error, but the function returns `int`, not a Result
 --> example.tpz:2:5
  |
2 |     value?
  |     ^^^^^^

example.tpz: 1 type diagnostic

$ topaz check example.tpz --compiler self · 기록에 사용한 토파즈 5.21.3

기대 결과

거절 단계 check. 종료 코드가 0이 아닙니다.

TPZ5001 →
propagation-requires-result-return at example.tpz:2:5

표준 출력 없음.

관측한 단언 · 통과 · 5.21.3

2026-11-06T13:59:24.4719845Z · checking · sha256:b6c3f574b78c558b526196fa04f5d835c9fe1df59d07397dbf4e5d279a3e1665

종료 코드 1.

표준 출력 없음.

관측한 표준 오류 출력

error[TPZ5001]: `?` propagates an error, but the function returns `int`, not a Result
--> example.tpz:2:5
|
2 | value?
| ^^^^^^
example.tpz: 1 type diagnostic

통과 · expected nonzero; observed 1
통과 · checking TPZ5001; cause propagation-requires-result-return; primary location asserted; additional diagnostics allow
통과 · stdout matches the authored expectation

Result return type

링크

check · checking · 검증 · 통과

example.tpzResult return type플레이그라운드 열기 →

function read(value: Result<int, string>) -> Result<int, string> {
let number: int = value?
Ok(number)
}

기록된 출력종료 코드 0

표준 출력 없음.

$ topaz check example.tpz --compiler self --format json · 기록에 사용한 토파즈 5.21.3

기대 결과

검사가 프로그램을 받아들입니다. 종료 코드 0.

표준 오류 출력 없음.

표준 출력 없음.

관측한 단언 · 통과 · 5.21.3

2026-11-06T13:59:24.5130704Z · checking · sha256:b6c3f574b78c558b526196fa04f5d835c9fe1df59d07397dbf4e5d279a3e1665

종료 코드 0.

표준 출력 없음.

표준 오류 출력 없음.

통과 · expected 0; observed 0
통과 · stdout matches the authored expectation
통과 · stderr matches the authored expectation

Incompatible error types

링크

reject · checking · 검증 · 통과

example.tpzIncompatible error types플레이그라운드 열기 →

function relay(value: Result<int, string>) -> Result<int, int> {
let number: int = value?
Ok(number)
}

기록된 출력종료 코드 1

표준 출력 없음.

error[TPZ5001]: expected `int`, found `string`
 --> example.tpz:2:23
  |
2 |     let number: int = value?
  |                       ^^^^^^

example.tpz: 1 type diagnostic

$ topaz check example.tpz --compiler self · 기록에 사용한 토파즈 5.21.3

기대 결과

거절 단계 check. 종료 코드가 0이 아닙니다.

TPZ5001 →
propagated-error-type-not-assignable at example.tpz:2:23

표준 출력 없음.

관측한 단언 · 통과 · 5.21.3

2026-11-06T13:59:24.5547659Z · checking · sha256:b6c3f574b78c558b526196fa04f5d835c9fe1df59d07397dbf4e5d279a3e1665

종료 코드 1.

표준 출력 없음.

관측한 표준 오류 출력

error[TPZ5001]: expected `int`, found `string`
--> example.tpz:2:23
|
2 | let number: int = value?
| ^^^^^^
example.tpz: 1 type diagnostic

통과 · expected nonzero; observed 1
통과 · checking TPZ5001; cause propagated-error-type-not-assignable; primary location asserted; additional diagnostics allow
통과 · stdout matches the authored expectation

Matching error types

링크

check · checking · 검증 · 통과

example.tpzMatching error types플레이그라운드 열기 →

function relay(value: Result<int, string>) -> Result<int, string> {
let number: int = value?
Ok(number)
}

기록된 출력종료 코드 0

표준 출력 없음.

$ topaz check example.tpz --compiler self --format json · 기록에 사용한 토파즈 5.21.3

기대 결과

검사가 프로그램을 받아들입니다. 종료 코드 0.

표준 오류 출력 없음.

표준 출력 없음.

관측한 단언 · 통과 · 5.21.3

2026-11-06T13:59:24.5960294Z · checking · sha256:b6c3f574b78c558b526196fa04f5d835c9fe1df59d07397dbf4e5d279a3e1665

종료 코드 0.

표준 출력 없음.

표준 오류 출력 없음.

통과 · expected 0; observed 0
통과 · stdout matches the authored expectation
통과 · stderr matches the authored expectation

Propagation at top level

링크

reject · checking · 검증 · 통과

example.tpzPropagation at top level플레이그라운드 열기 →

let value: Result<int, string> = Ok(1)
let number: int = value?

기록된 출력종료 코드 1

표준 출력 없음.

error[TPZ5001]: `return` outside a function
 --> example.tpz:2:19
  |
2 | let number: int = value?
  |                   ^^^^^^

example.tpz: 1 type diagnostic

$ topaz check example.tpz --compiler self · 기록에 사용한 토파즈 5.21.3

기대 결과

거절 단계 check. 종료 코드가 0이 아닙니다.

TPZ5001 →
propagation-outside-function at example.tpz:2:19

표준 출력 없음.

관측한 단언 · 통과 · 5.21.3

2026-11-06T13:59:25.5322070Z · checking · sha256:b6c3f574b78c558b526196fa04f5d835c9fe1df59d07397dbf4e5d279a3e1665

종료 코드 1.

표준 출력 없음.

관측한 표준 오류 출력

error[TPZ5001]: `return` outside a function
--> example.tpz:2:19
|
2 | let number: int = value?
| ^^^^^^
example.tpz: 1 type diagnostic

통과 · expected nonzero; observed 1
통과 · checking TPZ5001; cause propagation-outside-function; primary location asserted; additional diagnostics allow
통과 · stdout matches the authored expectation

Observe success and early error return

링크

run · runtime · 검증 · 통과

example.tpzObserve success and early error return플레이그라운드 열기 →

import std.io
function observe(value: Result<int, string>) -> Result<int, string> {
io.writeLine("operand")
value
}
function advance(value: Result<int, string>) -> Result<int, string> {
let number: int = observe(value)?
io.writeLine("continued")
Ok(number + 1)
}
let success: Result<int, string> = advance(Ok(4))
match (success) {
case Ok(number) => io.writeLine("ok {number}")
case Err(error) => io.writeLine("unexpected {error}")
}
let failure: Result<int, string> = advance(Err("missing"))
match (failure) {
case Ok(number) => io.writeLine("unexpected {number}")
case Err(error) => io.writeLine("error {error}")
}

기록된 출력종료 코드 0

operand
continued
ok 5
operand
error missing

$ topaz run example.tpz --compiler self · 기록에 사용한 토파즈 5.21.3

기대 결과

실행을 마칩니다. 종료 코드 0.

표준 오류 출력 없음.

기대 표준 출력

operand
continued
ok 5
operand
error missing

관측한 단언 · 통과 · 5.21.3

2026-11-06T13:59:25.6712784Z · runtime · sha256:b6c3f574b78c558b526196fa04f5d835c9fe1df59d07397dbf4e5d279a3e1665

종료 코드 0.

관측한 표준 출력

operand
continued
ok 5
operand
error missing

표준 오류 출력 없음.

통과 · expected 0; observed 0
통과 · stdout matches the authored expectation
통과 · stdout matches the authored expectation
통과 · stdout matches the authored expectation
통과 · stderr matches the authored expectation

An unknown Result error type requires an annotation

링크

reject · check · 검증 · 미실행

main.tpzAn unknown Result error type requires an annotation플레이그라운드 열기 →

function value() { Ok(1) }
let result = value()

기대 출력0이 아닌 종료 코드

표준 출력 없음.

$ topaz check main.tpz --compiler self · 대상 제품 5.21.3

기대 결과

거절 단계 check. 종료 코드가 0이 아닙니다.

TPZ5022 →
result-error-annotation-required at main.tpz:1:10

표준 출력 없음.

이 예제는 아직 실행하지 않았습니다.

A Result return annotation fixes the error type

링크

run · runtime · 검증 · 미실행

main.tpzA Result return annotation fixes the error type플레이그라운드 열기 →

import std.io
function value() -> Result<int, string> { Ok(1) }
let result = match (value()) {
case Ok(number) => number
case Err(_) => 0
}
io.writeLine("{result}")

기대 출력종료 코드 0

$ topaz run main.tpz --compiler self · 대상 제품 5.21.3

기대 결과

실행을 마칩니다. 종료 코드 0.

표준 오류 출력 없음.

기대 표준 출력

이 예제는 아직 실행하지 않았습니다.

Mapping a propagating lambda produces an array of Results

링크

run · runtime · 검증 · 통과

main.tpzMapping a propagating lambda produces an array of Results플레이그라운드 열기 →

import std.io
function surrounding() -> int {
let inputs: Array<Result<int, string>> = [Ok(1), Err("stop"), Ok(3)]
let advance: (Result<int, string>) -> Result<int, string> = (value) => {
let number = value?
io.writeLine("lambda {number}")
Ok(number + 1)
}
let results: Array<Result<int, string>> = inputs.map(advance)
io.writeLine("after map")
for result in (results) {
match (result) {
case Ok(number) => io.writeLine("ok {number}")
case Err(error) => io.writeLine("err {error}")
}
}
7
}
io.writeLine("{surrounding()}")

기록된 출력종료 코드 0

lambda 1
lambda 3
after map
ok 2
err stop
ok 4
7

$ topaz run main.tpz --compiler self · 기록에 사용한 토파즈 5.21.3

기대 결과

실행을 마칩니다. 종료 코드 0.

표준 오류 출력 없음.

기대 표준 출력

lambda 1
lambda 3
after map
ok 2
err stop
ok 4
7

관측한 단언 · 통과 · 5.21.3

2026-11-11T03:11:22.450Z · runtime · sha256:81111a53ac5da2ebc403438922b42fc1dfdd68782c6324fed4219297b7a7e445

종료 코드 0.

관측한 표준 출력

lambda 1
lambda 3
after map
ok 2
err stop
ok 4
7

표준 오류 출력 없음.

통과 · expected 0; observed 0
통과 · stdout matches the authored expectation
통과 · stderr matches the authored expectation

None returns from its lambda while the caller continues

링크

run · runtime · 검증 · 실패

main.tpzNone returns from its lambda while the caller continues플레이그라운드 열기 →

import std.io
let advance: (Option<int>) -> Option<int> = (value) => {
let number = value?
io.writeLine("some {number}")
Some(number + 1)
}
let missing = advance(None())
io.writeLine("after none")
match (missing) {
case Some(number) => io.writeLine("{number}")
case None() => io.writeLine("none")
}
let present = advance(Some(2))
match (present) {
case Some(number) => io.writeLine("{number}")
case None() => io.writeLine("none")
}

기록된 출력종료 코드 1

표준 출력 없음.

error[TPZ5001]: `?` requires a Result value, found `Option<int>`
 --> main.tpz:3:18
  |
3 |     let number = value?
  |                  ^^^^^^

main.tpz: 1 type diagnostic

$ topaz run main.tpz --compiler self · 기록에 사용한 토파즈 5.21.3

기대 결과

실행을 마칩니다. 종료 코드 0.

표준 오류 출력 없음.

기대 표준 출력

after none
none
some 2
3

관측한 단언 · 실패 · 5.21.3

2026-11-11T04:38:22.431Z · runtime · sha256:81111a53ac5da2ebc403438922b42fc1dfdd68782c6324fed4219297b7a7e445

종료 코드 1.

표준 출력 없음.

관측한 표준 오류 출력

error[TPZ5001]: `?` requires a Result value, found `Option<int>`
--> main.tpz:3:18
|
3 | let number = value?
| ^^^^^^
main.tpz: 1 type diagnostic

실패 · expected 0; observed 1
실패 · stdout matches the authored expectation
실패 · stderr matches the authored expectation

An integer-returning lambda cannot propagate a Result

링크

reject · check · 검증 · 통과

main.tpzAn integer-returning lambda cannot propagate a Result플레이그라운드 열기 →

let read: (Result<int, string>) -> int = (value) => {
value?
}

기록된 출력종료 코드 1

표준 출력 없음.

error[TPZ5001]: `?` propagates an error, but the function returns `int`, not a Result
 --> main.tpz:2:5
  |
2 |     value?
  |     ^^^^^^

main.tpz: 1 type diagnostic

$ topaz check main.tpz --compiler self · 기록에 사용한 토파즈 5.21.3

기대 결과

거절 단계 check. 종료 코드가 0이 아닙니다.

TPZ5001 →
propagation-requires-result-return at main.tpz:2:5

표준 출력 없음.

관측한 단언 · 통과 · 5.21.3

2026-11-11T03:11:22.450Z · check · sha256:81111a53ac5da2ebc403438922b42fc1dfdd68782c6324fed4219297b7a7e445

종료 코드 1.

표준 출력 없음.

관측한 표준 오류 출력

error[TPZ5001]: `?` propagates an error, but the function returns `int`, not a Result
--> main.tpz:2:5
|
2 | value?
| ^^^^^^
main.tpz: 1 type diagnostic

통과 · expected nonzero; observed 1
통과 · stdout matches the authored expectation
통과 · checking TPZ5001; cause propagation-requires-result-return; primary location asserted; additional diagnostics allow

A propagating lambda needs a determined Result error type

링크

reject · check · 검증 · 실패

main.tpzA propagating lambda needs a determined Result error type플레이그라운드 열기 →

let lift = () => {
let value = Ok(1)?
Ok(value)
}

기록된 출력종료 코드 0

main.tpz: types-ok (1 module)
main.tpz: resolve-ok (1 module)

$ topaz check main.tpz --compiler self · 기록에 사용한 토파즈 5.21.3

기대 결과

거절 단계 check. 종료 코드가 0이 아닙니다.

TPZ5022 →
result-error-annotation-required at main.tpz:1:12

표준 출력 없음.

관측한 단언 · 실패 · 5.21.3

2026-11-11T04:38:22.431Z · check · sha256:81111a53ac5da2ebc403438922b42fc1dfdd68782c6324fed4219297b7a7e445

종료 코드 0.

관측한 표준 출력

main.tpz: types-ok (1 module)
main.tpz: resolve-ok (1 module)

표준 오류 출력 없음.

실패 · expected nonzero; observed 0
실패 · stdout matches the authored expectation
실패 · checking TPZ5022; cause result-error-annotation-required; primary location asserted; additional diagnostics allow

Filter rejects a Result-returning callback where bool is required

링크

reject · check · 검증 · 통과

main.tpzFilter rejects a Result-returning callback where bool is required플레이그라운드 열기 →

let predicate: (Result<int, string>) -> Result<bool, string> = (value) => {
let number = value?
Ok(number > 0)
}
let inputs: Array<Result<int, string>> = [Ok(1)]
let selected = inputs.filter(predicate)

기록된 출력종료 코드 1

표준 출력 없음.

error[TPZ5001]: expected `(Result<int, string>) -> bool`, found `(Result<int, string>) -> Result<bool, string>`
 --> main.tpz:6:30
  |
6 | let selected = inputs.filter(predicate)
  |                              ^^^^^^^^^

main.tpz: 1 type diagnostic

$ topaz check main.tpz --compiler self · 기록에 사용한 토파즈 5.21.3

기대 결과

거절 단계 check. 종료 코드가 0이 아닙니다.

TPZ5001 →
callback-return-type-mismatch at main.tpz:6:30

표준 출력 없음.

관측한 단언 · 통과 · 5.21.3

2026-11-11T03:11:22.450Z · check · sha256:81111a53ac5da2ebc403438922b42fc1dfdd68782c6324fed4219297b7a7e445

종료 코드 1.

표준 출력 없음.

관측한 표준 오류 출력

error[TPZ5001]: expected `(Result<int, string>) -> bool`, found `(Result<int, string>) -> Result<bool, string>`
--> main.tpz:6:30
|
6 | let selected = inputs.filter(predicate)
| ^^^^^^^^^
main.tpz: 1 type diagnostic

통과 · expected nonzero; observed 1
통과 · stdout matches the authored expectation
통과 · checking TPZ5001; cause callback-return-type-mismatch; primary location asserted; additional diagnostics allow

Pending contracts

링크

구현 제약

Result error inference does not yet require TPZ5022

topaz.limitation.failure-and-propagation.result-error-annotation · current

The inspected checker leaves the missing error component of an inferred Ok result unresolved. Its TPZ5022 paths cover existing return-inference failures, not this missing Result error annotation. The unannotated example is therefore expected to pass checking in 5.21.3. The installed 5.21.3 run confirms that checking succeeds and prints its success lines. The lambda return inference path also leaves the error component unresolved without this annotation check. The lambda example was also executed on installed 5.21.3. Checking succeeded instead of the required TPZ5022 rejection. This difference is recorded under the Result error annotation limitation.

해결 방법

Write the complete Result return type, including its error type.

링크

TPZ5001 →

Functions and generics →

check →

TPZ5022 →

Scope and ownership

Propagation syntax

Postfix operand

이유

Values and early return

Operand evaluation

이유

Successful operand

이유

Error return

이유

Propagation returns from the current callable

이유

Operand fault

이유

Operand and return types

Success type

이유

Result operand requirement

이유

Enclosing function

이유

Result return requirement

이유

Error type compatibility

이유

Annotating an unresolved Result error type

이유

Examples and counterexamples

Option operand

기대 결과

Result operand

기대 결과

Integer return type

기대 결과

Result return type

기대 결과

Incompatible error types

기대 결과

Matching error types

기대 결과

Propagation at top level

기대 결과

Observe success and early error return

기대 결과

An unknown Result error type requires an annotation

기대 결과

A Result return annotation fixes the error type

기대 결과

Mapping a propagating lambda produces an array of Results

기대 결과

None returns from its lambda while the caller continues

기대 결과

An integer-returning lambda cannot propagate a Result

기대 결과

A propagating lambda needs a determined Result error type

기대 결과

Filter rejects a Result-returning callback where bool is required

기대 결과

Pending contracts

Related references