Using a result builder to gather source code locations for unit testing.

LocatedValueTest.swift

// example unit test:

func testAscii() async throws {
    locate {
        "Celcius"
        "Farenheit"
        "Kelvin"
        "yes?"
        "no?"
        "yes;no;cancel"
    }.forEach { string, file, line in
        let isAscii = string.allSatisfy { $0.isASCII }
        XCTAssert(isAscii, "not ascii", file: file, line: line)
    }
}

// impl:

public func locate<Value>(@LocatedValueBuilder<Value> content: () -> [(Value, StaticString, UInt)]) -> [(Value, StaticString, UInt)] {
    return content()
}

@resultBuilder
public struct LocatedValueBuilder<Value> {
    static func buildExpression(_ expression: Value, file: StaticString = #filePath, line: UInt = #line) -> (Value, StaticString, UInt) {
        (expression, file, line)
    }

    static func buildBlock(_ components: (Value, StaticString, UInt)...) -> [(Value, StaticString, UInt)] {
        Array(components)
    }
}