112 lines
4.4 KiB
TypeScript
112 lines
4.4 KiB
TypeScript
//// [typeGuardsInRightOperandOfOrOrOperator.ts]
|
|
// In the right operand of a || operation,
|
|
// the type of a variable or parameter is narrowed by any type guard in the left operand when false,
|
|
// provided the right operand contains no assignments to the variable or parameter.
|
|
function foo(x: number | string) {
|
|
return typeof x !== "string" || x.length === 10; // string
|
|
}
|
|
function foo2(x: number | string) {
|
|
// modify x in right hand operand
|
|
return typeof x !== "string" || ((x = 10) || x); // string | number
|
|
}
|
|
function foo3(x: number | string) {
|
|
// modify x in right hand operand with string type itself
|
|
return typeof x !== "string" || ((x = "hello") || x); // string | number
|
|
}
|
|
function foo4(x: number | string | boolean) {
|
|
return typeof x === "string" // string | number | boolean
|
|
|| typeof x === "number" // number | boolean
|
|
|| x; // boolean
|
|
}
|
|
function foo5(x: number | string | boolean) {
|
|
// usage of x or assignment to separate variable shouldn't cause narrowing of type to stop
|
|
var b: number | boolean;
|
|
return typeof x === "string" // string | number | boolean
|
|
|| ((b = x) || (typeof x === "number" // number | boolean
|
|
|| x)); // boolean
|
|
}
|
|
function foo6(x: number | string | boolean) {
|
|
// Mixing typeguard
|
|
return typeof x === "string" // string | number | boolean
|
|
|| (typeof x !== "number" // number | boolean
|
|
? x // boolean
|
|
: x === 10) // number
|
|
}
|
|
function foo7(x: number | string | boolean) {
|
|
var y: number| boolean | string;
|
|
var z: number| boolean | string;
|
|
// Mixing typeguard narrowing
|
|
// Assigning value to x deep inside another guard stops narrowing of type too
|
|
return typeof x === "string"
|
|
|| ((z = x) // string | number | boolean - x changed deeper in conditional expression
|
|
|| (typeof x === "number"
|
|
// change value of x
|
|
? (x = 10 && x.toString()) // number | boolean | string
|
|
// do not change value
|
|
: (y = x && x.toString()))); // number | boolean | string
|
|
}
|
|
function foo8(x: number | string) {
|
|
// Mixing typeguard
|
|
// Assigning value to x in outer guard shouldn't stop narrowing in the inner expression
|
|
return typeof x === "string"
|
|
|| (x = 10) // change x - number| string
|
|
|| (typeof x === "number"
|
|
? x // number
|
|
: x.length); // string
|
|
}
|
|
|
|
//// [typeGuardsInRightOperandOfOrOrOperator.js]
|
|
// In the right operand of a || operation,
|
|
// the type of a variable or parameter is narrowed by any type guard in the left operand when false,
|
|
// provided the right operand contains no assignments to the variable or parameter.
|
|
function foo(x) {
|
|
return typeof x !== "string" || x.length === 10; // string
|
|
}
|
|
function foo2(x) {
|
|
// modify x in right hand operand
|
|
return typeof x !== "string" || ((x = 10) || x); // string | number
|
|
}
|
|
function foo3(x) {
|
|
// modify x in right hand operand with string type itself
|
|
return typeof x !== "string" || ((x = "hello") || x); // string | number
|
|
}
|
|
function foo4(x) {
|
|
return typeof x === "string" // string | number | boolean
|
|
|| typeof x === "number" // number | boolean
|
|
|| x; // boolean
|
|
}
|
|
function foo5(x) {
|
|
// usage of x or assignment to separate variable shouldn't cause narrowing of type to stop
|
|
var b;
|
|
return typeof x === "string" // string | number | boolean
|
|
|| ((b = x) || (typeof x === "number" // number | boolean
|
|
|| x)); // boolean
|
|
}
|
|
function foo6(x) {
|
|
// Mixing typeguard
|
|
return typeof x === "string" // string | number | boolean
|
|
|| (typeof x !== "number" // number | boolean
|
|
? x // boolean
|
|
: x === 10); // number
|
|
}
|
|
function foo7(x) {
|
|
var y;
|
|
var z;
|
|
// Mixing typeguard narrowing
|
|
// Assigning value to x deep inside another guard stops narrowing of type too
|
|
return typeof x === "string"
|
|
|| ((z = x) // string | number | boolean - x changed deeper in conditional expression
|
|
|| (typeof x === "number"
|
|
? (x = 10 && x.toString()) // number | boolean | string
|
|
: (y = x && x.toString()))); // number | boolean | string
|
|
}
|
|
function foo8(x) {
|
|
// Mixing typeguard
|
|
// Assigning value to x in outer guard shouldn't stop narrowing in the inner expression
|
|
return typeof x === "string"
|
|
|| (x = 10) // change x - number| string
|
|
|| (typeof x === "number"
|
|
? x // number
|
|
: x.length); // string
|
|
}
|