=== tests/cases/conformance/expressions/typeGuards/typeGuardsInConditionalExpression.ts === // In the true expression of a conditional expression, // the type of a variable or parameter is narrowed by any type guard in the condition when true, // provided the true expression contains no assignments to the variable or parameter. // In the false expression of a conditional expression, // the type of a variable or parameter is narrowed by any type guard in the condition when false, // provided the false expression contains no assignments to the variable or parameter. function foo(x: number | string) { >foo : (x: string | number) => number >x : string | number return typeof x === "string" >typeof x === "string" ? x.length // string : x++ : number >typeof x === "string" : boolean >typeof x : string >x : string | number >"string" : string ? x.length // string >x.length : number >x : string >length : number : x++; // number >x++ : number >x : number } function foo2(x: number | string) { >foo2 : (x: string | number) => string | number >x : string | number // x is assigned in the if true branch, the type is not narrowed return typeof x === "string" >typeof x === "string" ? (x = 10 && x)// string | number : x : string | number >typeof x === "string" : boolean >typeof x : string >x : string | number >"string" : string ? (x = 10 && x)// string | number >(x = 10 && x) : string | number >x = 10 && x : string | number >x : string | number >10 && x : string | number >10 : number >x : string | number : x; // string | number >x : string | number } function foo3(x: number | string) { >foo3 : (x: string | number) => string | number >x : string | number // x is assigned in the if false branch, the type is not narrowed // even though assigned using same type as narrowed expression return typeof x === "string" >typeof x === "string" ? (x = "Hello" && x) // string | number : x : string | number >typeof x === "string" : boolean >typeof x : string >x : string | number >"string" : string ? (x = "Hello" && x) // string | number >(x = "Hello" && x) : string | number >x = "Hello" && x : string | number >x : string | number >"Hello" && x : string | number >"Hello" : string >x : string | number : x; // string | number >x : string | number } function foo4(x: number | string) { >foo4 : (x: string | number) => string | number >x : string | number // false branch updates the variable - so here it is not number // even though assigned using same type as narrowed expression return typeof x === "string" >typeof x === "string" ? x // string | number : (x = 10 && x) : string | number >typeof x === "string" : boolean >typeof x : string >x : string | number >"string" : string ? x // string | number >x : string | number : (x = 10 && x); // string | number >(x = 10 && x) : string | number >x = 10 && x : string | number >x : string | number >10 && x : string | number >10 : number >x : string | number } function foo5(x: number | string) { >foo5 : (x: string | number) => string | number >x : string | number // false branch updates the variable - so here it is not number return typeof x === "string" >typeof x === "string" ? x // string | number : (x = "hello" && x) : string | number >typeof x === "string" : boolean >typeof x : string >x : string | number >"string" : string ? x // string | number >x : string | number : (x = "hello" && x); // string | number >(x = "hello" && x) : string | number >x = "hello" && x : string | number >x : string | number >"hello" && x : string | number >"hello" : string >x : string | number } function foo6(x: number | string) { >foo6 : (x: string | number) => string | number >x : string | number // Modify in both branches return typeof x === "string" >typeof x === "string" ? (x = 10 && x) // string | number : (x = "hello" && x) : string | number >typeof x === "string" : boolean >typeof x : string >x : string | number >"string" : string ? (x = 10 && x) // string | number >(x = 10 && x) : string | number >x = 10 && x : string | number >x : string | number >10 && x : string | number >10 : number >x : string | number : (x = "hello" && x); // string | number >(x = "hello" && x) : string | number >x = "hello" && x : string | number >x : string | number >"hello" && x : string | number >"hello" : string >x : string | number } function foo7(x: number | string | boolean) { >foo7 : (x: string | number | boolean) => boolean >x : string | number | boolean return typeof x === "string" >typeof x === "string" ? x === "hello" // string : typeof x === "boolean" ? x // boolean : x == 10 : boolean >typeof x === "string" : boolean >typeof x : string >x : string | number | boolean >"string" : string ? x === "hello" // string >x === "hello" : boolean >x : string >"hello" : string : typeof x === "boolean" >typeof x === "boolean" ? x // boolean : x == 10 : boolean >typeof x === "boolean" : boolean >typeof x : string >x : number | boolean >"boolean" : string ? x // boolean >x : boolean : x == 10; // number >x == 10 : boolean >x : number >10 : number } function foo8(x: number | string | boolean) { >foo8 : (x: string | number | boolean) => boolean >x : string | number | boolean var b: number | boolean; >b : number | boolean return typeof x === "string" >typeof x === "string" ? x === "hello" : ((b = x) && // number | boolean (typeof x === "boolean" ? x // boolean : x == 10)) : boolean >typeof x === "string" : boolean >typeof x : string >x : string | number | boolean >"string" : string ? x === "hello" >x === "hello" : boolean >x : string >"hello" : string : ((b = x) && // number | boolean >((b = x) && // number | boolean (typeof x === "boolean" ? x // boolean : x == 10)) : boolean >(b = x) && // number | boolean (typeof x === "boolean" ? x // boolean : x == 10) : boolean >(b = x) : number | boolean >b = x : number | boolean >b : number | boolean >x : number | boolean (typeof x === "boolean" >(typeof x === "boolean" ? x // boolean : x == 10) : boolean >typeof x === "boolean" ? x // boolean : x == 10 : boolean >typeof x === "boolean" : boolean >typeof x : string >x : number | boolean >"boolean" : string ? x // boolean >x : boolean : x == 10)); // number >x == 10 : boolean >x : number >10 : number } function foo9(x: number | string) { >foo9 : (x: string | number) => boolean >x : string | number var y = 10; >y : number >10 : number // usage of x or assignment to separate variable shouldn't cause narrowing of type to stop return typeof x === "string" >typeof x === "string" ? ((y = x.length) && x === "hello") // string : x === 10 : boolean >typeof x === "string" : boolean >typeof x : string >x : string | number >"string" : string ? ((y = x.length) && x === "hello") // string >((y = x.length) && x === "hello") : boolean >(y = x.length) && x === "hello" : boolean >(y = x.length) : number >y = x.length : number >y : number >x.length : number >x : string >length : number >x === "hello" : boolean >x : string >"hello" : string : x === 10; // number >x === 10 : boolean >x : number >10 : number } function foo10(x: number | string | boolean) { >foo10 : (x: string | number | boolean) => string >x : string | number | boolean // Mixing typeguards var b: boolean | number; >b : number | boolean return typeof x === "string" >typeof x === "string" ? x // string : ((b = x) // x is number | boolean && typeof x === "number" && x.toString()) : string >typeof x === "string" : boolean >typeof x : string >x : string | number | boolean >"string" : string ? x // string >x : string : ((b = x) // x is number | boolean >((b = x) // x is number | boolean && typeof x === "number" && x.toString()) : string >(b = x) // x is number | boolean && typeof x === "number" && x.toString() : string >(b = x) // x is number | boolean && typeof x === "number" : boolean >(b = x) : number | boolean >b = x : number | boolean >b : number | boolean >x : number | boolean && typeof x === "number" >typeof x === "number" : boolean >typeof x : string >x : number | boolean >"number" : string && x.toString()); // x is number >x.toString() : string >x.toString : (radix?: number) => string >x : number >toString : (radix?: number) => string } function foo11(x: number | string | boolean) { >foo11 : (x: string | number | boolean) => string | number | boolean >x : string | number | boolean // Mixing typeguards // Assigning value to x deep inside another guard stops narrowing of type too var b: number | boolean | string; >b : string | number | boolean return typeof x === "string" >typeof x === "string" ? x // number | boolean | string - changed in the false branch : ((b = x) // x is number | boolean | string - because the assignment changed it && typeof x === "number" && (x = 10) // assignment to x && x) : string | number | boolean >typeof x === "string" : boolean >typeof x : string >x : string | number | boolean >"string" : string ? x // number | boolean | string - changed in the false branch >x : string | number | boolean : ((b = x) // x is number | boolean | string - because the assignment changed it >((b = x) // x is number | boolean | string - because the assignment changed it && typeof x === "number" && (x = 10) // assignment to x && x) : string | number | boolean >(b = x) // x is number | boolean | string - because the assignment changed it && typeof x === "number" && (x = 10) // assignment to x && x : string | number | boolean >(b = x) // x is number | boolean | string - because the assignment changed it && typeof x === "number" && (x = 10) : number >(b = x) // x is number | boolean | string - because the assignment changed it && typeof x === "number" : boolean >(b = x) : string | number | boolean >b = x : string | number | boolean >b : string | number | boolean >x : string | number | boolean && typeof x === "number" >typeof x === "number" : boolean >typeof x : string >x : string | number | boolean >"number" : string && (x = 10) // assignment to x >(x = 10) : number >x = 10 : number >x : string | number | boolean >10 : number && x); // x is number | boolean | string >x : string | number | boolean } function foo12(x: number | string | boolean) { >foo12 : (x: string | number | boolean) => number >x : string | number | boolean // Mixing typeguards // Assigning value to x in outer guard shouldn't stop narrowing in the inner expression var b: number | boolean | string; >b : string | number | boolean return typeof x === "string" >typeof x === "string" ? (x = 10 && x.toString().length) // number | boolean | string - changed here : ((b = x) // x is number | boolean | string - changed in true branch && typeof x === "number" && x) : number >typeof x === "string" : boolean >typeof x : string >x : string | number | boolean >"string" : string ? (x = 10 && x.toString().length) // number | boolean | string - changed here >(x = 10 && x.toString().length) : number >x = 10 && x.toString().length : number >x : string | number | boolean >10 && x.toString().length : number >10 : number >x.toString().length : number >x.toString() : string >x.toString : () => string >x : string | number | boolean >toString : () => string >length : number : ((b = x) // x is number | boolean | string - changed in true branch >((b = x) // x is number | boolean | string - changed in true branch && typeof x === "number" && x) : number >(b = x) // x is number | boolean | string - changed in true branch && typeof x === "number" && x : number >(b = x) // x is number | boolean | string - changed in true branch && typeof x === "number" : boolean >(b = x) : string | number | boolean >b = x : string | number | boolean >b : string | number | boolean >x : string | number | boolean && typeof x === "number" >typeof x === "number" : boolean >typeof x : string >x : string | number | boolean >"number" : string && x); // x is number >x : number }