300 lines
9.2 KiB
TypeScript
300 lines
9.2 KiB
TypeScript
//// [typeGuardsInIfStatement.ts]
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// In the true branch statement of an <20>if<69> statement,
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// the type of a variable or parameter is narrowed by any type guard in the <20>if<69> condition when true,
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// provided the true branch statement contains no assignments to the variable or parameter.
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// In the false branch statement of an <20>if<69> statement,
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// the type of a variable or parameter is narrowed by any type guard in the <20>if<69> condition when false,
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// provided the false branch statement contains no assignments to the variable or parameter
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function foo(x: number | string) {
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if (typeof x === "string") {
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return x.length; // string
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}
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else {
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return x++; // number
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}
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}
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function foo2(x: number | string) {
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// x is assigned in the if true branch, the type is not narrowed
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if (typeof x === "string") {
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x = 10;
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return x; // string | number
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}
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else {
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return x; // string | number
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}
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}
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function foo3(x: number | string) {
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// x is assigned in the if true branch, the type is not narrowed
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if (typeof x === "string") {
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x = "Hello"; // even though assigned using same type as narrowed expression
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return x; // string | number
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}
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else {
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return x; // string | number
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}
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}
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function foo4(x: number | string) {
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// false branch updates the variable - so here it is not number
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if (typeof x === "string") {
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return x; // string | number
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}
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else {
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x = 10; // even though assigned number - this should result in x to be string | number
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return x; // string | number
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}
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}
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function foo5(x: number | string) {
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// false branch updates the variable - so here it is not number
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if (typeof x === "string") {
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return x; // string | number
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}
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else {
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x = "hello";
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return x; // string | number
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}
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}
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function foo6(x: number | string) {
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// Modify in both branches
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if (typeof x === "string") {
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x = 10;
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return x; // string | number
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}
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else {
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x = "hello";
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return x; // string | number
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}
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}
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function foo7(x: number | string | boolean) {
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if (typeof x === "string") {
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return x === "hello"; // string
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}
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else if (typeof x === "boolean") {
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return x; // boolean
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}
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else {
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return x == 10; // number
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}
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}
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function foo8(x: number | string | boolean) {
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if (typeof x === "string") {
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return x === "hello"; // string
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}
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else {
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var b: number | boolean = x; // number | boolean
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if (typeof x === "boolean") {
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return x; // boolean
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}
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else {
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return x == 10; // number
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}
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}
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}
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function foo9(x: number | string) {
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var y = 10;
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if (typeof x === "string") {
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// usage of x or assignment to separate variable shouldn't cause narrowing of type to stop
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y = x.length;
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return x === "hello"; // string
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}
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else {
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return x == 10; // number
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}
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}
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function foo10(x: number | string | boolean) {
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// Mixing typeguard narrowing in if statement with conditional expression typeguard
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if (typeof x === "string") {
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return x === "hello"; // string
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}
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else {
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var y: boolean | string;
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var b = x; // number | boolean
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return typeof x === "number"
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? x === 10 // number
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: x; // x should be boolean
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}
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}
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function foo11(x: number | string | boolean) {
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// Mixing typeguard narrowing in if statement with conditional expression typeguard
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// Assigning value to x deep inside another guard stops narrowing of type too
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if (typeof x === "string") {
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return x; // string | number | boolean - x changed in else branch
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}
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else {
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var y: number| boolean | string;
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var b = x; // number | boolean | string - because below we are changing value of x in if statement
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return typeof x === "number"
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? (
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// change value of x
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x = 10 && x.toString() // number | boolean | string
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)
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: (
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// do not change value
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y = x && x.toString() // number | boolean | string
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);
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}
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}
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function foo12(x: number | string | boolean) {
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// Mixing typeguard narrowing in if statement with conditional expression typeguard
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// Assigning value to x in outer guard shouldn't stop narrowing in the inner expression
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if (typeof x === "string") {
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return x.toString(); // string | number | boolean - x changed in else branch
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}
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else {
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x = 10;
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var b = x; // number | boolean | string
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return typeof x === "number"
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? x.toString() // number
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: x.toString(); // boolean | string
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}
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}
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//// [typeGuardsInIfStatement.js]
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// In the true branch statement of an <20>if<69> statement,
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// the type of a variable or parameter is narrowed by any type guard in the <20>if<69> condition when true,
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// provided the true branch statement contains no assignments to the variable or parameter.
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// In the false branch statement of an <20>if<69> statement,
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// the type of a variable or parameter is narrowed by any type guard in the <20>if<69> condition when false,
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// provided the false branch statement contains no assignments to the variable or parameter
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function foo(x) {
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if (typeof x === "string") {
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return x.length; // string
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}
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else {
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return x++; // number
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}
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}
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function foo2(x) {
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// x is assigned in the if true branch, the type is not narrowed
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if (typeof x === "string") {
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x = 10;
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return x; // string | number
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}
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else {
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return x; // string | number
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}
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}
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function foo3(x) {
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// x is assigned in the if true branch, the type is not narrowed
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if (typeof x === "string") {
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x = "Hello"; // even though assigned using same type as narrowed expression
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return x; // string | number
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}
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else {
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return x; // string | number
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}
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}
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function foo4(x) {
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// false branch updates the variable - so here it is not number
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if (typeof x === "string") {
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return x; // string | number
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}
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else {
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x = 10; // even though assigned number - this should result in x to be string | number
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return x; // string | number
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}
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}
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function foo5(x) {
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// false branch updates the variable - so here it is not number
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if (typeof x === "string") {
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return x; // string | number
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}
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else {
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x = "hello";
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return x; // string | number
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}
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}
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function foo6(x) {
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// Modify in both branches
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if (typeof x === "string") {
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x = 10;
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return x; // string | number
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}
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else {
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x = "hello";
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return x; // string | number
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}
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}
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function foo7(x) {
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if (typeof x === "string") {
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return x === "hello"; // string
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}
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else if (typeof x === "boolean") {
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return x; // boolean
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}
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else {
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return x == 10; // number
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}
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}
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function foo8(x) {
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if (typeof x === "string") {
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return x === "hello"; // string
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}
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else {
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var b = x; // number | boolean
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if (typeof x === "boolean") {
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return x; // boolean
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}
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else {
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return x == 10; // number
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}
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}
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}
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function foo9(x) {
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var y = 10;
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if (typeof x === "string") {
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// usage of x or assignment to separate variable shouldn't cause narrowing of type to stop
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y = x.length;
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return x === "hello"; // string
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}
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else {
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return x == 10; // number
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}
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}
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function foo10(x) {
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// Mixing typeguard narrowing in if statement with conditional expression typeguard
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if (typeof x === "string") {
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return x === "hello"; // string
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}
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else {
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var y;
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var b = x; // number | boolean
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return typeof x === "number"
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? x === 10 // number
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: x; // x should be boolean
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}
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}
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function foo11(x) {
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// Mixing typeguard narrowing in if statement with conditional expression typeguard
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// Assigning value to x deep inside another guard stops narrowing of type too
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if (typeof x === "string") {
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return x; // string | number | boolean - x changed in else branch
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}
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else {
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var y;
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var b = x; // number | boolean | string - because below we are changing value of x in if statement
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return typeof x === "number"
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? (
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// change value of x
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x = 10 && x.toString() // number | boolean | string
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)
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: (
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// do not change value
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y = x && x.toString() // number | boolean | string
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);
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}
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}
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function foo12(x) {
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// Mixing typeguard narrowing in if statement with conditional expression typeguard
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// Assigning value to x in outer guard shouldn't stop narrowing in the inner expression
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if (typeof x === "string") {
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return x.toString(); // string | number | boolean - x changed in else branch
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}
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else {
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x = 10;
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var b = x; // number | boolean | string
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return typeof x === "number"
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? x.toString() // number
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: x.toString(); // boolean | string
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}
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}
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