// In an intersection everything absorbs unknowntypeT00=unknown&null;// nulltypeT01=unknown&undefined;// undefinedtypeT02=unknown&null&undefined;// null & undefined (which becomes never in union)typeT03=unknown&string;// stringtypeT04=unknown&string[];// string[]typeT05=unknown&unknown;// unknowntypeT06=unknown&any;// any// In a union an unknown absorbs everythingtypeT10=unknown|null;// unknowntypeT11=unknown|undefined;// unknowntypeT12=unknown|null|undefined;// unknowntypeT13=unknown|string;// unknowntypeT14=unknown|string[];// unknowntypeT15=unknown|unknown;// unknowntypeT16=unknown|any;// any// Type variable and unknown in union and intersectiontypeT20<T>=T&{};// T & {}typeT21<T>=T|{};// T | {}typeT22<T>=T&unknown;// TtypeT23<T>=T|unknown;// unknown// unknown in conditional typestypeT30<T>=unknownextendsT ?true :false;// DeferredtypeT31<T>=Textendsunknown ?true :false;// Deferred (so it distributes)typeT32<T>=neverextendsT ?true :false;// truetypeT33<T>=Textendsnever ?true :false;// Deferred// keyof unknowntypeT40=keyofany;// string | number | symboltypeT41=keyofunknown;// never// Only equality operators are allowed with unknownfunctionf10(x:unknown){x==5;x!==10;x>=0;// Errorx+1;// Errorx*2;// Error-x;// Error+x;// Error}// No property accesses, element accesses, or function callsfunctionf11(x:unknown){x.foo;// Errorx[5];// Errorx();// Errornewx();// Error}// typeof, instanceof, and user defined type predicatesdeclarefunctionisFunction(x:unknown):x isFunction;functionf20(x:unknown){if(typeofx==="string"||typeofx==="number"){x;// string | number}if(xinstanceofError){x;// Error}if(isFunction(x)){x;// Function}}// Homomorphic mapped type over unknowntypeT50<T>={[PinkeyofT]:number};typeT51=T50<any>;// { [x: string]: number }typeT52=T50<unknown>;// {}// Anything is assignable to unknownfunctionf21<T>(pAny:any,pNever:never,pT:T){letx:unknown;x=123;x="hello";x=[1,2,3];x=newError();x=x;x=pAny;x=pNever;x=pT;}// unknown assignable only to itself and anyfunctionf22(x:unknown){letv1:any=x;letv2:unknown=x;letv3:object=x;// Errorletv4:string=x;// Errorletv5:string[]=x;// Errorletv6:{}=x;// Errorletv7:{}|null|undefined=x;// Error}// Type parameter 'T extends unknown' not related to objectfunctionf23<Textendsunknown>(x:T){lety:object=x;// Error}// Anything but primitive assignable to { [x: string]: unknown }functionf24(x:{[x:string]:unknown}){x={};x={a:5};x=[1,2,3];x=123;// Error}// Locals of type unknown always considered initializedfunctionf25(){letx:unknown;lety=x;}// Spread of unknown causes result to be unknownfunctionf26(x:{},y:unknown,z:any){leto1={a:42, ...x};// { a: number }leto2={a:42, ...x, ...y};// unknownleto3={a:42, ...x, ...y, ...z};// any}// Functions with unknown return type don't need return expressionsfunctionf27():unknown{}// Rest type cannot be created from unknownfunctionf28(x:unknown){let{ ...a}=x;// Error}// Class properties of type unknown don't need definite assignmentclassC1{a:string;// Errorb:unknown;c:any;}