=== tests/cases/conformance/expressions/contextualTyping/functionExpressionContextualTyping1.ts === // When a function expression with no type parameters and no parameter type annotations // is contextually typed (section 4.19) by a type T and a contextual signature S can be extracted from T enum E { red, blue } >E : E >red : E >blue : E // A contextual signature S is extracted from a function type T as follows: // If T is a function type with exactly one call signature, and if that call signature is non- generic, S is that signature. var a0: (n: number, s: string) => number = (num, str) => { >a0 : (n: number, s: string) => number >n : number >s : string >(num, str) => { num.toExponential(); return 0;} : (num: number, str: string) => number >num : number >str : string num.toExponential(); >num.toExponential() : string >num.toExponential : (fractionDigits?: number) => string >num : number >toExponential : (fractionDigits?: number) => string return 0; >0 : number } class Class { >Class : Class >T : T foo() { } >foo : () => void } var a1: (c: Class) => number = (a1) => { >a1 : (c: Class) => number >c : Class >Class : Class >Number : Number >(a1) => { a1.foo(); return 1;} : (a1: Class) => number >a1 : Class a1.foo(); >a1.foo() : void >a1.foo : () => void >a1 : Class >foo : () => void return 1; >1 : number } // A contextual signature S is extracted from a function type T as follows: // If T is a union type, let U be the set of element types in T that have call signatures. // If each type in U has exactly one call signature and that call signature is non- generic, // and if all of the signatures are identical ignoring return types, // then S is a signature with the same parameters and a union of the return types. var b1: ((s: string, w: boolean) => void) | ((s: string, w: boolean) => string); >b1 : ((s: string, w: boolean) => void) | ((s: string, w: boolean) => string) >s : string >w : boolean >s : string >w : boolean b1 = (k, h) => { }; >b1 = (k, h) => { } : (k: string, h: boolean) => void >b1 : ((s: string, w: boolean) => void) | ((s: string, w: boolean) => string) >(k, h) => { } : (k: string, h: boolean) => void >k : string >h : boolean var b2: typeof a0 | ((n: number, s: string) => string); >b2 : ((n: number, s: string) => number) | ((n: number, s: string) => string) >a0 : (n: number, s: string) => number >n : number >s : string b2 = (foo, bar) => { return foo + 1; } >b2 = (foo, bar) => { return foo + 1; } : (foo: number, bar: string) => number >b2 : ((n: number, s: string) => number) | ((n: number, s: string) => string) >(foo, bar) => { return foo + 1; } : (foo: number, bar: string) => number >foo : number >bar : string >foo + 1 : number >foo : number >1 : number b2 = (foo, bar) => { return "hello"; } >b2 = (foo, bar) => { return "hello"; } : (foo: number, bar: string) => string >b2 : ((n: number, s: string) => number) | ((n: number, s: string) => string) >(foo, bar) => { return "hello"; } : (foo: number, bar: string) => string >foo : number >bar : string >"hello" : string var b3: (name: string, num: number, boo: boolean) => void; >b3 : (name: string, num: number, boo: boolean) => void >name : string >num : number >boo : boolean b3 = (name, number) => { }; >b3 = (name, number) => { } : (name: string, number: number) => void >b3 : (name: string, num: number, boo: boolean) => void >(name, number) => { } : (name: string, number: number) => void >name : string >number : number var b4: (n: E) => string = (number = 1) => { return "hello"; }; >b4 : (n: E) => string >n : E >E : E >(number = 1) => { return "hello"; } : (number?: E) => string >number : E >1 : number >"hello" : string var b5: (n: {}) => string = (number = "string") => { return "hello"; }; >b5 : (n: {}) => string >n : {} >(number = "string") => { return "hello"; } : (number?: {}) => string >number : {} >"string" : string >"hello" : string // A contextual signature S is extracted from a function type T as follows: // Otherwise, no contextual signature can be extracted from T and S is undefined. var b6: ((s: string, w: boolean) => void) | ((n: number) => number); >b6 : ((s: string, w: boolean) => void) | ((n: number) => number) >s : string >w : boolean >n : number var b7: ((s: string, w: boolean) => void) | ((s: string, w: number) => string); >b7 : ((s: string, w: boolean) => void) | ((s: string, w: number) => string) >s : string >w : boolean >s : string >w : number b6 = (k) => { k.toLowerCase() }; >b6 = (k) => { k.toLowerCase() } : (k: any) => void >b6 : ((s: string, w: boolean) => void) | ((n: number) => number) >(k) => { k.toLowerCase() } : (k: any) => void >k : any >k.toLowerCase() : any >k.toLowerCase : any >k : any >toLowerCase : any b6 = (i) => { >b6 = (i) => { i.toExponential(); return i;} : (i: any) => any >b6 : ((s: string, w: boolean) => void) | ((n: number) => number) >(i) => { i.toExponential(); return i;} : (i: any) => any >i : any i.toExponential(); >i.toExponential() : any >i.toExponential : any >i : any >toExponential : any return i; >i : any }; // Per spec, no contextual signature can be extracted in this case. (Otherwise clause) b7 = (j, m) => { }; // Per spec, no contextual signature can be extracted in this case. (Otherwise clause) >b7 = (j, m) => { } : (j: any, m: any) => void >b7 : ((s: string, w: boolean) => void) | ((s: string, w: number) => string) >(j, m) => { } : (j: any, m: any) => void >j : any >m : any class C { >C : C >T : T >U : U constructor() { var k: ((j: T, k: U) => (T|U)[]) | ((j: number,k :U) => number[]) = (j, k) => { >k : ((j: T, k: U) => (T | U)[]) | ((j: number, k: U) => number[]) >j : T >T : T >k : U >U : U >T : T >U : U >j : number >k : U >U : U >(j, k) => { return [j, k]; } : (j: any, k: any) => any[] >j : any >k : any return [j, k]; >[j, k] : any[] >j : any >k : any } // Per spec, no contextual signature can be extracted in this case. } }