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