TypeScript/tests/baselines/reference/arrayLiterals3.types at e0bffe88751ee5ac361d7f3eabc5ea26722e3406 · microsoft/TypeScript · GitHub

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//// [tests/cases/conformance/expressions/arrayLiterals/arrayLiterals3.ts] ////

=== arrayLiterals3.ts ===
// Each element expression in a non-empty array literal is processed as follows:
//    - If the array literal contains no spread elements, and if the array literal is contextually typed (section 4.19)
//      by a type T and T has a property with the numeric name N, where N is the index of the element expression in the array literal,
//      the element expression is contextually typed by the type of that property.

// The resulting type an array literal expression is determined as follows:
//     - If the array literal contains no spread elements and is contextually typed by a tuple-like type,
//       the resulting type is a tuple type constructed from the types of the element expressions.

var a0: [any, any, any] = [];                             // Error
>a0 : [any, any, any]
>   : ^^^^^^^^^^^^^^^
>[] : []
>   : ^^

var a1: [boolean, string, number] = ["string", 1, true];  // Error
>a1 : [boolean, string, number]
>   : ^^^^^^^^^^^^^^^^^^^^^^^^^
>["string", 1, true] : [string, number, boolean]
>                    : ^^^^^^^^^^^^^^^^^^^^^^^^^
>"string" : "string"
>         : ^^^^^^^^
>1 : 1
>  : ^
>true : true
>     : ^^^^

// The resulting type an array literal expression is determined as follows:
//     - If the array literal contains no spread elements and is an array assignment pattern in a destructuring assignment (section 4.17.1),
//       the resulting type is a tuple type constructed from the types of the element expressions.

var [b1, b2]: [number, number] = [1, 2, "string", true];
>b1 : number
>   : ^^^^^^
>b2 : number
>   : ^^^^^^
>[1, 2, "string", true] : [number, number, string, boolean]
>                       : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>1 : 1
>  : ^
>2 : 2
>  : ^
>"string" : "string"
>         : ^^^^^^^^
>true : true
>     : ^^^^

// The resulting type an array literal expression is determined as follows:
//      - the resulting type is an array type with an element type that is the union of the types of the
//        non - spread element expressions and the numeric index signature types of the spread element expressions
var temp = ["s", "t", "r"];
>temp : string[]
>     : ^^^^^^^^
>["s", "t", "r"] : string[]
>                : ^^^^^^^^
>"s" : "s"
>    : ^^^
>"t" : "t"
>    : ^^^
>"r" : "r"
>    : ^^^

var temp1 = [1, 2, 3];
>temp1 : number[]
>      : ^^^^^^^^
>[1, 2, 3] : number[]
>          : ^^^^^^^^
>1 : 1
>  : ^
>2 : 2
>  : ^
>3 : 3
>  : ^

var temp2: [number[], string[]] = [[1, 2, 3], ["hello", "string"]];
>temp2 : [number[], string[]]
>      : ^^^^^^^^^^^^^^^^^^^^
>[[1, 2, 3], ["hello", "string"]] : [number[], string[]]
>                                 : ^^^^^^^^^^^^^^^^^^^^
>[1, 2, 3] : number[]
>          : ^^^^^^^^
>1 : 1
>  : ^
>2 : 2
>  : ^
>3 : 3
>  : ^
>["hello", "string"] : string[]
>                    : ^^^^^^^^
>"hello" : "hello"
>        : ^^^^^^^
>"string" : "string"
>         : ^^^^^^^^

interface tup {
    0: number[]|string[];
>0 : string[] | number[]
>  : ^^^^^^^^^^^^^^^^^^^

    1: number[]|string[];
>1 : string[] | number[]
>  : ^^^^^^^^^^^^^^^^^^^
}
interface myArray extends Array<Number> { }
interface myArray2 extends Array<Number|String> { }
var c0: tup = [...temp2];                         // Error
>c0 : tup
>   : ^^^
>[...temp2] : [number[], string[]]
>           : ^^^^^^^^^^^^^^^^^^^^
>...temp2 : string[] | number[]
>         : ^^^^^^^^^^^^^^^^^^^
>temp2 : [number[], string[]]
>      : ^^^^^^^^^^^^^^^^^^^^

var c1: [number, number, number] = [...temp1];    // Error cannot assign number[] to [number, number, number]
>c1 : [number, number, number]
>   : ^^^^^^^^^^^^^^^^^^^^^^^^
>[...temp1] : number[]
>           : ^^^^^^^^
>...temp1 : number
>         : ^^^^^^
>temp1 : number[]
>      : ^^^^^^^^

var c2: myArray = [...temp1, ...temp];            // Error cannot assign (number|string)[] to number[]
>c2 : myArray
>   : ^^^^^^^
>[...temp1, ...temp] : (string | number)[]
>                    : ^^^^^^^^^^^^^^^^^^^
>...temp1 : number
>         : ^^^^^^
>temp1 : number[]
>      : ^^^^^^^^
>...temp : string
>        : ^^^^^^
>temp : string[]
>     : ^^^^^^^^