TypeScript/tests/cases/conformance/expressions/contextualTyping/arrayLiteralExpressionContextualTyping.ts

14 lines
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TypeScript

// In a contextually typed array literal expression containing no spread elements, an element expression at index N is contextually typed by
// the type of the property with the numeric name N in the contextual type, if any, or otherwise
// the numeric index type of the contextual type, if any.
var array = [1, 2, 3];
var array1 = [true, 2, 3]; // Contextual type by the numeric index type of the contextual type
var tup: [number, number, number] = [1, 2, 3, 4];
var tup1: [number|string, number|string, number|string] = [1, 2, 3, "string"];
var tup2: [number, number, number] = [1, 2, 3, "string"]; // Error
// In a contextually typed array literal expression containing one or more spread elements,
// an element expression at index N is contextually typed by the numeric index type of the contextual type, if any.
var spr = [1, 2, 3, ...array];
var spr1 = [1, 2, 3, ...tup];
var spr2:[number, number, number] = [1, 2, 3, ...tup]; // Error