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Merged
merged 5 commits into from
Apr 7, 2020
Merged

Accurate Array.prototype.flat definition #32131

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ade67c6
Better Array.prototype.flat definition
eilvelia Jun 27, 2019
7b74bd8
Resolve merge conflicts
eilvelia Feb 27, 2020
1b31861
Use more meaningful names
eilvelia Feb 27, 2020
c92d25f
Rename 'Flat' to 'FlatArray'
eilvelia Mar 27, 2020
a7404d1
Merge branch 'master' into array-flat
eilvelia Mar 27, 2020
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168 changes: 15 additions & 153 deletions src/lib/es2019.array.d.ts
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Original file line number Diff line number Diff line change
@@ -1,3 +1,10 @@
type Flat<A, D extends number> = {
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we should check for existing types named Flat in some code base -- probably it's fine, but might not be.

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Probably Definitely Typed is a big enough sample -- grepping for class Flat, interface Flat, type Flat should give you (almost?) all of the uses.

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  • seen has class Flat (appropriate for a 3D renderer)
  • array.prototype.flat has interface Flat (and FlatMap)

Seen is barely used, but array.prototype.flat usage is quite widespread.

'1': A,
'0': A extends ReadonlyArray<infer T>
? Flat<T, [-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20][D]>
: A
}[D extends -1 ? '1' : '0']

interface ReadonlyArray<T> {

/**
Expand All @@ -22,94 +29,10 @@ interface ReadonlyArray<T> {
*
* @param depth The maximum recursion depth
*/
flat<U>(this:
ReadonlyArray<U[][][][]> |

ReadonlyArray<ReadonlyArray<U[][][]>> |
ReadonlyArray<ReadonlyArray<U[][]>[]> |
ReadonlyArray<ReadonlyArray<U[]>[][]> |
ReadonlyArray<ReadonlyArray<U>[][][]> |

ReadonlyArray<ReadonlyArray<ReadonlyArray<U[][]>>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U>[][]>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>[][]> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U>[]>[]> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U[]>>[]> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U[]>[]>> |

ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<U[]>>>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<U>[]>>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>[]>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>>[]> |

ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>>>>,
depth: 4): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this:
ReadonlyArray<U[][][]> |

ReadonlyArray<ReadonlyArray<U>[][]> |
ReadonlyArray<ReadonlyArray<U[]>[]> |
ReadonlyArray<ReadonlyArray<U[][]>> |

ReadonlyArray<ReadonlyArray<ReadonlyArray<U[]>>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U>[]>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>[]> |

ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>>>,
depth: 3): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this:
ReadonlyArray<U[][]> |

ReadonlyArray<ReadonlyArray<U[]>> |
ReadonlyArray<ReadonlyArray<U>[]> |

ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>>,
depth: 2): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this:
ReadonlyArray<U[]> |
ReadonlyArray<ReadonlyArray<U>>,
depth?: 1
): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this:
ReadonlyArray<U>,
depth: 0
): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth. If no depth is provided, flat method defaults to the depth of 1.
*
* @param depth The maximum recursion depth
*/
flat<U>(depth?: number): any[];
flat<A, D extends number = 1>(
this: A,
depth?: D
): Flat<A, D>[]
}

interface Array<T> {
Expand All @@ -135,69 +58,8 @@ interface Array<T> {
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][][][][][][][], depth: 7): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][][][][][][], depth: 6): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][][][][][], depth: 5): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][][][][], depth: 4): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][][][], depth: 3): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][][], depth: 2): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][], depth?: 1): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[], depth: 0): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth. If no depth is provided, flat method defaults to the depth of 1.
*
* @param depth The maximum recursion depth
*/
flat<U>(depth?: number): any[];
flat<A, D extends number = 1>(
this: A,
depth?: D
): Flat<A, D>[]
}