Add tests

tests/baselines/reference/arrayConcat2.js

@@ -6,6 +6,24 @@ a.concat('Hello');
 
 var b = new Array<string>();
 b.concat('hello');
+
+const expected1: undefined = undefined as Flatten<undefined>;
+
+// #19535
+
+let [actual2] = (undefined as unknown as string[][]).concat([""]);
+const expected2: string | string[] = actual2;
+actual2 = undefined as unknown as string | string[];
+
+// #26378
+
+let [actual3] = [""].concat([1]);
+const expected3: string | number = actual3;
+actual3 = undefined as unknown as string | number;
+
+// #26976
+
+[].concat([""]);
 
 
 //// [arrayConcat2.js]
@@ -14,3 +32,14 @@ a.concat("hello", 'world');
 a.concat('Hello');
 var b = new Array();
 b.concat('hello');
+var expected1 = undefined;
+// #19535
+var actual2 = undefined.concat([""])[0];
+var expected2 = actual2;
+actual2 = undefined;
+// #26378
+var actual3 = [""].concat([1])[0];
+var expected3 = actual3;
+actual3 = undefined;
+// #26976
+[].concat([""]);

tests/baselines/reference/arrayConcat2.symbols

@@ -21,3 +21,45 @@ b.concat('hello');
 >b : Symbol(b, Decl(arrayConcat2.ts, 5, 3))
 >concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
 
+const expected1: undefined = undefined as Flatten<undefined>;
+>expected1 : Symbol(expected1, Decl(arrayConcat2.ts, 8, 5))
+>undefined : Symbol(undefined)
+>Flatten : Symbol(Flatten, Decl(lib.es5.d.ts, --, --))
+
+// #19535
+
+let [actual2] = (undefined as unknown as string[][]).concat([""]);
+>actual2 : Symbol(actual2, Decl(arrayConcat2.ts, 12, 5))
+>(undefined as unknown as string[][]).concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>undefined : Symbol(undefined)
+>concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+const expected2: string | string[] = actual2;
+>expected2 : Symbol(expected2, Decl(arrayConcat2.ts, 13, 5))
+>actual2 : Symbol(actual2, Decl(arrayConcat2.ts, 12, 5))
+
+actual2 = undefined as unknown as string | string[];
+>actual2 : Symbol(actual2, Decl(arrayConcat2.ts, 12, 5))
+>undefined : Symbol(undefined)
+
+// #26378
+
+let [actual3] = [""].concat([1]);
+>actual3 : Symbol(actual3, Decl(arrayConcat2.ts, 18, 5))
+>[""].concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+const expected3: string | number = actual3;
+>expected3 : Symbol(expected3, Decl(arrayConcat2.ts, 19, 5))
+>actual3 : Symbol(actual3, Decl(arrayConcat2.ts, 18, 5))
+
+actual3 = undefined as unknown as string | number;
+>actual3 : Symbol(actual3, Decl(arrayConcat2.ts, 18, 5))
+>undefined : Symbol(undefined)
+
+// #26976
+
+[].concat([""]);
+>[].concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+

tests/baselines/reference/arrayConcat2.types

@@ -1,7 +1,7 @@
 === tests/cases/compiler/arrayConcat2.ts ===
 var a: string[] = [];
 >a : string[]
->[] : undefined[]
+>[] : never[]
 
 a.concat("hello", 'world');
 >a.concat("hello", 'world') : string[]
@@ -30,3 +30,66 @@ b.concat('hello');
 >concat : { (...items: ConcatArray<string>[]): string[]; <U extends any[]>(...items: U): (string | Flatten<U[number]>)[]; }
 >'hello' : "hello"
 
+const expected1: undefined = undefined as Flatten<undefined>;
+>expected1 : undefined
+>undefined as Flatten<undefined> : undefined
+>undefined : undefined
+
+// #19535
+
+let [actual2] = (undefined as unknown as string[][]).concat([""]);
+>actual2 : string | string[]
+>(undefined as unknown as string[][]).concat([""]) : (string | string[])[]
+>(undefined as unknown as string[][]).concat : { (...items: ConcatArray<string[]>[]): string[][]; <U extends any[]>(...items: U): (string[] | Flatten<U[number]>)[]; }
+>(undefined as unknown as string[][]) : string[][]
+>undefined as unknown as string[][] : string[][]
+>undefined as unknown : unknown
+>undefined : undefined
+>concat : { (...items: ConcatArray<string[]>[]): string[][]; <U extends any[]>(...items: U): (string[] | Flatten<U[number]>)[]; }
+>[""] : string[]
+>"" : ""
+
+const expected2: string | string[] = actual2;
+>expected2 : string | string[]
+>actual2 : string | string[]
+
+actual2 = undefined as unknown as string | string[];
+>actual2 = undefined as unknown as string | string[] : string | string[]
+>actual2 : string | string[]
+>undefined as unknown as string | string[] : string | string[]
+>undefined as unknown : unknown
+>undefined : undefined
+
+// #26378
+
+let [actual3] = [""].concat([1]);
+>actual3 : string | number
+>[""].concat([1]) : (string | number)[]
+>[""].concat : { (...items: ConcatArray<string>[]): string[]; <U extends any[]>(...items: U): (string | Flatten<U[number]>)[]; }
+>[""] : string[]
+>"" : ""
+>concat : { (...items: ConcatArray<string>[]): string[]; <U extends any[]>(...items: U): (string | Flatten<U[number]>)[]; }
+>[1] : number[]
+>1 : 1
+
+const expected3: string | number = actual3;
+>expected3 : string | number
+>actual3 : string | number
+
+actual3 = undefined as unknown as string | number;
+>actual3 = undefined as unknown as string | number : string | number
+>actual3 : string | number
+>undefined as unknown as string | number : string | number
+>undefined as unknown : unknown
+>undefined : undefined
+
+// #26976
+
+[].concat([""]);
+>[].concat([""]) : string[]
+>[].concat : { (...items: ConcatArray<never>[]): never[]; <U extends any[]>(...items: U): Flatten<U[number]>[]; }
+>[] : never[]
+>concat : { (...items: ConcatArray<never>[]): never[]; <U extends any[]>(...items: U): Flatten<U[number]>[]; }
+>[""] : string[]
+>"" : ""
+

tests/baselines/reference/arrayFlat.js

@@ -0,0 +1,15 @@
+//// [arrayFlat.ts]
+// #24579 and #29604
+
+let [actual] = [[""], [1]].flat();
+const expected: string | number = actual;
+actual = undefined as string | number;
+const f: any extends typeof actual ? true : false = false;
+
+
+//// [arrayFlat.js]
+// #24579 and #29604
+var actual = [[""], [1]].flat()[0];
+var expected = actual;
+actual = undefined;
+var f = false;

tests/baselines/reference/arrayFlat.symbols

@@ -0,0 +1,20 @@
+=== tests/cases/compiler/arrayFlat.ts ===
+// #24579 and #29604
+
+let [actual] = [[""], [1]].flat();
+>actual : Symbol(actual, Decl(arrayFlat.ts, 2, 5))
+>[[""], [1]].flat : Symbol(Array.flat, Decl(lib.es2019.array.d.ts, --, --), Decl(lib.es2019.array.d.ts, --, --), Decl(lib.es2019.array.d.ts, --, --), Decl(lib.es2019.array.d.ts, --, --), Decl(lib.es2019.array.d.ts, --, --) ... and 1 more)
+>flat : Symbol(Array.flat, Decl(lib.es2019.array.d.ts, --, --), Decl(lib.es2019.array.d.ts, --, --), Decl(lib.es2019.array.d.ts, --, --), Decl(lib.es2019.array.d.ts, --, --), Decl(lib.es2019.array.d.ts, --, --) ... and 1 more)
+
+const expected: string | number = actual;
+>expected : Symbol(expected, Decl(arrayFlat.ts, 3, 5))
+>actual : Symbol(actual, Decl(arrayFlat.ts, 2, 5))
+
+actual = undefined as string | number;
+>actual : Symbol(actual, Decl(arrayFlat.ts, 2, 5))
+>undefined : Symbol(undefined)
+
+const f: any extends typeof actual ? true : false = false;
+>f : Symbol(f, Decl(arrayFlat.ts, 5, 5))
+>actual : Symbol(actual, Decl(arrayFlat.ts, 2, 5))
+

tests/baselines/reference/arrayFlat.types

@@ -0,0 +1,31 @@
+=== tests/cases/compiler/arrayFlat.ts ===
+// #24579 and #29604
+
+let [actual] = [[""], [1]].flat();
+>actual : string | number
+>[[""], [1]].flat() : (string | number)[]
+>[[""], [1]].flat : { (depth: 4): (string | number)[]; (depth: 3): (string | number)[]; (depth: 2): (string | number)[]; (depth?: 1): (string | number)[]; (depth: 0): (string[] | number[])[]; (depth: number): (string[] | number[])[] | (string | number)[]; }
+>[[""], [1]] : (string[] | number[])[]
+>[""] : string[]
+>"" : ""
+>[1] : number[]
+>1 : 1
+>flat : { (depth: 4): (string | number)[]; (depth: 3): (string | number)[]; (depth: 2): (string | number)[]; (depth?: 1): (string | number)[]; (depth: 0): (string[] | number[])[]; (depth: number): (string[] | number[])[] | (string | number)[]; }
+
+const expected: string | number = actual;
+>expected : string | number
+>actual : string | number
+
+actual = undefined as string | number;
+>actual = undefined as string | number : string | number
+>actual : string | number
+>undefined as string | number : string | number
+>undefined : undefined
+
+const f: any extends typeof actual ? true : false = false;
+>f : boolean
+>actual : string | number
+>true : true
+>false : false
+>false : false
+

tests/baselines/reference/arrayFlatMap.js

@@ -3,10 +3,20 @@ const array: number[] = [];
 const readonlyArray: ReadonlyArray<number> = [];
 array.flatMap((): ReadonlyArray<number> => []); // ok
 readonlyArray.flatMap((): ReadonlyArray<number> => []); // ok
+
+// #19535
+
+let [actual] = [""].flatMap(undefined as () => string[] | string[][]);
+const expected: string | string[] = actual;
+actual = undefined as string | string[];
 
 
 //// [arrayFlatMap.js]
 var array = [];
 var readonlyArray = [];
 array.flatMap(function () { return []; }); // ok
 readonlyArray.flatMap(function () { return []; }); // ok
+// #19535
+var actual = [""].flatMap(undefined)[0];
+var expected = actual;
+actual = undefined;

tests/baselines/reference/arrayFlatMap.symbols

@@ -18,3 +18,19 @@ readonlyArray.flatMap((): ReadonlyArray<number> => []); // ok
 >flatMap : Symbol(ReadonlyArray.flatMap, Decl(lib.es2019.array.d.ts, --, --))
 >ReadonlyArray : Symbol(ReadonlyArray, Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2016.array.include.d.ts, --, --), Decl(lib.es2019.array.d.ts, --, --))
 
+// #19535
+
+let [actual] = [""].flatMap(undefined as () => string[] | string[][]);
+>actual : Symbol(actual, Decl(arrayFlatMap.ts, 7, 5))
+>[""].flatMap : Symbol(Array.flatMap, Decl(lib.es2019.array.d.ts, --, --))
+>flatMap : Symbol(Array.flatMap, Decl(lib.es2019.array.d.ts, --, --))
+>undefined : Symbol(undefined)
+
+const expected: string | string[] = actual;
+>expected : Symbol(expected, Decl(arrayFlatMap.ts, 8, 5))
+>actual : Symbol(actual, Decl(arrayFlatMap.ts, 7, 5))
+
+actual = undefined as string | string[];
+>actual : Symbol(actual, Decl(arrayFlatMap.ts, 7, 5))
+>undefined : Symbol(undefined)
+

tests/baselines/reference/arrayFlatMap.types

@@ -23,3 +23,25 @@ readonlyArray.flatMap((): ReadonlyArray<number> => []); // ok
 >(): ReadonlyArray<number> => [] : () => readonly number[]
 >[] : undefined[]
 
+// #19535
+
+let [actual] = [""].flatMap(undefined as () => string[] | string[][]);
+>actual : string | string[]
+>[""].flatMap(undefined as () => string[] | string[][]) : (string | string[])[]
+>[""].flatMap : <U>(callbackfn: (value: string, index: number, array: string[]) => U, thisArg?: any) => Flatten<U>[]
+>[""] : string[]
+>"" : ""
+>flatMap : <U>(callbackfn: (value: string, index: number, array: string[]) => U, thisArg?: any) => Flatten<U>[]
+>undefined as () => string[] | string[][] : () => string[] | string[][]
+>undefined : undefined
+
+const expected: string | string[] = actual;
+>expected : string | string[]
+>actual : string | string[]
+
+actual = undefined as string | string[];
+>actual = undefined as string | string[] : string | string[]
+>actual : string | string[]
+>undefined as string | string[] : string | string[]
+>undefined : undefined
+

tests/cases/compiler/arrayConcat2.ts

@@ -5,3 +5,22 @@ a.concat('Hello');
 
 var b = new Array<string>();
 b.concat('hello');
+
+const expected1: undefined = undefined as Flatten<undefined>;
+
+// #19535
+
+let [actual2] = (undefined as unknown as string[][]).concat([""]);
+const expected2: string | string[] = actual2;
+actual2 = undefined as unknown as string | string[];
+
+// #26378
+
+let [actual3] = [""].concat([1]);
+const expected3: string | number = actual3;
+actual3 = undefined as unknown as string | number;
+
+// #26976
+
+// @strictNullChecks: true
+[].concat([""]);

tests/cases/compiler/arrayFlat.ts

@@ -0,0 +1,8 @@
+// @lib: es2019
+
+// #24579 and #29604
+
+let [actual] = [[""], [1]].flat();
+const expected: string | number = actual;
+actual = undefined as string | number;
+const f: any extends typeof actual ? true : false = false;

tests/cases/compiler/arrayFlatMap.ts

@@ -4,3 +4,9 @@ const array: number[] = [];
 const readonlyArray: ReadonlyArray<number> = [];
 array.flatMap((): ReadonlyArray<number> => []); // ok
 readonlyArray.flatMap((): ReadonlyArray<number> => []); // ok
+
+// #19535
+
+let [actual] = [""].flatMap(undefined as () => string[] | string[][]);
+const expected: string | string[] = actual;
+actual = undefined as string | string[];