newtests/array_literal_tuple_spread/test.js

/* @flow */


import type {Suite} from "flow-dev-tools/src/test/Suite";
const {suite, test} = require('flow-dev-tools/src/test/Tester');

module.exports = (suite(({addFile, addFiles, addCode}) => [
  test("any flowing to spreads", [
    addCode(`
      function withoutAny(tup: [1,2], notAny: [3, 4]): [1, 2, 3, 4] {
        return [...tup, ...notAny];
      }
      function withAny(tup: [1,2], any: any): [1, 2, 3, 4] {
        return [...tup, ...any];
      }
    `)
      .noNewErrors()
      .because('Adding any should not cause new errors'),
  ]),
  /* We used to try to "summarize" elements of non-tuple arrays, which would
   * strip away literal information from string and number types. However, this
   * was pretty broken, and Sam found this following example to demonstrate how.
   */
  test("Sam's example of multiple lower bounds and SummarizeT", [
    addCode(`
      function f(b: boolean): [Array<?number>] {
        var x = null;
        if (b) {
          x = 0;
        }
        var [xs] = f(b);
        return [[...xs, x]];
      }
    `).noNewErrors()
      .because(
        'x has multiple lower bounds, so if we unify prematurely we can get ' +
          'an error when figuring out the summarized element type for x',
      ),
  ]),
  test('Avoid infinite recursion due to a loop', [
    addCode(`
      let foo = [0];
      for (let x = 1; x < 3; x++) {
        foo = [...foo, x];
      }
      (foo: [0, 1, 2]);
    `)
      .newErrors(
        `
          test.js:8
            8:       (foo: [0, 1, 2]);
                      ^^^ Cannot cast \`foo\` to tuple type because array literal [1] has an arity of 1 but tuple type [2] has an arity of 3. [invalid-tuple-arity]
            References:
              4:       let foo = [0];
                                 ^^^ [1]
              8:       (foo: [0, 1, 2]);
                             ^^^^^^^^^ [2]

          test.js:8
            8:       (foo: [0, 1, 2]);
                      ^^^ Cannot cast \`foo\` to tuple type because array literal [1] has an arity of 2 but tuple type [2] has an arity of 3. [invalid-tuple-arity]
            References:
              6:         foo = [...foo, x];
                               ^^^^^^^^^^^ [1]
              8:       (foo: [0, 1, 2]);
                             ^^^^^^^^^ [2]

          test.js:8
            8:       (foo: [0, 1, 2]);
                      ^^^ Cannot cast \`foo\` to tuple type because array literal [1] has an unknown number of elements, so is incompatible with tuple type [2]. [invalid-tuple-arity]
            References:
              6:         foo = [...foo, x];
                               ^^^^^^^^^^^ [1]
              8:       (foo: [0, 1, 2]);
                             ^^^^^^^^^ [2]

          test.js:8
            8:       (foo: [0, 1, 2]);
                      ^^^ Cannot cast \`foo\` to tuple type because number [1] is incompatible with number literal \`1\` [2] in index 1. [incompatible-cast]
            References:
              5:       for (let x = 1; x < 3; x++) {
                                              ^^^ [1]
              8:       (foo: [0, 1, 2]);
                                 ^ [2]

          test.js:8
            8:       (foo: [0, 1, 2]);
                      ^^^ Cannot cast \`foo\` to tuple type because number [1] is incompatible with number literal \`2\` [2] in index 2. [incompatible-cast]
            References:
              5:       for (let x = 1; x < 3; x++) {
                                    ^ [1]
              8:       (foo: [0, 1, 2]);
                                    ^ [2]

          test.js:8
            8:       (foo: [0, 1, 2]);
                      ^^^ Cannot cast \`foo\` to tuple type because number [1] is incompatible with number literal \`2\` [2] in index 2. [incompatible-cast]
            References:
              5:       for (let x = 1; x < 3; x++) {
                                              ^^^ [1]
              8:       (foo: [0, 1, 2]);
                                    ^ [2]
        `,
      ),
  ]),
  test('Avoid infinite recursion due to polymorphic recursion', [
    addCode(`
      function foo<T: Array<any>>(arr: T) {
        if (arr.length > 10) return arr;
        return foo([...arr, 1]);
      }
      const ret = foo([1]);
    `),
    addCode('(ret: void);')
      .newErrors(
        `
          test.js:11
           11: (ret: void);
                ^^^ Cannot cast \`ret\` to undefined because array type [1] is incompatible with undefined [2]. [incompatible-cast]
            References:
              4:       function foo<T: Array<any>>(arr: T) {
                                                        ^ [1]
             11: (ret: void);
                       ^^^^ [2]
        `,
      )
      .because('The constant folding should turn the tuple into an array'),
    addCode(`
      (ret[5]: 1);
      (ret[5]: 2);
    `)
  ]),
  test('Avoid infinite recursion due to recursion', [
    addCode(`
      function foo(arr) {
        if (arr.length > 10) return arr;
        return foo([...arr, 1]);
      }
      const ret = foo([1]);
    `),
    addCode('(ret: void);')
      .newErrors(
        `
          test.js:11
           11: (ret: void);
                ^^^ Cannot cast \`ret\` to undefined because array literal [1] is incompatible with undefined [2]. [incompatible-cast]
            References:
              6:         return foo([...arr, 1]);
                                    ^^^^^^^^^^^ [1]
             11: (ret: void);
                       ^^^^ [2]

          test.js:11
           11: (ret: void);
                ^^^ Cannot cast \`ret\` to undefined because array literal [1] is incompatible with undefined [2]. [incompatible-cast]
            References:
              8:       const ret = foo([1]);
                                       ^^^ [1]
             11: (ret: void);
                       ^^^^ [2]
        `,
      )
      .because('The constant folding should turn the tuple into an array'),
    addCode(`
      (ret[5]: 1);
      (ret[5]: 2);
    `)
      .newErrors(
        `
          test.js:15
           15:       (ret[5]: 2);
                      ^^^^^^ Cannot cast \`ret[5]\` to number literal \`2\` because number [1] is incompatible with number literal \`2\` [2]. [incompatible-cast]
            References:
              8:       const ret = foo([1]);
                                        ^ [1]
             15:       (ret[5]: 2);
                                ^ [2]
        `,
      )
      .because('The element type should be `1`'),
  ]),
  test('Spreading in a tuple should produce another tuple', [
    addCode(`
      var a = [2];
      var b = [4, 5];
      var x: [1,20,30,4,5,60] = [1, ...a, 3, ...b, 6];
    `).newErrors(
        `
          test.js:6
            6:       var x: [1,20,30,4,5,60] = [1, ...a, 3, ...b, 6];
                                               ^^^^^^^^^^^^^^^^^^^^^ Cannot assign array literal to \`x\` because number [1] is incompatible with number literal \`20\` [2] in index 1. [incompatible-type]
            References:
              4:       var a = [2];
                                ^ [1]
              6:       var x: [1,20,30,4,5,60] = [1, ...a, 3, ...b, 6];
                                 ^^ [2]

          test.js:6
            6:       var x: [1,20,30,4,5,60] = [1, ...a, 3, ...b, 6];
                                                         ^ Cannot assign array literal to \`x\` because number [1] is incompatible with number literal \`30\` [2] in index 2. [incompatible-type]
            References:
              6:       var x: [1,20,30,4,5,60] = [1, ...a, 3, ...b, 6];
                                                           ^ [1]
              6:       var x: [1,20,30,4,5,60] = [1, ...a, 3, ...b, 6];
                                    ^^ [2]

          test.js:6
            6:       var x: [1,20,30,4,5,60] = [1, ...a, 3, ...b, 6];
                                                                  ^ Cannot assign array literal to \`x\` because number [1] is incompatible with number literal \`60\` [2] in index 5. [incompatible-type]
            References:
              6:       var x: [1,20,30,4,5,60] = [1, ...a, 3, ...b, 6];
                                                                    ^ [1]
              6:       var x: [1,20,30,4,5,60] = [1, ...a, 3, ...b, 6];
                                           ^^ [2]
        `,
      )
  ]),
  test('Explicit union should become an explicit union', [
    addCode(`
      function test(arr: [1] | [2, 3]): [1, 10] | [2, 3, 10] {
        return [...arr, 10];
      }
    `).noNewErrors(),
  ]),
  test('Non-polymorphic function', [
    addCode(`
      function foo(arr) {
        return [...arr, 1];
      }
      const ret1 = foo([2]);
      const ret2 = foo([3]);
    `)
      .noNewErrors(),
    addCode('(ret1[0]: 2);')
      .newErrors(
        `
          test.js:11
           11: (ret1[0]: 2);
                ^^^^^^^ Cannot cast \`ret1[0]\` to number literal \`2\` because number [1] is incompatible with number literal \`2\` [2]. [incompatible-cast]
            References:
              8:       const ret2 = foo([3]);
                                         ^ [1]
             11: (ret1[0]: 2);
                           ^ [2]
        `,
      )
      .because('Flow infers the return type to [2,1] | [3,1]'),
    addCode('(ret2[0]: 3);')
      .newErrors(
        `
          test.js:13
           13: (ret2[0]: 3);
                ^^^^^^^ Cannot cast \`ret2[0]\` to number literal \`3\` because number [1] is incompatible with number literal \`3\` [2]. [incompatible-cast]
            References:
              7:       const ret1 = foo([2]);
                                         ^ [1]
             13: (ret2[0]: 3);
                           ^ [2]
        `,
      )
      .because('Flow infers the return type to [2,1] | [3,1]'),
  ]),
  test('Spreading an Array<T> should result in a non-tuple array', [
    addCode(`
      const tup: Array<number> = [1,2,3];
      const nonTup = [...tup];
      (nonTup: [1,2,3]);
    `).newErrors(
        `
          test.js:6
            6:       (nonTup: [1,2,3]);
                      ^^^^^^ Cannot cast \`nonTup\` to tuple type because array literal [1] has an unknown number of elements, so is incompatible with tuple type [2]. [invalid-tuple-arity]
            References:
              5:       const nonTup = [...tup];
                                      ^^^^^^^^ [1]
              6:       (nonTup: [1,2,3]);
                                ^^^^^^^ [2]
        `,
      )
  ]),
  test('Spreading a $ReadOnlyArray should result in a non-tuple array', [
    addCode(`
      const tup: $ReadOnlyArray<number> = [1,2,3];
      const nonTup = [...tup];
      (nonTup: [1,2,3]);
    `).newErrors(
        `
          test.js:6
            6:       (nonTup: [1,2,3]);
                      ^^^^^^ Cannot cast \`nonTup\` to tuple type because array literal [1] has an unknown number of elements, so is incompatible with tuple type [2]. [invalid-tuple-arity]
            References:
              5:       const nonTup = [...tup];
                                      ^^^^^^^^ [1]
              6:       (nonTup: [1,2,3]);
                                ^^^^^^^ [2]
        `,
      )
  ]),
  test('Spreading a string', [
    addCode('const arr: Array<number> = [..."hello"];')
      .newErrors(
        `
          test.js:3
            3: const arr: Array<number> = [..."hello"];
                                          ^^^^^^^^^^^^ Cannot assign array literal to \`arr\` because string [1] is incompatible with number [2] in array element. [incompatible-type]
            References:
            1083:     @@iterator(): Iterator<string>;
                                             ^^^^^^ [1]. See lib: [LIB] core.js:1083
              3: const arr: Array<number> = [..."hello"];
                                  ^^^^^^ [2]
        `,
      )
      .because('String is an Iterable<string>'),
  ]),
  test('Spreading a generator', [
    addCode(`
      function *foo(): Generator<string, void, void> {
        yield "hello";
      }
      const arr: Array<number> = [...foo()];
    `).newErrors(
        `
          test.js:7
            7:       const arr: Array<number> = [...foo()];
                                                ^^^^^^^^^^ Cannot assign array literal to \`arr\` because string [1] is incompatible with number [2] in array element. [incompatible-type]
            References:
              4:       function *foo(): Generator<string, void, void> {
                                                  ^^^^^^ [1]
              7:       const arr: Array<number> = [...foo()];
                                        ^^^^^^ [2]
        `,
      )
      .because('Generators are iterables too!'),
  ]),
  test('Spreading an iterator', [
    addCode(`
      function test(iter: Iterable<string>): Array<number> {
        return [...iter];
      }
    `).newErrors(
        `
          test.js:5
            5:         return [...iter];
                              ^^^^^^^^^ Cannot return array literal because string [1] is incompatible with number [2] in array element. [incompatible-return]
            References:
              4:       function test(iter: Iterable<string>): Array<number> {
                                                    ^^^^^^ [1]
              4:       function test(iter: Iterable<string>): Array<number> {
                                                                    ^^^^^^ [2]
        `,
      )
      .because('Spec says you can spread iterables')
  ]),
  test('Spreading Object', [
    addCode(`
      function test(iter: Object): string {
        return [...iter];
      }
    `).noNewErrors()
      .because(
        'You can spread Object since it might be an Iterable. It is treated ' +
          'like spreading any, which results in any'
      ),
  ]),
]): Suite);