Support intersection of array type and object type

[samwgoldman]

/* @flow */                                                                                                                           

type T = { foo: string } & number[];                                                                                                  

function foo(): T {                                                                                                                   
  let x = [];                                                                                                                         
  x.foo = "";                                                                                                                         
  return x; // Can't create an inhabitant                                                                                             
}                                                                                                                                     

function foo(x: T): void {                                                                                                            
  // $ExpectError x.foo is a string, not a number                                                                                     
  (x.foo : number);                                                                                                                   

  // $ExpectError x.length is a number (from Array.prototype.length), not a string                                                    
  (x.length : string);                                                                                                                

  // $ExpectError x[0] is a number, not a string                                                                                      
  (x[0] : string);                                                                                                                    
}                                                                                                                                     

test.js:7
  7:   x.foo = "";
         ^^^ property `foo`. Property not found in
  7:   x.foo = "";
       ^^^^^ Array

test.js:8
  8:   return x; // Can't create an inhabitant
              ^ empty array literal. This type is incompatible with
  3: type T = { foo: string } & number[];
              ^^^^^^^^^^^^^^^ object type

test.js:18
 18:   // $ExpectError x[0] is a number, not a string
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Error suppressing comment. Unused suppression

[SamChou19815]

https://flow.org/try/#1N4Igxg9gdgZglgcxALlAIwIZoKYBsD6uEEAztvhgE6UYCe+JADpdhgCYowa5kA0I2KAFcAtiRQAXSkOz9sADwxgJ+NPTbYuQ3BMnTZA+Y2yU4IwRO4A6SFBIrGVDGM7c+h46fNRLuKxJIGWh8MeT0ZfhYlCStpHzNsFBAMIQkIEQwJODAQfiEyfBE4eWw2fDgofDBMsAALfAA3KjgsXGxxZC4eAw0G-GhcWn9aY3wWZlduuSMTBJC-Mgz4sHwNSBos6A6u9w1mbGqJUoBaCRHEzrcDEgBrbAk62mPhXFxJ91v7x+fRHEp3gxCKBgNpUU7nAF5KBQA7tEhUJ4VJqmDA+SEgIEwsBwhHHCCMTZQbjHOoYCrooHwmDYY4Ie5HSgkY5kCQM7ZXKH5E7MdJwMgAgC+-EgGiSAHoAFQAAgAAjAiAB3KUSsVStXqjWarXanW6vX6g2Go3G9UAHSg5rOxilABUpQBeKXAKUwYjIKX2UxQBBSgVSgBkUuEIj+AG0ALoAbhNMdjcfjOvN5pgQOUcGgLuIAEYABQASnddudCZLpbLZfNaraEil8kLDqlEej5ZbrbbRsrtasrogDdNIH7zfbw5H7c7LAkQkoUFr0bFqoAwqiAOQ1sBRI5S1FSiq1LBwSw+UfHtvmv0ni+X1tJ2CpwmZiAAJhzddtBalDQgcDYTqvf+PnbzlKAAkACiMzKKB1AQJQXY9juJBbh6UgVAgvBBhANYYEGvwmP++Fap2L7dsQUrusGfx5kOBE0WOFozlKQFgRBEhQZQMFdm03oSLUCFIRReE5jA7EiFKACC1B0FYPJpFa2BWFxCA8Xm6FQJhSGeqhtG6kR8gKYISm8e6mnelR2nmaWN5qkx4HGJB0GwfIoYAAzhnx2ECZQqnqdhJk+hZ-66S5bnGShpnUQFkUxme8a5CADQmCQ6ZQEkDTOVYj4ACwAMxWM5IACkAA

This seems to be supported now, except that it's still impossible to create a value that satisfies the type, but that's expected