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jashkenas--coffeescript/test/operators.coffee
Chris Connelly 8d81804fee [CS2] Compile class constructors to ES2015 classes (#4354) 
* Compile classes to ES2015 classes

Rather than compiling classes to named functions with prototype and
class assignments, they are now compiled to ES2015 class declarations.

Backwards compatibility has been maintained by compiling ES2015-
incompatible properties as prototype or class assignments. `super`
continues to be compiled as before.

Where possible, classes will be compiled "bare", without an enclosing
IIFE. This is possible when the class contains only ES2015 compatible
expressions (methods and static methods), and has no parent (this last
constraint is a result of the legacy `super` compilation, and could be
removed once ES2015 `super` is being used). Classes are still assigned
to variables to maintain compatibility for assigned class expressions.

There are a few changes to existing functionality that could break
backwards compatibility:

- Derived constructors that deliberately don't call `super` are no
  longer possible. ES2015 derived classes can't use `this` unless the
  parent constructor has been called, so it's now called implicitly when
  not present.

- As a consequence of the above, derived constructors with @ parameters
  or bound methods and explicit `super` calls are not allowed. The
  implicit `super` must be used in these cases.

* Add tests to verify class interoperability with ES

* Refactor class nodes to separate executable body logic

Logic has been redistributed amongst the class nodes so that:

- `Class` contains the logic necessary to compile an ES class
  declaration.
- `ExecutableClassBody` contains the logic necessary to compile CS'
  class extensions that require an executable class body.

`Class` still necessarily contains logic to determine whether an
expression is valid in an ES class initializer or not. If any invalid
expressions are found then `Class` will wrap itself in an
`ExecutableClassBody` when compiling.

* Rename `Code#static` to `Code#isStatic`

This naming is more consistent with other `Code` flags.

* Output anonymous classes when possible

Anonymous classes can be output when:

- The class has no parent. The current super compilation needs a class
  variable to reference. This condition will go away when ES2015 super
  is in use.
- The class contains no bound static methods. Bound static methods have
  their context set to the class name.

* Throw errors at compile time for async or generator constructors

* Improve handling of anonymous classes

Anonymous classes are now always anonymous. If a name is required (e.g.
for bound static methods or derived classes) then the class is compiled
in an `ExecutableClassBody` which will give the anonymous class a stable
reference.

* Add a `replaceInContext` method to `Node`

`replaceInContext` will traverse children looking for a node for which
`match` returns true. Once found, the matching node will be replaced by
the result of calling `replacement`.

* Separate `this` assignments from function parameters

This change has been made to simplify two future changes:

1. Outputting `@`-param assignments after a `super` call.
   In this case it is necessary that non-`@` parameters are available
   before `super` is called, so destructuring has to happen before
   `this` assignment.
2. Compiling destructured assignment to ES6
   In this case also destructuring has to happen before `this`,
   as destructuring can happen in the arguments list, but `this`
   assignment can not.

A bonus side-effect is that default values for `@` params are now output
as ES6 default parameters, e.g.

    (@a = 1) ->

becomes

    function a (a = 1) {
      this.a = a;
    }

* Change `super` handling in class constructors

Inside an ES derived constructor (a constructor for a class that extends
another class), it is impossible to access `this` until `super` has been
called. This conflicts with CoffeeScript's `@`-param and bound method
features, which compile to `this` references at the top of a function
body. For example:

    class B extends A
      constructor: (@param) -> super
      method: =>

This would compile to something like:

    class B extends A {
      constructor (param) {
        this.param = param;
        this.method = bind(this.method, this);
        super(...arguments);
      }
    }

This would break in an ES-compliant runtime as there are `this`
references before the call to `super`. Before this commit we were
dealing with this by injecting an implicit `super` call into derived
constructors that do not already have an explicit `super` call.
Furthermore, we would disallow explicit `super` calls in derived
constructors that used bound methods or `@`-params, meaning the above
example would need to be rewritten as:

    class B extends A
      constructor: (@param) ->
      method: =>

This would result in a call to `super(...arguments)` being generated as
the first expression in `B#constructor`.

Whilst this approach seems to work pretty well, and is arguably more
convenient than having to manually call `super` when you don't
particularly care about the arguments, it does introduce some 'magic'
and separation from ES, and would likely be a pain point in a project
that made use of significant constructor overriding.

This commit introduces a mechanism through which `super` in constructors
is 'expanded' to include any generated `this` assignments, whilst
retaining the same semantics of a super call. The first example above
now compiles to something like:

    class B extends A {
      constructor (param) {
        var ref
        ref = super(...arguments), this.param = param, this.method = bind(this.method, this), ref;
      }
   }

* Improve `super` handling in constructors

Rather than functions expanding their `super` calls, the `SuperCall`
node can now be given a list of `thisAssignments` to apply when it is
compiled.

This allows us to use the normal compiler machinery to determine whether
the `super` result needs to be cached, whether it appears inline or not,
etc.

* Fix anonymous classes at the top level

Anonymous classes in ES are only valid within expressions. If an
anonymous class is at the top level it will now be wrapped in
parenthses to force it into an expression.

* Re-add Parens wrapper around executable class bodies

This was lost in the refactoring, but it necessary to ensure
`new class ...` works as expected when there's an executable body.

* Throw compiler errors for badly configured derived constructors

Rather than letting them become runtime errors, the following checks are
now performed when compiling a derived constructor:

- The constructor **must** include a call to `super`.
- The constructor **must not** reference `this` in the function body
  before `super` has been called.

* Add some tests exercising new class behaviour

- async methods in classes
- `this` access after `super` in extended classes
- constructor super in arrow functions
- constructor functions can't be async
- constructor functions can't be generators
- derived constructors must call super
- derived constructors can't reference `this` before calling super
- generator methods in classes
- 'new' target

* Improve constructor `super` errors

Add a check for `super` in non-extended class constructors, and
explicitly mention derived constructors in the "can't reference this
before super" error.

* Fix compilation of multiple `super` paths in derived constructors

`super` can only be called once, but it can be called conditionally from
multiple locations. The chosen fix is to add the `this` assignments to
every super call.

* Additional class tests, added as a separate file to simplify testing and merging.
Some methods are commented out because they currently throw and I'm not sure how
to test for compilation errors like those.

There is also one test which I deliberately left without passing, `super` in an external prototype override.
This test should 'pass' but is really a variation on the failing `super only allowed in an instance method`
tests above it.

* Changes to the tests. Found bug in super in prototype method. fixed.

* Added failing test back in, dealing with bound functions in external prototype overrides.

* Located a bug in the compiler relating to assertions and escaped ES6 classes.

* Move tests from classes-additional.coffee into classes.coffee; comment out console.log

* Cleaned up tests and made changes based on feedback.  Test at the end still has issues, but it's commented out for now.

* Make HoistTarget.expand recursive

It's possible that a hoisted node may itself contain hoisted nodes (e.g.
a class method inside a class method). For this to work the hoisted
fragments need to be expanded recursively.

* Uncomment final test in classes.coffee

The test case now compiles, however another issue is affecting the test
due to the error for `this` before `super` triggering based on source
order rather than execution order. These have been commented out for
now.

* Fixed last test TODOs in test/classes.coffee

Turns out an expression like `this.foo = super()` won't run in JS as it
attempts to lookup `this` before evaluating `super` (i.e. throws "this
is not defined").

* Added more tests for compatability checks, statics, prototypes and ES6 expectations.  Cleaned test "nested classes with super".

* Changes to reflect feedback and to comment out issues that will be addressed seperately.

* Clean up test/classes.coffee

- Trim trailing whitespace.
- Rephrase a condition to be more idiomatic.

* Remove check for `super` in derived constructors

In order to be usable at runtime, an extended ES class must call `super`
OR return an alternative object. This check prevented the latter case,
and checking for an alternative return can't be completed statically
without control flow analysis.

* Disallow 'super' in constructor parameter defaults

There are many edge cases when combining 'super' in parameter defaults
with @-parameters and bound functions (and potentially property
initializers in the future).

Rather than attempting to resolve these edge cases, 'super' is now
explicitly disallowed in constructor parameter defaults.

* Disallow @-params in derived constructors without 'super'

@-parameters can't be assigned unless 'super' is called.
2017-01-12 21:55:30 -08:00

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# Operators
# ---------
# * Operators
# * Existential Operator (Binary)
# * Existential Operator (Unary)
# * Aliased Operators
# * [not] in/of
# * Chained Comparison
test "binary (2-ary) math operators do not require spaces", ->
a = 1
b = -1
eq +1, a*-b
eq -1, a*+b
eq +1, a/-b
eq -1, a/+b
test "operators should respect new lines as spaced", ->
a = 123 +
456
eq 579, a
b = "1#{2}3" +
"456"
eq '123456', b
test "multiple operators should space themselves", ->
eq (+ +1), (- -1)
test "compound operators on successive lines", ->
a = 1
a +=
1
eq a, 2
test "bitwise operators", ->
eq 2, (10 & 3)
eq 11, (10 | 3)
eq 9, (10 ^ 3)
eq 80, (10 << 3)
eq 1, (10 >> 3)
eq 1, (10 >>> 3)
num = 10; eq 2, (num &= 3)
num = 10; eq 11, (num |= 3)
num = 10; eq 9, (num ^= 3)
num = 10; eq 80, (num <<= 3)
num = 10; eq 1, (num >>= 3)
num = 10; eq 1, (num >>>= 3)
test "`instanceof`", ->
ok new String instanceof String
ok new Boolean instanceof Boolean
# `instanceof` supports negation by prefixing the operator with `not`
ok new Number not instanceof String
ok new Array not instanceof Boolean
test "use `::` operator on keywords `this` and `@`", ->
nonce = {}
obj =
withAt: -> @::prop
withThis: -> this::prop
obj.prototype = prop: nonce
eq nonce, obj.withAt()
eq nonce, obj.withThis()
# Existential Operator (Binary)
test "binary existential operator", ->
nonce = {}
b = a ? nonce
eq nonce, b
a = null
b = undefined
b = a ? nonce
eq nonce, b
a = false
b = a ? nonce
eq false, b
a = 0
b = a ? nonce
eq 0, b
test "binary existential operator conditionally evaluates second operand", ->
i = 1
func = -> i -= 1
result = func() ? func()
eq result, 0
test "binary existential operator with negative number", ->
a = null ? - 1
eq -1, a
# Existential Operator (Unary)
test "postfix existential operator", ->
ok (if nonexistent? then false else true)
defined = true
ok defined?
defined = false
ok defined?
test "postfix existential operator only evaluates its operand once", ->
semaphore = 0
fn = ->
ok false if semaphore
++semaphore
ok(if fn()? then true else false)
test "negated postfix existential operator", ->
ok !nothing?.value
test "postfix existential operator on expressions", ->
eq true, (1 or 0)?, true
# `is`,`isnt`,`==`,`!=`
test "`==` and `is` should be interchangeable", ->
a = b = 1
ok a is 1 and b == 1
ok a == b
ok a is b
test "`!=` and `isnt` should be interchangeable", ->
a = 0
b = 1
ok a isnt 1 and b != 0
ok a != b
ok a isnt b
# [not] in/of
# - `in` should check if an array contains a value using `indexOf`
# - `of` should check if a property is defined on an object using `in`
test "in, of", ->
arr = [1]
ok 0 of arr
ok 1 in arr
# prefixing `not` to `in and `of` should negate them
ok 1 not of arr
ok 0 not in arr
test "`in` should be able to operate on an array literal", ->
ok 2 in [0, 1, 2, 3]
ok 4 not in [0, 1, 2, 3]
arr = [0, 1, 2, 3]
ok 2 in arr
ok 4 not in arr
# should cache the value used to test the array
arr = [0]
val = 0
ok val++ in arr
ok val++ not in arr
val = 0
ok val++ of arr
ok val++ not of arr
test "`of` and `in` should be able to operate on instance variables", ->
obj = {
list: [2,3]
in_list: (value) -> value in @list
not_in_list: (value) -> value not in @list
of_list: (value) -> value of @list
not_of_list: (value) -> value not of @list
}
ok obj.in_list 3
ok obj.not_in_list 1
ok obj.of_list 0
ok obj.not_of_list 2
test "#???: `in` with cache and `__indexOf` should work in argument lists", ->
eq 1, [Object() in Array()].length
test "#737: `in` should have higher precedence than logical operators", ->
eq 1, 1 in [1] and 1
test "#768: `in` should preserve evaluation order", ->
share = 0
a = -> share++ if share is 0
b = -> share++ if share is 1
c = -> share++ if share is 2
ok a() not in [b(),c()]
eq 3, share
test "#1099: empty array after `in` should compile to `false`", ->
eq 1, [5 in []].length
eq false, do -> return 0 in []
test "#1354: optimized `in` checks should not happen when splats are present", ->
a = [6, 9]
eq 9 in [3, a...], true
test "#1100: precedence in or-test compilation of `in`", ->
ok 0 in [1 and 0]
ok 0 in [1, 1 and 0]
ok not (0 in [1, 0 or 1])
test "#1630: `in` should check `hasOwnProperty`", ->
ok undefined not in length: 1
test "#1714: lexer bug with raw range `for` followed by `in`", ->
0 for [1..2]
ok not ('a' in ['b'])
0 for [1..2]; ok not ('a' in ['b'])
0 for [1..10] # comment ending
ok not ('a' in ['b'])
# lexer state (specifically @seenFor) should be reset before each compilation
CoffeeScript.compile "0 for [1..2]"
CoffeeScript.compile "'a' in ['b']"
test "#1099: statically determined `not in []` reporting incorrect result", ->
ok 0 not in []
test "#1099: make sure expression tested gets evaluted when array is empty", ->
a = 0
(do -> a = 1) in []
eq a, 1
# Chained Comparison
test "chainable operators", ->
ok 100 > 10 > 1 > 0 > -1
ok -1 < 0 < 1 < 10 < 100
test "`is` and `isnt` may be chained", ->
ok true is not false is true is not false
ok 0 is 0 isnt 1 is 1
test "different comparison operators (`>`,`<`,`is`,etc.) may be combined", ->
ok 1 < 2 > 1
ok 10 < 20 > 2+3 is 5
test "some chainable operators can be negated by `unless`", ->
ok (true unless 0==10!=100)
test "operator precedence: `|` lower than `<`", ->
eq 1, 1 | 2 < 3 < 4
test "preserve references", ->
a = b = c = 1
# `a == b <= c` should become `a === b && b <= c`
# (this test does not seem to test for this)
ok a == b <= c
test "chained operations should evaluate each value only once", ->
a = 0
ok 1 > a++ < 1
test "#891: incorrect inversion of chained comparisons", ->
ok (true unless 0 > 1 > 2)
ok (true unless (this.NaN = 0/0) < 0/0 < this.NaN)
test "#1234: Applying a splat to :: applies the splat to the wrong object", ->
nonce = {}
class C
method: -> @nonce
nonce: nonce
arr = []
eq nonce, C::method arr... # should be applied to `C::`
test "#1102: String literal prevents line continuation", ->
eq "': '", '' +
"': '"
test "#1703, ---x is invalid JS", ->
x = 2
eq (- --x), -1
test "Regression with implicit calls against an indented assignment", ->
eq 1, a =
1
eq a, 1
test "#2155 ... conditional assignment to a closure", ->
x = null
func = -> x ?= (-> if true then 'hi')
func()
eq x(), 'hi'
test "#2197: Existential existential double trouble", ->
counter = 0
func = -> counter++
func()? ? 100
eq counter, 1
test "#2567: Optimization of negated existential produces correct result", ->
a = 1
ok !(!a?)
ok !b?
test "#2508: Existential access of the prototype", ->
eq NonExistent?::nothing, undefined
ok Object?::toString
test "power operator", ->
eq 27, 3 ** 3
test "power operator has higher precedence than other maths operators", ->
eq 55, 1 + 3 ** 3 * 2
eq -4, -2 ** 2
eq false, !2 ** 2
eq 0, (!2) ** 2
eq -2, ~1 ** 5
test "power operator is right associative", ->
eq 2, 2 ** 1 ** 3
test "power operator compound assignment", ->
a = 2
a **= 3
eq 8, a
test "floor division operator", ->
eq 2, 7 // 3
eq -3, -7 // 3
eq NaN, 0 // 0
test "floor division operator compound assignment", ->
a = 7
a //= 1 + 1
eq 3, a
test "modulo operator", ->
check = (a, b, expected) ->
eq expected, a %% b, "expected #{a} %%%% #{b} to be #{expected}"
check 0, 1, 0
check 0, -1, -0
check 1, 0, NaN
check 1, 2, 1
check 1, -2, -1
check 1, 3, 1
check 2, 3, 2
check 3, 3, 0
check 4, 3, 1
check -1, 3, 2
check -2, 3, 1
check -3, 3, 0
check -4, 3, 2
check 5.5, 2.5, 0.5
check -5.5, 2.5, 2.0
test "modulo operator compound assignment", ->
a = -2
a %%= 5
eq 3, a
test "modulo operator converts arguments to numbers", ->
eq 1, 1 %% '42'
eq 1, '1' %% 42
eq 1, '1' %% '42'
test "#3361: Modulo operator coerces right operand once", ->
count = 0
res = 42 %% valueOf: -> count += 1
eq 1, count
eq 0, res
test "#3363: Modulo operator coercing order", ->
count = 2
a = valueOf: -> count *= 2
b = valueOf: -> count += 1
eq 4, a %% b
eq 5, count
test "#3598: Unary + and - coerce the operand once when it is an identifier", ->
# Unary + and - do not generate `_ref`s when the operand is a number, for
# readability. To make sure that they do when the operand is an identifier,
# test that they are consistent with another unary operator as well as another
# complex expression.
# Tip: Making one of the tests temporarily fail lets you easily inspect the
# compiled JavaScript.
assertOneCoercion = (fn) ->
count = 0
value = valueOf: -> count++; 1
fn value
eq 1, count
eq 1, 1 ? 0
eq 1, +1 ? 0
eq -1, -1 ? 0
assertOneCoercion (a) ->
eq 1, +a ? 0
assertOneCoercion (a) ->
eq -1, -a ? 0
assertOneCoercion (a) ->
eq -2, ~a ? 0
assertOneCoercion (a) ->
eq 0.5, a / 2 ? 0
ok -2 <= 1 < 2
ok -2 <= +1 < 2
ok -2 <= -1 < 2
assertOneCoercion (a) ->
ok -2 <= +a < 2
assertOneCoercion (a) ->
ok -2 <= -a < 2
assertOneCoercion (a) ->
ok -2 <= ~a < 2
assertOneCoercion (a) ->
ok -2 <= a / 2 < 2
arrayEq [0], (n for n in [0] by 1)
arrayEq [0], (n for n in [0] by +1)
arrayEq [0], (n for n in [0] by -1)
assertOneCoercion (a) ->
arrayEq [0], (n for n in [0] by +a)
assertOneCoercion (a) ->
arrayEq [0], (n for n in [0] by -a)
assertOneCoercion (a) ->
arrayEq [0], (n for n in [0] by ~a)
assertOneCoercion (a) ->
arrayEq [0], (n for n in [0] by a * 2 / 2)
ok 1 in [0, 1]
ok +1 in [0, 1]
ok -1 in [0, -1]
assertOneCoercion (a) ->
ok +a in [0, 1]
assertOneCoercion (a) ->
ok -a in [0, -1]
assertOneCoercion (a) ->
ok ~a in [0, -2]
assertOneCoercion (a) ->
ok a / 2 in [0, 0.5]
test "'new' target", ->
nonce = {}
ctor = -> nonce
eq (new ctor), nonce
eq (new ctor()), nonce
ok new class
ctor = class
ok (new ctor) instanceof ctor
ok (new ctor()) instanceof ctor
# Force an executable class body
ctor = class then a = 1
ok (new ctor) instanceof ctor
get = -> ctor
ok (new get()) not instanceof ctor
ok (new (get())()) instanceof ctor
# classes must be called with `new`. In this case `new` applies to `get` only
throws -> new get()()
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