[CS1] fix #4260 and #1349: splat error with soak properties or expressions (#4643)

* fix splat error with soak properties or expressions

* Add test based on #4260

* Add test based on #1349

* remove 'void 0' replacement; add Splat::compileNode

Author: zdenko

lib/coffee-script/nodes.js

@@ -1812,7 +1812,7 @@ exports.Splat = class Splat extends Base
   assigns: (name) ->
     @name.assigns name
 
-  compileToFragments: (o) ->
+  compileNode: (o) ->
     @name.compileToFragments o
 
   unwrap: -> @name

src/nodes.coffee

@@ -36,9 +36,7 @@ test "array splat expansions with assignments", ->
   eq 4, b
   arrayEq [0,1,2,3,4], list
 
-
 test "mixed shorthand objects in array lists", ->
-
   arr = [
     a:1
     'b'
@@ -58,7 +56,6 @@ test "mixed shorthand objects in array lists", ->
   eq arr[2].b, 1
   eq arr[3], 'b'
 
-
 test "array splats with nested arrays", ->
   nonce = {}
   a = [nonce]
@@ -70,6 +67,30 @@ test "array splats with nested arrays", ->
   list = [1, 2, a...]
   arrayEq list, [1, 2, [nonce]]
 
+test "#4260: splat after existential operator soak", ->
+  a = {b: [3]}
+  foo = (a) -> [a]
+  arrayEq [a?.b...], [3]
+  arrayEq [c?.b ? []...], []
+  arrayEq foo(a?.b...), [3]
+  arrayEq foo(c?.b ? []...), [undefined]
+  e = yes
+  f = null
+  arrayEq [(a if e)?.b...], [3]
+  arrayEq [(a if f)?.b ? []...], []
+  arrayEq foo((a if e)?.b...), [3]
+  arrayEq foo((a if f)?.b ? []...), [undefined]
+
+test "#1349: trailing if after splat", ->
+  a = [3]
+  b = yes
+  c = null
+  foo = (a) -> [a]
+  arrayEq [a if b...], [3]
+  arrayEq [(a if c) ? []...], []
+  arrayEq foo((a if b)...), [3]
+  arrayEq foo((a if c) ? []...), [undefined]
+
 test "#1274: `[] = a()` compiles to `false` instead of `a()`", ->
   a = false
   fn = -> a = true