Merge master.

1 files changed, 79 insertions, 29 deletions

diff --git a/doc/limitations.md b/doc/limitations.md
index 9b4ed9c6f..6958d396f 100644
--- a/doc/limitations.md
+++ b/doc/limitations.md
@@ -14,17 +14,17 @@ This document does not contain a complete list of limitations.
 Please help to improve it by submitting your findings.
 
 
-## ```1/2``` gives ```0.5```
+## `1/2` gives `0.5`
 
-Since mruby does not have ```Bignum```, bigger integers are represented
-by ```Float``` numbers. To enhance interoperability between ```Fixnum```
-and ```Float```, mruby provides ```Float#upto``` and other iterating
-methods for the ```Float``` class.  As a side effect, ```1/2``` gives ```0.5```
-not ```0```.
+Since mruby does not have `Bignum`, bigger integers are represented
+by `Float` numbers. To enhance interoperability between `Fixnum`
+and `Float`, mruby provides `Float#upto` and other iterating
+methods for the `Float` class.  As a side effect, `1/2` gives `0.5`
+not `0`.
 
-## ```Array``` passed to ```puts```
+## `Array` passed to `puts`
 
-Passing an Array to ```puts``` results in different output.
+Passing an Array to `puts` results in different output.
 
 ```ruby
 puts [1,2,3]
@@ -44,9 +44,9 @@ puts [1,2,3]
 [1, 2, 3]
 ```
 
-## ```Kernel.raise``` in rescue clause
+## `Kernel.raise` in rescue clause
 
-```Kernel.raise``` without arguments does not raise the current exception within
+`Kernel.raise` without arguments does not raise the current exception within
 a rescue clause.
 
 ```ruby
@@ -59,7 +59,7 @@ end
 
 #### Ruby [ruby 2.0.0p645 (2015-04-13 revision 50299)]
 
-```ZeroDivisionError``` is raised.
+`ZeroDivisionError` is raised.
 
 #### mruby [2.0.1 (2019-4-4)]
 
@@ -67,13 +67,13 @@ No exception is raised.
 
 ## Fiber execution can't cross C function boundary
 
-mruby's ```Fiber``` is implemented in a similar way to Lua's co-routine. This
+mruby's `Fiber` is implemented in a similar way to Lua's co-routine. This
 results in the consequence that you can't switch context within C functions.
-Only exception is ```mrb_fiber_yield``` at return.
+Only exception is `mrb_fiber_yield` at return.
 
-## ```Array``` does not support instance variables
+## `Array` does not support instance variables
 
-To reduce memory consumption ```Array``` does not support instance variables.
+To reduce memory consumption `Array` does not support instance variables.
 
 ```ruby
 class Liste < Array
@@ -87,16 +87,16 @@ p Liste.new "foobar"
 
 #### Ruby [ruby 2.0.0p645 (2015-04-13 revision 50299)]
 
-``` [] ```
+` [] `
 
 #### mruby [2.0.1 (2019-4-4)]
 
-```ArgumentError``` is raised.
+`ArgumentError` is raised.
 
 ## Method visibility
 
 For simplicity reasons no method visibility (public/private/protected) is
-supported.
+supported. Those methods are defined but they are dummy methods.
 
 ```ruby
 class VisibleTest
@@ -126,10 +126,46 @@ true
 true
 ```
 
-## defined?
+### Visibility Declaration
 
-The ```defined?``` keyword is considered too complex to be fully
-implemented. It is recommended to use ```const_defined?``` and
+The declaration form of following visibility methods are not implemented.
+
+* `public`
+* `private`
+* `protected`
+* `module_function`
+
+Especially, `module_function` method is not dummy, but no declaration form.
+
+```
+module TestModule
+  module_function
+  def test_func
+    p 'test_func called'
+  end
+
+  test_func
+end
+
+p 'ok'
+```
+
+#### Ruby [ruby 2.5.5p157 (2019-03-15 revision 67260)]
+
+```
+ok
+```
+
+#### mruby [2.0.1 (2019-4-4)]
+
+```
+test.rb:8: undefined method 'test_func' (NoMethodError)
+```
+
+## `defined?`
+
+The `defined?` keyword is considered too complex to be fully
+implemented. It is recommended to use `const_defined?` and
 other reflection methods instead.
 
 ```ruby
@@ -144,9 +180,9 @@ nil
 
 #### mruby [2.0.1 (2019-4-4)]
 
-```NameError``` is raised.
+`NameError` is raised.
 
-## ```alias``` on global variables
+## `alias` on global variables
 
 Aliasing a global variable works in CRuby but is not part
 of the ISO standard.
@@ -157,7 +193,7 @@ alias $a $__a__
 
 #### Ruby [ruby 2.0.0p645 (2015-04-13 revision 50299)]
 
-``` nil ```
+` nil `
 
 #### mruby [2.0.1 (2019-4-4)]
 
@@ -178,15 +214,15 @@ end
 
 #### Ruby [ruby 2.0.0p645 (2015-04-13 revision 50299)]
 
-```ArgumentError``` is raised.
-The re-defined ```+``` operator does not accept any arguments.
+`ArgumentError` is raised.
+The re-defined `+` operator does not accept any arguments.
 
 #### mruby [2.0.1 (2019-4-4)]
 
-``` 'ab' ```
+` 'ab' `
 Behavior of the operator wasn't changed.
 
-## Kernel#binding is not supported
+## `Kernel#binding` is not supported
 
 `Kernel#binding` method is not supported.
 
@@ -238,7 +274,7 @@ Destructured arguments (`b` and `c` in above example) cannot be accessed
 from the default expression of optional arguments and keyword arguments,
 since actual assignment is done after the evaluation of those default
 expressions. Thus:
-    
+
 ```ruby
 def f(a,(b,c),d=b)
   p [a,b,c,d]
@@ -247,3 +283,17 @@ f(1,[2,3])
 ```
 
 CRuby gives `[1,2,3,nil]`. mruby raises `NoMethodError` for `b`.
+
+## `nil?` redefinition in conditional expressions
+
+Redefinition of `nil?` is ignored in conditional expressions.
+
+```ruby
+a = "a"
+def a.nil?
+  true
+end
+puts(a.nil? ? "truthy" : "falsy")
+```
+
+Ruby outputs `falsy`. mruby outputs `truthy`.