Issue #15780 has been reported by fxn (Xavier Noria).

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Bug #15780: Module#const_defined?(String) executes autoloads
https://bugs.ruby-lang.org/issues/15780

* Author: fxn (Xavier Noria)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.6.1p33 (2019-01-30 revision 66950) [x86_64-darwin18]
* Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN
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The documentation of `Module#const_defined?` says that autoloads are not executed:

> [...] if the constant is not present but there is an autoload for it, true is returned directly without autoloading.

While this seems to work as documented for symbols, constant names passed as strings trigger the autoload:

```
$ cat x.rb
p X = 1

$ cat foo.rb
Object.autoload("X", "x")
p Object.const_defined?("X")

$ ruby -I. foo.rb
1
true
```



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