8000 flow-sensitivity should understand instance_of? (or we should warn about it) · Issue #48 · sorbet/sorbet · GitHub
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flow-sensitivity should understand instance_of? (or we should warn about it) #48

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DarkDimius opened this issue Jan 16, 2019 · 2 comments · Fixed by #8868
Closed

flow-sensitivity should understand instance_of? (or we should warn about it) #48

DarkDimius opened this issue Jan 16, 2019 · 2 comments · Fixed by #8868
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good first issue Good for newcomers

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@DarkDimius
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https://ruby-doc.org/core-2.4.3/Object.html#method-i-instance_of-3F looks to be a synonym for {{is_a?}}

@btidor-stripe just ran into this and was confused

Originally reported by @nelhage-stripe at https://jira.corp.stripe.com/browse/RUBYPLAT-1371
@DarkDimius DarkDimius added the good first issue Good for newcomers label Jan 16, 2019
marianosimone added a commit that referenced this issue Aug 15, 2020
@marianosimone
Make flow-sensitivity understand instance_of?
5cbe0bd 
This makes sure that, after calling `instance_of?` on an object, Sorbet
knows about the type.

Fixes #48
@marianosimone marianosimone mentioned this issue Aug 15, 2020
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@marianosimone marianosimone self-assigned this Aug 15, 2020
@marianosimone
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Taking a stab at this...

For completeness-sake, this is how I reproduced the issue:

view on sorbet.run

# typed: true
class A; end

def main
  a = T.let(A.new, T.any(A, Float))
  if a.is_a?(A)
    T.assert_type!(a, A)
  end
    if a.instance_of?(A)
    T.assert_type!(a, A)
  end
end

Output:

editor.rb:10: Argument does not have asserted type A https://srb.help/7007
    10 |    T.assert_type!(a, A)
            ^^^^^^^^^^^^^^^^^^^^
  Got T.any(Float, A) originating from:
    editor.rb:5:
     5 |  a = T.let(A.new, T.any(A, Float))
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    editor.rb:6:
     6 |  if a.is_a?(A)
             ^^^^^^^^^^
Errors: 1

Expected: No errors

Note that instance_of? is NOT a synonym of is_a?, as the latter takes inheritance into account, while the former does not.

@marianosimone marianosimone removed their assignment Aug 15, 2020
@marianosimone
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My original attempt won't work (as seen in #3364).

The basic reason is that we can't make assumptions for instance_of? the same way it doe about is_a?: is_a? ensures that something is of a particular type or any of its descendants, while instance_of? tests for a specific type.

@Morriar Morriar mentioned this issue Jun 30, 2021
Merged
elliottt pushed a commit that referenced this issue Jul 30, 2021
@jez
Random improvements to wrap-intrinsics.rb (#48)
05ec14b 
* Add two extern special-cases (rb_int_powm, rb_f_send)

* Explicit whitelist of methods to export

* Ensure sorted output order

* Better printing information

* Ignore -2 calling convention

* Don't clang-format WrappedIntrinsics.h

* Add whitelist of valid SymbolRefs

* Make patch regex more strict

* (cd compiler/IREmitter/Intrinsics/ && make)
@jez jez mentioned this issue May 14, 2025
Merged
@jez jez closed this as completed in #8868 May 14, 2025
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