Compiler: let Proc(T) pass a restriction of Proc(Nil) #8969
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asterite
changed the title
| # If checking the return type, any type matches Nil | ||
| if i == other.type_vars.size - 1 && nil_type?(other_type_var, context) | ||
| # Also, all other types matched, so the matching type is this proc type | ||
| # except that it has a Nil return type |
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I thought the proc were honoring subtyping of arrow types.
It is safe for the following example to compile.
class Foo
end
class Bar < Foo
end
def foo(x : Proc(Bar, Nil))
x
end
a = 1
proc = foo(->(b : Foo) { a = 2 })
r = proc.call(Bar.new)It is subject for a later change, but is the subtying of arrow type in procs that we are missing it seems.
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Yeah, we need to make subtyping work, but it won't work all of the time: only for class references. For structs it's not possible because the representation is different. Also for unions, I think. So for now I didn't implement it until we think it well. But matching against Nil is more common and easier to check.
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I won't merge any more PRs because I don't know whether they should be in 0.34.0 or later. |
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I think this is safe to fit into 0.34 since it's handling more cases without loosing or changing others. On my end, feel free to merge it if you want. |
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Thanks @asterite! |
Fixes #8964