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subtyping bug in rule for var <: T #26131

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JeffBezanson opened this issue Feb 20, 2018 · 0 comments
Closed

subtyping bug in rule for var <: T #26131

JeffBezanson opened this issue Feb 20, 2018 · 0 comments
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@JeffBezanson
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domain:types and dispatch Types, subtyping and method dispatch kind:bug Indicates an unexpected problem or unintended behavior

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@JeffBezanson
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Found by @julbinb:

julia> Vector{Vector{Number}}  <:
           Vector{Union{Vector{Number}, Vector{S}}} where S<:Integer
true

The cause is in the function var_lt. A comment there claims that updating bb->ub = a instead of bb->ub = meet(bb->ub, a) is correct, but it turns out not to be. It should be possible to fix this for many practical cases by defining a simple_meet (to go with simple_join) and using it here.
@JeffBezanson JeffBezanson added kind:bug Indicates an unexpected problem or unintended behavior domain:types and dispatch Types, subtyping and method dispatch labels Feb 20, 2018
@JeffBezanson JeffBezanson self-assigned this Apr 3, 2018
JeffBezanson added a commit that referenced this issue Apr 6, 2018
@JeffBezanson
fix #26131, unsound updating of variable upper bounds in subtyping
a8160ab
JeffBezanson added a commit that referenced this issue May 28, 2018
@JeffBezanson
fix #26131, unsound updating of variable upper bounds in subtyping
02d4fdd
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