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do not fetch variance for items when equating - #41913
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Fixesrust-lang#41849. Problem was that evaluating the constant expression required evaluating a trait, which would equate types, which would request variance information, which it would then discard. However, computing the variance information would require determining the type of a field, which would evaluate the constant expression. (This problem will potentially arise *later* as we move to more sophisticated constants, however, where we need to check subtyping. We can tackle that when we come to it.)
nikomatsakis
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May 11, 2017
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Nominated for beta -- regression. |
eddyb
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May 11, 2017
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@bors r+ |
bors
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May 11, 2017
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📌 Commit d22d1fe has been approved by |
bors
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May 11, 2017
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May 11, 2017
do not fetch variance for items when equating Fixes#41849. Problem was that evaluating the constant expression required evaluating a trait, which would equate types, which would request variance information, which it would then discard. However, computing the variance information would require determining the type of a field, which would evaluate the constant expression. (This problem will potentially arise *later* as we move to more sophisticated constants, however, where we need to check subtyping. We can tackle that when we come to it.) r? @eddyb
bors
commented
May 11, 2017
Collaborator
☀️ Test successful - status-appveyor, status-travis |
brson
commented
May 23, 2017
Contributor
Accepted for beta because I trust niko. |
brson
commented
May 23, 2017
Contributor
Doesn't pick cleanly @nikomatsakis |
Merged
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Fixes#41849. Problem was that evaluating the constant expression
required evaluating a trait, which would equate types, which would
request variance information, which it would then discard. However,
computing the variance information would require determining the type of
a field, which would evaluate the constant expression.
(This problem will potentially arise later as we move to more sophisticated
constants, however, where we need to check subtyping. We can tackle that
when we come to it.)
r? @eddyb