@@ -18,7 +18,29 @@ limitations under the License.
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package transport
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+ // this is just to make the "unused" linter rule happy
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+ var _ = isCacheKeyComparable [tlsCacheKey ]
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+
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// assert at compile time that tlsCacheKey is comparable in a way that will never panic at runtime.
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- var _ = isComparable [tlsCacheKey ]
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+ //
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+ // Golang 1.20 introduced an exception to type constraints that allows comparable, but not
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+ // necessarily strictly comparable type arguments to satisfy the `comparable` type constraint,
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+ // thus allowing interfaces to fulfil the `comparable` constraint.
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+ // However, by definition, "A comparison of two interface values with identical
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+ // dynamic types causes a run-time panic if that type is not comparable".
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+ //
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+ // We want to make sure that comparing two `tlsCacheKey` elements won't cause a
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+ // runtime panic. In order to do that, we'll force the `tlsCacheKey` to be strictly
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+ // comparable, thus making it impossible for it to contain interfaces.
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+ // To assert strict comparability, we'll use another definition: "Type
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+ // parameters are comparable if they are strictly comparable".
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+ // Below, we first construct a type parameter from the `tlsCacheKey` type so that
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+ // we can then push this type parameter to a comparable check, thus checking these
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+ // are strictly comparable.
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+ //
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+ // Original suggestion from https://github.com/golang/go/issues/56548#issuecomment-1317673963
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+ func isCacheKeyComparable [K tlsCacheKey ]() {
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+ _ = isComparable [K ]
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+ }
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func isComparable [T comparable ]() {}
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