Slava Pestov 8e4598e622 GSB: Narrow scope of conditional requirement inference ...

If we have a conformance requirement T : P, and a concrete type
requirement T == G<...>, and G _conditionally_ conforms to P,
we would infer the conditional requirements of G needed to
satisfy the conformance.

However, if the conformance requirement T : P was not explicit,
this would mean in practice that we would need to infer an
infinite number of conditional requirements, because there
might be an infinite number of types T for which T : P.

Previously we would infer these up to some limit, based on
how many levels of nested types the GSB had expanded.

Since this is untenable, let's instead change the rules so
that conditional requirement inference is only performed
when the concretizing requirement was explicit.

2021-03-16 23:29:13 -04:00

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