[PATCH] D99560: Utility to construct visitors from lambdas.

[David Blaikie via Phabricator via llvm-commits]

dblaikie added a comment.

In D99560#2667327 <https://reviews.llvm.org/D99560#2667327>, @ezhulenev wrote:

> It’s impossible to statically dispatch to the correct lambda with such API (or at least a very difficult exercise). std::visit takes a single visitor and multiple variants, not the other way around. Stitching lambdas together is just one way of constructing a visitor type, it can be a plain old class with overloaded operator() set.

ah, fair point about the std::visit API design taking a type with op() overloads and using that to resolve which call, etc.

could makeVisitor at least be improved to support move-only functors (& avoid unnecessary copies of copyable functors too, when they could instead be efficiently moved), perhaps? I hope that wouldn't add too much complexity (probably a few std::forwards here and there)


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