tree dc6b595b64a773740705702c10398be2c6092099
parent 60da08ac03ae07aa593c7265fab148d460d301f5
author Heschi Kreinick <heschi@google.com> 1594935432 -0400
committer Heschi Kreinick <heschi@google.com> 1595957686 +0000

internal/lsp: pass snapshot/view to memoize.Functions

Due to the runtime's inability to collect cycles involving finalizers,
we can't close over handles in memoize.Functions without causing memory
leaks. Up until now we've dealt with that by closing over all the bits
of the snapshot that we want, but it distorts the design of all the code
used in the Functions.

We can solve the problem another way: instead of closing over the
snapshot/view, we can force the caller to pass it in. This is somewhat
scary: there is no requirement that the argument matches the data that
we're working with. But the reality is that this is not a new problem:
the Function used to calculate a cache value is not necessarily the one
that the caller expects. As long as the cache key fully identifies all
the inputs to the Function, the output should be correct. And since the
caller used the snapshot/view to calculate that cache key, it should
always be safe to pass in that snapshot/view. If it's not, then we
already had a bug.

The Arg type in memoize is clumsy, but I thought it would be nice to
have at least a little bit of type safety. I'm open to suggestions.

Change-Id: I23f546638b0c66a4698620a986949087211f4762
Reviewed-on: https://go-review.googlesource.com/c/tools/+/244019
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>