commit 07295caad09cddc39fc3b5631934f4780c2014de
author Heschi Kreinick <heschi@google.com> Thu Apr 08 17:58:25 2021 -0400
committer Heschi Kreinick <heschi@google.com> Fri Apr 16 22:42:28 2021 +0000
tree 85a286b09db9fe3150e32be529751cc883a67d60
parent 1a0c6081c56a37d2e11f78315a6a63af8bd9b51b

internal/lsp/cache: prune types.Info entries in slice literals

The type checker emits a TypeAndValue entry for (among other things)
every constant in a Go file. Normally, that cost is moderate. However,
in the case of a large slice literal, it can get out of control very
quickly. Imagine a code generator that creates a 2KB byte slice literal;
that's 2K TypeAndValue entries, each of which is considerably larger
than the 1-3 bytes for the source text.

Unfortunately, there are a number of such code generators. Notably,
there are such slice literals in proto code, e.g.
https://github.com/grpc/grpc-go/blob/master/examples/route_guide/routeguide/route_guide.pb.go#L360

This CL changes the type checking code to remove the TypeAndValue
entries for slice literals of basic types after the checker returns.
In the extreme case of https://github.com/googleapis/go-genproto, which
is nothing but protos, I see a ~40% drop in heap usage.

I believe this change is generally safe, but there's no way to guarantee
it. I don't think any editor features need to know the type or value of
an arbitrary slice element, but it is just barely possible that an
analyzer does.

Change-Id: Iee1af2369f994597a42fd1dcbf8af20faa43410e
Reviewed-on: https://go-review.googlesource.com/c/tools/+/308730
Trust: Heschi Kreinick <heschi@google.com>
Run-TryBot: Heschi Kreinick <heschi@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>