internal/lsp/source: speed up completion candidate formatting

Completion could be slow due to calls to astutil.PathEnclosingInterval
for every candidate during formatting. There were two reasons we
called PEI:

1. To properly render type alias names, we must refer to the AST
   because the alias name is not available in the typed world.
   Previously we would call PEI to find the *type.Var's
   corresponding *ast.Field, but now we have a PosToField cache that
   lets us jump straight from the types.Object's token.Pos to the
   corresponding *ast.Field.

2. To display an object's documentation we must refer to the AST. We
   need the object's declaring node and any containing ast.Decl. We
   now maintain a special PosToDecl cache so we can avoid the PEI call
   in this case as well.

We can't use a single cache for both because the *ast.Field's position
is present in both caches (but points to different nodes). The caches
are memoized to defer generation until they are needed and to save
work creating them if the *ast.Files haven't changed.

These changes speed up completing the fields of
github.com/aws/aws-sdk-go/service/ec2 from 18.5s to 45ms on my laptop.

Fixes golang/go#37450.

Change-Id: I25cc5ea39551db728a2348f346342ebebeddd049
Reviewed-on: https://go-review.googlesource.com/c/tools/+/221021
Run-TryBot: Muir Manders <muir@mnd.rs>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
11 files changed
tree: 57c6e559b93fc5aeac44f79712154978cad28288
  1. benchmark/
  2. blog/
  3. cmd/
  4. container/
  5. cover/
  6. go/
  7. godoc/
  8. gopls/
  9. imports/
  10. internal/
  11. playground/
  12. present/
  13. refactor/
  14. txtar/
  15. .gitattributes
  16. .gitignore
  17. .prettierrc
  18. AUTHORS
  19. codereview.cfg
  20. CONTRIBUTING.md
  21. CONTRIBUTORS
  22. go.mod
  23. go.sum
  24. LICENSE
  25. PATENTS
  26. README.md
README.md

Go Tools

This subrepository holds the source for various packages and tools that support the Go programming language.

Some of the tools, godoc and vet for example, are included in binary Go distributions.

Others, including the Go guru and the test coverage tool, can be fetched with go get.

Packages include a type-checker for Go and an implementation of the Static Single Assignment form (SSA) representation for Go programs.

Download/Install

The easiest way to install is to run go get -u golang.org/x/tools/.... You can also manually git clone the repository to $GOPATH/src/golang.org/x/tools.

JS/CSS Formatting

This repository uses prettier to format JS and CSS files.

The version of prettier used is 1.18.2.

It is encouraged that all JS and CSS code be run through this before submitting a change. However, it is not a strict requirement enforced by CI.

Report Issues / Send Patches

This repository uses Gerrit for code changes. To learn how to submit changes to this repository, see https://golang.org/doc/contribute.html.

The main issue tracker for the tools repository is located at https://github.com/golang/go/issues. Prefix your issue with “x/tools/(your subdir):” in the subject line, so it is easy to find.