Code intelligence 3.3 tracking issue

Created by: chrismwendt

User story

The default code intelligence is not very precise and doesn't always find definitions for symbols that you're hovering over.

• Support language-specific callbacks for filtering defs/refs https://github.com/sourcegraph/sourcegraph-basic-code-intel/pull/66
• Poor quality Swift regexes https://github.com/sourcegraph/sourcegraph/issues/2903
  • https://github.com/sourcegraph/sourcegraph/pull/2912
  • https://github.com/sourcegraph/sourcegraph/pull/2945
• Fall back to basic code intel when hovers take over 500ms https://github.com/sourcegraph/sourcegraph/issues/2571
  • Implemented in https://github.com/sourcegraph/sourcegraph-go/pull/55
  • Disabled in https://github.com/sourcegraph/sourcegraph-go/pull/58 pending a different approach (see https://github.com/sourcegraph/sourcegraph-go/pull/57) and making sure it doesn't cause confusion
• Single-click j2d https://github.com/sourcegraph/enterprise/issues/11047
• Support j2d on parameters and local variables for various files (using tree-sitter)
• Use @sourcegraph/lsp-client https://github.com/sourcegraph/sourcegraph-go/issues/28
  • WIP PR https://github.com/sourcegraph/sourcegraph-go/issues/28
  • Go langserver needs updates described in https://github.com/sourcegraph/sourcegraph-go/issues/28#issuecomment-469488194
• Do not show "Find references" over comments or whitespace https://github.com/sourcegraph/sourcegraph/issues/2159
  • Attempt 1 (tie refs to the presence of a definition) https://github.com/sourcegraph/sourcegraph/pull/3188
  • Attempt 2 (add a token type provider to the extension API) https://github.com/sourcegraph/sourcegraph/pull/3239
• Highlight variables https://github.com/sourcegraph/sourcegraph/issues/3037
• Dependency graph
• Filter definitions for all languages https://github.com/sourcegraph/sourcegraph-basic-code-intel/pull/67
• Implement document highlights using tree-sitter
• Filter definitions by parent (from ctags)
• Go code intel slow https://sourcegraph.slack.com/archives/C0C324C91/p1554154297030300
  • Recommend -freeosmemory=false https://github.com/sourcegraph/sourcegraph-go/pull/56
  • Set -freeosmemory=false on Sourcegraph.com https://github.com/sourcegraph/deploy-sourcegraph-dot-com/commit/fe24ddf48cdb5195247ffbf5d03032d89e33ef98