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internal/lsp/cache: trim more stuff in ParseExported mode
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Despite the name, ParseExported only hollowed out declarations -- it
didn't actually drop any from the AST. This leaves a fair amount of
unexported crud behind. Unfortunately, there are a *lot* of ways to
expose an unexported declaration from an exported one, and it can be
done across files. Because of that, discarding unexported declarations
requires a lot of work.

This CL implements a decent attempt at pruning as much as possible from
the AST in ParseExported mode.

First, we analyze the AST of all the files in the package for exported
uses of unexported identifiers, iterating to a fixed point. Then, we
type check those ASTs. If there are missing identifiers (probably due to
a bug in the dependency analysis) we use those errors to re-parse. After
that we give up and fall back to the older, less effective trimming. The
pkg type changes slightly to accomodate the new control flow.

We have to analyze all the files at once because an unexported type
might be exposed in another file. Unfortunately, that means we can't
parse a single file at a time any more -- the result of parsing a file
depends on the result of parsing its siblings. To avoid cache
corruption, we have to do the parsing directly in type checking,
uncached.

This, in turn, required changes to the PosTo* functions. Previously,
they operated just on files, but a file name is no longer sufficient to
get a ParseExported AST. Change them to work on Packages instead. I
squeezed in a bit of refactoring while I was touching them.

Change-Id: I61249144ffa43ad645ed38d79e873e3998b0f38d
Reviewed-on: https://go-review.googlesource.com/c/tools/+/312471
Trust: Heschi Kreinick <[email protected]>
Run-TryBot: Heschi Kreinick <[email protected]>
gopls-CI: kokoro <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Robert Findley <[email protected]>
Reviewed-by: Rebecca Stambler <[email protected]>
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heschi committed May 11, 2021
1 parent 2db0265 commit cd1d088
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Showing 13 changed files with 709 additions and 276 deletions.
2 changes: 1 addition & 1 deletion internal/lsp/cache/analysis.go
Original file line number Diff line number Diff line change
Expand Up @@ -403,7 +403,7 @@ func (s *snapshot) DiagnosePackage(ctx context.Context, spkg source.Package) (ma
analyzers = append(analyzers, a)
}
var errorAnalyzerDiag []*source.Diagnostic
if pkg.hasTypeErrors {
if pkg.HasTypeErrors() {
var err error
errorAnalyzerDiag, err = s.Analyze(ctx, pkg.ID(), analyzers)
if err != nil {
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